JP2004187326A - Data transmitting method, data transmitting apparatus, and data receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a quality of transmission data in a transmission line including a wireless zone by reducing the number of packets which are discarded on a receiving side because of an error incurred in the wireless zone when performing data transmission using a packet by compressing data (transmission information) stored in the packet. <P>SOLUTION: A packet creating means 12 for creating, in accordance with packet judgement information Jp, any one of either a non-compressed packet Pa stored without compressing the transmission information or a compressed packet Pb stored while compressing the transmission information, and a transmission means 16 for transmitting each of packets, are included, and the compressed packet Pb stores differential information based on the transmission information in the latest non-compressed packet Pa which is transmitted before the compressed packet. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a data transmission method, a data transmission device, and a data reception device, and in particular, when transmitting data in a packet unit between a plurality of information processing devices, the transmission side compresses data corresponding to a predetermined packet, On the receiving side, it relates to data transmission processing for restoring compressed data corresponding to a predetermined packet.

  At present, TCP / IP (Transmission Control Protocol / Internet Protocol), UDP / IP (User Datagram Protocol / Internet Protocol), and the like are used as typical transmission protocols for transmitting data on the Internet.

  However, when data is transmitted in packet units using these transmission protocols via transmission paths of low to medium bit rates (9600 bps to 64 Kbps), each transmission protocol such as TCP, UDP, and IP is included in a packet. Is included, which may cause a problem that the communication overhead, that is, the information amount of the header portion in the packet becomes considerably larger than the information amount of the data portion.

  For example, when transmitting 10-byte data by the UDP / IP protocol, the total size of the UDP / IP packet is 38 bytes, even though the size of the data portion of the UDP / IP packet used for transmission by this protocol is 10 bytes. It becomes. In other words, the total size of the UDP / IP packet is about four times the information amount of the data actually transmitted. When such communication overhead occurs frequently, the effective transmission speed of data on the transmission path is significantly reduced as a result.

  At present, as a method of reducing communication overhead by using a plurality of transmission protocols, a header compression method of V. Jacobson specified in RFC (Request For Comments) 1144 and RFC (Request For Comments) 2508 is used.

Hereinafter, this header compression method will be described.
FIG. 28A shows a data transmission system to which a conventional V. Jacobson header compression method is applied.

  In this data transmission system Cs1, a gateway server Sga is connected to the Internet In, and terminal equipment Teq such as a personal computer, a modem, an integrated service digital network (ISDN), and a local area network (LAN) are connected to the gateway server Sga. ) Are connected via a wired line. Here, the connection between the terminal device Teq and the gateway server Sga is a point-to-point connection that directly connects the transmission source and the transmission destination via a wired line, and is connected on a transmission path between the terminal device Teq and the gateway server Sga. In, a packet subjected to data compression processing by the V. Jacobson header compression method is transmitted by a transmission protocol such as a PPP (Point to Point Protocol) protocol.

  In the data transmission system Cs1, when data is transmitted from the gateway server Sga to the terminal device Teq, the gateway server Sga functions as a transmitting device, and the terminal device Teq functions as a receiving device. Conversely, when data is transmitted from the terminal device Teq to the gateway server Sga, the gateway server Sga plays the role of the receiving device, and the terminal device Teq plays the role of the transmitting device.

Hereinafter, data transmission using packets in the data transmission system Cs1 will be briefly described.
FIG. 28B shows processing required for data transmission in the data transmission system divided into a plurality of layers. FIGS. 29A to 29E show the data structure of a packet generated by the processing of each layer.

  First, as shown in FIG. 28 (b), in the data transmission system, data is transferred from a server (transmission device) Sin on the Internet In to a terminal device (reception device) via a gateway server (relay device) Sga. The case of transmission to Teq (see data flow Df) will be described.

  The data held by the transmission side device Sin is subjected to the processing of the first layer (application layer) Ls1 and then to the processing of the second layer Ls2. As a result, an RTP packet Prtp corresponding to the RTP (Realtime Transport Protocol) protocol is generated. The RTP packet Prtp is composed of an RTP header section Hrtp storing header information and an RTP payload (data section) Drtp storing the data. Here, the information in the RTP header section Hrtp includes a sequence number Isn that is incremented by one every time one packet is transmitted, time information (time stamp) Its used for processing on the data receiving side, and other header information. Ith (see FIG. 29A). The size of the RTP header Hrtp is generally 12 bytes, 2 bytes are allocated to the sequence number Isn, and 4 bytes are allocated to the time stamp Its.

  Next, the RTP packet Prtp is subjected to the processing of the third layer Ls3, whereby a UDP packet Pudp corresponding to the UDP (User Datagram Protocol) protocol is generated. The UDP packet Pudp is composed of a UDP header part Hudp storing header information and a data part Dudp storing the RTP packet Prtp (see FIG. 29 (b)).

Subsequently, the UDP packet Pudp is subjected to the processing of the fourth hierarchy Ls4, thereby generating an IP packet Pipa corresponding to the IP (Internet Protocol) protocol. The IP packet Pipa is composed of an IP header section Hipa storing header information and a data section Dip storing the UDP packet Pudp (see FIG. 29C).
Then, the IP packet Pipa is transmitted to the gateway server Sga via the transmission path Cin according to a predetermined transmission standard (for example, Ethernet (registered trademark)) by the processing of the fifth layer Ls5.

  Then, in the gateway server Sga, the IP packet Pipa from the server Sin on the Internet In receives a predetermined transmission standard (for example, Ethernet (registered trademark)) by processing of the lower layer Lin2 corresponding to processing of the fifth layer Ls5 in the transmitting apparatus. ). The received IP packet Pipa is separated into its header portion Hipa and data portion Dip by the processing of the upper layer Lin1 corresponding to the processing of the fourth layer Ls4 in the transmitting device. Then, by the processing of the upper layer Leq1 corresponding to the predetermined layer (here, the fourth layer Lr4) in the receiving apparatus, the separated data section Dip includes the header section Hipb including information different from the information of the header section Hipa. Thus, the IP packet Pipb is generated (see FIG. 29D).

  Thereafter, the IP packet Pipb is subjected to the processing of the lower layer Leq2 corresponding to the predetermined layer (here, the fifth layer Lr5) in the receiving apparatus, and the PPP packet Pppp corresponding to the PPP (point-to-point Protocol) protocol is performed. Is transmitted to the terminal device Teq via the wired line Ceq. This PPP packet Pppp is composed of a header section Hppp that stores the PPP header information Ippp and a CRC code Icrc for checking received data, and a data section Dppp that stores the IP packet Pipb (FIG. 29 ( e)).

  When the PPP packet Pppp is received by the terminal device Teq as a receiving device, the PPP packet Pppp is converted into a header portion Hppp and a data portion Dppp by the processing of the fifth layer Lr5 corresponding to the lower layer Leq2 in the gateway server Sga. Separated.

Next, the IP packet Pipb stored in the PPP data portion Dppp is separated into an IP header portion Hipg and an IP data portion Dip by the processing of the fourth layer above the fifth layer Lr5. Subsequently, the UDP packet Pudp stored in the IP data part Dip is separated into a UDP header part Hudp and a UDP data part Dudp by the processing of the third hierarchy Lr3, which is higher than the fourth hierarchy Lr4. Further, the RTP packet Prtp stored in the UDP data portion Dudp is separated into an RTP header portion Hrtp and an RTP data portion Drtp by the processing of the second layer Lr2 higher than the third layer Lr3.
Then, the data stored in the RTP payload (RTP data section) Drtp is subjected to the processing of the first layer (application layer) Lr1.

  When data is transmitted from the terminal device Teq to the server Sin on the Internet, the terminal device Teq becomes the transmitting device and the server Sin becomes the receiving device. In this case, a process completely opposite to the case where data is transmitted from the server Sin on the Internet to the terminal device Teq via the gateway server Sga is performed. That is, in each layer Lr2 to Lr5 of the terminal device Teq, a process of generating a packet corresponding to each layer is performed, and in the gateway server Sga, the IP packet Pipb is extracted from the PPP packet Pppp from the terminal device Teq. The packet is converted into an IP packet Pipa and transmitted to the server Sin on the Internet In based on Ethernet (registered trademark). In the server Sin, the IP packet Pipa is received by the processing of the fifth layer Ls5 and stored in the RTP payload Drtp by the processing of the layers Ls4 to Ls2 in the server Sin corresponding to the respective layers Lr2 to Lr4 of the terminal device Teq. Is retrieved, and the data is subjected to the processing of the application layer Ls1.

  In the above description, the processing of the third layer Ls3 and Lr3 shows the case where the UDP packet Pudp corresponding to the UDP protocol is generated. However, in the processing of the third layer, the TCP (Transmission Control Protocol) protocol is used. May be generated.

  In the data transmission system Cs1 as described above, when data is transmitted by the PPP protocol using the V. Jacobson header compression method, the PPP packet Pppp transmitted by the protocol is roughly divided into two as shown in FIG. Types of packets are used. One is a compressed packet Py (see FIG. 30 (b)) in which data (transmission information) stored in the data portion is compressed, and the other is data (transmission information) stored in the data portion. ) Is an uncompressed uncompressed packet Px (see FIG. 30A). FIG. 30 shows in detail a part of the data structure of the PPP packet which is necessary for describing the V. Jacobson header compression method.

  That is, the uncompressed packet Px includes a header section Hpx storing header information and a data section Dpx storing transmission information (D) as uncompressed information Ir transmitted by the PPP protocol. The information of the header section Hpx is composed of a compressed / uncompressed identifier Ih1 indicating whether or not the information of the data section Dpx is compressed, and other header information Ih3. In the uncompressed packet Px, the compression / non-compression identifier Ih1 indicates non-compression.

  The compressed packet Py includes a header section Hpy storing header information, and a data section Dpy storing difference information (ΔD) as compression information Id transmitted by the PPP protocol. The information of the header section Hpy includes a compression / non-compression identifier Ih1 indicating whether or not the information of the data section Dpy is compressed, and other header information Ih3. In the compressed packet Py, the compression / non-compression identifier Ih1 indicates compression.

Needless to say, the other header information Ih3 includes the CRC code Icrc shown in FIG.
In the transmission process of the PPP packet using the V. Jacobson header compression method, an uncompressed packet Px is transmitted from the transmission side to the reception side as an initial PPP packet, and a compressed packet Py is transmitted as a subsequent PPP packet.

  Here, the data portion Dpy of the compressed packet Py to be transmitted stores difference information (ΔD) using transmission information corresponding to the PPP packet transmitted immediately before as reference information. The difference information (ΔD) is, specifically, a difference between the transmission information to be transmitted by the transmission target compressed packet and the transmission information as the reference source information.

FIG. 31 is a diagram conceptually illustrating a conventional PPP packet transmission process using the V. Jacobson header compression method.
Here, a case where transmission information (D1) to (D4) corresponding to each PPP packet are sequentially transmitted will be described.

  First, an uncompressed packet Px (1) is transmitted from the transmitting side to the receiving side as the first PPP packet. In the data part Dpx of the uncompressed packet Px (1), transmission information (D1) is stored as uncompressed information Ir.

  Thereafter, the compressed packets Py (2) to Py (4) are sequentially transmitted from the transmitting side to the receiving side as PPP packets. In the data portion Dpy of these compressed packets Py (2), Py (3), and Py (4), differential information (D1-D2), (D2-D3), and (D3-D4) are provided as compression information Id. Is stored.

  Here, the difference information (D1-D2) is difference information between the transmission information (D1) and (D2), and the difference information (D2-D3) is difference information between the transmission information (D2) and (D3). The difference information (D3-D4) is difference information between the transmission information (D3) and (D4). As described above, in each compressed packet, the difference information (ΔD) between the transmission information corresponding to each compressed packet and the transmission information corresponding to the packet transmitted immediately before is stored as the compression information Id.

The transmission of such a compressed packet is continued until a transmission error occurs.
On the receiving side, the uncompressed packet Px (1) is received as the first PPP packet, and thereafter, the compressed packets Py (2) to Py (4) are sequentially received as PPP packets.

  Then, the uncompressed packet Px (1) is processed by the PPP protocol, and the transmission information (D1) stored in the data portion Dpx is extracted. The compressed packets Py (2), Py (3) and Py (4) are processed by the PPP protocol and stored in the data part Dpy of the difference information (D1-D2), (D2-D3), (D2-D3), D3-D4) are taken out, and the transmission information D2, D3, D4 corresponding to each compressed packet is restored by the V. Jacobson header compression method. For example, the restoration of the transmission information (D2) is performed by the addition operation of the difference information (D1-D2) and the transmission information D1, and the restoration of the other transmission information (D3) and (D4) is performed in the same manner.

Next, a case where a transmission error occurs in a transmission process by the PPP protocol using the conventional V. Jacobson compression method will be described.
FIG. 32 shows transmission and reception of signals between the transmission side and the reception side when the transmission error occurs.
If the receiving side detects a transmission error of a predetermined PPP packet, the receiving side cannot recover the PPP packet received after the occurrence of the error, and thus notifies the transmitting side that a recovery error has occurred.

  For example, as shown in FIG. 32, when the compressed packet Py (2) is not normally transmitted to the receiving side due to a transmission error, the receiving side receives the compressed packet Py (2) following the compressed packet Py (2). Even if this is done, the transmission information (D3) that is the original information of the difference information stored in the compressed packet Py (3) cannot be restored. This is because the transmission information (D2) which is the original information of the difference information stored in the compressed packet Py (2) has not been restored. Therefore, in this case, the receiving side notifies the transmitting side that a restoration error has occurred.

  When the transmitting side receives the notification of the occurrence of the restoration error, immediately after receiving the notification, the uncompressed packet Px (5) is transmitted to the receiving side as a PPP packet. On the other hand, on the receiving side, all the compressed packets Py (2) to Py (4) received from the time when the transmission error occurs until the time when the uncompressed packet is received thereafter are discarded.

  By the way, at present, the application of the Internet using a mobile phone, for example, the access of mail to the mobile phone and the service of text information, etc., have been advanced, and the third-generation mobile communication (W-CDMA: Wideband-Code Division). Infrastructure for next-generation wireless data communication (up to 384 Kbps) is being prepared for the practical use of Multiple Access.

FIG. 33 (a) is a diagram showing a data transmission system for the wireless terminal device supporting W-CDMA.
In this data transmission system Cs2, a gateway server Sga is connected to the Internet In, and a portable wireless terminal device (such as a visual terminal) Tmo is connected to the gateway server Sga via a wireless telephone network Cwr such as W-CDMA. It is connected. Also in such a data transmission system Cs2, communication of a packet subjected to data compression processing by the V. Jacobson header compression method is performed on a transmission path between the portable wireless terminal device Tmo and the gateway server Sga by PPP (Point to Point). Point Protocol).

FIG. 33 (b) shows the processing required for data transmission in the data transmission system Cs2 divided into a plurality of layers.
In this data transmission system Cs2, since the transmission path between the portable radio terminal device Tmo and the gateway server Sga includes the radio telephone network Cwr, the data transmission process between them is performed by the terminal device and the gateway server. Is different from the data transmission system Cs1 connected by a wired line only in the following points.

  That is, when transmitting a PPP packet from the gateway server Sga to the portable wireless terminal device Tmo, the gateway server Sga converts the PPP packet obtained by the processing of the second layer Lmo2 into a processing corresponding to the W-CDMA method of the third layer Lmo3. Is transmitted to the portable wireless terminal device Tmo via the wireless line Cmo.

  Then, the portable wireless terminal device Tmo receives the PPP packet by the processing corresponding to the W-CDMA system of the sixth layer Lr6. Thereafter, similarly to the data transmission system Cs1, the data stored in the RTP payload Drtp is extracted by the processing of the fifth to second layers Lr5 to Lr2, and the data is subjected to the processing of the application layer Lr1. .

  The other communication processing in the data transmission system Cs2 shown in FIG. 33B is the same as that in the data transmission system Cs1 shown in FIG. For example, the processing of the first layer Lmo1 and the second layer Lmo2 on the terminal side in the gateway server Sga in the data transmission system Cs2 is performed by the first layer Leq1 and the second layer Leq2 on the terminal side in the gateway server Sga in the data transmission system Cs1. Is the same as the process of

However, while the bit error rate in data transmission in a wired section is 10 ⁻⁵ to 10 ⁻⁷ , the bit error rate in data transmission in a wireless section is about 10 ⁻³ , and V. Jacobson's header compression In the data transmission processing by the PPP protocol using the method (RFC1144, RFC2508), quality degradation of transmission data due to a transmission error in a wireless section becomes a problem.

  In other words, in the data transmission system Cs2 including the wireless section, if data transmission by the PPP protocol is performed by using the V. Jacobson header compression method, the data transmission system Cs2 performs the case shown in FIG. There is a problem that the case of frequently discarding the received packet occurs, and as a result, the number of transmission packets discarded increases dramatically.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and when performing data transmission in a packet by compressing data (transmission information) stored in the packet, an error occurs in a radio section due to an error in a wireless section. It is possible to obtain a data transmission method, a data transmission device, and a data reception device that can reduce the number of packets discarded in the transmission path, thereby improving the quality of transmission data in a transmission path including a wireless section. Aim.

  A data transmission method according to the present invention is a data transmission method for sequentially transmitting information from a transmitting side to a receiving side for each piece of transmission information corresponding to a packet, wherein the predetermined transmission information is stored as uncompressed information. A transmission side process of transmitting a packet at a fixed period and continuously transmitting a compressed packet in which at least a part of transmission information following the predetermined transmission information is compressed and stored as compression information is included. And compression processing for creating compression information to be stored in a compressed packet to be transmitted, based on transmission information corresponding to the uncompressed packet and transmission information corresponding to the compressed packet.

  According to the present invention, in the above data transmission method, the transmitting side process transmits an uncompressed packet storing the same transmission information to the receiving side continuously plural times.

  According to the present invention, in the data transmission method, further, when there is a decompression error of the uncompressed packet, the transmission side process receives a notification indicating the occurrence of a decompression error from a reception side, and based on the notification And transmits an uncompressed packet.

  A data transmission method according to the present invention is a data transmission method for sequentially transmitting information from a transmitting side to a receiving side for each piece of transmission information corresponding to a packet, wherein the predetermined transmission information is stored as uncompressed information. The receiving side processing includes receiving a packet at a constant cycle, and continuously receiving a compressed packet in which at least a part of the transmission information following the predetermined transmission information is compressed and stored as compression information. And a decompression process for decompressing transmission information corresponding to a compressed packet to be decompressed based on transmission information corresponding to an uncompressed packet and compression information included in the decompressed compressed packet.

  According to the present invention, in the data transmission method, the reception-side processing is to continuously receive an uncompressed packet storing the same transmission information a plurality of times.

  According to the present invention, in the above data transmission method, the receiving side process discards only an error packet when a restoration error occurs.

  According to the present invention, in the data transmission method, further, when there is a decompression error of the uncompressed packet, the reception side process transmits a notification indicating the occurrence of the decompression error to the transmission side, based on the notification, An uncompressed packet transmitted from the transmitting side is received.

  A data transmission device according to the present invention is a data transmission device that sequentially transmits information from a transmission side to a reception side for each piece of transmission information corresponding to a packet, wherein the predetermined transmission information is transmitted as uncompressed information. The stored uncompressed packet is transmitted at a fixed period, and the transmission information following the predetermined transmission information is transmitted at least partially as compressed information, and the compressed packet is continuously transmitted. A compression process for creating compression information to be stored in a compressed packet based on the transmission information corresponding to the uncompressed packet and the transmission information corresponding to the compressed packet.

  According to the present invention, in the above data transmission apparatus, an uncompressed packet storing the same transmission information is continuously transmitted to a receiving side a plurality of times.

  According to the present invention, in the data transmission device, further, when there is a decompression error of the uncompressed packet, a notification indicating the occurrence of the decompression error is received from the receiving side, and based on the notification, the uncompressed packet is What to send.

  A data receiving device according to the present invention is a data receiving device for receiving information transmitted in packet units from a transmitting side, wherein the data receiving device has an uncompressed format in which predetermined transmission information is stored as uncompressed information. Packets are received at regular intervals, and the transmission information subsequent to the predetermined transmission information is continuously received at least partially as a compressed packet stored as compressed information, and corresponds to the compressed packet to be restored. The transmission information is restored based on the transmission information corresponding to the uncompressed packet and the compression information included in the compressed packet to be restored.

  According to the present invention, in the above data receiving apparatus, the receiving side process continuously receives an uncompressed packet storing the same transmission information a plurality of times.

  According to the present invention, in the data receiving apparatus, when a restoration error occurs, only the error packet is discarded.

  According to the present invention, in the data receiving device, when there is a decompression error of an uncompressed packet, a notification indicating the occurrence of a decompression error is transmitted to the transmission side, and the non-compression packet transmitted from the transmission side is transmitted based on the notification. It receives compressed packets.

