JP4814809B2 - Data transmission apparatus and program thereof - Google Patents

Description

The present invention relates to a data transmission equipment for transmitting a digital signal.

In recent years, various transmission methods have been standardized as methods for transmitting digital signals. For example, in satellite digital broadcasting, ISDB-S (Integrated Services Digital Broadcasting-Satellite; see Non-Patent Document 1) developed in Japan and DVB-S (Digital Video Broadcasting-Satellite; Non-Patent Document) developed in Europe. 2).
These ISDB-S and DVB-S are systems suitable for transmission of MPEG-2 (Moving Picture Experts Group-2) transport stream (hereinafter referred to as TS), which is encoded data obtained by encoding video and audio. It is.

Recently, with the diversification of broadcasting, it is necessary to transmit other digital signals such as IP (Internet Protocol) packets as broadcast waves in addition to MPEG-2TS.
In this case, in ISDB-S and DVB-S, an IP packet or the like is transmitted as MPEG-2TS data. That is, in ISDB-S and DVB-S, IP is positioned as an upper layer of MPEG-2TS, and IP packets are transmitted as MPEG-2TS data.

  In particular, in Japanese BS digital broadcasting, which uses ISDB-S, radio waves in the 12 GHz band are attenuated by rain and are likely to become unreceivable. Transmit (hereinafter referred to as “higher layer”), and simultaneously transmit low-quality images in a time-division manner (hereinafter referred to as “lower layer”) using a modulation scheme that is low in efficiency but resistant to rain attenuation. Judging from this, a technique called hierarchical modulation is used in which a high layer is received when the reception state is good and a low layer is received when the reception state is bad and the high layer cannot be received.

  In this broadcasting, high-quality video and low-quality video are multiplexed in different PID packets within the same TS, and each modulation scheme is high in efficiency but weak in rain attenuation, and low in efficiency but strong in rain attenuation. This is realized by transmitting in a system. In addition, in a state where high layer reception is not possible, bit errors often occur at the same time in PID values of packets transmitted in the high layer, and if such a packet is left unattended, a bit error occurs. In some cases, the PID of a low-layer packet that can be normally received matches with the probability. As a result, the higher layer error packet interferes with lower layer reception. In order to avoid this, the receiver side needs to invalidate the packet when the higher layer becomes unreceivable.

The BS digital broadcast receiver applies an RS (Reed-Solomon) code to each MPEG-TS, and performs a process of invalidating this packet when RS decoding fails (see Patent Document 1).
ISDB-S: ARIB (Association of Radio Industries and Businesses) STD-B20, “Transmission System for Satellite Digital Broadcasting”, May 31, 2001, version 3.0 DVB-S: ETSI (European Telecommunications Standards Institute) EN 300 421, “Digital broadcasting systems for television, sound and data services; Framing structure, channel coding and modulation for 11/12 GHz satellite services”, 1997 August, V1.1.2 Japanese Patent No. 2912323

However, in the above-mentioned ISDB-S and DVB-S, when transmitting a digital signal such as an IP packet, it is necessary to encapsulate and transmit the MPEG-2TS even if the signal is not related to the MPEG-2TS protocol. There is. In this case, a variable-length packet such as an IP packet has a data structure independent of the slot for transmitting MPEG-2 TS.
For this reason, the above-mentioned ISDB-S or the like is separate from MPEG-2TS in order to specify the range of packets in which transmission errors have occurred, for example, when invalidating packets in which transmission errors have occurred in data transmission. It is necessary to manage the beginning of the packet and the data length, which is difficult to implement.

The present invention has been made to solve the above-described problems. When transmitting digital signals, not only MPEG-2TS transmission but also other data structures such as IP packets are mixed. even the case of transmitting the data structure to easily identify when a transmission error occurs, it possible to disable exact error packet, the data transmission apparatus and a program performing the possible data transmission hierarchical modulation The purpose is to provide.