  According to the data transmission method of the present invention, when transmitting information in packet units, the transmitting side continuously transmits a compressed packet containing compressed transmission information, followed by an uncompressed packet containing uncompressed transmission information. At this time, the compression information to be stored in the compressed packet to be transmitted is determined based on the transmission information corresponding to the reference packet, which is the uncompressed packet, and the transmission information corresponding to the target packet as the transmission target. On the receiving side, the transmission information corresponding to the compressed packet is restored based on the compression information included in the compressed packet and the transmission information corresponding to the reference packet. Occurs, the receiving side decompresses the subsequent compressed packet based on the transmission information corresponding to the uncompressed packet as the reference packet. Can. This makes it possible to reduce the number of packets discarded on the receiving side due to the occurrence of an error in a wireless section, thereby improving the quality of transmission data on a transmission path including the wireless section.

  According to the present invention, in the data transmission method, the transmitting side transmits, as each compressed packet following the uncompressed packet, a packet including a reference packet identifier indicating the uncompressed packet as the reference packet together with the compression information. Therefore, on the receiving side, the reference packet required for the decompression process on the compressed packet can be specified by the reference packet identifier.

  Further, since the difference information between the transmission information corresponding to the reference packet and the transmission information corresponding to the compressed packet is created as the compression information, the compression information included in the compressed packet is created by a simple calculation process. Can be.

  According to the present invention, in the data transmission method, the transmitting side stores, in the compressed packet, additional information for calculating the difference information based on the transmission information corresponding to the reference packet, Then, since the difference information in the compressed packet is calculated from the transmission information corresponding to the reference packet based on the additional information, the information amount of the difference information can be reduced, and the data compression efficiency can be improved. As a result, data transmission efficiency can be improved.

  According to the present invention, in the data transmission method, as the additional information, a sequence number capable of identifying an order number of the compressed packet transmitted after transmission of the uncompressed packet as the reference packet is used. Therefore, for transmission information that increases by a fixed amount each time a packet is transmitted, the difference information can be set to 0 bits.

  According to the present invention, in the data transmission method, a variable of a calculation formula for calculating difference information in the compressed packet from transmission information corresponding to the reference packet is used as the additional information. For the transmission information that fluctuates according to the function, the difference information can be greatly reduced.

  According to the present invention, in the data transmission method, the transmitting side uses a plurality of uncompressed packets created so as to be transmitted earlier than the compressed packet as reference packets, and the compressed packet includes The difference information between the transmission information corresponding to the packet and the transmission information corresponding to the compressed packet and the reference packet identifier corresponding to each of the reference packets are associated with each other, and the corresponding difference information and the reference packet identifier are compared with the compression information. In the receiving-side process, the transmission information corresponding to the compressed packet is restored using the differential information and the packet identifier of one of the sets in the compressed packet, so that it is necessary to restore the compressed packet. The reliability of the transmission process for uncompressed packets containing information can be improved, thereby improving the quality of data transmitted wirelessly. It can be greatly improved.

  According to the present invention, in the data transmission method, in the transmission-side processing, the uncompressed packet is transmitted at a fixed period, so that the data size of the compressed packet is prevented from becoming extremely large, and the compression efficiency of the transmission information is reduced. Can be kept within a substantially constant fluctuation range. As a result, not only the quality of wirelessly transmitted data but also data transmission efficiency can be improved.

  According to the present invention, in the data transmission method, the transmitting side transmits the uncompressed packet when the size of the compressed information included in the compressed packet transmitted to the receiving side exceeds a certain value. It is possible to increase the compression efficiency of transmission information by keeping the data size small, and to improve not only the quality of wireless transmission data, but also the data transmission efficiency.

  According to the present invention, in the data transmission method, the receiving side requests the transmitting side to transmit an uncompressed packet when the size of the compressed information included in the compressed packet from the transmitting side exceeds a certain value, The transmitting side transmits the uncompressed packet to the receiving side in response to the request for transmitting the uncompressed packet from the receiving side, so that it is possible to suppress the data size of the compressed packet and increase the compression efficiency of the transmission information. It is possible to improve not only the quality of the transmission data but also the data transmission efficiency.

  According to the present invention, in the above data transmission method, the transmitting side transmits the uncompressed packet storing the same transmission information to the receiving side a plurality of times in succession. The reliability of the transmission processing can be improved, and the quality of data transmitted wirelessly can be greatly improved.

  According to the present invention, in the data transmission method, when the receiving side detects a decompression error of the compression information stored in the compressed packet, it notifies the transmitting side that a decompression error has occurred, and the transmitting side Since the number of times the uncompressed packet is continuously transmitted to the receiving side is changed based on the frequency of notification indicating the occurrence of a restoration error from the receiving side, continuous transmission of the uncompressed packet can be performed efficiently. .

  According to the present invention, in the data transmission method, the transmitting side transmits the auxiliary transmission packet including the packet identifier and the transmission information stored in the uncompressed packet to the receiving side a predetermined number of times after transmitting the uncompressed packet. Therefore, the reliability of the transmission process for the information necessary for restoring the compressed packet can be enhanced, and the quality of data transmitted wirelessly can be greatly improved.

  According to the present invention, in the data transmission method, on the transmitting side, the uncompressed packet is transmitted to the receiving side by adding an error correction code thereto, and in the receiving side processing, Since the error correction process is performed by the error correction code added to this, the reliability of the transmission process for the non-compressed packet including the information necessary for restoring the compressed packet can be greatly improved, and thereby, the radio transmission is performed. Data quality can be greatly improved.

  According to the present invention, in the data transmission method, the transmitting side assigns an error correction code to a packet identifier and transmission information in the uncompressed packet, and the receiving side includes a packet identifier included in the uncompressed packet. Since error correction processing is performed on the transmission information using the error correction code assigned thereto, the reliability of the transmission processing for the information necessary for decompressing the compressed packet can be greatly improved, thereby enabling wireless transmission. The quality of the data obtained can be greatly improved.

  According to the present invention, in the data transmission method, when the receiving side detects a decompression error of the compression information stored in the compressed packet, it notifies the transmitting side that a decompression error has occurred, and the transmitting side According to the frequency of the notification indicating the occurrence of the decompression error from the receiving side, a process of transmitting the uncompressed packet with an error correction code thereto, and transmitting the uncompressed packet with an error correction code. Since one of the transmission processes is performed, the process of adding an error correction code to the uncompressed packet and the error correction process of the uncompressed packet can be performed effectively.

  According to the present invention, in the above data transmission method, the transmitting side holds only the uncompressed packet in the retransmission buffer as retransmission data, and responds to the error packet retransmission request from the receiving side to change the error packet. Only when the corresponding uncompressed packet is held in the retransmission buffer, the uncompressed packet corresponding to the error packet is retransmitted to the receiving side, so that the reliability of the transmission process for the information necessary for restoring the compressed packet is increased. As well as improving the efficiency of retransmission of uncompressed packets, the quality of data transmitted wirelessly and the transmission efficiency of data can be greatly improved.

  According to the present invention, in the above data transmission method, the transmitting side holds the packet identifier and the transmission information stored in the uncompressed packet in the retransmission buffer as retransmission data, In response to the stored packet identifier and transmission information retransmission request, only when the packet identifier and transmission information in the uncompressed packet corresponding to the error packet are held in the retransmission buffer, the packet identifier and transmission information are Since the data is retransmitted to the receiving side, the reliability of the transmission process for the information necessary to decompress the compressed packet is greatly improved, the retransmission of the uncompressed packet can be performed efficiently, and the data recording capacity of the retransmission buffer is reduced. it can.

  According to the data transmission method according to the present invention, the transmitting side continuously transmits a compressed packet including compressed transmission information following an uncompressed packet including uncompressed transmission information, and is a transmission target at this time. Compressed information to be stored in the compressed packet is created based on the transmission information corresponding to the reference packet, which is the uncompressed packet, and the transmission information corresponding to the target packet as the transmission target. A first data transmission process for restoring transmission information corresponding to the packet based on the compression information included in the compressed packet and the transmission information corresponding to the reference packet; The information is created by a method different from the method of creating the compressed information in the first data transmission process, and the information stored in the compressed packet is received on the receiving side. And a second data transmission process for restoring information by a method different from the compression information restoration method in the first data transmission process, wherein the first and second data transmission processes are compressed by the compression method on the receiving side. Since switching is performed in accordance with the state of occurrence of packet restoration processing errors, the quality of wireless transmission data can be improved when the frequency of errors is high, and the compression efficiency of transmission information is improved when the frequency of errors is low. Can be done.

  According to the present invention, in the data transmission method, as the second data transmission process, the transmitting side transmits the compression information stored in the compressed packet to be transmitted before the compressed information transmitted immediately before the compressed packet. It is created based on the transmission information corresponding to the packet and the transmission information corresponding to the compressed packet as the transmission target, and on the receiving side, the compression information included in the compression packet to be decompressed corresponds to the previous packet. Since the data transmission process for restoring using the transmission information is performed, the compression efficiency of the transmission information can be greatly improved when the frequency of error occurrence is low.

  According to the present invention, in the data transmission method, when the frequency of notification of the occurrence of an error from the receiving side exceeds a predetermined value, the first data transmission process is performed on the transmitting side, and the notification of the occurrence of the error is performed. When the frequency falls below a certain value, the compression process in the second data transmission process is performed. Therefore, a transmission method with high quality of wireless transmission data when an error occurrence frequency is high, and a transmission method with a low error occurrence frequency It is possible to adaptively switch between a transmission method having high transmission information compression efficiency.

  According to the present invention, in the data transmission method, when the frequency of occurrence of a decompression process error for the compressed packet exceeds a predetermined value, the first data transmission process is performed on the receiving side, and the error of the decompression process is performed. When the occurrence frequency is equal to or less than a predetermined value, the second data transmission process is performed. Therefore, a transmission method with high quality of wireless transmission data when an error occurrence frequency is high, and transmission information with a low error occurrence frequency when transmission information is low. A transmission method with high compression efficiency can be adaptively switched.

  According to the data transmission method of the present invention, when transmitting information in packet units, the transmitting side puts the compressed information to be stored in the compressed packet to be transmitted into the packet transmitted earlier than the compressed packet. Created based on the related update information and the transmission information corresponding to the compressed packet as the transmission target, at this time, set the information related to the uncompressed packet as an initial value of the update information, and then specify Each time a compressed packet is created, the update information is updated to information related to the specific compressed packet, and the receiving side receives transmission information corresponding to the compressed packet to be decompressed before the compressed packet. And decompressing using the update information related to the compressed packet. At this time, information related to the uncompressed packet is set as an initial value of the update information. Each time the transmission information corresponding to a fixed compressed packet is restored, the above-mentioned update information is updated to information related to the specific compressed packet. As a result, the data compression efficiency can be improved, and as a result, the time and cost required for unrecoverable packet transmission can be significantly reduced. Furthermore, since the transmission of a specific compressed packet updates the reference information necessary for the decompression process into the compressed packet, the transmission efficiency of the transmission information can be increased while the data transmission efficiency is kept high.

  According to the present invention, in the data transmission method, the compressed packet includes a reference packet identifier indicating the uncompressed packet or a specific compressed packet as a reference packet, and an information update indicating whether the update information should be updated. Since the flag is stored, the receiving side can easily determine whether or not the update information should be updated based on the information update flag.

  According to the present invention, in the data transmission method, in the transmission-side processing, the specific compressed packet is transmitted to the receiving side every time a predetermined time elapses, so that an increase in the amount of difference information in the compressed packet can be suppressed. Thus, it is possible to improve the quality of transmission data in the radio section to improve the effective speed of data transmission, and to further increase the data compression efficiency.

  According to the present invention, in the data transmission method, the transmitting side processing sends the specific compressed packet to the receiving side every time a fixed number of compressed packets are transmitted. , The quality of the transmission data in the wireless section is improved, the effective data transmission speed is improved, and the data compression efficiency can be further increased.

  According to the present invention, in the data transmission method, in the transmission-side processing, when the transmission of the specific compressed packet is requested from the reception side, the specific compression packet is transmitted to the reception side. In addition to improving the quality of transmitted data and improving the effective speed of data transmission, the data compression efficiency can be further increased.

  According to the present invention, in the data transmission method, in the transmission-side processing, when the size of the compression information included in the compression packet transmitted to the reception side exceeds a certain value, the specific compression packet is transmitted. In addition, an increase in the amount of difference information in the compressed packet can be suppressed.

  According to the present invention, in the above data transmission method, in the transmitting side processing, when the average value of the size of the compressed information included in the compressed packet transmitted to the receiving side exceeds a certain value, the specific compressed packet is Since the transmission is performed, it is possible to suppress an increase in the amount of difference information in the compressed packet, and to stably control the fluctuation of the difference information. Also in this case, it goes without saying that the time and cost required for unrecoverable packet transmission can be further greatly reduced.

  According to the invention, in the data transmission method, the transmission information includes item-specific transmission information corresponding to a plurality of items, the compression information includes item-specific compression information corresponding to a plurality of items, The item-specific compression information corresponding to each item in the compression information included in the packet corresponds to the item-specific compression information corresponding to each item in the transmission information corresponding to the compressed packet, to the uncompressed packet or the specific compressed packet. This is information obtained by compression using the item-specific transmission information corresponding to each item in the transmission information, and the item-specific compression information includes an item type flag for specifying the corresponding item. A compression process can be performed for each item, an optimal compression effect can be realized for each item, and a RAM or the like that stores update information and the like It is possible to reduce the Ranaru storage area. As a result, not only the time and cost required for packet transmission that cannot be restored can be reduced, but also the cost required for manufacturing the transmitting terminal device and the receiving terminal device can be reduced.

  According to the present invention, in the data transmission method, the item-specific compression information includes data length information indicating the data length, so that the decompression process for the item-specific compression information can be performed efficiently.

  According to the present invention, in the data transmission method, the item-specific compression information includes decompression method specifying information indicating a decompression method corresponding to the compression method for decompressing the item-specific compression information. The decompression process can be efficiently performed on a plurality of item-by-item compression information on which the compression process has been performed.

  According to the data transmitting apparatus of the present invention, the received transmission information is received, and the uncompressed packet in which the predetermined transmission information is stored as the uncompressed information, and the transmission information following the predetermined transmission information is at least one of them. Packet creating means for creating a compressed packet whose section is compressed and stored as compressed information, and reference information management for accumulating and managing information relating to the uncompressed packet created by the packet creating means as reference information Means for storing the compressed information to be stored in the compressed packet to be created by the means, transmission information corresponding to the compressed packet, and the reference information managing means. Since it is created based on the reference information, even if a transmission error of the compressed packet occurs in the radio section, the receiving side will generate a subsequent compressed packet. And it can be restored on the basis of the transmission information corresponding to the uncompressed packet as the reference packet. This makes it possible to reduce the number of packets discarded on the receiving side due to the occurrence of an error in the wireless section, and to improve the quality of transmission data on a transmission path including the wireless section.

  According to the data receiving apparatus according to the present invention, the data receiving apparatus receives information transmitted in packet units from the transmitting side as a transmission signal, and sequentially restores transmission information corresponding to each packet. An uncompressed packet in which predetermined transmission information is stored as uncompressed information, and a packet which outputs a compressed packet in which at least a part of transmission information following the predetermined transmission information is compressed and stored as compressed information Receiving means, packet decompression means for performing decompression processing on each packet based on the information stored in each of the packets, and information relating to the uncompressed packet decompressed by the packet decompression means. Reference information management means for accumulating and managing as reference information, wherein the packet decompression means corresponds to the compressed packet. Since the transmission information is restored based on the compression information included in the compressed packet and the reference information stored in the reference information management means, a transmission error of the compressed packet occurs in the wireless section. Also, the subsequent compressed packet can be restored based on the transmission information corresponding to the uncompressed packet as the reference packet, thereby improving the quality of the transmission data on the transmission path including the radio section.

  According to the data transmitting apparatus of the present invention, the received transmission information is received, and the uncompressed packet in which the predetermined transmission information is stored as the uncompressed information, and the transmission information following the predetermined transmission information is at least one of them. Packet creating means for creating a compressed packet whose section is compressed and stored as compressed information, and information for managing information relating to the uncompressed packet and the specific compressed packet created by the packet creating means as update information Management means, wherein the information management means sets information relating to the uncompressed packet as an initial value of the update information, and thereafter, every time a specific compressed packet is created, specifies the update information to the identification information. The packet creating means is configured to be updated to the information related to the compressed packet, and the packet creating means is stored in the compressed packet to be created by the means. The compression information to be generated is created based on the transmission information corresponding to the compressed packet and the update information stored in the reference information management means. As well as improving the effective transmission speed, it is also possible to increase the data compression efficiency, and as a result, the time and cost required for unrecoverable packet transmission can be significantly reduced. Furthermore, by transmitting a specific compressed packet, the reference information necessary for the decompression process is updated to the compressed packet, so that the number of times of transmission of the uncompressed packet is reduced, and the transmission information is compressed while maintaining high data transmission efficiency. Efficiency can be increased.

  According to the data receiving apparatus according to the present invention, the data receiving apparatus receives information transmitted in packet units from the transmitting side as a transmission signal, and sequentially restores transmission information corresponding to each packet. An uncompressed packet in which predetermined transmission information is stored as uncompressed information, and a packet which outputs a compressed packet in which at least a part of transmission information following the predetermined transmission information is compressed and stored as compressed information Receiving means, packet restoring means for restoring each packet based on the information stored in each packet, uncompressed packets and specific compressed packets restored by the packet restoring means Reference information management means for accumulating and managing information related to the information as reference information, wherein the information management means The information related to the uncompressed packet is set as an initial value of the information, and thereafter, each time the decompression process for the specific compressed packet is performed, the update information is updated to information related to the specific compressed packet. The packet restoring unit is configured to restore transmission information corresponding to the compressed packet based on the compression information included in the compressed packet and the reference information stored in the reference information management unit. Therefore, it is possible to improve the quality of the transmission data in the wireless section, improve the effective data transmission speed, and also increase the data compression efficiency. As a result, the time and cost for unrecoverable packet transmission are greatly reduced. can do. Further, each time a specific compressed packet is restored, the reference information necessary for the restoration processing is updated to the compressed packet, so that the number of times of transmitting the uncompressed packet is reduced, and the data transmission efficiency and the transmission information compression efficiency are reduced. High transmission processing can be realized.

Hereinafter, the viewpoint and the basic principle of the present invention will be described.
The inventor of the present invention has conducted intensive studies on a method for improving the quality of transmission data in a network including a wireless transmission path, and as a result, a compressed packet to be transmitted has been replaced with an existing header compression method such as the V. Jacobson header compression method. By using a header compression method that stores difference information obtained using transmission information corresponding to an uncompressed packet transmitted earlier than the compressed packet as compressed transmission information, It was found that the quality of transmitted data can be improved.

  In the following embodiments, data communication is performed in a unidirectional manner from a server Sin on the Internet to a portable wireless terminal device (such as a visual terminal) Tmo as shown by a data flow Df in FIG. Although only transmission will be described, a data communication process for simultaneously communicating data in two directions by configuring a communication device such as a server or a terminal device for data communication to have both functions of a transmission side and a reception side. Can be realized. In the data communication from the server Sin on the Internet to the portable wireless terminal device Tmo as described above, the gateway server Sga (see FIG. 33B) performs a reception process of receiving data from the server Sin on the Internet, and a reception process. The mobile radio terminal device Tmo performs a receiving process of receiving data from the gateway server Sga.

  Also, in each embodiment of the present invention, as transmission information including various header information, an RTP / UDP / IP packet corresponding to an IP packet Pipb (see FIG. A case of transmission by a protocol will be described, but transmission information and its transmission protocol are not limited to the RTP / UDP / IP packet and the PPP protocol.

(Embodiment 1)
1 to 11 are diagrams for explaining a data transmission method according to the first embodiment of the present invention. The first embodiment corresponds to claims 1 to 9, 18 to 21, 32, 33, 36, and 37.

  In the data transmission method according to the first embodiment, an uncompressed packet and a compressed packet are created and transmitted by a transmitting device while data is transmitted from a transmitting device to a receiving device in packet units, and transmitted by the receiving device. In the data transmission method of receiving a packet from the side device and sequentially restoring the received packet, a compressed packet to be transmitted includes, as transmission information corresponding to the compressed packet, The difference information based on the transmission information stored in the uncompressed packet closest to the compressed packet is stored. Here, the difference information stored in the compressed packet as the transmission target should be transmitted by the transmission target compressed packet from the reference source information using the transmission information stored in the uncompressed packet as the reference source information. This is obtained by subtracting the transmission information.

  In the following description, transmission information stored in an uncompressed packet is also referred to as transmission information corresponding to an uncompressed packet, and transmission information to be transmitted by a compressed packet is also referred to as transmission information corresponding to a compressed packet. Say.

  FIG. 1 is a diagram for explaining a data transmission method according to the first embodiment of the present invention, in which an uncompressed packet (FIG. 1A) and a compressed packet (FIG. The data structure of b)) is shown. Note that FIG. 1 shows in detail the data structure of the PPP packet, which is necessary for explaining the header compression method, as in FIG.

  More specifically, the uncompressed packet Pa includes a header section Hpa storing header information and a data section Dpa storing uncompressed information Ir transmitted by the PPP protocol. The information in the header portion Hpa includes a compressed / uncompressed identifier Ih1 indicating whether the information in the data portion Dpa is compressed, a packet identifier (ID) Ih2a for identifying the uncompressed packet itself, and other information. Header information Ih3. Here, the compression / non-compression identifier Ih1 of the non-compression packet Pa indicates non-compression. The uncompressed information Ir is transmission information (D) transmitted by the uncompressed packet.

  On the other hand, the compressed packet Pb is composed of a header section Hpb storing header information and a data section Dpb storing compression information Id transmitted by the PPP protocol. The information in the header portion Hpb includes a compressed / uncompressed identifier Ih1 indicating whether or not the information in the data portion Dpb is compressed, and an uncompressed packet (reference packet) storing the transmission information used as the reference source information. It is composed of a reference packet identifier (ID) Ih2b for identifying the ID and other header information Ih3. Here, the compression / non-compression identifier Ih1 of the compressed packet Pb indicates compression. The compression information Id includes transmission information (reference information) corresponding to an uncompressed packet (reference packet) closest to the compressed packet transmitted before the compressed packet Pb, and transmission information corresponding to the compressed packet. And difference information.

Needless to say, the other header information Ih3 includes the CRC code Icrc shown in FIG.
FIG. 2 is a block diagram illustrating a data transmission device in a data transmission system that performs data transmission by the data transmission method according to the first embodiment.

  This data transmission device 101 corresponds to the gateway server Sga in the data transmission system Cs2 shown in FIG. The data transmitting apparatus 101 receives a first transmission signal S1 including transmission information transmitted from the Internet In side to the reception side (portable wireless terminal device Tmo), and outputs the transmission information as a reception signal Src. 11, a compressed / uncompressed packet creating means 12 for packetizing transmission information from the receiving means 11 based on a transmission standard such as a PPP protocol and outputting an uncompressed packet Pa or a compressed packet Pb; And a packet transmitting means 16 for transmitting the packet created by the above method as a second transmission signal S2 to the receiving side by a method such as W-CDMA.

  The data transmitting apparatus 101 further includes an error occurrence notification receiving unit 14 that receives a restoration error notification signal Ne indicating that a restoration error has occurred and outputs an error notification reception signal Sn, which is transmitted from the receiving side. The type of the packet created by the packet creation means 12 is managed, and the type of the packet to be created next is determined based on the managed packet type information and the error notification reception signal Sn. Compression / non-compression determination means 13 for outputting a signal Jp. Here, in the determination unit 13, the management of the packet type is performed by recording the uncompressed / compressed identifier Ih1 of the created packet in association with each packet. In the determination means 13, the type of the packet created first after transmission starts and the type of the packet created immediately after receiving the error notification reception signal Sn are uncompressed, and the other packet types are compressed. Thus, the packet type is determined.

  Further, the data transmitting apparatus 101 transmits the transmission information (D) stored as the uncompressed information Ir in the uncompressed packet Pa in association with the packet identifier (ID) Ih2a for identifying the uncompressed packet. It has reference information management means 15 that manages it as side reference information Im1. The transmission-side reference information Im1 includes an identifier (ID) having the same value as the packet identifier (ID) Ih2a and reference source information (D) equal to the transmission information (D) corresponding to the uncompressed packet Pa. Have been. Each time an uncompressed packet is created by the packet creation unit 12, the management unit 15 receives the identifier (ID) recorded as the transmission-side reference information Im1 by the transmission-side management control signal Cm1 from the creation unit 12. ) And reference source information (D) are updated.

  Then, in the data transmitting apparatus 101, the compressed / uncompressed packet creating means 12 creates one of the uncompressed packet Pa and the compressed packet Pb based on the packet determination signal Jp. When creating the uncompressed packet Pa, the transmission information (D) is stored in the data portion Dpa as uncompressed information Ir, and the uncompressed packet Pa is specified in the header portion Hpa as the packet identifier Ih2a. Is stored. When the compressed packet Pb is created, difference information (ΔD) based on the transmission information (D) corresponding to the uncompressed packet as the reference packet is stored in the data portion Dpb as the compressed information Id. In the header portion Hpb, a value (ID) for specifying the uncompressed packet Pa as the reference packet is stored as the reference packet identifier Ih2b.

  Here, the difference information (ΔD) corresponding to each of the compressed packets Pb is difference information between transmission information corresponding to the compressed packet and transmission information corresponding to an uncompressed packet as a reference packet. The uncompressed packet as the reference packet is the last uncompressed packet among the uncompressed packets created before the compressed packet Pb.

FIG. 3 is a block diagram for explaining a data receiving device in a data transmission system that performs data transmission by the data transmission method according to the first embodiment.
This data receiving device 201 corresponds to the portable wireless terminal device Tmo in the data transmission system Cs2 shown in FIG.

  The data receiving apparatus 201 receives a packet transmitted from the transmitting side as the second transmission signal S2 by a method such as W-CDMA and receives a packet Rp output from the receiving means 21. And an error packet detecting means 22 for detecting an error packet in which an error has occurred during transmission and outputting a normally transmitted received packet Rp as a normal packet Pno.

  The data receiving device 201 receives the normal packet Pno from the detecting unit 22, performs a restoration process on the packet Pno, outputs restoration information Irs, and outputs an error occurrence signal Se when a restoration error occurs. Packet restoring means 23, an error occurrence notice sending means 24 receiving the error occurrence signal Se, and sending a restoration error notice signal Ne notifying the transmission side that a restoration error has occurred, and transmitting the restoration information Irs. Output means 26 for outputting information (D) as an output signal S3.

  Here, in the packet decompression means 23, as a decompression process for the uncompressed packet, a process of extracting the transmission information (D) from the data portion Dpa of the uncompressed packet Pa based on the PPP protocol or the like is performed. Further, as a decompression process for the compressed packet, the difference information Id is extracted from the data part Dpb of the compressed packet Pb based on the PPP protocol or the like, and the transmission information corresponding to the uncompressed packet as a reference packet is referred to. Processing for restoring the corresponding transmission information is performed.

  When the decompression unit 23 performs the decompression process on the uncompressed packet Pa, the data receiving device 201 transmits the packet identifier (ID) Ih2a and the transmission information of the uncompressed packet Pa targeted for the decompression process. (D) is associated with a reference information management unit 25 that manages the information as reception-side reference information Im2. The receiving-side reference information Im2 includes an identifier (ID) having the same value as the packet identifier (ID) Ih2a and reference source information (D) equal to the transmission information (D) corresponding to the uncompressed packet Pa. Have been. Each time the decompression process is performed on the uncompressed packet by the packet decompression unit 23, the management unit 25 uses the reception-side management control signal Cm2 from the decompression unit 23 to store the identifier recorded as the reception-side reference information Im2. (ID) and reference source information (D) are updated.

  In the data receiving apparatus 201, when the packet decompression means 23 performs the decompression processing on the compressed packet, the reference packet identifier (ID) in the compressed packet and the transmission information (D) corresponding to the reference packet are respectively The identifier (ID) managed by the reference information management unit 25 and the reference source information (D) corresponding to the identifier (ID) are collated. As a result of the comparison, unless the identifiers (ID) and the information (D) match each other, that is, the management unit 25 refers to the reference necessary for the decompression process of the compressed packet to be decompressed. When one of the packet identifier (ID) and the transmission information (D) is not stored, an error occurrence signal Se indicating that a restoration error has occurred is output from the packet restoration unit 23 to the error occurrence notification transmission unit 24. Is done.

Next, the operation and effect will be described.
4 and 5 are diagrams for explaining the data transmission method according to the first embodiment. FIG. 4 shows a flow of a plurality of packets from the transmission side to the reception side in a normal transmission state, and FIG. 5 shows a flow of a plurality of packets from the transmission side to the reception side when a transmission error occurs. .

  Here, the transmission information (D1) to (D4) are information corresponding to each packet, which are collected so as to be transmitted in packet units. In the first embodiment, the transmission information (D1) is not compressed. The transmission information (D2) to (D4) is transmitted by the uncompressed packet Pa (1), and is sequentially transmitted by the compressed packets Pb (2) to Pb (4) following the uncompressed packet Pa (1). .

  On the transmitting side, first, the uncompressed packet Pa (1) is generated, and the uncompressed packet Pa (1) is transmitted to the receiving side. At this time, the transmission information (D1) is stored in the data part Dpa of the uncompressed packet Pa (1) as the uncompressed information Ir, and the header Hpa has an identifier Ih indicating uncompression, a packet identifier for identifying this packet. (ID = 0) Ih2a and other header information Ih3 are stored.

  Next, the compressed packet Pb (2) is generated, and the compressed packet Pb (2) is transmitted to the receiving side. At this time, difference information (D1-D2) is stored as compression information Id in the data part Dpb of the compressed packet Pb (2), and the header part Hpb has an identifier Ih1 indicating compression and a reference packet identifier (ID). = 0) Ih2b and other header information Ih3 are stored. The difference information (D1-D2) is obtained by subtracting the transmission information (D2) corresponding to the compressed packet Pb (2) from the transmission information (D1) corresponding to the uncompressed packet Pa (1) as the reference packet. Information that can be obtained.

  Subsequently, the compressed packet Pb (3) is generated, and the compressed packet Pb (3) is transmitted to the receiving side. At this time, difference information (D1-D3) is stored as compression information Id in the data part Dpb of the compressed packet Pb (3), and the identifier Ih1b indicating compression and the reference packet identifier (ID) are stored in the header Hpb. = 0) Ih2b and other header information Ih3 are stored. The difference information (D1-D3) is obtained by subtracting the transmission information (D3) corresponding to the compressed packet Pb (3) from the transmission information (D1) corresponding to the uncompressed packet Pa (1) as the reference packet. This is the information that can be obtained.

  Further, the compressed packet Pb (4) is generated, and the compressed packet Pb (4) is transmitted to the receiving side. At this time, difference information (D1-D4) is stored as compression information Id in a data part Dpb of the compressed packet Pb (4), and an identifier Ih1 indicating compression and a reference packet identifier (ID) are stored in a header Hpb thereof. = 0) Ih2b and other header information Ih3 are stored. The difference information (D1-D4) is obtained by subtracting the transmission information (D4) corresponding to the compressed packet Pb (4) from the transmission information (D1) corresponding to the uncompressed packet Pa (1) as the reference packet. This is the information that can be obtained.

  Here, the reference packet identifier (ID = 0) Ih2b stored in the header portion Hpb of each of the compressed packets Pb (2), Pb (3), and Pb (4) is used in the decompression process for each of the compressed packets. Is an identifier indicating that the reference packet required for the above is the uncompressed packet Pa (1).

  The uncompressed packet Pa (1) and the compressed packets Pb (2) to Pb (4) successively transmitted from the transmitting side as described above are sequentially received by the receiving side in a normal data transmission state, and each packet is received. The transmission information (D1) to (D4) corresponding to is restored.

  That is, when the receiving side receives the uncompressed packet Pa (1), the transmission information (D1) is extracted from the data part Dpa. Subsequently, when the compressed packet Pb (2) is received, the difference information (D1-D2) is extracted from the data part Dpb, and the uncompressed packet Pa specified as the reference packet by the reference packet identifier (ID = 0) Ih2b. With reference to the transmission information (D1) corresponding to (1), the transmission information (D2) corresponding to the compressed packet Pb (2) is restored from the difference information (D1-D2).

  Thereafter, when the compressed packets Pb (3) and (4) are received, the difference information (D1-D3) and (D1-D4) are extracted from the data part Dpb, as in the case of the compressed packet Pb (2). Then, by referring to the transmission information (D1) corresponding to the uncompressed packet Pa (1) specified as the reference packet by the reference packet identifier (ID = 0) Ih2b, the difference information (D1-D3), (D1-D4) ), The transmission information (D3) and (D4) corresponding to the compressed packets Pb (3) and (4) are restored.

  In the first embodiment, even if a transmission error of the compressed packet Pb (2) occurs as shown in FIG. 5 in a state where the packet is being transmitted as described above, the compressed packet Pb ( When the compressed packets Pb (3) and (4) subsequent to 2) are received, the transmission information (D3) and (D4) corresponding to the compressed packets Pb (3) and (4) are normally restored. Is

  That is, in the first embodiment, the difference information (ΔD) stored in the data part Dpb of each compressed packet Pb is obtained by comparing the transmission information corresponding to each compressed packet Pb with the transmission information corresponding to the immediately preceding packet. Is not the difference information, but the difference information between the transmission information corresponding to each compressed packet Pb and the transmission information corresponding to the most recent uncompressed packet Pa transmitted before the compressed packet Pb. Therefore, in the data transmission system according to the first embodiment, even when a transmission error of a compressed packet occurs, the transmission error does not affect the restoration processing of the next normally received compressed packet. Therefore, when a compressed packet transmission error occurs, only the error packet is discarded, and the receiving side does not notify the transmitting side of the restoration error.

  If a transmission error of the uncompressed packet Pa (1) occurs during transmission of information by packet, a notification signal Ne indicating the occurrence of a restoration error is transmitted from the receiving side in the same procedure as the procedure shown in FIG. Transmitted to the side. Immediately after the transmission side receives the restoration error notification signal Ne, an uncompressed packet is transmitted from the transmission side, and a compressed packet is sequentially transmitted following the uncompressed packet. At this time, the receiving side discards the error packet and the subsequent compressed packet, that is, the error received from the occurrence of the transmission error until the uncompressed packet is normally received.

Next, the operation of the data transmission apparatus 101 in the data transmission system will be described.
In the data transmitting apparatus 101, as shown in FIG. 4 or FIG. 5, the transmission information (D1) to (D4) are sequentially transmitted to the receiving side by the corresponding uncompressed packet and compressed packet.

  More specifically, for example, transmission information (D1) to (D4) (see FIG. 4) transmitted from a server Sin on the Internet (see FIG. 33A) by a transmission method such as Ethernet (registered trademark) is When the data transmission apparatus 101 is input as a first transmission signal S1, the receiving means 11 receives the transmission information (D1) to (D4) according to the transmission method. The received transmission information (D1) to (D4) are sequentially output to the packet creation unit 12 as a reception signal Src.

  The packet creating means 12 creates a packet for transmitting each piece of transmission information to the receiving side based on a transmission protocol such as a PPP protocol. At this time, the type of the packet to be created is inquired to the compression / non-compression determination unit 13. In response to this inquiry, the determination means 13 provides the packet creation means 12 with a packet determination signal Jp indicating the packet type.

  Specifically, when the transmission information (D1) is input to the packet creation unit 12, since this case is the case where the first packet is created after the start of communication, the determination unit 13 determines that Information indicating creation of an uncompressed packet is output to the packet creation means 12 as the packet determination signal Jp.

  Then, the creation unit 12 determines creation of an uncompressed packet based on the packet determination signal Jp, and creates an uncompressed packet Pa (1) in which the transmission information (D1) is stored as uncompressed information Ir. .

  At this time, a value “uncompressed” is set in the compressed / uncompressed identifier Ih1 of the uncompressed packet Pa (1), and an identifier (ID = ID) indicating the uncompressed packet Pa (1) is set in the packet identifier Ih2a. 0) is set. When the uncompressed packet Pa (1) is created by the creation unit 12, the reference information management unit 15 uses the transmission-side management control signal Cm1 from the creation unit 12 to generate the reference packet as the transmission-side reference information Im1. The identifier (ID) and the reference source information (D) are set in the identifier (ID = 0) indicating the uncompressed packet Pa (1) and the transmission information (D1) corresponding to the uncompressed packet Pa (1), respectively. You.

  Then, the uncompressed packet Pa (1) is output to the packet transmitting unit 16 and transmitted to the receiving side by the packet transmitting unit 16 by a predetermined wireless communication method (for example, W-CDMA or the like).

  Next, when the transmission information (D2) output from the receiving means 11 is input to the packet creating means 12, even if this case creates the first packet after the start of communication, restoration from the receiving side is performed. Since the first packet is not created after receiving the error notification signal, the determination means 13 outputs information indicating creation of the compressed packet to the packet creation means 12 as the packet determination signal Jp.

  Then, the creation unit 12 inquires the management unit 15 about the transmission-side reference information Im1. In this case, the management unit 15 sets the reference packet identifier (ID) to the identifier (ID = 0) and the reference source information (D) to the transmission information (D1). The transmission information (D2) is compressed using transmission information (D1) corresponding to the uncompressed packet Pa (1) indicated by the identifier (ID = 0) as reference source information. As a result, difference information (D1-D2) between the transmission information (D1) and the transmission information (D2) is generated as the compression information Id stored in the compressed packet.

  Subsequently, the packet creating means 12 generates a compressed packet Pb (2) in which difference information (D1-D2) is stored as the compressed information Id of the transmission information (D2). The value “compression” is set in the compression / non-compression identifier Ih1 of the compressed packet Pb (2), and the reference packet identifier Ih2b is set as the reference packet necessary for the restoration processing of the compressed packet Pb (2). An identifier (ID = 0) indicating the compressed packet Pa (1) is set. When the creating unit 12 creates the compressed packet Pb (2), the reference information management unit 15 updates the reference packet identifier (ID) and the reference source information (D) as the transmission-side reference identification Im1. Not done.

  Then, the compressed packet Pb (2) is output to the packet transmitting means 16, and the packet transmitting means 16 transmits the compressed packet Pb (2) to the receiving side (portable wireless terminal device) by a predetermined wireless communication method (for example, W-CDMA or the like). .

  Thereafter, when the transmission information (D3) and (D4) output from the reception unit 11 are input to the packet creation unit 12, the difference is calculated in the same manner as when the transmission information (D2) is input. A compressed packet Pb (3) storing information (D1-D3) and a compressed packet Pb (4) storing difference information (D1-D4) are generated.

FIG. 6 shows a flow of processing in the packet creating means 12, which will be briefly described below.
When the transmission information (D) received by the receiving means 11 is input (step Sa1), the packet creating means 12 inquires of the determining means 13 which of an uncompressed packet and a compressed packet should be created. (Step Sa2), the type of the packet to be created is determined based on the packet determination signal Jp from the determination means 13 (Step Sa3).

  As a result, when an uncompressed packet is to be created, an identifier (ID) is assigned to the uncompressed packet as the packet identifier Ih2a, and an uncompressed packet Pa including the packet identifier Ih2a is created (step Sa7). Thereafter, in response to an instruction (transmission-side management control signal Cm1) from the packet creation unit 12, the transmission-side reference information (that is, the identifier (ID) and the reference source information (D)) Im1 managed by the reference information management unit 15 is Im1. Is updated (step Sa8).

  On the other hand, when a compressed packet is to be created, the packet creation unit 12 sends the reference information management unit 15 an identifier (ID) and reference source information (D) as transmission-side reference information Im1. It is inquired whether it is managed (step Sa4). Next, the data part Dpb of the compressed packet Pb is created based on the transmission-side reference information (identifier (ID) and reference source information (D)) Im1 from the management unit 15 (step Sa5). Further, the identifier (ID) is stored as the reference packet identifier Ih2b in the header section Hpb together with the other header information Ih3, and the compressed packet Pb is created (step Sa6).

Then, the created uncompressed packet Pa or compressed packet Pb is sent to the transmitting means 16 (step Sa9). After that, the process of the creation unit 12 returns to the process of step Sa2.
Such processing of the creation unit 12 is performed until the transmission of the last transmission information is completed.

Next, the operation of the data receiving device 201 in the data transmission system will be described.
In the data receiving apparatus 201, as shown in FIG. 4 or 5, an uncompressed packet and a compressed packet transmitted from the transmitting side are sequentially received, and a decompression process is performed on each packet.

  More specifically, for example, the packet receiving unit 21 receives the uncompressed packet Pa (1) and the compressed packets Pb (2) to Pb (4) transmitted from the transmitting side in order, and detects the received packet Rp as an error packet. Output to the means 22. Then, the error packet detection unit 22 performs an error detection process on each received packet Rp. As a result, when it is confirmed that the received packet Rp has been transmitted correctly, the received packet Rp is output to the packet restoring means 23 as a normal packet Pno. On the other hand, if it is not confirmed that the received packet Rp has been transmitted correctly, the received packet Rp is discarded. Here, a CRC (Cyclic Redundancy Check), which is widely used for the error detection method, is used, but the error detection method is not limited to this.