  The present invention was devised to achieve the above object. First, the data transmission device according to claim 1 is configured such that continuous transmission data of a data structure is independent of the structure of the data structure. A data transmitting apparatus for transmitting a transmission frame having one or a plurality of data areas and a control area to which control information for the data area is added as a frame structure, the data structure arrangement means, and an error detection code addition Means, pointer information generating means, and framing means.

In such a configuration, the data transmitting apparatus arranges the data structure of the transmission data for each data area by the data structure arranging unit. Here, the data structure means data having a specific data structure such as a TS packet or an IP packet, and the data length may be a fixed length or a variable length. As a result, the transmission data is divided according to the length of the data area.
Then, the data transmission apparatus adds an error detection code to each data area arranged by the data structure arrangement unit by the error detection code addition unit. As a result, a transmission error can be detected for each data area on the receiving apparatus side. The error detection code may be a code for simply detecting an error or a code capable of error correction.

Further, the data transmission device uses the pointer information generation means to specify the start pointer information for specifying the start position of the first data structure arranged from the start data of the data structure in the data area in which the data structure is arranged, and the data End pointer information for specifying the end position of the last data structure arranged up to the end data of the structure is generated.
Then, the data transmission apparatus configures the control area and the data area as a predetermined frame structure by the framing means, and adds the start pointer information and the end pointer information to the control area to add the transmission frame. Generate.
As a result, the position of the data structure on the transmission frame is specified by the pointer information added to the control area.

  The data transmission device according to claim 2 is the data transmission device according to claim 1, wherein when the framing means configures the control region and the data region, the control region It is characterized in that it is framed into an area where modulation is performed using a modulation method having a higher transmission error tolerance than the data area.

  In such a configuration, the data transmitting apparatus frames the control area and the data area into areas modulated by different modulation schemes by the framing means. At this time, the control area is framed into an area having a modulation scheme having a higher transmission error tolerance than the data area, so that the information for synchronizing the data structure is more strongly protected.

  Furthermore, the data transmission device according to claim 3 is the data transmission device according to claim 1 or 2, wherein the pointer information generation unit is arranged in the data area from the top data of the data structure. When the data structure does not exist, the head pointer information is generated as a value that is larger than the maximum position indicating the inside of the data area or smaller than the minimum position, and is arranged up to the end data of the data structure in the data area. When the data structure does not exist, the tail pointer information is generated as a value larger than the maximum position indicating the inside of the data area or smaller than the minimum position.

  In such a configuration, the data transmitting apparatus can be used for a data structure or a data structure arranged from the first data of the data structure in one data area when the length of the data structure is longer than the length of the data area. When there is no data structure arranged up to the end data, each pointer information uses a value indicating a position larger than the maximum position pointing in the data area or smaller than the minimum position. This makes it possible to determine the validity of each piece of pointer information on the receiving side.

  The data transmitting apparatus according to claim 4 is the data transmitting apparatus according to any one of claims 1 to 3, wherein the framing means synchronizes the data structure between transmission and reception. A predetermined synchronization pattern is added to the control area.

  In such a configuration, when a transmission error occurs in the data structure by adding a synchronization pattern that is a reference for synchronizing the data structure in advance to the control area, the data transmitting apparatus, on the receiving apparatus side, By writing this synchronization pattern in the data structure, at least synchronization of the data structure can be ensured.

  Furthermore, the data transmission program according to claim 5 adds continuous transmission data of the data structure, one or a plurality of data areas independent of the structure of the data structure, and control information for the data area. In order to transmit a transmission frame having a control area as a frame structure, the computer of the data transmission device is configured to function as a data structure arrangement unit, an error detection code addition unit, a pointer information generation unit, and a framing unit. .

In such a configuration, the data transmission program arranges the data structure of the transmission data for each data area by the data structure arrangement unit. Then, the data transmission program adds an error detection code to each data area arranged by the data structure arrangement unit by the error detection code addition unit.
Further, the data transmission program uses the pointer information generating means to specify the top pointer information for specifying the top position of the first data structure arranged from the top data of the data structure in the data area in which the data structure is arranged, and the data End pointer information for specifying the end position of the last data structure arranged up to the end data of the structure is generated.
Then, the data transmission program configures the control area and the data area as a predetermined frame structure by the framing means, and adds the start pointer information and the end pointer information to the control area to add the transmission frame. Generate.

The present invention has the following excellent effects.
According to the first to fifth aspects of the present invention, even when the data area of the frame structure and the data structure arranged in the data area have independent data structures, the head pointer information and the tail The arrangement of the data structure can be specified by the pointer information. Thereby, the arrangement of the data structure can be easily recognized without being aware of the data length of the data structure on the receiving side.

According to the second aspect of the present invention, the control information such as the position of the data structure can be protected with higher strength, and the strength of the control information can be improved against noise on the transmission path.
According to the third aspect of the present invention, even if the data area contains no head data or tail data, the data area contains the head data or tail data of the data structure. The fact that it is not included can be expressed by pointer information. As a result, as pointer information, information indicating the position of the pointer and information indicating that the head data and tail data of the data structure are not included can be expressed in the same area, and transmission efficiency can be improved. it can.

  Furthermore, according to the invention described in claim 4, even when data of a different data structure is transmitted by adding a synchronization pattern of the data structure to the control area on the transmission side, processing is performed on the reception side. There is no need to make any changes. For this reason, according to the present invention, it is possible to construct a highly flexible system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Transmission frame structure]
First, the structure of a transmission frame of a transmission signal transmitted from a data transmission apparatus according to an embodiment of the present invention to a transmission path will be described with reference to FIG. FIG. 1 is an explanatory diagram for explaining the structure of a transmission frame of a transmission signal transmitted by a data transmission apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the transmission frame includes a plurality of slots (slots # 1 to #Nx) indicating a data area and error correction codes (error correction inner / outer codes) of the data area. It includes a transmission control signal (TMCC: Transmission add Multiplexing Configuration Control) indicating control information such as the number of slots in the data area and modulation scheme.

  Data structures (packets) are sequentially arranged in the data area. At this time, since the length of the data structure generally has no special relationship with the length of the data area, the data structure is not necessarily arranged from the head of the slot.

Therefore, in the data transmitting apparatus according to the embodiment of the present invention, in the slot, a head pointer (head pointer information) for specifying the head position of the first packet arranged from the head data of the packet (data structure), and the slot The end pointer (end pointer information) for specifying the end position of the last packet arranged up to the end data of the packet is managed as pointer information. Here, the first packet does not include a packet continued from the previous frame, and the last packet does not include a packet continued in the subsequent frame.
The general case of a fixed-length packet (data structure) is indicated by * 1 in FIG.

  * 2 in FIG. 1 is a diagram showing a case where the data structure is a TS packet (188 bytes) and the data area is an integer multiple of the TS packet (188 × n bytes) as a special case of the fixed-length packet. . The data structure (TS packet) is arranged from the head of each data area (slot). That is, by setting the slot length to an integer multiple of the data length of the fixed data structure, the data structure can be always arranged from the beginning of the slot.

  * 3 in FIG. 1 is a variable length packet. When the data structure has a variable length, the data structure cannot always be arranged from the beginning of the slot.

In FIG. 1, an error detecting code (EDC) is added to each data area (slot). It is detected by this error detection code that an error is included in the data area.
Hereinafter, a data transmitting apparatus that transmits digital signal transmission data in units of transmission frames and a data receiving apparatus that receives the transmission frames will be described.

[Configuration of data transmission device]
First, the configuration of the data transmission apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the data transmission apparatus according to the embodiment of the present invention.

  The data transmitting apparatus 1 transmits a plurality of transmission data (packet signals) in which packets (data structures) are continuous as transmission frames (digital modulation signals) having a frame structure. Here, the data transmission apparatus 1 includes a packet arrangement unit 10, a pointer information generation unit 11, an error detection code addition unit 12, a framing unit 13, and a modulation unit 14.