  When the uncompressed packet Pa (1) is input as the normal packet Pno, the decompression means 23 determines the normal packet Pno by using the compression / non-compression identifier Ih1 included in the header of the normal packet Pno. It is determined which one is. In this case, since the normal packet Pno received by the decompression unit 23 is the uncompressed packet Pa (1), the decompression unit 23 extracts the transmission information (D1) from the data part Dpa of the uncompressed packet Pa (1). A restoration process is performed.

  Next, in the management means 25, the receiving side reference information (identifier (ID) and reference source information (D)) Im2 managed by the management means 25 according to the instruction (reception side management control information) Cm2 from the restoration means 23. Is updated. Thereby, the identifier (ID) and the reference source information (D) recorded in the management unit 25 are changed to the identifier (ID = 0) and the transmission information (D1), respectively. Thereafter, in the restoring means 23, the transmission information (D1), which is the restoration information Irs, is sent to the output means 26, and the transmission information (D1) is output by the output means 26.

  Next, when the compressed packet Pb (2) is input as the normal packet Pno, the decompression unit 23 converts the normal packet Pno into the compressed packet and the non-compressed packet by the compression / non-compression identifier Ih1 included in the header of the normal packet Pno. It is determined which of the packets is. In this case, since the normal packet Pno is the compressed packet Pb (2), the decompression means 23 instructs the reference information management means 25 to identify (ID = 0) the reference packet identifier Ih2b included in the compressed packet, It is inquired whether reference source information (D1) corresponding to the identifier (ID = 1) is stored in the management means 25.

  In this case, since the identifier (ID = 0) and the reference source information (D1) corresponding to the identifier (ID = 0) are stored in the management unit 25, the restoration unit 23 stores the reference source stored in the management unit 25. Using the information (D1) and the difference information (D1-D2) stored in the compressed packet Pb (2), the transmission information (D2) corresponding to the compressed packet Pb (2) is restored. Thereafter, the transmission information (D2) is sent from the restoration means 23 to the output means 26 as restoration information Irs of the difference information (D1-D2), and the transmission information (D2) is output by the output means 26.

  Thereafter, when the compressed packets Pb (3) and Pb (4) are input to the packet restoring means 23 as the normal packet Pno, the difference is calculated in the same manner as when the compressed packet Pb (2) is input. Transmission information (D3) and (4) are generated as restoration information Irs for the information (D1-D3) and the difference information (D1-D4). Then, the transmission information (D3) and (4) are sent to the output unit 26 and output by the output unit 26.

Also, either one of the identifier (ID = 0) stored in the normal packet Pno input as a compressed packet to the decompression unit 23 and the corresponding reference source information (D1) is stored in the management unit 25. If the packet is not stored, the decompression means 23 discards the normal packet Pno input as a compressed packet, and outputs an error occurrence signal Se indicating that a decompression error has occurred from the decompression means 23 to the error occurrence notifying means 24. Is output.
When the error occurrence signal Se is input to the notifying unit 24, the notifying unit 24 notifies the transmitting side of the occurrence of the restoration error by the restoration error notification signal Ne.

FIG. 7 shows a flow of processing in the packet restoring means 23, which will be briefly described below.
When the normal packet Pno is input from the error packet detecting unit 22 (step Sb1), the packet restoring unit 23 determines whether the normal packet Pno is an uncompressed packet or a compressed packet (step Sb2).

  When the normal packet Pno is the uncompressed packet Pa, the transmission information (D) is extracted from the data portion Dpa of the uncompressed packet Pa by the decompression process for the uncompressed packet Pa (step Sb6). Then, the identifier (ID) and the reference source information (D) as the receiving side reference information Im2 in the reference information managing unit 25 are updated by the instruction (receiving side management control signal Cm2) of the packet restoring unit 23 (step Sb7). . The transmission information (D) extracted from the data part Dpa of the uncompressed packet Pa is sent to the output means 26 (step Sb10).

  On the other hand, when the normal packet Pno is the compressed packet Pb, the packet restoring unit 23 inquires the reference information managing unit 25 whether the identifier (ID) and the reference source information (D) are managed as the receiving side reference information Im2 ( Step Sb3).

  Next, it is determined whether or not an uncompressed packet as a reference packet necessary for restoring the difference information of the compressed packet has been received (step Sb4). This determination is based on the identifier (ID) stored as the reference packet identifier Ih2b in the compressed packet Pb, the transmission information (D) corresponding to the compressed packet Pb, and the identifier (ID) stored in the reference information management means 25. And the corresponding reference source information (D).

  Then, when the uncompressed packet Pa as the reference packet corresponding to the compressed packet Pb is received, the compressed packet Pb is converted into the compressed packet Pb using the reference source information (D) stored in the reference information management means 25. The corresponding transmission information (D) is restored (step Sb5). Further, the restored transmission information (D) is sent to the output means 26 (step Sb10). After that, the process of the restoration unit 23 returns to the process of step Sb2.

  If the result of the determination in step Sb4 is that an uncompressed packet as a reference packet corresponding to the received compressed packet has not been received, the packet restoring means 23 outputs the compressed packet which is the received normal packet Pno. The packet Pb is discarded (step Sb8). Then, the error occurrence signal Se is output to the error occurrence notifying means 24 (step Sb9). After that, the process of the restoration unit 23 returns to the process of step Sb2.

Such processing of the restoration means 23 is performed until the last packet is received.
As described above, in the data transmission method according to the first embodiment, the transmission information is transmitted in units of packets by using the uncompressed packet Pa that stores the transmission information without compression and the compressed packet Pb that stores the transmission information by compressing it. At the time of transmission, difference information (ΔD) between the transmission information corresponding to the compressed packet Pb and the transmission information corresponding to the most recent uncompressed packet Pa transmitted before the compressed packet is used as the compression information Id in the compressed packet. Since the compressed packet Pb is stored, even if a transmission error of the compressed packet Pb occurs while the uncompressed packet Pa is normally transmitted, the difference information (ΔD) of the normally transmitted compressed packet Pb after the error packet is transmitted. ) Can be restored using the transmission information of the uncompressed packet Pa. Therefore, the number of compressed packets to be discarded due to the occurrence of a transmission error of the compressed packet is greatly reduced. As a result, it is possible to improve the quality of data transmitted in the wireless section. In other words, the effective speed of data transmission can be improved, and the time and cost required for transmitting an unrecoverable packet can be significantly reduced.

  In the first embodiment, the header portion Hpb of the compressed packet Pb has one reference packet identifier (ID) Ih2b, but the header portion Hpb includes a plurality of the reference packet identifiers (ID). It is also possible. However, in this case, it is necessary to continuously transmit a plurality of uncompressed packets.

(Modification 1 of Embodiment 1)
FIG. 8A shows the data structure of an uncompressed packet Paa used when the compressed packet includes two reference packet identifiers (IDs). In this case, the uncompressed packet Paa is transmitted twice consecutively.

  The uncompressed packet Paa includes a header section Hpaa storing header information and a data section Dpaa storing transmission information (D) as uncompressed information Ir transmitted by the PPP protocol. Here, the information in the header section Hpaa includes the compressed / uncompressed identifier Ih1, the packet identifier (ID) Ih2a, and other header information Ih3. The compression / non-compression identifier Ih1 of the uncompressed packet Paa indicates non-compression.

FIG. 8B shows a data structure of a compressed packet Pbb including two reference packet identifiers (identification IDs).
The compressed packet Pbb includes a header section Hpbb storing header information and a data section Dpbb storing first and second compressed information Id1 and Id2 transmitted by the PPP protocol. Here, the information in the header section Hpbb includes the compressed / uncompressed identifier Ih1, first and second reference packet identifiers (ID1, ID2) Ih2b1, Ih2b2 for identifying an uncompressed packet as a reference packet, and It consists of other header information Ih3. The compression / non-compression identifier Ih1 of the compressed packet Pbb indicates compression. Here, the second compressed information Id2 is difference information (Δ2D) between the transmission information corresponding to the latest uncompressed packet Paa transmitted before the compressed packet Pbb and the transmission information corresponding to the compressed packet Pbb. It is. The first compressed information Id1 is difference information between transmission information corresponding to the uncompressed packet Paa transmitted immediately before the latest uncompressed packet Paa and transmission information corresponding to the compressed packet Pbb. (Δ1D).

In this case, the transmission information (D1) to (D4) shown in FIG. 4 in the first embodiment is transmitted as follows.
FIG. 9 shows a flow of a plurality of packets from the transmission side to the reception side in a normal transmission state.

  In the first modification of the first embodiment, the transmission information (D1) and (D2) are sequentially transmitted by the uncompressed packets Paa (1) and Paa (2) without being compressed, and the transmission information (D3) and (D4) are transmitted. ) Are compressed and transmitted sequentially by compressed packets Pb (3) and Pb (4) following the uncompressed packet Paa (2).

  On the transmitting side, first, the uncompressed packet Paa (1) is generated, and the uncompressed packet Paa (1) is transmitted to the receiving side. At this time, the transmission information (D1) is stored as uncompressed information Ir in the data portion Dpaa of the uncompressed packet Paa (1), and the header portion Hpaa has an identifier Ih1 indicating uncompressed and a packet for identifying this packet. The identifier (ID = 0) Ih2a and other header information Ih3 are stored.

  Subsequently, the uncompressed packet Paa (2) is generated, and the uncompressed packet Paa (2) is transmitted to the receiving side. At this time, the transmission information (D2) is stored as uncompressed information Ir in the data portion Dpaa of the uncompressed packet Paa (2), and the header portion Hpaa has an identifier Ih1 indicating uncompressed and a packet identifier for identifying this packet. (ID = 1) Ih2a and other header information Ih3 are stored.

  Thereafter, the compressed packet Pbb (3) is generated, and the compressed packet Pbb (3) is transmitted to the receiving side. At this time, the data part Dpbb of the compressed packet Pbb (3) stores the first and second compression information Id1 and Id2 for the transmission information (D3), and the header part Hpbb stores identifiers Ih1 and Ih1 indicating the compression. The first reference packet identifier (ID = 0) Ih2b1, the second reference packet identifier (ID = 1) Ih2b2, and other header information Ih3 are stored.

  Here, the first compressed information Id1 corresponds to the compressed packet Pbb (3) from the transmission information (D1) corresponding to the packet Paa (1) using the uncompressed packet Pa (1) as a reference packet. It is difference information (D1-D3) obtained by subtracting the transmission information (D3). The compressed information Id2 is obtained by using the uncompressed packet Paa (2) as a reference packet and converting the transmission information (D2) corresponding to the packet Paa (2) to the transmission information (D3) corresponding to the compressed packet Pbb (3). ) Is difference information (D2−D3) obtained by subtracting ()).

  Further, the compressed packet Pbb (4) is generated, and the compressed packet Pbb (4) is transmitted to the receiving side. At this time, the data part Dpbb of the compressed packet Pbb (4) stores the first and second compressed information Id1 and Id2 for the transmission information (D4), and the header part Hpbb has identifiers Ih1 and Ih1 indicating the compression. The first reference packet identifier (ID = 0) Ih2b1, the second reference packet identifier (ID = 1) Ih2b2, and other header information Ih3 are stored.

  Here, the first compressed information Id1 corresponds to the compressed packet Pb (4) from the transmission information (D1) corresponding to the packet Paa (1) using the uncompressed packet Paa (1) as a reference source packet. (D1-D4) obtained by subtracting the transmission information (D4) to be transmitted. The second compressed information Id2 corresponds to the compressed packet Pb (4) from the transmission information (D2) corresponding to the packet Paa (2) using the uncompressed packet Paa (2) as a reference source packet. It is difference information (D2-D4) obtained by subtracting the transmission information (D4).

  Note that the first packet identifier (ID = 0) Ih2b1 stored in the header portion Hpbb of each of the compressed packets Pbb (3) and Pbb (4) is such that the reference packet is the uncompressed packet Paa (1). It indicates that there is. The second packet identifier (ID = 1) Ih2b2 stored in the header portion Hpbb of each of the compressed packets Pbb (3) and Pbb (4) is such that the reference packet is the uncompressed packet Paa (2). It indicates that there is.

  As described above, the uncompressed packets Paa (1) and Paa (2) sequentially transmitted from the transmitting side and the compressed packets Pbb (3) and Pbb (4) following them are sequentially transmitted to the receiving side in a normal data transmission state. The received transmission information (D1) to (D4) corresponding to each packet is restored.

  That is, when the receiving side receives the uncompressed packets Paa (1) and Paa (2), the transmission information (D1) and (D2) are extracted from the data part Dpaa. Subsequently, when the compressed packet Pbb (3) is received, the second difference information (D2-D3) is extracted from the data portion Dpbb, and the second difference information (ID = 1) Ih2b2 specified by the second reference packet identifier (ID = 1) The transmission information (D3) corresponding to the compressed packet Pbb (3) is restored from the difference information (D2-D3) with reference to the transmission information (D2) corresponding to the second uncompressed packet Pa (2).

  Thereafter, when the compressed packet Pbb (4) is received, as in the case of the compressed packet Pbb (3), the difference information (D2-D4) is extracted from the data part Dpbb, and the second reference packet identifier (ID) = 1) With reference to the transmission information (D2) corresponding to the uncompressed packet Paa (2) specified by Ih2b2, the transmission information (D4) corresponding to the compressed packet Pbb (4) is obtained from the difference information (D2-D4). ) Is restored.

  Here, since the uncompressed packets Paa (1) and Paa (2), which are reference packets for the compressed packets Pbb (3) and Pbb (4), are both normally received, the uncompressed packets close to the compressed packets Although Paa (2) is used as a reference packet, when a transmission error of uncompressed packet Paa (2) close to each compressed packet occurs, the previous uncompressed packet Paa (1) is used as a reference packet and A restoration process is performed.

  In this manner, two uncompressed packets Paa are continuously transmitted, and as subsequent compressed packets Pbb, difference information (Δ1D), (Δ2D) based on the transmission information of both uncompressed packets, and both uncompressed packets Pab By transmitting a packet storing the first and second reference packet identifiers (ID1, ID2) Ih2b1 and Ih2b2 indicating that the packet is a reference packet, a plurality of identifiers (ID1) and (ID2) in the compressed packet are transmitted. If at least one of the identifiers and the reference source information corresponding to this identifier are stored in the reference information management unit 25, the compressed packet can be restored. In other words, the number of compressed packets discarded due to transmission errors of uncompressed packets can be reduced.

  Further, in the first embodiment, the compression / non-compression determination unit 13 in the data transmission apparatus 101 creates an uncompressed packet immediately after starting communication and immediately after receiving the decoding error notification signal Ne from the error occurrence notification receiving unit 14. Thereafter, until the decoding error notification signal Ne is received, the packet generating unit 12 is controlled so that a compressed packet is generated. The present invention is not limited to the configuration, and the configuration may be such that the packet creation unit 12 is controlled so that uncompressed packets are transmitted periodically.

  In other words, in this case, in a state where the restoration error is not notified from the receiving side, the transmitting side performs compression / non-compression so that one uncompressed packet is transmitted every time a predetermined number of compressed packets are transmitted. The compression determination unit 13 gives an instruction to the packet creation unit 12. For example, when the number of compressed packets predetermined as the transmission interval of uncompressed packets is 3, transmission of one uncompressed packet and subsequent transmission of three compressed packets are repeated.

The effect of such a configuration will be briefly described.
Image information and audio information, and header information such as TCP / IP packets and UDP / IP packets necessary for transmitting them are stored in PPP packets transmitted by the PPP protocol (that is, FIGS. 1A and 1B). ) Are stored as transmission information in the data portions Dpa and Dpb of the packet).

  However, usually, the difference information between the two adjacent packets of the image information, the audio information, and the header information is often very small or 0, but the difference information between the distant packets tends to be large. There is. For this reason, by transmitting uncompressed packets periodically, the average value of the difference information is reduced while improving the quality of data transmitted wirelessly, that is, the information compression efficiency in the data part is also improved. be able to.

  Further, the compression / non-compression determination means 13 in the data transmitting apparatus 101 of the first embodiment obtains the average size m of the difference information stored in the data part of the compressed packet, and this size exceeds a certain value x. In such a case, the configuration may be such that the packet creation means 12 is controlled to transmit an uncompressed packet.

  Here, the average size m of the difference information is obtained as an average value of the difference information of a plurality of compressed packets transmitted from the last transmission of the uncompressed packet to the current time. Specifically, four compressed packets are transmitted since the last transmission of the uncompressed packet, and the size of the difference information of these four compressed packets is “2”, “4”, “4”, respectively. , “6”, the average size m of the difference information at the present time is 4 = (2 + 4 + 4 + 6) / 4.

  Also in this case, it is possible to reduce the average value of the difference information, that is, improve the compression efficiency of the information in the data portion while improving the quality of the data transmitted wirelessly.

  The measurement of the average size m of the difference information may be performed by the data receiving device 201.

  Specifically, on the receiving side, the packet restoring means 23 measures the average size m of the difference information, and outputs an oversize signal to the error occurrence notifying means 24 when the average size m exceeds a certain value x. Configuration. Further, the error occurrence notification transmitting means 24 not only transmits the restoration error notification signal Ne to the transmission side when receiving the error generation signal Se, but also transmits the uncompressed packet to the transmission side when receiving the size excess signal. It is configured to transmit a packet request signal requesting transmission.

  On the other hand, on the transmitting side, the error occurrence notifying means 14 of the data transmitting terminal 101 compresses the error notification receiving signal Sn not only when receiving the restoration error notification signal Ne but also when receiving the packet request signal. The output is provided to the non-compression determining means 13.

  Further, the transmission of the uncompressed packet is not performed when the average size x of the difference information exceeds the fixed value x as described above, but is transmitted or received when the compressed packet whose difference information size exceeds the fixed value m. It may be performed at a time.

  For example, when the size of the compressed information included in the compressed packet to be transmitted exceeds a certain value, the data transmitting apparatus 101 may transmit an uncompressed packet following the compressed packet to be transmitted. Good.

  The data receiving apparatus 201 requests the transmitting side to transmit an uncompressed packet when the size of the compressed information included in the compressed packet to be subjected to the decompression processing received from the transmitting side exceeds a certain value. The transmitting apparatus 101 may transmit the uncompressed packet to the receiving side immediately after receiving the transmission request of the uncompressed packet from the receiving side.

(Modification 2 of Embodiment 1)
Further, in the first embodiment, as shown in FIG. 1, the data portion Dpb of the compressed packet Pb contains difference information (total of the transmission information corresponding to the compressed packet and the entire transmission information corresponding to the uncompressed packet). Although ΔD) is stored, information obtained by compressing only a part of the transmission information corresponding to the compressed packet may be stored in the data portion Dpb of the compressed packet Pb.

  In other words, the transmission information is divided into compression target information to be compressed and non-compression target information not to be compressed, and the data portion of the compressed packet contains the compression target information in the transmission information corresponding to the uncompressed packet. And the difference information from the compression target information in the transmission information corresponding to the compressed packet, and the non-compression target information in the transmission information corresponding to the compressed packet.

FIG. 10A shows the data structure of an uncompressed packet Pc used when transmission information is composed of information to be compressed and information not to be compressed.
This uncompressed packet Pc is composed of a header section Hpc storing header information and a data section Dpc storing uncompressed information Ir transmitted by the PPP protocol. The information in the header portion Hpc is, like the uncompressed packet Pa shown in FIG. 1A, used to identify a compressed / uncompressed identifier Ih1 indicating whether or not the information in the data portion is compressed, and to identify the uncompressed packet. , A packet identifier (ID) Ih2a and other header information Ih3. Here, the data part Dpc stores uncompressed compression target information and non-compression target information Inc, and the uncompressed compression target information includes first, second, and third information. It is composed of item-specific non-compression information Ira, Irb, Irc corresponding to the item to be compressed. More specifically, the item-specific uncompressed information Ira, Irb, and Irc are information (Da) and (Da) corresponding to the first, second, and third compression target items, respectively, in the transmission information corresponding to the uncompressed packet. Db) and (Dc).

FIG. 10B shows the data structure of the compressed packet Pd used when the transmission information is composed of the information to be compressed and the information not to be compressed.
The compressed packet Pd is composed of a header section HPd storing header information and a data section Dpb storing partially compressed information transmitted by the PPP protocol. The information in the header portion Hpb includes a compressed / uncompressed identifier Ih1 indicating whether or not the information in the data portion is compressed, and a reference packet for identifying the reference packet, similarly to the compressed packet Pb shown in FIG. It consists of an identifier (ID) Ih2b and other header information Ih3.