The packet arrangement means (data structure arrangement means) 10 arranges input transmission data (packet signal) in a slot (data area). For example, the packet placement unit 10 writes one or more consecutive packets in a predetermined slot length unit in a storage unit such as a memory (not shown). The slot in which the packet is arranged by the packet arrangement unit 10 is referred to by the error detection code addition unit 12.
The packet placement unit 10 outputs the placement position (address) for each packet placed in the slot to the pointer information generation unit 11 as a placement result.

  Here, it is assumed that the packet placement unit 10 individually inputs a plurality of transmission data (packet signals), multiplexes a plurality of slots in which the respective transmission data are arranged, and outputs the multiplexed data to the error detection code addition unit 12. The multiplexed transmission data may be the same type of data, or may be different types of data (TS packet, IP packet, etc.). Further, the packet arrangement means 10 may arrange only one type of transmission data in the slot without multiplexing.

  Based on the result of arrangement of the packet arranged by the packet arrangement unit 10, the pointer information generation unit 11 pointer information indicating the position of the first data of the first packet among the packets arranged from the beginning of the packet in the slot (first pointer) Information) and pointer information (end pointer information) indicating the position of the end data of the last packet among the packets arranged up to the end of the packet in the slot.

  Here, when there is a packet arranged from the leading data of the packet in the slot, the pointer information generating unit 11 sets a pointer that specifies the position (leading position) of the leading data of the first packet of the packet as the leading pointer. Generate as information. Further, when there is a packet arranged up to the end data of the packet in the slot, the pointer information generation unit 11 uses the end pointer information as a pointer for specifying the position (end position) of the end data of the last packet among the packets. Generate as Note that these pointer information need not strictly indicate the position of the head data or the tail data. For example, the pointer that specifies the position of the end data may indicate the position of the last byte of the packet, or may indicate “last byte + 1”.

In addition, when there is no packet arranged from the head data of the packet in the slot, a value that does not exist as a pointer indicating the position in the slot (a value that is larger than the maximum position indicating the inside of the slot or smaller than the minimum position) starts. It is used as pointer information.
In addition, when there is no packet arranged up to the end of the packet in the slot, a value that does not exist as a pointer indicating the position in the slot (a value greater than the maximum position or smaller than the minimum position indicating in the slot) ends. It is used as pointer information.
For example, when the slot length is 4862 bytes and 2 bytes are used to represent the pointer, the leading pointer information is “0” to “4861”, and the trailing pointer information is “1” to “4862”. Therefore, the value of each pointer is set to “65535” (0xFFFF) as a value that does not exist as a pointer indicating the position in the slot.

  Here, the maximum value that can be expressed in 2 bytes is used as a value that does not exist as a pointer. However, this value does not have to be the maximum value, and any value that does not exist as a pointer indicating the position in the slot can be used. Any value is acceptable. For example, “4863” may be used. In addition, as a value that does not exist as a pointer, different values may be used for the head pointer information and the tail pointer information, and it is not necessary to fix the value to a constant value. The head pointer information and tail pointer information generated in this way are output to the framing means 13.

Here, with reference to FIG. 6 (refer to FIG. 2 as appropriate), the pointer information generated by the pointer information generation unit 11 will be specifically described. FIG. 6 is a schematic diagram illustrating an arrangement example of slots and packets for explaining the pointer information. 6 shows (a) shows a state in which the packet P ₁ is placed in the slot #N. (B) shows a state in which the packet _{P 2} is disposed to extend over a slot #N and slot # (N + 1). (C) shows a state in which the packet _{P 3} is disposed across the slot # a (N-1) and the slot #N. (D) shows a state in which the packet P ₄ is arranged across the slot # (N−1) to the slot # (N + 1). Further, here, the description will be made with reference to the pointer information in the slot #N.

As shown in FIG. 6A, when the packet (here P ₁ ) is arranged in one slot #N, the pointer information generating means 11 uses the head pointer information as the head data of the packet P ₁ . the value of the head pointer to the location, the tail pointer information, the value of the tail pointer indicating the position of the last data packet P _1.
Note that, here, an example is shown in which one packet is arranged in the slot, but when a plurality of packets are arranged in the slot, the position of the first data of the first packet in which the first data of the packet exists Is a head pointer, and a pointer indicating the position of the tail data of the last packet in which the tail data of the packet exists is a tail pointer.

Also, as shown in FIG. 6B, when the packet (here P ₂ ) is arranged across the slot #N and the slot # (N + 1), the tail data of the packet P ₂ is the slot #N. Will not exist. In this case, the pointer information generating means 11, showing the head pointer information, the value of the head pointer to the location of the head data of the packet P _2, the tail pointer information, the position of the last data of the previous packet of the packet P ₂ The value of the tail pointer.

Also, as shown in FIG. 6C, when the packet (here P ₃ ) is arranged across the slot # (N−1) and the slot #N, the leading data of the packet P ₃ is the slot It will not exist in #N. In this case, the pointer information generating means 11 uses the head pointer information as the value of the head pointer indicating the position of the head data of the packet next to the packet P ₃ , and uses the tail pointer information as the position of the tail data of the packet P _3. The value of the tail pointer.

Further, as shown in FIG. 6 (d), when the packet (here, P ₄ ) is arranged from slot # (N−1) to slot # (N + 1), the leading data and the end of packet P ₄ Data does not exist in slot #N. In this case, the pointer information generation unit 11 sets both the start pointer information and the end pointer information as values that do not exist as pointers indicating positions in the slots.
Returning to FIG. 2, the description of the configuration of the data transmission device 1 will be continued.

The error detection code adding means 12 adds a predetermined error detection code for each slot. This makes it possible to detect an error in the data area on the receiving side.
Here, the error detection code adding means 12 performs convolutional code, BCH (Bose Chaudhuri Hocquengham) code, RS (Reed Solomon) code, LDPC (Low-Density Parity Check) code, CRC (Cyclic Redundancy) on the data for each slot. An error detection code such as a (Check) code is added and output to the framing means 13. Note that the error detection code referred to here includes an error correction / detection code having error correction capability.

The framing means 13 constitutes a slot and a TMCC (control area) to which control information for the slot is added as a predetermined frame structure.
Here, the framing unit 13 includes a slot configuration unit 13a, a pointer information addition unit 13b, and a synchronization pattern addition unit 13c.

  The slot configuration unit 13a configures the slot to which the error detection code is added by the error detection code addition unit into a predetermined transmission frame structure. The slot configuration means 13a configures a transmission frame in units of frames, but when slots are multiplexed, configures a plurality of slots into one frame (see FIG. 1).

  The pointer information adding unit 13b adds the pointer information (start pointer information and end pointer information) generated by the pointer information generation unit 11 to the TMCC area of the transmission frame.

The synchronization pattern adding means 13c adds a synchronization pattern, which is a signal sequence for synchronizing packets transmitted every predetermined slot, to the TMCC area of the transmission frame.
In addition to the pointer information and the synchronization pattern, the framing means 13 adds control information for transmission control such as the data type (TS packet, IP packet, etc.) for each slot to the TMCC, and configures a transmission frame. To do.

Here, a configuration example of TMCC will be described with reference to FIG. FIG. 7 is a configuration diagram illustrating a configuration example of TMCC. Here, only the configuration added to realize the present invention with respect to the conventional TMCC will be described, and the description of the conventional configuration will be omitted.
As shown in FIG. 7, in the present invention, “slot / data type information”, “synchronization pattern byte length”, “synchronization pattern”, and “pointer information” are added to constitute a TMCC.

  “Slot / data type information” indicates the type of data arranged in the slot (data area). The data type is information for identifying, for example, a TS packet, an IP packet, and other packets.

The “synchronization pattern byte length” is information indicating the length of the synchronization pattern of the packet arranged in the slot in byte length.
The “synchronization pattern” is a signal sequence serving as a reference when performing packet synchronization. This synchronization pattern is a pattern specific to the packet to be transmitted. Note that the method of using this synchronization pattern will be described in the description of the data receiving apparatus described later.