  Here, the data section Dpb stores compressed information to be compressed and non-compression target information Inc. The compressed information to be compressed is stored in the first, second, and third compressed data. It is composed of item-specific compression information Ida, Idb, Idc corresponding to the target item. Specifically, the item-specific compression information Ida includes information (Da) corresponding to the first compression target item in the transmission information corresponding to the uncompressed packet, and first information (Da) in the transmission information corresponding to the compression packet. This is difference information (ΔDa) from information (Da) corresponding to the item to be compressed. The item-specific compression information Idb corresponds to the information (Db) corresponding to the second item to be compressed in the transmission information corresponding to the non-compressed packet, and corresponds to the second item to be compressed in the transmission information corresponding to the compressed packet. This is difference information (ΔDb) from the information (Db) to be executed. The item-specific compression information Idc corresponds to the information (Dc) corresponding to the third item to be compressed in the transmission information corresponding to the uncompressed packet, and corresponds to the third item to be compressed in the transmission information corresponding to the compressed packet. This is difference information (ΔDc) from the information (Dc) to be performed.

  In this case, the reference information management unit 15 in the data transmitting apparatus 101 transmits the reference packet identifier (ID), each item to be compressed, and information (corresponding to each compression target item in the reference source information (transmission information in the reference packet)). (Reference information for each item) is stored in a table.

  The reference information management unit 25 in the data receiving device 201 also tabulates the reference packet identifier (ID), each of the compression target items, and the item-by-item reference source information, like the reference information management unit 15. It is configured to store.

  In such a configuration, the compression of the transmission information is performed for each individual compression target item. Therefore, while maintaining the effect of reducing a certain amount of information by information compression, the management unit 15 and the management unit It is possible to reduce the storage capacity of a memory such as a RAM mounted on the storage device 25.

(Modification 3 of Embodiment 1)
Further, in the first embodiment and the first modification or the second modification, the data portion of the compressed packet includes, as information obtained by compressing all or a part of the transmission information corresponding to the compressed packet, as shown in FIG. ) Or as shown in FIG. 10B, the difference information between the whole or a part of the transmission information corresponding to the uncompressed packet and the whole or a part of the transmission information corresponding to the compressed packet is stored. Instead of the difference information or together with the difference information, the difference specifying additional information (K) for calculating the difference information may be stored in a header portion or a data portion of the compressed packet.

For example, in the compressed packet Pb shown in FIG. 1B, instead of this difference information, difference specifying additional information (K) for calculating the difference information can be stored.
In the compressed packet Pd shown in FIG. 10B, instead of the difference information which is at least a part of the item-specific compressed information among the plurality of item-specific compressed information, a difference specifying addition for calculating the difference information is provided. Information (K) can be stored.

FIG. 11 is a diagram for explaining the data structure of the packet used when the difference specifying additional information (K) is stored in the compressed packet.
FIGS. 11A and 11B show the data structures of the uncompressed packet Pe and the compressed packet Pf used in this case, respectively.

  The uncompressed packet Pe is composed of a header portion Hpe storing header information and a data portion Dpe storing transmission information transmitted by the PPP protocol. The uncompressed packet Pc shown in FIG. It has the same configuration as.

  The compressed packet Pf includes a header section Hpf storing header information and a data section Dpf storing partially compressed information transmitted by the PPP protocol. In the header section Hpf, in addition to the compressed / uncompressed identifier Ih1, the reference packet identifier (ID) Ih2b, and other header information Ih3 in the compressed packet Pd shown in FIG. ) Ih4 is stored. Further, the data part Dpf contains three items of compression information Ida, Idb, Idc and non-compression target information Inc, like the compressed packet Pd shown in FIG. 10B.

  Here, the difference specifying additional information (K) is a sequence number indicating the order of the compressed packet that is located from the uncompressed packet referred to in the decompression process. The difference information (ΔDa) and (ΔDb) as the item-specific compression information Ida and Idb are equal to the difference specifying additional information (K). Therefore, the data size of the difference information (ΔDa) and (ΔDb) is 0 byte.

Hereinafter, the case where the difference specifying additional information (K) is stored in a compressed packet will be described using data transmission using an RTP (Real Time Protocol) protocol as an example.
Specifically, image information or audio information is converted into RTP format data according to the RTP protocol specified in RFC 1889/1890, and the RTP format data is further converted into UDP / IP format data according to the UDP protocol and the IP protocol. A case will be described in which data in the RTP / UDP / IP format is transmitted from the data transmission terminal 101 to the data reception terminal 201. The data in the RTP / UDP / IP format is equivalent to the IP packet Pipb shown in FIG.

  Normally, the sequence number Isn (see FIG. 29A) included in the header Hrtp of the RTP packet Prtp increases its value by one each time one RTP packet is created. Further, the value of the packet identification ID (IPv4 (Internet Protocol version 4) ID) (not shown) included in the header Hipb of the IP packet Pipb increases by one each time one IP packet is created. Things. When these values are stored as difference information in the compressed packet, if it is known how many positions the compressed packet is counted from the uncompressed packet as the reference packet corresponding to the compressed packet, 0 Can be

  In other words, when the sequence number Isn in the header portion Hrtp of the RTP packet Prtp is stored in the compressed packet as simple difference information, the information amount of the sequence number Isn always needs to be 1 byte or more. By using this, the size of the difference information corresponding to the sequence number Isn is usually 0 bytes, and the compression efficiency can be increased.

  For example, when the size of the difference specifying additional information (K) is 1 byte, the size of the difference information of the sequence number Isn in the header portion Hrtp of the RTP packet is usually 0 byte, and the sum of the difference specifying additional information and the difference information is usually It becomes 1 byte. In this case, even if the difference specifying additional information (K) is used, the information amount of the RTP packet does not change.

  However, if the transmission information includes a plurality of pieces of compression target information that can be restored using the same calculation method as the above calculation method (that is, the sum of the difference specifying additional information and the difference information), for example, as described above, When there are two types of information such as the sequence number in the header part and the IPv4 ID in the header part of the IP packet, a substantial effect can be obtained by using the difference specifying additional information, and the compression efficiency can be improved. Can be.

Further, using the difference specifying additional information as a variable, difference information corresponding to the target compressed packet is obtained from the transmission information corresponding to the reference packet (uncompressed packet) used for the decompression process of the target compressed packet to be processed. A calculation formula may be used.
Here, as the above calculation formula, for example, a formula that defines four arithmetic operations (addition, subtraction, integration, division) and a function operation such as sin and cos can be considered.

  Further, the calculation formula using the difference specifying additional information as a variable may be determined in advance on the transmission side and the reception side, or may be dynamically changed during data transmission according to a certain rule. This makes it possible to further improve the compression efficiency of the transmission information stored in the data portion of the PPP packet, and to further improve the quality and the effective transmission speed of the data wirelessly transmitted.

(Embodiment 2)
FIG. 12 is a block diagram for explaining a data transmission method according to the second embodiment of the present invention, and shows a data transmission device in a data transmission system using this data transmission method. The second embodiment corresponds to claims 1, 2, 10 to 12, 18 to 21, 32, 33, 36, and 37.

  The data transmitting apparatus 102 has the same configuration as the data transmitting apparatus 101 according to the first embodiment, and further includes a non-compressed packet for monitoring the number of transmissions of the uncompressed packet output from the compressed / uncompressed packet creating unit 12 to the receiving side. It comprises a packet transmission number monitoring means 31. The transmission count monitor 31 receives the packet from the compressed / uncompressed packet generator 12 and outputs the same uncompressed packet Pa to the packet transmitter 16 continuously for a fixed number of times (here, twice). The configuration is such that a compressed packet Pb following the compressed packet Pa is output to the packet transmitting means 16. Other configurations of the data transmitting apparatus 102 are the same as those of the data transmitting apparatus 101 of the first embodiment.

  The data receiving device in the data transmission system according to the second embodiment has the same configuration as the data receiving device 201 in the data transmission system according to the first embodiment.

Next, the operation and effect will be described.
In the data transmitting apparatus 102 according to the second embodiment having such a configuration, the number of transmissions of the uncompressed packet is monitored by the transmission number monitoring unit 31, and the uncompressed packet is output from the packet generation unit 12 to the transmission number monitoring unit 31 Then, the same uncompressed packet Pa (1) is output from the transmission count monitoring unit 31 to the packet transmitting unit 16 continuously a predetermined number of times (here, twice), as shown in FIG. 13, for example. Thereafter, the compressed packets Pb (2), Pb (3), and Pb (4) following the uncompressed packet are sequentially output to the packet transmitting means 16. Then, the packet transmitting unit 16 sequentially transmits the packets supplied from the transmission count monitoring unit 31 by a predetermined wireless transmission method such as W-CDMA.

Other operations in data transmitting apparatus 102 are performed in the same manner as data transmitting apparatus 101 of the first embodiment.
In the data receiving apparatus, when two consecutive uncompressed packets Pa (1) are normally received as shown in FIG. 13, the reference information management unit 25 sequentially transmits the identifier (ID) and the reference source information ( D) is updated. As a result, when the compressed packets Pb (2), Pb (3), and Pb (4) are received following the uncompressed packet, the identifier (ID = 0) held in the reference information management unit 25 and the reference source information (D1) will be referred to.

  Further, even if one of the two consecutive uncompressed packets Pa (1) is not transmitted to the receiving side due to a transmission error, the normally transmitted uncompressed packet is transmitted via the error packet detecting unit 22 to the packet restoring unit. 23. Therefore, in the reference information management unit 25, the identifier (ID) and the reference source information (D), which are the receiving side reference information Im2, are updated to those for the uncompressed packet Pa (1).

As described above, in the second embodiment, in addition to the configuration of the first embodiment, the uncompressed packet Pa is transmitted twice consecutively, and then the compressed packet Pb following the uncompressed packet Pa is transmitted. Even if a transmission error occurs in one of a plurality of uncompressed transmitted packets, the receiving side can correctly restore the differential information of the subsequent compressed packet. As a result, the number of received packets discarded due to a restoration error on the receiving side is reduced, and the quality of wirelessly transmitted data can be improved.
In the second embodiment, the uncompressed packet is transmitted twice consecutively. However, the number of continuous transmissions of the uncompressed packet may be three or more.

  In the second embodiment, the transmission count monitoring unit 31 manages the transmission count of the uncompressed packet so that the uncompressed packet itself is transmitted a plurality of times. After the uncompressed packet is transmitted, an auxiliary packet different from the uncompressed packet storing the packet identifier (ID) and the transmission information (D) corresponding to the uncompressed packet is transmitted one or more predetermined times continuously. The configuration may be such that the number of packet transmissions is managed in such a manner.

  In this case, after creating the uncompressed packet, the packet creating means 12 creates an auxiliary packet storing the packet identifier (ID) and the transmission information (D) corresponding to the uncompressed packet. Thereafter, a plurality of compressed packets corresponding to the uncompressed packets (that is, compressed packets storing difference information created using the transmission information of the uncompressed packets) are created. When the uncompressed packet, the auxiliary packet, and each compressed packet are supplied to the transmission count monitoring unit 31 in the order of their creation, the transmission count monitoring unit 31 transmits the uncompressed packet, and then the auxiliary packet is transmitted. It is transmitted a predetermined number of times continuously. Thereafter, each compressed packet is transmitted sequentially.

  In such a configuration, the reference packet identifier and the reference source information are transmitted at least twice by one uncompressed packet and a predetermined number of auxiliary packets before the compressed packet corresponding to the uncompressed packet is transmitted. Therefore, even if a transmission error occurs in one of the uncompressed packet and the auxiliary packet, the receiving side can correctly restore the differential information of the succeeding compressed packet.

As a result, the number of received packets discarded due to a restoration error on the receiving side is reduced, and the quality of wirelessly transmitted data can be improved.
Further, in the second embodiment, the uncompressed packet or the auxiliary packet is continuously transmitted a predetermined number of times. However, the number of consecutive transmissions of the uncompressed packet or the auxiliary packet is It may be changed according to the notification frequency of the restoration error to be performed.

  For example, when changing the number of continuous transmissions of uncompressed packets, the compression / non-compression transmission determination unit 13 counts the number of times the error notification reception signal Sn from the error occurrence notification reception unit 14 is input per unit time, The count value is compared with a fixed reference value Y, and a transmission count control signal is output to the transmission count monitoring means 31 according to the comparison result. The transmission count monitoring means 31 increases or decreases the transmission count of the uncompressed packet or the auxiliary packet based on the transmission count control signal. Specifically, when the count value exceeds a certain reference value Y, the number of transmissions of the uncompressed packet or auxiliary packet increases, and when the count value becomes equal to or less than the reference value Y, the uncompressed packet Alternatively, the number of transmissions of the auxiliary packet decreases.

  In such a configuration, when the quality of the transmission data is relatively stable, the transmission efficiency can be increased by reducing the number of transmissions of the uncompressed packet or the auxiliary packet, and when the quality of the transmission data is unstable. Can reduce the number of packets discarded on the receiving side due to a decompression error due to an increase in the number of transmissions of uncompressed packets or auxiliary packets.

(Embodiment 3)
14 and 15 are diagrams illustrating a data transmission method according to the third embodiment of the present invention. The third embodiment corresponds to claims 1, 2, 13 to 15, 18 to 21, 32, 33, 36, and 37.
FIG. 14 is a block diagram illustrating a data transmission device in a data transmission system that performs data transmission by this data transmission method.

  The data transmitting apparatus 103 receives the uncompressed packet Pa and the compressed packet Pb output from the compressed / uncompressed packet creating means 12 in addition to the configuration of the data transmitting apparatus 101 of the first embodiment, and An ECC-added uncompressed packet Pac provided with an error correction code by the means 32, and a compressed packet passed through the means 32. Pb is supplied to the packet transmitting means 16. Other configurations of the data transmitting apparatus 103 according to the third embodiment are the same as those of the data transmitting apparatus 101 according to the first embodiment.

FIG. 15 is a block diagram illustrating a data receiving device in a data transmission system that performs data transmission by the data transmission method according to the third embodiment.
The data receiving apparatus 203 according to the third embodiment has the same configuration as the data receiving apparatus 201 according to the first embodiment, except that an error correction code is added to the received packet Rp output from the packet receiving unit 21. Error correction means 41 for applying error correction processing to the uncompressed packet Pac and outputting the compressed packet Pb to which no error correction code is added as it is. This is supplied to the error packet detecting means 22. Other configurations of the data receiving device 203 are the same as those of the data receiving device 201 of the first embodiment.

Next, the operation and effect will be described.
In the data transmitting apparatus 103 according to the third embodiment having such a configuration, the non-compressed packet created by the packet creating unit 12, that is, the packet storing the reference source information used for the decompression process of the compressed packet, has an error. When input to the correction code adding means 32, the error correction code adding means 32 adds an error correction code to the uncompressed packet Pa, and sends the ECC added uncompressed packet Pac with the error correction code added to the packet transmitting means 16. Is output. The compressed packet Pb created by the packet creating unit 12 is output to the packet transmitting unit 16 without being processed by the error correction code adding unit 32. Other operations of the data transmitting apparatus 103 are the same as those of the data transmitting apparatus 101 of the first embodiment.

  On the other hand, in the data receiving device 203, when the received packet Rp output from the packet receiving unit 21 is input to the error correcting unit 41, the ECC-added uncompressed packet to which the error correction code is added among the received packets Rp. Pac is subjected to error correction processing and output to the error packet detection means 22, and the compressed packet Pb to which no error correction code is added is output to the error packet detection means 22 as it is. Other operations of the data receiving device 203 are the same as those of the data transmitting device 201 of the first embodiment.

  As described above, in the third embodiment, the ECC-added uncompressed packet Pac is transmitted by adding an error correction code to the uncompressed packet Pa on the transmitting side, and the ECC-added uncompressed packet Pac is corrected on the receiving side. Since error correction processing is performed using codes, even if a transmission error occurs, most of the uncompressed packets on the receiving side will be remedied by the error correction processing, and a bad received uncompressed packet due to the transmission error will be recovered. Generation can be suppressed.

  As a result, the number of received packets discarded due to a decompression error of a compressed packet subsequent to an uncompressed packet is reduced, and the quality of data transmitted wirelessly can be improved.

  In the third embodiment, the error correction code is added to the uncompressed packet itself. However, the reference information (identifier (identifier) necessary for the restoring process of a part of the uncompressed packet, that is, the subsequent compressed packet. An error correction code may be added only to a portion including the ID) and the reference source information (D)).

In this case, on the receiving side, an error correction process is performed on at least the identifier (ID) and the reference source information (D) necessary for restoring the compressed packet.
As a result, the number of received packets discarded due to a decompression error of a compressed packet subsequent to an uncompressed packet is reduced, and the quality of data transmitted wirelessly can be improved.

  Further, in the third embodiment, the error correction code is always added to the non-compressed packet. However, according to the frequency of the notification of the restoration error performed from the receiving side to the transmitting side, the uncompressed packet is May be determined whether or not to add an error correction code.

  In this case, the compression / non-compression transmission determination means 13 counts the number of times the error notification reception signal Sn from the error occurrence notification reception means 14 is input per unit time, and calculates the count value and the fixed reference value Y. The comparison is performed, and an error correction control signal is output to the creation unit 12 according to the comparison result. The creating unit 12 notifies the error correcting code adding unit 32 of whether or not to add an error correcting code to the uncompressed packet based on the error correction control signal. Specifically, when the count value exceeds a certain reference value Y, the error correction code adding means 32 adds an error correction code to the uncompressed packet and outputs the uncompressed packet from the means 32. When the value becomes equal to or less than the value Y, the error correction code adding means 32 outputs the uncompressed packet without applying the error correction code to the uncompressed packet.

  In such a configuration, when the quality of the transmission data is relatively stable, by transmitting the uncompressed packet as it is, the size of the entire uncompressed packet can be reduced and the effective data transmission speed can be increased. When the quality of transmission data is unstable, the number of packets discarded on the receiving side due to a restoration error can be reduced by adding an error correction code to an uncompressed packet.

(Embodiment 4)
16 and 17 are block diagrams for explaining a data transmission method according to Embodiment 4 of the present invention, and FIG. 16 shows data transmission device 104 in a data transmission system using this transmission method. The fourth embodiment corresponds to claims 1, 2, 16 to 21, 32, 33, 36, and 37.

  The data transmitting apparatus 104 receives the retransmission request notification signal Nr of the uncompressed packet from the receiving side instead of the error occurrence notification receiving means 14 in the data transmitting apparatus 101 of the first embodiment, and receives the retransmission request receiving signal Sr And a retransmission request notification receiving means 14d for outputting a packet generation means 12 and a compression / non-compression transmission determination means 13 in the data transmitting apparatus 101 so that an uncompressed packet is generated according to the retransmission request reception signal Sr. Is changed.

  That is, the compression / non-compression transmission determination unit 13d in the data transmission device 104 outputs the packet determination signal Jp indicating the type of the packet generated by the packet generation unit 12d to the packet generation unit 12d, and receives the retransmission request. When receiving the signal Sr, a re-creation command signal Sc is output to the packet creation means 12d so that an uncompressed packet to be retransmitted is created again, instead of the packet determination signal Jp.

  Further, the packet creation means 12d in the data transmission device 104 creates one of an uncompressed packet and a compressed packet based on the packet determination signal Jp, and stores it in the reference management means 15 when receiving the re-creation command signal Sc. Based on the identifier (ID) and the reference source information (D), the last created uncompressed packet is created again. The retransmission request notification signal Nr, the retransmission request reception signal Sr, and the re-creation command signal Sc include an identifier (ID) for specifying an uncompressed packet to be retransmitted.

The other configuration of the data transmitting apparatus 104 according to the fourth embodiment is the same as that of the data transmitting apparatus 101 according to the first embodiment.
FIG. 17 shows a data receiving device 204 in the data transmission system according to the fourth embodiment.

  The data receiving apparatus 204 according to the fourth embodiment temporarily adds a compressed packet determined as a decompression error packet Pre among received compressed packets in addition to the configuration of the data receiving apparatus 201 according to the first embodiment. The data receiving apparatus 201 is provided with an error recovery unit 42 for storing an error in the data receiving apparatus 201 so as to perform a decompression process on a compressed packet determined as a decompression error packet Pre based on reference information of a retransmitted uncompressed packet. The configuration of the notification transmitting unit 24 and the packet restoring unit 23 is changed.

  That is, in the data receiving device 204, instead of the error occurrence notification transmitting means 24 in the data receiving device 201 of the first embodiment, when a restoration error occurs, the restoration process of the restoration error packet is performed based on the error occurrence signal Sre. A retransmission request transmitting unit 24d for outputting a signal (retransmission request notification signal) Nr for requesting retransmission of an uncompressed packet as a required reference packet to the transmitting side is provided.

  The packet decompression unit 23d of the data receiving device 204 stores the identifier (ID) and the reference source information (D), which are the reception side reference information Im2, necessary for the decompression processing of the received compressed packet, in the reference information management unit 25. When the packet is not stored, it is determined that the received compressed packet is a decompression error packet, and the error occurrence signal Sre is output to the retransmission request notification transmitting unit 24d. The error occurrence signal Sre contains an identifier (ID) for specifying an uncompressed packet to be retransmitted.