  “Pointer information” is the value of the pointer from the start position of the slot to the start position of the first packet placed from the start data of the packet and the end position of the last packet placed up to the end data of the packet. Information indicating the value of the pointer (head pointer information and tail pointer information).

  Here, with reference to FIG. 8 (refer to FIG. 2 as appropriate), a TMCC setting example using pointer information as an example will be described. FIG. 8 is an explanatory diagram for explaining an example of setting of TMCC pointer information in a certain slot. FIG. 8 shows an example of TMCC setting for slot #N when the packet placement unit 10 places a packet in the slot as described in FIG.

As shown in FIG. 8A, when there is a head pointer and a tail pointer in slot #N, the pointer information adding unit 13b of the framing unit 13 sets the value A of the head pointer in the head pointer information of TMCC. Then, the value B of the end pointer is set in the end pointer information of TMCC.
Further, as shown in FIG. 8 (b), if the tail pointer of the previous packet of the head pointer and P ₂ of the packet P ₂ in the slot #N exists, the pointer information appending unit 13b is the head pointer information of the TMCC Is set to the head pointer value D, and the tail pointer value C is set to the TMCC tail pointer information.

Further, as shown in FIG. 8 (c), if the head pointer of the next packet of the tail pointer and P ₃ of the packet P ₃ in the slot #N exists, the pointer information appending unit 13b is the head pointer information of the TMCC Is set to the head pointer value F, and the tail pointer value E is set to the TMCC tail pointer information.
Further, as shown in FIG. 8D, when the head pointer and the tail pointer do not exist in the slot #N, the pointer information adding unit 13b sets “0xFFFF” in both the head pointer information and the tail pointer information of TMCC. To do.
Thus, the position of the head data of the first packet where the head data of the packet in the slot exists and the position of the tail data of the last packet where the tail data of the packet exists are specified by the pointer information. .
Returning to FIG. 2, the description of the configuration of the data transmission device 1 will be continued.

The modulation means 14 generates a digital modulation signal by modulating the transmission frame framed by the framing means 13 by a predetermined modulation method.
Here, the modulation means 14 modulates the TMCC and the slot by the designated modulation method. For modulation of TMCC, it is desirable to use a modulation scheme having higher transmission error resistance than slot modulation because of the importance of the contents. For example, the modulation unit 14 modulates BPSK for TMCC and 8PSK for slots.

  By configuring the data transmission device 1 in this way, the data transmission device 1 can transmit a plurality of transmission data in which data structures such as TS packets and IP packets are continuous as a digital modulation signal having a frame structure. it can.

  Here, the data transmission device 1 is configured to include the modulation unit 14, but the modulation unit 14 may be provided externally as a modulation device. In this case, the transmission frame is output from the framing means 13 to the modulation device.

  The data transmitting apparatus 1 can be configured by a general computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. (not shown). It can be operated by a data transmission program that functions as each means.

[Operation of data transmitter]
Next, the operation of the data transmission apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a flowchart showing the operation of the data transmission apparatus according to the embodiment of the present invention.

First, the data transmission apparatus 1 arranges the input transmission data for each slot (data area) by the packet arrangement unit 10 (step S11). Note that, when there are a plurality of transmission data, the packet placement unit 10 places each of them in the data area in parallel.
Then, the data transmission device 1 uses the pointer information generation unit 11 to indicate the head position of the first packet placed from the head data of the packet in the slot based on the placement result of the packet placed in step S11. Information (start pointer information) and pointer information (end pointer information) indicating the end position of the last packet arranged up to the end data of the packet are generated (step S12).

  At this time, when there is no packet arranged from the leading data of the packet in the slot, the pointer information generating means 11 has a value that does not exist as a pointer indicating the position in the slot (for example, “0xFFFF”). ”). When there is no packet arranged up to the end data of the packet in the slot, a value that does not exist as a pointer indicating the position in the slot (for example, “0xFFFF”) is set in the end pointer information.