Then, in the data receiving device 204, a decompression process is performed on the compressed packet determined as the decompression error packet Pre based on the identifier (ID) of the retransmitted uncompressed packet and the transmission information (D). I have.
The other configuration of the data receiving apparatus 204 of this embodiment is the same as that of the data receiving apparatus 201 of the first embodiment.

Next, the operation and effect will be described.
In the data transmission system according to the fourth embodiment having such a configuration, when a restoration error of the compressed packet Pb occurs, an uncompressed packet is retransmitted from the transmission side by the retransmission request notification signal Nr from the reception side.

  In other words, on the receiving side, the packet decompression unit 23d stores the identifier (ID) and the reference source information (D), which are the reference information Im2 on the reception side, necessary for the decompression processing, in the reference information management unit 25. When the compressed packet Pre is determined to be a decompression error packet Pre because it has not been output, the compressed packet Pre is output from the packet decompression unit 23d to the decompression information storage unit 42 and is temporarily stored. At this time, an error occurrence signal Sre including the reference packet identifier (ID) of the restoration error packet Pre is output to the retransmission request notifying unit 24d. Then, the retransmission request notification transmitting unit 24d transmits a retransmission request notification signal Nr including the reference packet identifier (ID) to the transmitting side.

  In the data transmission device 104, when the retransmission request notification signal Nr including the reference packet identifier (ID) is received by the receiving unit 14d, the retransmission request reception signal Sr is output from the receiving unit 14d to the determination unit 13d. The determination unit 13 outputs a signal (re-creation instruction signal) Sc for instructing the creation of the uncompressed packet specified by the reference packet identifier to the packet creation unit 12d. Then, based on the identifier (ID), which is the transmission-side reference information Im1 and the reference source information (D), stored in the reference information management means 15, the packet creation unit 12d performs the non-recovery processing required for the restoration error packet. The compressed packet is created again, and the created uncompressed packet is retransmitted by the packet transmitting means 16 to the receiving side.

  On the receiving side, when the retransmitted uncompressed packet is received by the packet receiving means 21, it is supplied to the packet restoring means 23d via the error packet detecting means 22. Then, in the packet restoring unit 23d, the identifier (ID) and the transmission information (D) are extracted from the retransmitted uncompressed packet, and based on the extracted identifier (ID) and the transmission information (D), the restoration waiting information storage unit The difference information (ΔD) of the compressed packet stored in 42 is restored. On the other hand, the extracted identifier (ID) and transmission information (D) are supplied to the reference information management unit 25, and the identifier (ID) and the reference source information (D), which are the reference information Im2 on the receiving side, are updated by the information. Is done.

  As described above, according to the fourth embodiment, when a decompression error of a compressed packet occurs, the transmitting side responds to the retransmission request notification signal Nr from the receiving side to transmit the uncompressed packet necessary for the decompression processing of the compressed packet. Since retransmission is performed, the received compressed packet has a decompression error because the receiving side does not have the receiving side reference information (identifier (ID) and reference source information (D)) necessary for the decompression processing of the received compressed packet. Even if it is determined that the packet is a packet, after the retransmission processing of the uncompressed packet is completed, the restoration error packet can be correctly restored. As a result, the number of received packets discarded due to a compressed packet decompression error can be reduced, and the quality of wirelessly transmitted data can be improved.

In the fourth embodiment, the reference information management unit 15 stores the identifier (ID) and the transmission information (D) included in the uncompressed packet. The compressed packet itself may be stored.
In this case, when retransmitting the uncompressed packet, the process of creating the uncompressed packet in the packet creating unit 12d can be omitted.

  In the fourth embodiment, the uncompressed packet itself is retransmitted in response to a retransmission request from the receiving side. However, when there is a retransmission request from the receiving side, the identifier (ID) in the uncompressed packet is used. Alternatively, only a portion including the transmission information (D) may be stored in a predetermined retransmission packet and retransmitted.

  Also in this case, the decompression process for the received compressed packet determined to be the decompression error packet becomes possible after the transmission of the retransmission packet, and the number of received packets discarded due to the decompression error of the compressed packet is reduced and the radio packet is transmitted wirelessly. Data quality can be improved.

  Further, in the first to fourth embodiments, the compressed packet stores, as the compressed information, difference information (first difference information) between the transmission information corresponding to the uncompressed packet and the transmission information corresponding to the compressed packet. However, the compression information stored in the compressed packet is switched between the first difference information and other difference information (second difference information) according to the packet transmission status. You may.

  Here, as the second difference information, the difference information defined in the document of V. Jacobson described in the related art, that is, the transmission information corresponding to the compressed packet and the packet created immediately before that Difference information from the corresponding transmission information (see FIG. 31) is given.

  Hereinafter, as described above, the data transmission method for switching the compression information stored in the compressed packet between the first difference information and the second difference information according to the packet transmission status will be described. A case where the present invention is applied to a data transmission system will be briefly described with reference to FIGS.

  In this case, the error occurrence notification receiving means 14 in the data receiving apparatus 101 is configured to calculate the reception frequency (z) of the restoration error notification signal Ne per unit time transmitted from the receiving side. Further, the compressed / uncompressed packet creating means 12 receives the signal indicating the reception frequency (z) calculated by the error occurrence notification receiving means 14, and the reception frequency (z) exceeds a certain reference value Y. In this case, the first difference information is created as compression information to be stored in a compressed packet. On the other hand, when the reception frequency (z) becomes smaller than the reference value Y, the second difference information is created as the compression information. Is configured to create the difference information.

The operation in this case will be briefly described.
First, when an error occurs in a restoration process for restoring compression information included in a compressed packet on the receiving side, the receiving side notifies the transmitting side of the occurrence of the error. Then, on the transmission side, when the notification frequency of the error occurrence exceeds a certain value, a process change notification to the reception side is made to change the restoration process on the reception side to the restoration process using the first difference information. . Thereafter, on the transmitting side, compression processing using the first difference information is performed. On the other hand, on the transmission side, when the notification frequency of the error occurrence becomes equal to or lower than a certain value, a process change notification is sent to the reception side to change the restoration process on the reception side to the restoration process using the second difference information. Then, on the transmitting side, compression processing using the second difference information is performed. Then, on the receiving side, a decompression process corresponding to the compression process on the transmitting side is performed.

In this case, the compressed packet Pb may include an identifier indicating whether the compression information is the first or second difference information.
In the method of switching the compression information Id stored in the compressed packet Pb between the first difference information and the second difference information, the following effects can be obtained.

  That is, usually, the difference between two consecutive packets of information such as the transmission information (image information and audio information) and the header information is often very small or 0, but the difference between distant packets is Tends to be larger. Therefore, by switching and using the first difference information and the second difference information as the compression information, the average value of the difference information can be reduced while improving the quality of data transmitted by radio, that is, the data part can be reduced. The compression efficiency of the information stored in the storage device can be improved.

  In the method of using the above-mentioned compression information by switching between the first difference information and the second difference information, the transmitting side determines which of the first and second difference information is used. However, whether to use the first or second difference information as the compression information may be determined by a command from the receiving side.

In this case, switching between the first difference information and the second difference information may be performed based on, for example, the number of occurrences of transmission errors per unit time.
In this case, the number of transmission errors per unit time (transmission error rate) is determined by the error packet detecting means 22 of the data receiving apparatus, and the determined transmission error rate is transmitted by the error occurrence notifying means 24. To be notified.

Further, the switching between the first difference information and the second difference information may be performed in accordance with the frequency of occurrence of the restoration error on the receiving side.
In this case, the restoration error occurrence frequency (z) per unit time is obtained by the packet restoration means 23 on the receiving side, the restoration error occurrence frequency (z) is compared with a certain reference value Y, and the comparison result is obtained. The error is notified to the transmitting side by the error occurrence notifying unit 24, and the transmitting side uses one of the first and second difference information as compression information according to the notified comparison result.

The operation in this case will be briefly described.
On the receiving side, when an error occurrence frequency at which an error of the decompression process for decompressing the compression information included in the compressed packet occurs exceeds a predetermined value, the compression process on the transmission side is performed by the compression process using the first difference information. A request to change the process is made to the transmitting side. On the other hand, on the receiving side, when the error occurrence frequency of the above-mentioned restoration processing becomes equal to or less than a predetermined value, a processing change request to the transmitting side is made to change the compression processing on the transmission side to the compression processing using the second difference information. Be done.

  Then, on the transmission side, compression processing using difference information according to the processing change request from the reception side is performed, and on the reception side also, restoration processing corresponding to the compression processing using difference information requested to the transmission side Is performed.

(Embodiment 5)
FIGS. 18 to 27 illustrate a data transmission method according to a fifth embodiment of the present invention and a data transmission system using the data transmission method. The fifth embodiment corresponds to claims 22 to 31, 34, 35, 38 to 40.

  The data transmission system according to the fifth embodiment is a system for transmitting information from a transmitting side to a receiving side in packet units. The transmitting side stores uncompressed packets storing transmission information and compressed transmission information. When creating a compressed packet, the transmission information is compressed using transmission information (reference information) corresponding to an uncompressed packet and a specific compressed packet, and the receiving side converts the compressed transmission information into the reference information. And restore it.

  FIG. 18 is a diagram showing a data structure (format) of an uncompressed packet (FIG. 18A) and a compressed packet (FIG. 18B) used in the data transmission system according to the fifth embodiment.

  The uncompressed packet Pg includes a header portion Hpg storing header information and a data portion Dpg storing uncompressed information Ir transmitted by the PPP protocol. The information of the header part Hpg is, like the header part Hpa of the uncompressed packet Pa of the first embodiment, a compressed / uncompressed identifier Ih1 indicating whether or not the information of the data part is compressed, and identifies the uncompressed packet. And a header information Ih3. Here, the uncompressed information Ir is transmission information (D) transmitted by the uncompressed packet.

  The compressed packet Ph includes a header section Hph storing header information and a data section Dph storing compression information Id transmitted by the PPP protocol. The information of the header portion Hph includes a compressed / uncompressed identifier Ih1 indicating whether or not the information of the data portion is compressed, and a reference packet identifier (referred to as a reference packet necessary for the restoration process of the compressed information Id). ID) Ih2b, a reference information update flag Ih5 indicating whether or not to update the reference source information used in the above-described restoration processing, and other header information Ih3.

  Here, in a normal compressed packet Ph, the reference information update flag Ih5 is set to a value “Off” indicating that the reference source information is not updated, and in a specific compressed packet Ph, the reference information update flag Ih5 is set. Is set to a value “On” indicating that the reference source information is updated. Further, the compression information Id includes transmission information (D) corresponding to an uncompressed packet closest to the compressed packet or a specific compressed packet transmitted before the compressed packet Pb to be transmitted, and the transmission target Is the difference information (ΔD) from the transmission information (D) corresponding to the compressed packet.

Needless to say, the other header information Ih3 includes the CRC code Icrc shown in FIG.
FIG. 19 is a block diagram showing a data transmission device in the data transmission system according to the fifth embodiment.

  The data transmitting apparatus 105 receives the first transmission signal S1 including the transmission information (D) and outputs a reception signal Src, similarly to the data transmission apparatus 101 of the first embodiment, In response to the Src, the transmission information (D) is packetized based on the control signal to generate an uncompressed packet Pg or a compressed packet Ph. Packet transmitting means 16 for transmitting a packet as a second transmission signal S2 to the receiving side.

  Further, similarly to the data transmission apparatus 101, the data transmission apparatus 105 receives the restoration error notification signal Ne from the receiving side and outputs an error notification reception signal Sn, and the packet generation means 12e manages the type of the packet created, and determines the type of the packet to be created next based on the managed packet type information and the error notification reception signal Sn to determine the packet determination signal Jp And a compression / non-compression transmission determination unit 13 that outputs the control signal to the packet generation unit 12e as the control signal. Here, the packet creating means 12e creates one of the uncompressed packet Pg and the compressed packet Ph according to the packet determination signal Jp.

  The data transmitting apparatus 105 manages the transmission history of the compressed packet transmitted to the receiving side based on the compression / non-compression identifier Ih1 and the reference information update flag Ih5 from the packet generation unit 12e, and generates the compressed packet. A reference information update determining unit 17 for determining whether to update the reference source information at times. Here, the reference information update determination means 17 outputs a reference information update signal Jr for instructing the update of the reference source information to the packet creation means 12e as the control signal every time a packet is created n times (for example, three times). Configuration. When the reference information update signal Jr is input as a control signal, the packet creation means 12e sets the reference information update flag Ih5 in the header portion Hph of the compressed packet Ph as a value "On" indicating that the reference source information is to be updated. Is stored, and a specific compressed packet is created. On the other hand, when the reference information update signal Jr is not input, a value “Off” indicating that the reference source information is not updated is stored in the header portion Hph of the compressed packet Ph as a reference information update flag Ih5, and a normal value is stored. A compressed packet is created.

  Further, the data transmitting apparatus 105 transmits transmission information (D) referred to when creating compression information corresponding to each compressed packet, and a reference packet identifier (ID) indicating a reference packet corresponding to the transmission information (D). ) Are associated with each other and managed as transmission-side reference information (reference source information (D) and identifier (ID)) Im1. In the reference information management unit 15e, when a non-compressed packet is created or when a specific compressed packet including the update discrimination flag “On” Ih5 is created, the transmission-side management control signal Cm1 from the packet creation unit 12e is used. The reference source information (D) and the identifier (ID), which are the transmission-side reference information Im1, are updated.

FIG. 20 is a block diagram illustrating a data receiving device in the data transmission system according to the fifth embodiment.
The data receiving device 205 receives the packet transmitted from the transmitting side as the second transmission signal S2 and outputs a received packet Rp, as in the data receiving device 201 of the first embodiment. An error packet detecting unit 22 that receives the received packet Rp and outputs a normally transmitted normal packet Pno by an error packet detecting process, receives a normal packet Pno from the detecting unit 22, and stores the received packet in each packet. It has packet decompression means 23e for decompressing uncompressed information or compressed information, and output means 26 for outputting decompression information (transmission information (D)) Irs obtained by the decompression processing as an output signal S3.

  Further, the data receiving device 205 transmits transmission information (D) referred to when decompressing the compression information corresponding to each compressed packet, and a reference packet identifier (ID) for identifying the reference packet corresponding to the transmission information (D). The reference information management unit 25e manages the reference information (reference information (D) and the identifier (ID)) Im2 in association with the reference information (ID). When the decompression process is performed on the uncompressed packet, or when the decompression process is performed on a specific compressed packet including the update determination flag “On” Ih5, the reference information management unit 25e receives the packet from the packet decompression unit 23e. The reference information (D) and the identifier (ID), which are the receiving side reference information Im2, are updated by the side management control signal Cm2.

  Further, when performing the decompression process on the compressed packet Ph, the packet decompression unit 23e stores the reference packet identifier (ID) stored in the compressed packet Ph and the reference source information (D) corresponding to the identifier (ID). Is stored in the reference information management unit 25e, and an error occurrence signal Se indicating that a decompression error has occurred in the compressed packet is output in accordance with the determination result.

  Further, the data receiving apparatus 205 receives an error occurrence signal Se indicating the occurrence of a restoration error from the packet restoration unit 23e, and notifies the transmission side of the occurrence of the restoration error to the transmission side by the restoration error notification signal Ne on the reception side. It has a notification transmitting unit 24.

Next, the operation and effect will be described.
FIGS. 21 and 22 are diagrams for explaining the data transmission method according to the fifth embodiment. FIG. 21 shows a flow of a plurality of packets from the transmission side to the reception side in a normal transmission state, and FIG. 22 shows a flow of a plurality of packets from the transmission side to the reception side when a transmission error occurs. .

  Here, the transmission information (D1) to (D11) are information corresponding to each packet, which are collected so as to be transmitted in packet units. In the fifth embodiment, the transmission information (D1) is not compressed. The transmission information (D2) to (D11) is transmitted by the uncompressed packet Pg (1), and is transmitted sequentially by the compressed packets Ph (2) to Ph (11) following the uncompressed packet Pg (1). .

On the transmitting side, first, the uncompressed packet Pg (1) is generated, and the uncompressed packet Pg (1) is transmitted to the receiving side. At this time, the transmission information (D1) is stored as uncompressed information Ir in the data portion Dpg of the uncompressed packet Pg (1), and the header portion Hpg has an identifier Ih indicating uncompressed and a packet identifier for identifying this packet. (ID = 0) Ih2a and other header information Ih3 are stored.
Thereafter, compressed packets Ph (2) to Ph (11) are sequentially created and transmitted to the receiving side.

  When creating such a compressed packet, for example, the header portion Hph of the compressed packets Ph (2) to Ph (5) includes an identifier Ih indicating compression, a reference packet identifier (ID = 0) Ih2b, and a reference. The information update flag Ih5 and other header information Ih3 are stored. The data portions Dph of the compressed packets Ph (2) to Ph (5) respectively include difference information (D1-D2), difference information (D1-D3), difference information (D1-D4), and difference information (D1-D1). D5) is stored.

  However, in the fifth embodiment, the reference information is updated every time three packets are transmitted. Therefore, in the compressed packets Ph (2) to Ph (4), the reference information update flag of the header Hph is used. The value of Ih5 is a value “Off” indicating that the reference source information is not updated. On the other hand, in the compressed packet Ph (5), the value of the reference information update flag Ih5 of the header portion Hph indicates that the reference source information is not updated. The value indicates “On” to be updated. That is, after the transmission of the compressed packet Ph (5), the transmission information (D5) whose reference packet identifier corresponds to the value (ID = 1) indicating the compressed packet Ph (5) and whose reference source information corresponds to the reference packet Ph (5) ) Is updated.

  Accordingly, the header portion Hph of the four compressed packets Ph (6) to Ph (9) following the compressed packet Ph (5) has an identifier Ih indicating compression, a reference packet identifier (ID = 1) Ih2b, and an update determination flag Ih5. , And other header information Ih3. The data portions Dph of the compressed packets Ph (6) to Ph (9) respectively include difference information (D5-D6), difference information (D5-D7), difference information (D5-D8), and difference information (D5-D6). D9) is stored.

  In these compressed packets Ph (6) to Ph (8), the value of the reference information update flag Ih5 of the header part Hph is a value “Off” indicating that the reference source information is not updated. In Ph (9), the value of the reference information update flag Ih5 of the header portion Hph is “On” indicating that the reference source information is updated. That is, after the transmission of the compressed packet Ph (9), the transmission information (D9) whose reference packet identifier corresponds to the value (ID = 2) indicating the compressed packet Ph (9) and whose reference source information corresponds to the reference packet Ph (9) ) Has been updated.

Therefore, in the header portion Hph of the compressed packets Ph (10) and Ph (11) following the compressed packet Ph (9), the identifier Ih indicating the compression, the reference packet identifier (ID = 2) Ih2b, the update determination flag Ih5, and Other header information Ih3 is stored. Further, difference information (D9-D10) and difference information (D9-D11) are stored in the data portions Dph of the compressed packets Ph (10) and Ph (11), respectively.
In these compressed packets Ph (10) and Ph (11), the value of the reference information update flag Ih5 of the header part Hph is a value “Off” indicating that the reference source information is not updated.

The uncompressed packet Pg (1) and the compressed packets Ph (2) to Ph (11) successively transmitted from the transmitting side as described above are sequentially received by the receiving side in a normal data transmission state, and each packet is received. The transmission information (D1) to (D11) corresponding to is restored.
That is, on the receiving side, when the uncompressed packet Pg (1) is received, the transmission information (D1), which is the uncompressed information Ir, is extracted from the data part Dpg. Thereafter, when the compressed packets Ph (2) to Ph (11) are received, the difference information of the data part Dph is restored to the transmission information based on the reference source information.

  Specifically, the difference information (D1-D2), (D1-D3), (D1-D4), (D1-D4) of the packets Ph (2), Ph (3), Ph (4), and Ph (5). D5) is restored with reference to the transmission information (D1) corresponding to the uncompressed packet Pg (1) specified by the identifier (ID = 0).

  The difference information (D5-D6), (D5-D7), (D5-D8), and (D5-D9) of the packets Ph (6), Ph (7), Ph (8), and Ph (9) are , Is restored with reference to the transmission information (D5) corresponding to the compressed packet Ph (5) specified by the identifier (ID = 1).

  Further, the difference information (D9-D10) and (D9-D11) between the packets Ph (10) and Ph (11) is the transmission information (D9-D10) corresponding to the compressed packet Ph (9) specified by the identifier (ID = 2). D9).

  Then, in the state where the packet is being transmitted as described above, as shown in FIG. 22, when a transmission error of the compressed packet Ph (10) occurs, when the compressed packet Pb (11) is received, The restoration of the difference information (D9-D11) stored in the compressed packet Pb (11) is performed in the same manner as when no transmission error has occurred in the compressed packet Pb (10).

  That is, also in the fifth embodiment, as in the first embodiment, when restoring the difference information (ΔD) stored in each compressed packet Ph, the compression target to be processed is always used as the reference source information. Instead of using the transmission information corresponding to the packet immediately before the packet, the transmission information corresponding to the uncompressed packet transmitted first or immediately after the occurrence of the decompression error, and the specific information transmitted every time a predetermined number of packets are transmitted The transmission information corresponding to the compressed packet is used.

  Therefore, in the fifth embodiment, even when a transmission error of a compressed packet other than a specific compressed packet occurs, the transmission error does not affect the restoration processing of the next normally received compressed packet. In this case, on the receiving side, only the error packet is discarded, and the receiving side does not notify the transmitting side of the restoration error.

  When a transmission error of the uncompressed packet Pg (1) or a transmission error of a specific compressed packet occurs during transmission of information by packet, a notification of the occurrence of a decompression error is performed in the same procedure as the procedure shown in FIG. Is transmitted to the transmission side. Immediately after the transmission side receives the notification of the occurrence of the restoration error, the transmission side transmits an uncompressed packet, and thereafter, a normal compressed packet and a specific compressed packet are repeatedly transmitted. At this time, on the receiving side, the error packet and the subsequent compressed packet are discarded.

Next, the operation of data transmitting apparatus 105 when data transmission is performed as described above will be described.
For example, continuous transmission information (D1) to (D11) (see FIGS. 21 and 22) transmitted from the information providing side by a transmission method such as Ethernet (registered trademark) is transmitted to the data transmitting apparatus 105 by a first transmission. When input as the signal S1, the receiving means 11 receives the transmission information (D1) to (D11) by the transmission method. Then, the received transmission information is sequentially output to the compressed / uncompressed packet creating unit 12e as received information Src.

  The packet creating means 12e creates a packet for transmitting each piece of transmission information to the receiving side based on a transmission protocol such as a PPP protocol. At this time, in response to the packet determination signal Jp from the compression / non-compression transmission determination unit 13 and the reference information update signal Jr from the reference information update determination unit 17, the non-compression packet, the normal compression packet, and the specific compression packet are Either is created. The uncompressed packet Pg and the compressed packet Ph created in this way are sequentially output to the packet transmitting unit 16 and transmitted to the receiving side as the second transmission signal S2 by the packet transmitting unit 16.

  Specifically, when communication is started, and when the error notification reception signal Sn is input from the error occurrence notification reception unit 14 to the determination unit 13, the generation of the uncompressed packet is instructed by the packet determination signal Jp, In other cases, the generation of the compressed packet is instructed by the packet determination signal Jp.

  When the creation of a compressed packet is instructed, when the reference information update signal Jr instructs to update the transmission-side reference information Im1, a specific compressed packet is created as a compressed packet, and the reference information update signal Jr is transmitted to the transmission side. When the update of the reference information Im1 is not instructed, a normal compressed packet is created as a compressed packet.

  Here, the compression / non-compression determining unit 13 determines which of an uncompressed packet and a compressed packet is to be created based on the created compressed / uncompressed identifier Ih1 of each packet and the error notification reception signal Sn. , A packet determination signal Jp indicating the type of packet to be created is output. Specifically, immediately after the communication is started, a packet determination signal Jp indicating that an uncompressed packet should be created is output, and when the notification reception signal Sn is input, a packet indicating that a compressed packet should be created. A determination signal Jp is output.

  Further, the packet creating means 12e creates the uncompressed packet Pg in the same manner as in the first embodiment. The compressed packet Ph is created based on the transmission-side reference information Im1 (specifically, the identifier (ID) and the reference source information (D)) managed by the reference information management unit 15e. At this time, the reference information update flag Ih5 whose value is set to “Off” is stored in the header portion Hph of the normal compressed packet together with the compressed / uncompressed identifier Ih1, the reference packet identifier Ih2b, and other header information Ih3. Is done. The reference information update flag Ih5 whose value is set to "On" is stored in the header portion Hph of a specific compressed packet together with the compressed / uncompressed identifier Ih1, the reference packet identifier Ih2b, and other header information Ih3. You. The data section Dph of these compressed packets stores difference information (ΔD) based on reference source information managed by the reference information management means 15e.

  When the uncompressed packet Pg or the specific compressed packet Ph is created, the reference information management unit 15e uses the identifier as the transmission-side reference information Im1 based on the transmission-side update control signal Cm1 from the packet creation unit 12e. The (ID) and the corresponding reference source information (D) are updated to the reference packet identifier (D) for identifying the packet Pg or Ph and the corresponding transmission information (D).

  The reference information update determining means 17 transmits the uncompressed packet or the specific compressed packet after the transmission based on the created compressed / uncompressed identifier Ih1 of each packet and the reference information update flag Ih5 of the compressed packet. The number of normal compressed packets is counted. When the count value reaches a predetermined value (here, 3), a reference information update signal Jr is output, and the count value is reset. When the count value is less than a predetermined value (here, 3), the reference information update signal Jr is not output.

Hereinafter, the processing in the packet creation means 12e will be described according to the flow shown in FIG.
When the transmission information received by the receiving means 11 is input (step Sc1), the packet creating means 12e inquires of the determining means 13 which of an uncompressed packet and a compressed packet should be created (step Sc1). Sc2), the type of the packet to be created is determined based on the packet determination signal Jp from the determination unit 13 (Step Sc3).

  As a result, when an uncompressed packet is to be created, an identifier (ID) for identifying the uncompressed packet is assigned as a packet identifier Ih2a, and an uncompressed packet Pg including the packet identifier (ID) is created. Is performed (Step Sc11). After that, according to an instruction (transmitting-side management control signal Cm1) from the packet creating unit 12e, the identifier (ID) managed by the reference information managing unit 15e as the transmitting-side reference information Im1 and the corresponding reference source information (D) are changed. It is updated (step Sc12).

  On the other hand, when a compressed packet is to be created, the packet creation unit 12e sends the reference information management unit 15 an identifier (ID) and reference source information (ID) managed as transmission-side reference information Im1 by the management unit 15. D) is inquired (step Sc4). Then, the data part Dph of the compressed packet is created based on the identifier (ID) obtained by the inquiry and the reference source information (D) (step Sc5).

  Thereafter, the packet creation unit 12e inquires of the determination unit 17 whether or not to update the transmission-side reference information Im1 (step Sc6). Based on the reference information update signal Jr from the determination unit 17, the transmission-side reference information Im1 is updated. It is determined whether to update Im1 (step Sc7).

  As a result, when the transmission-side reference information Im1 is to be updated, the identifier (ID) and the reference source information (D) managed by the reference information management unit 15e are updated according to an instruction from the packet creation unit 12e. (Step Sc8), a specific compressed packet Ph is created (Step Sc9).

On the other hand, when the transmission-side reference information Im1 should not be updated, a normal compressed packet is created (step Sc10).
Then, each of the packets is sent to the transmitting means 16 (step Sc13).
After that, the process of the packet creating unit 12e returns to Step Sc2. Such processing is performed until the last packet is transmitted.

Next, an operation of the data receiving apparatus 205 when packets are sequentially transmitted as shown in FIGS. 21 and 22 will be described.
In the packet receiving means 21, the packets Pg (1), Ph (2) to Ph (11) transmitted from the transmitting side are sequentially received and output to the error packet detecting means 22. When it is confirmed that the received packet has been transmitted correctly, the error packet detecting means 22 outputs the received packet to the packet restoring means 23e as a normal packet Pno. If it is not confirmed that the received packet has been transmitted correctly, the received packet is discarded as an error packet. Here, the CRC (Cyclic Redundancy Check), which is widely used for the error detection method, is used, but the error detection method is not limited to this.

  In the packet restoring means 23e, the normal received packet Pno is determined to be either a compressed packet or an uncompressed packet by the compressed / uncompressed identifier Ih1 included in the header of the received normal packet (hereinafter, also referred to as a normally received packet) Pno. It is determined whether there is.

  For example, when the normally received packet Pno input to the decompression unit 23e is the uncompressed packet Pg (1), the decompression unit 23e transmits the transmission information (D1) from the data part Dpg of the uncompressed packet Pg (1). A retrieval process is performed to retrieve the image.

  Next, in the management unit 25e, the identifier (ID) and the reference source information (D) stored as the reception-side reference information Im2 are updated by the reception-side management control signal Cm2 from the restoration unit 23e. Thereby, the identifier (ID) and the reference source information (D) recorded as the receiving side reference information Im2 in the management unit 25e are changed to the identifier (ID = 0) and the transmission information (D1), respectively. Thereafter, in the restoring unit 23e, the transmission information (D1) which is the restored information is output to the output unit 26, and the transmission information (D1) is output from the output unit 26.

  On the other hand, when the packet input to the decompression unit 23e is, for example, a specific compressed packet Ph (5), the reference information management unit 25e is notified of the reference packet identifier (ID = 0) included in the compressed packet and An inquiry is made as to whether reference source information (D1) corresponding to this is stored. When the reference packet identifier (ID = 0) and the corresponding reference source information (D1) are stored in the management unit 25e, the restoration unit 23e stores the reference source information (D1) and the difference information (D1-D5). , The transmission information (D5) corresponding to this packet is restored.

  At this time, if any one of the reference packet identifier (ID = 0) and the corresponding reference source information (D1) is not stored in the management unit 25e, the received compressed packet is discarded as an error packet, An error occurrence signal Se indicating that a restoration error has occurred is output to the error occurrence notifying means 24. Then, the notifying unit 24 transmits a restoration error notification signal Ne to the transmitting side.

  Further, the restoration unit 23e checks the reference information update flag Ih5 of the header Hph, and when this indicates that the reception-side reference information Im2 is to be updated, the reception-side update control signal Cm2 is transmitted to the reference information management unit 25e. Is output. In the management unit 25e, the stored identifier (ID) and the corresponding reference source information (D) are converted into new information, for example, the reference packet identifier (ID = 1) and the reference source information by the reception side update control signal Cm2. It is updated to (D5). Thereafter, the transmission information (D5) restored by the restoration unit 23e is output to the output unit 26, and the transmission information (D5) is output by the output unit 26 as a reception signal S3.

  When the packet input to the decompression unit 23e is a normal compressed packet, the decompression unit 23e and the reference information management unit 25e operate in the same manner as in the first embodiment except for the process of checking the reference information update flag Ih5. Processing is performed.

Hereinafter, the processing in the packet restoration unit 23e will be described with reference to the flow shown in FIG.
When the normally received packet Pno is input from the error packet detecting unit 22 (step Sd1), the packet restoring unit 23e determines whether the normally received packet is an uncompressed packet or a compressed packet (step Sd2). .

  If the normally received packet is an uncompressed packet, the transmission information (D) is extracted from the data portion Dpg of the uncompressed packet Pg by a decompression process for the uncompressed packet (step Sd12). Then, according to the instruction of the packet restoring unit 23e, the identifier (ID) and the reference source information (D) as the receiving side reference information Im2 in the reference information management unit 25e are updated to the packet identifier and the transmission information of the uncompressed packet ( Step Sd13). The transmission information extracted from the data part of the uncompressed packet is sent to the output means 26 (step Sd9).

  If the normal received packet is a compressed packet, the packet decompression unit 23e sends the reference information management unit 25e the reference packet identifier (ID) Ih2b stored in the compressed packet and the reference source information (D) corresponding to the identifier Ih2b. ) Are recorded (step Sd3), and it is determined whether or not these are stored in the reference information management unit 25e (step Sd4).

  When the reference packet identifier (ID) Ih2b and the corresponding reference source information (D) are not stored in the reference information management means 25e, the normally received packet is discarded as an error packet (step Sd10), and an error occurrence signal is output. Se is output to the error occurrence notification transmitting means 24 (step Sd11). Thereafter, the processing by the packet restoring means 23e returns to the processing of step Sd2.

  On the other hand, when the reference packet identifier (ID) Ih2b and the corresponding reference source information (D) are stored in the reference information management unit 25e, the difference information of the compressed packet is included in the transmission information based on the reference source information. It is restored (step Sd5).

Next, it is determined whether or not the reference information update flag Ih5 stored in the compressed packet indicates that the reference information is to be updated (step Sd6). The identifier (ID) and the reference source information (D) stored in the reference information management unit 25e as the receiving side reference information Im2 are updated to new information (step Sd8). Thereafter, the transmission information is output to the output means 26 (step Sd9). If the result of determination in step Sd6 does not indicate that reference information should be updated, the transmission information is output to the output unit 26 without updating the receiving-side reference information Im2 (step Sd9). )
After that, the process of the packet restoration unit 23e returns to Step Sd2. Such processing is performed until the last packet is received.

  As described above, in the data transmission method according to the fifth embodiment, transmission information is transmitted in packet units by using an uncompressed packet in which transmission information is stored without compression and a compressed packet in which transmission information is compressed and stored. Since the transmission information corresponding to the compressed packet is compressed using the previously transmitted uncompressed packet or the transmission information corresponding to the specific compressed packet as reference source information, the uncompressed packet and the specific compressed packet are used. In a state where the transmission is normal, even if a transmission error of the compressed packet occurs, the difference information of the normally transmitted compressed packet after the error packet is the transmission information corresponding to the uncompressed packet or the specific compressed packet. Can be restored using Therefore, the number of compressed packets to be discarded due to the occurrence of a transmission error of the compressed packet is greatly reduced. As a result, it is possible to improve the quality of data transmitted in the wireless section. In other words, the effective data transmission speed can be improved, and the time and cost required for unrecoverable packet transmission can be significantly reduced.

  In the fifth embodiment, the timing for updating the reference information on the transmission side and the reception side, in other words, transmitting one specific compressed packet every time a predetermined number (three) of compressed packets are transmitted to the transmission side. However, the transmission of the specific compressed packet may be performed every time a predetermined time (n seconds) elapses, and the size of the difference information stored in the compressed packet may be a predetermined threshold value. May be performed when the number exceeds the limit.

Also, transmission of the specific compressed packet is performed when a request for updating reference source information is received from the receiving side, or when the size of the difference information or the average value of the difference information exceeds a certain threshold value. It may be.
For example, on the transmission side, when transmission of the specific compressed packet is requested from the reception side, the specific compression packet is transmitted to the reception side.

Further, the transmitting side transmits the specific compressed packet when the size of the compressed information included in the compressed packet transmitted to the receiving side exceeds a certain value.
Further, in the processing on the transmitting side, the specific compressed packet is transmitted when the average value of the size of the compressed information included in the compressed packet transmitted to the receiving side exceeds a certain value.
Further, the method of determining the timing for updating the transmission-side and reception-side reference information may be a combination of the above methods.

By determining the timing for updating the transmission side and reception side reference information as described above, the following effects can be obtained.
Usually, the difference between the two adjacent packets of the image information, the audio information, and the header information is often very small or 0, but the difference between the distant packets tends to be large. Therefore, it is expected that by transmitting uncompressed packets periodically, the average value of the difference information is reduced, that is, the compression efficiency of the data portion is improved, while improving the quality of data transmitted by radio. it can.

(Modification of Embodiment 5)
Further, in the fifth embodiment, as shown in FIGS. 18, 21, and 22, the compressed information stored in the data portion Dph of the compressed packet Ph includes the entire transmission information corresponding to the compressed packet and the uncompressed packet. Although the difference information (ΔD) with the entire corresponding transmission information has been described, the compression information stored in the data portion Dph of the compressed packet Ph may be obtained by compressing only a part of the transmission information corresponding to the compressed packet. .

  That is, the transmission information is divided into compression target information corresponding to a plurality of items to be compressed and non-compression target information not to be compressed, and the data portion Dph of the compressed packet Ph contains an uncompressed packet. The difference information between the compression target information in the corresponding transmission information and the compression target information in the transmission information corresponding to the compressed packet is stored as item-specific compression information, and the non-compression target information in the transmission information corresponding to the compression packet is stored. .

FIG. 25A shows the data structure of an uncompressed packet used when the transmission information is composed of compression target information and compression non-target information.
The uncompressed packet Pi includes a header portion Hpi storing header information and a data portion Dpi storing transmission information (D) transmitted by the PPP protocol as uncompressed information Ir. As in the case of the uncompressed packet Pg shown in FIG. 18A, the header portion Hpi has a compressed / uncompressed identifier Ih1 indicating whether or not information in the data portion is compressed, and a packet identifier for identifying the uncompressed packet. (ID) Ih2a and other header information Ih3. Here, the non-compressed information Ir is composed of item-specific compression target information Ira, Irb, Irc, Ird corresponding to four items to be compressed, and non-compression target information Inc not to be compressed. I have. Here, item-specific transmission information (Da), (Db), (Dc), and (Dd) are stored as the item-specific compression target information (item-specific uncompressed information) Ira, Irb, Irc, and Ird.

FIG. 25B shows the data structure of a compressed packet Pj used when the transmission information is composed of information to be compressed and information not to be compressed.
The compressed packet Pj includes a header portion Hpj storing header information and a data portion Dpj storing partially compressed information (ΔD) transmitted by the PPP protocol. The header section Hpj stores a compressed / uncompressed identifier Ih1, a reference packet identifier (ID) Ih2b, a reference information update flag Ih5, a difference information presence / absence flag Ih6, and other header information Ih3. Here, the difference information presence / absence flag Ih6 is a flag indicating whether or not the compressed item-specific compression target information whose value is not 0 is included in the compressed packet.

  Here, the data part Dpj includes item-specific compression information Ida, Idb, Idc, Idd corresponding to the four compression target items, and uncompressed non-compression target information Inc. The compressed information Ida is the difference between the item-specific transmission information (Da) in the transmission information corresponding to the uncompressed packet and the item-specific transmission information (Da) in the transmission information corresponding to the compressed packet (item-specific difference information (ΔDa)). ). The compressed information Idb is a difference between the item-specific transmission information (Db) in the transmission information corresponding to the uncompressed packet and the item-specific transmission information (Db) in the transmission information corresponding to the compressed packet (item-specific difference information (ΔDb)). ). The compressed information Idc is the difference between the item-specific transmission information (Dc) in the transmission information corresponding to the uncompressed packet and the item-specific transmission information (Dc) in the transmission information corresponding to the compressed packet (item-specific difference information (ΔDc)). ). The compressed information Idd is the difference between the item-specific transmission information (Dd) in the transmission information corresponding to the uncompressed packet and the item-specific transmission information (Dd) in the transmission information corresponding to the compressed packet (item-specific difference information (ΔDd)). ).

  In this case, the reference information management unit 15e of the data transmitting apparatus 105 transmits the reference packet identifier (ID), information indicating each compression target item to be compressed, and the reference source compression (item) corresponding to each compression target item. (A separate reference source information) is stored in a table and stored as transmission-side reference information Im1.

  Similarly to the reference information management unit 15e, the reference information management unit 25e in the data receiving device 205 also includes a reference packet identifier (ID), information indicating each compression target item to be compressed, and each compression target item. Is stored in the form of a table with reference source compression (item-specific reference source information) corresponding to.

FIG. 25C specifically shows a process of creating the compressed packet Pj (Y) by compressing the transmission information D (Y).
In this case, the reference information management unit 15e stores the reference packet identifier (ID = X) and the item-specific reference source information (Da (X)), (Db (X)), (Dc ( X)) and (Dd (X)).

The difference information (ΔDa), (ΔDb), (ΔDc), and (ΔDd) for each item are referred to by each item as the transmission-side reference information Im1 as shown in (Equation 1) to (Equation 4) below. Original information (Da (X)), (Db (X)), (Dc (X)), (Dd (X)) and the corresponding item-specific transmission information (Da ( Y)), (Db (Y)), (Dc (Y)), and (Dd (Y)).
ΔDa = Da (X) −Da (Y) = 0 (Equation 1)
ΔDb = Db (X) −Db (Y) ≠ 0 (Formula 2)
ΔDc = Dc (X) −Dc (Y) ≠ 0 (Equation 3)
ΔDd = Dd (X) −Dd (Y) = 0 (Equation 4)

  As described above, the values of the item-by-item difference information (ΔDa) and (ΔDd) are 0, but the values of the item-by-item difference information (ΔDb) and (ΔDc) are not 0, so that the header portion of the compressed packet Pj (Y) is used. In the difference information presence / absence flag Ih6 of Hj, a value “On” indicating that the value is not 0 among a plurality of item-by-item difference information is set, and the data of the compressed packet Pj (Y) is set. The section Dj stores only the item-by-item difference information (ΔDb) and (ΔDc).

FIG. 26 is an enlarged view showing a part of the compressed packet Pj (Y).
The item-specific difference information includes a subsequent difference information presence / absence flag and a reference source information type flag as information (format) common to these items. Here, the value of the subsequent difference information presence / absence flag Ico1 in the compression information (item-specific difference information (ΔDb)) Idb stores the other item-specific difference information in the data portion Dpj following the item-specific difference information (ΔDb). And that the reference source information type flag Ico2 in the compression information Idb should refer to the item-specific transmission information (Db) when restoring the item-specific difference information Idb. Is shown. The value of the subsequent difference information presence / absence flag Ico1 in the compression information (item-specific difference information (ΔDd)) Idc is a value “Off” indicating that there is no compression information following the item-specific difference information (ΔDd) in the data portion Dpj. And the reference source information type flag Ico2 in the compression information Idc indicates that the item-specific transmission information (Dc) should be referred to when the compression information is restored.

  As described above, by including the subsequent difference information presence / absence flag Ico1 and the reference source information type flag Ico2 in each item-specific difference information, only the item-specific difference information having an information amount other than 0 is included in the data portion of the compressed packet. Can be included as an element.

  This makes it possible to compress the transmission information for each component (information corresponding to each compression target item) in the transmission information, and to maintain a constant compression effect while maintaining the reference information management unit 15e on the transmission side. In addition, the storage area including the RAM and the like in the reference information management unit 25e on the receiving side can be reduced.

Further, the item-specific difference information Idc includes common information (subsequent difference information presence / absence flag and reference source information type flag) and difference information length data Iun1 and compression method type flag Inu2 as unique information (format) separately. I have it.
Here, the difference information length data Iun1 indicates the data size of the item-by-item difference information Idc, and the compression method type flag Inu2 indicates the restoration method for restoring the item-by-item difference information Idc by using a plurality of restoration methods. It is specified from among.

By including the difference information length data Iun1 in the item-by-item difference information (ΔDc), when the item-by-item difference information (ΔDc) is small, its size can be reduced, and the compression efficiency can be further increased. Can be.
Further, the compression method type flag Iun2 is composed of, for example, 2-bit information, and by preliminarily defining a compression method according to the value, the compression efficiency can be further increased.

  For example, when the value of the compression method type flag Iun2 is “00”, the item-by-item difference information is a difference (ΔDn) from the reference source information, and when the value is “01”, the item-by-item difference information is ( ΔDn / 2), and when the value is “10”, the difference information by item is (ΔDn / 8), and when the value is “11”, the difference information by item is (ΔDn / 64) I do.

  FIG. 27 is a diagram for explaining specific information stored in the uncompressed packet Pi and the compressed packet Pj. FIG. 27A shows data (transmission information) to be transmitted by the packet. 27 (b) shows transmission information in an uncompressed packet and difference information in a compressed packet, and FIG. 27 (c) shows item-specific compression information Ida as the difference information. Here, the case of transmitting RTP data (only a part is described) is described as an example.

  The transmission information is an IP packet (RTP / UDP / IP data) Pipb shown in FIG. 29D, and the transmission information includes information corresponding to the first to fourth compression target items K1 to K4. Have been. Information corresponding to the first and second compression target items K1 and K2 (compression target information Ira and Irb shown in FIG. 25A) is a sequence number (SN) and a time stamp (ST) of the RTP packet, respectively. The information corresponding to the third compression target item K3 (compression target information Irc shown in FIG. 25A) is the identifier (ID) of the IP packet, and the information corresponding to the fourth compression target item K4 (FIG. 25A ) Is a UDP port number (Port No.). The specific information corresponding to each compression target item in each of the transmission information (D1) to (D5) is No. in the table of FIG. 1 to No. As shown in column 5.

  When RTP / UDP / IP data is actually transmitted as the transmission information (D1) to (D5), the transmission information is stored in a PPP packet (uncompressed packet and compressed packet) by a PPP protocol, and the data transmission device 105 to the data receiving device 205.

  At this time, the compression target information Ira, Irb, Irc, Ird in the transmission information (D1) is stored in the data portion Dpi of the uncompressed packet Pi (1) without being compressed. In the header portion Hpi, a 1-bit compressed / uncompressed identifier Ih1, a 5-bit packet identifier (ID) Ih2a, Ih2b and other header information Ih3 (not shown in FIG. 27B) are stored. .

  In the data part Dpj of the compressed packets Pj (2) and Pj (3), item-specific compression target information (item-specific non-compression information) corresponding to each compression target item in the transmission information (D2) and (D3). Ira, Irb, Irc, and Ird are compressed, and the item-specific compression information Ida, Idb, Idc, and Idd are stored. Here, the item-specific compression information Ida corresponding to the sequence number (SN) in the compressed packets Pj (2) and Pj (3) is 8-bit difference information “1” and “2”, respectively. The item-specific compression information Idb corresponding to the time stamp (ST) in the compressed packets Pj (2) and Pj (3) is 16-bit difference information “50” and “100”, respectively. The item-specific compression information Idc corresponding to the identifier (ID) of the IP packet in the compressed packets Pj (2) and Pj (3) is 8-bit difference information “1” and “2”, respectively. Each item of compression information Idd corresponding to the UDP port number (Port No.) in the compressed packets Pj (2) and Pj (3) is 0 bit.

  The header part Hpj of the compressed packets Pj (2) and Pj (3) includes a 1-bit compressed / uncompressed identifier Ih1, a 5-bit reference packet identifier (identification ID) Ih2b, and a 1-bit reference information update flag Ih5. And a 1-bit difference information presence flag Ih6 and other header information Ih3 (not shown in FIG. 27B).

  In FIGS. 26 and 27, as the data structure of the packet, the reference information type flag Ico2, the difference information length data Iun1, and the compression method type flag Iun2 are shown as being included in the difference information (ΔDn). However, these are generated when the reference source information is updated, that is, when an uncompressed packet Pi is created, or when a specific compressed packet (compressed packet in which the value of the reference information update flag Ih5 is “On”) Pj is created. At this time, it may be added to the header part Hpi, Hpj or the data part Dpi, Dpj.

  In this case, the reference information management unit 15e on the transmission side and the reference information management unit 25e on the reception side are configured to manage the difference information length data Iun1 and the compression method type flag Iun2 for each item of reference source information. On the receiving side, it is possible to perform a decompression process on the compressed packet based on the data Iun1 and the flag Iun2.

  This eliminates the need to include the difference information length data Iun1 and the compression method type flag Iun2 each time the compressed packet is transmitted in the item-specific difference information (ΔDn) in the compressed packet, and can further increase the compression efficiency.

  When the item-by-item reference source information as described above is updated, the reference information type flag Ico2, the difference information length data Iun1, and the compression method type flag Iun2 are added to the header portion or data portion of the uncompressed packet or the specific compressed packet. Although the compression method for transmission information is complicated and there are a plurality of methods, the method is particularly effective when the compression method changes at regular intervals, and the effect of increasing the compression efficiency is further increased. We can expect that.

In the fifth embodiment, the method of using an uncompressed packet, a specific compressed packet, and a normal compressed packet has been described as a data transmission process for transmitting information for each piece of transmission information corresponding to a packet. The transmission process may switch between the data transmission method described in the fifth embodiment and another data transmission method according to the packet transmission status.
Here, as the other data transmission method, the data transmission method of the first to fourth embodiments or the data transmission method using the conventional V. Jacobson header compression method (see FIG. 31) can be used.

  A data transmission method, a data transmission device, and a data reception device according to the present invention compress data and transmit the data in packet units, and determine the number of packets to be discarded on the receiving side due to occurrence of an error in a wireless section. This is extremely useful in that the transmission data quality can be improved in a transmission path including a wireless section.

FIG. 4 is a diagram for explaining a data transmission method according to the first embodiment of the present invention, and shows a data structure of an uncompressed packet used in the data transmission method. FIG. 4 is a diagram for explaining a data transmission method according to the first embodiment, and shows a data structure of a compressed packet used in the data transmission method. FIG. 2 is a block diagram for explaining a data transmission system using the data transmission method according to the first embodiment, and shows a data transmission device in the data transmission system. FIG. 2 is a block diagram for explaining a data transmission system using the data transmission method according to the first embodiment, and shows a data receiving device in the data transmission system. FIG. 4 is a diagram for explaining the data transmission method according to the first embodiment, showing a flow of a plurality of packets from a transmission side to a reception side in a normal transmission state. FIG. 4 is a diagram for explaining the data transmission method according to the first embodiment, showing a flow of a plurality of packets from a transmission side to a reception side when a transmission error occurs. FIG. 4 is a diagram showing a flow of a packet creation process in the data transmission device of the first embodiment. FIG. 9 is a diagram showing a flow of a packet restoration process in the data receiving device of the first embodiment. FIG. 9 is a diagram for explaining a data transmission method according to a first modification of the first embodiment of the present invention, and shows a data structure of an uncompressed packet used in the data transmission method. FIG. 9 is a diagram for explaining a data transmission method according to a first modification of the first embodiment, and shows a data structure of a compressed packet used in the data transmission method. FIG. 9 is a diagram for explaining a data transmission method according to Modification 1 of Embodiment 1 and shows a flow of a plurality of packets from a transmitting side to a receiving side in a normal transmission state. FIG. 9 is a diagram for explaining a data transmission method according to Modification 2 of Embodiment 1 of the present invention, and shows a data structure of an uncompressed packet used in the data transmission method. FIG. 9 is a diagram for explaining a data transmission method according to Modification 2 of Embodiment 1 and shows a data structure of a compressed packet used in the data transmission method. FIG. 13 is a diagram for explaining a data transmission method according to Modification 3 of Embodiment 1 of the present invention, and shows a data structure of an uncompressed packet used in the data transmission method. FIG. 9 is a diagram for explaining a data transmission method according to a third modification of the first embodiment, and shows a data structure of a compressed packet used in the data transmission method. FIG. 6 is a block diagram for explaining a data transmission system using a data transmission method according to a second embodiment of the present invention, and shows a data transmission device in the data transmission system. FIG. 9 is a diagram for explaining a data transmission method according to the second embodiment, and shows a flow of a plurality of packets from a transmission side to a reception side in a normal transmission state. FIG. 9 is a block diagram for explaining a data transmission system using a data transmission method according to a third embodiment of the present invention, and shows a data transmission device in the data transmission system. FIG. 13 is a block diagram for explaining a data transmission system using the data transmission method according to the third embodiment, and shows a data receiving device in the data transmission system. FIG. 13 is a block diagram for explaining a data transmission system using a data transmission method according to a fourth embodiment of the present invention, and shows a data transmission device in the data transmission system. FIG. 14 is a block diagram for explaining a data transmission system using the data transmission method according to the fourth embodiment, and shows a data receiving device in the data transmission system. FIG. 14 is a diagram for explaining a data transmission method according to a fifth embodiment of the present invention, and shows a data structure of an uncompressed packet used in the data transmission method. FIG. 15 is a diagram for explaining a data transmission method according to the fifth embodiment, and shows a data structure of a compressed packet used in the data transmission method. FIG. 14 is a block diagram for explaining a data transmission system using the data transmission method according to the fifth embodiment, and shows a data transmission device in the data transmission system. FIG. 14 is a block diagram for explaining a data transmission system using the data transmission method according to the fifth embodiment, and shows a data receiving device in the data transmission system. FIG. 18 is a diagram for explaining the data transmission method according to the fifth embodiment, and shows a flow of a plurality of packets from a transmission side to a reception side in a normal transmission state. FIG. 18 is a diagram for explaining the data transmission method according to the fifth embodiment, and shows a flow of a plurality of packets from a transmission side to a reception side when a transmission error occurs. FIG. 19 is a diagram illustrating a flow of a packet creation process in the data transmission device of the fifth embodiment. FIG. 21 is a diagram illustrating a flow of a packet restoration process in the data receiving device of the fifth embodiment. FIG. 21 is a diagram for explaining a data transmission method according to a modification of the fifth embodiment of the present invention, and shows a data structure of an uncompressed packet used in the data transmission method. FIG. 21 is a diagram for explaining a data transmission method according to a modification of the fifth embodiment, and shows a data structure of a compressed packet used in the data transmission method. FIG. 21 is a diagram for describing a data transmission method according to a modification of the fifth embodiment, and shows a process of compressing transmission information D (Y) to create a compressed packet Pj (Y). FIG. 21 is an enlarged view showing a part of a compressed packet Pj (Y) in a modification of the fifth embodiment. FIG. 21 is a diagram for describing transmission information (D) to be transmitted in a modification of the fifth embodiment. FIG. 21 is a diagram for describing specific information stored in an uncompressed packet Pi and a compressed packet Pj according to a modification of the fifth embodiment. It is a figure which shows the compression information Ida classified by item which is the difference information of the compression packet Pj in the modification of Embodiment 5 above. FIG. 1 is a diagram for explaining a data transmission system to which conventional V. Jacobson header compression is applied, and shows an overall configuration of the data transmission system. FIG. 10 is a diagram for explaining a data transmission system to which conventional V. Jacobson header compression is applied, and shows processing required for data transmission in the data transmission system. FIG. 4 is a diagram showing a data structure of an RTP packet Prtp used in the conventional data transmission system. FIG. 8 is a diagram showing a data structure of a UDP packet Pudp used in the conventional data transmission system. It is a figure showing the data structure of IP packet Pipa used in the above-mentioned conventional data transmission system. It is a figure showing the data structure of IP packet Pipb used in the above-mentioned conventional data transmission system. FIG. 8 is a diagram showing a data structure of a PPP packet Pppp used in the conventional data transmission system. It is a figure showing the data structure of the PPP packet used in the data transmission system to which the conventional V. Jacobson header compression is applied, and shows an uncompressed packet. It is a figure which shows the data structure of the PPP packet used in the data transmission system to which the conventional V.Jacobson header compression is applied, and shows a compressed packet. FIG. 10 is a diagram conceptually illustrating a conventional PPP packet transmission process using the V. Jacobson header compression method. FIG. 11 is a diagram for explaining a case where a transmission error occurs in transmission processing of a PPP packet using a conventional V. Jacobson header compression method. FIG. 1 is a diagram for explaining a data transmission system having a wireless transmission section to which conventional V. Jacobson header compression is applied, and shows an overall configuration of the data transmission system. FIG. 10 is a diagram for explaining a data transmission system having a wireless transmission section to which conventional V. Jacobson header compression is applied, and shows processing required for data transmission in the data transmission system.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 11 Receiving means 12 Compressed / uncompressed packet creating means 13 Compressed / uncompressed sending determining means 14 Error occurrence receiving means 15 Reference information managing means 16 Packet transmitting means 17 Reference information updating determining means 21 Packet receiving means 22 Error packet detecting means 23 Packet restoration means 24 Error occurrence notification transmission means 25 Reference information management means 26 Output means 31 Uncompressed packet transmission count monitoring means 32 Error correction code addition means 41 Error correction means 42 Restoration waiting information storage means 101, 102, 103, 104, 105 Data transmitting device 201, 203, 204, 205 Data receiving device Cm1 Transmission-side management control signal Cm2 Reception-side management control signal Dcp Compressed data Dpa, Dpaa, Dpb, Dpbb, Dpc, Dpd, Dpe, Dpf, Dpg, Dph, Dpi Data Parts Hpa, Hpaa, Hpb, pbb, Hpc, Hpd, Hpe, Hpf, Hpg, Hph, Hpj header Ico1 subsequent difference information whether the flag Ico2 reference information type flag Id compression information (difference information ([Delta] D))
Ida, Idb, Idc, Idd Item-specific compression information Id1 First compression information (difference information (Δ1D))
Id2 Second compression information (difference information (Δ2D))
Ih1 Compressed / uncompressed identifier Ih2a Packet identifier (ID)
Ih2b First reference packet identifier (ID1)
Ih2b1 Second reference packet identifier (ID2)
Ih2b2 reference packet identifier (ID)
Ih3 Other header information Ih4 Difference additional information Ih5 Reference information update flag Ih6 Difference information presence / absence flag Im1 Transmitter reference information Im2 Received term reference information Inc Non-compression target information Ir Uncompressed information (Transmission information (D))
Ira, Irb, Irc, Ird Compression target information by item Irs restoration information (transmission information (D))
Iun1 Difference information length data Iun2 Compression method type flag Jp Packet discrimination signal Jr Reference information update signal K1 to K4 First to fourth compression target items Ne Decompression error notification signal Nr Retransmission request notification signal Pa, Pa (1), Paa ( 1), Pc, Pe, Pg, Pg (1), Pi, Pi (1) Uncompressed packet Pac ECC added uncompressed packet Pb, Pb (2) to Pb (4), Pbb (2) to Pbb (4) , Pd, Pf, Ph, Ph (2) to Ph (11), Pj, Pj (Y), Pj (2), Pj (3) Compressed packet Pno Normal packet Pre Restoration error packet Rp Received packet S1, S2 First , Second transmission signal S3 output signal Sc re-creation command signal Se error occurrence signal Sn error notification reception signal Sr retransmission request reception signal Src reception signal

Claims (14)

A data transmission method for sequentially transmitting information from a transmission side to a reception side for each transmission information corresponding to a packet,
A non-compressed packet in which predetermined transmission information is stored as non-compressed information is transmitted at a fixed period, and a transmission packet subsequent to the predetermined transmission information is compressed as at least a part of the transmission information and stored as compressed information. Including a transmitting side process for continuously transmitting
The transmission-side process includes a compression process of creating compression information to be stored in a compressed packet to be transmitted based on transmission information corresponding to the uncompressed packet and transmission information corresponding to the compressed packet. A data transmission method, comprising: The data transmission method according to claim 1,
The data transmission method according to claim 1, wherein the transmitting side process transmits the uncompressed packet storing the same transmission information to the receiving side continuously plural times. The data transmission method according to claim 1,
Further, the transmitting side process, when there is a decompression error of the uncompressed packet, receives a notification indicating the occurrence of a decompression error from the receiving side,
A data transmission method, comprising transmitting an uncompressed packet based on the notification. A data transmission method for sequentially transmitting information from a transmission side to a reception side for each transmission information corresponding to a packet,
An uncompressed packet in which predetermined transmission information is stored as uncompressed information is received at a fixed period, and a transmission packet following the predetermined transmission information is compressed as at least a part of the transmission information and stored as compression information. Including receiving side processing for continuously receiving
The receiving side processing includes a decompression process for decompressing transmission information corresponding to a compressed packet to be decompressed based on transmission information corresponding to an uncompressed packet and compression information included in the compressed packet to be decompressed. A data transmission method comprising: The data transmission method according to claim 4,
The data transmission method according to claim 1, wherein the receiving side process receives the uncompressed packet storing the same transmission information continuously plural times. The data transmission method according to claim 4,
Further, in the data transmission method, the receiving-side process discards only an error packet when a restoration error occurs. The data transmission method according to claim 4,
Further, when there is a decompression error of the uncompressed packet, the reception side process transmits a notification indicating the occurrence of the decompression error to the transmission side,
A data transmission method comprising: receiving an uncompressed packet transmitted from the transmission side based on the notification. A data transmission device for sequentially transmitting information from a transmission side to a reception side for each transmission information corresponding to a packet,
The data transmission device transmits an uncompressed packet in which predetermined transmission information is stored as uncompressed information at a fixed period, and at least a part of the transmission information following the predetermined transmission information is compressed as compressed information. While continuously transmitting the stored compressed packets,
Data for performing compression processing for creating compressed information to be stored in a compressed packet to be transmitted based on transmission information corresponding to the uncompressed packet and transmission information corresponding to the compressed packet. Transmission equipment. The data transmission device according to claim 8,
The data transmission device transmits the uncompressed packet storing the same transmission information to the receiving side continuously plural times. The data transmission device according to claim 8,
Further, in the data transmission device, when there is a decompression error of the uncompressed packet, a notification indicating the occurrence of a decompression error is received from the receiving side,
A data transmission device for transmitting an uncompressed packet based on the notification. A data receiving device for receiving information transmitted in packet units from a transmitting side,
The data receiving apparatus receives an uncompressed packet in which predetermined transmission information is stored as non-compressed information at a fixed period, and at least a part of the transmission information following the predetermined transmission information is compressed as compressed information. While continuously receiving the stored compressed packets,
A data receiving apparatus for restoring transmission information corresponding to a compressed packet to be decompressed based on transmission information corresponding to an uncompressed packet and compression information included in the compressed packet to be decompressed. The data receiving device according to claim 11,
The data receiving device according to claim 1, wherein the receiving side process continuously receives the uncompressed packet storing the same transmission information a plurality of times. The data receiving device according to claim 11,
Further, the data receiving device discards only the error packet when a restoration error occurs. The data receiving device according to claim 11,
When there is a decompression error of the uncompressed packet, a notification indicating the occurrence of the decompression error is transmitted to the transmitting side,
A data receiving apparatus which receives an uncompressed packet transmitted from the transmitting side based on the notification.

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