Then, the data transmitting apparatus 1 adds a predetermined error detection code to each slot in which the packet is arranged in step S11 by the error detection code adding means 12 (step S13).
Then, the data transmitting apparatus 1 uses the slot composing means 13a of the framing means 13 to convert the slot to which the error detection code is added in step S13 and the TMCC to which control information for the slot is added into a predetermined transmission frame. As a structure, a transmission frame is generated (step S14).

Further, the data transmitting apparatus 1 arranges (adds) the pointer information (start pointer information and end pointer information) generated in step S12 in the TMCC by the pointer information adding means 13b of the framing means 13, and the synchronization pattern adding means 13c. Thus, a synchronization pattern for synchronizing packets is arranged (added) to the TMCC (step S15).
Then, the data transmitting apparatus 1 modulates the TMCC and the slot with different modulation schemes by the modulation unit 14 to generate a digital modulation signal (step S16).

  With the above operation, the data transmission device 1 generates a transmission frame that specifies the positions of the beginning and end of the packet arranged in the slot even when the data structure of the packet is independent of the data structure of the slot. Can be sent. As a result, the receiving side can easily specify the arrangement of the packets.

[Data receiver configuration]
Next, the configuration of the data receiving apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the data receiving apparatus according to the embodiment of the present invention.

  The data receiving apparatus 2 receives a digital modulation signal (transmission frame) having a frame structure transmitted from the data transmitting apparatus 1 described with reference to FIG. 2 and extracts transmission data. Here, the data receiving apparatus 2 includes a demodulating unit 20, a frame decoding unit 21, an error detecting unit 22, a data invalidating unit 23, and a packet extracting unit 24.

  The demodulating means 20 demodulates the input digital modulation signal. The demodulating means 20 performs demodulation using the same modulation method as the modulation performed in the modulating means 14 of the data transmitting apparatus 1. For example, when TMCC is modulated by BPSK and a slot is modulated by 8PSK, the demodulating means 20 demodulates TMCC by BPSK and slot by 8PSK, respectively. The demodulated digital modulation signal (demodulation signal) is output to the frame decoding means 21.

The frame decoding means 21 detects a frame synchronization signal from the demodulated signal demodulated by the demodulation means 20, and decodes the transmission frame. The decoded transmission frame has the frame structure described with reference to FIG.
Here, the frame decoding means 21 includes a slot extracting means 21a, a pointer information extracting means 21b, and a synchronization pattern extracting means 21c.

  The slot extracting means (data area extracting means) 21a extracts data for each slot from the transmission frame (demodulated signal) demodulated by the demodulating means 20. The slot data extracted by the slot extraction means 21 a is output to the error detection means 22.

  The pointer information extracting unit 21b extracts pointer information (first pointer information and last pointer information) from the TMCC of the demodulated signal. The pointer information extracted by the pointer information extraction unit 21 b is output to the data invalidation unit 23 and the packet extraction unit 24.

  The synchronization pattern extraction means 21c extracts a synchronization pattern from the TMCC of the demodulated signal. The synchronization pattern extracted by the synchronization pattern extraction unit 21c is output to the data invalidation unit 23.

The error detection means 22 detects a slot error based on an error detection code added to the slot. For example, the error detection means 22 detects slot errors using a convolutional code, BCH (Bose Chaudhuri Hocquengham) code, RS (Reed Solomon) code, LDPC (Low-Density Parity Check) code, CRC (Cyclic Redundancy Check) code, and the like. Do. When an error is detected by the error detection code, the error detection means 22 determines that a transmission error has occurred in the slot. The error detection means 22 may be an error correction / detection code having an error correction function. In that case, an error correctable by the error correction / detection code is corrected. If the error cannot be corrected by the error correction / detection code, the error detection means 22 determines that a transmission error has occurred in the slot.
Then, the error detection means 22 outputs the slot data to the data invalidation means 23 together with a detection result indicating whether or not an error has been detected.

  When an error is detected by the error detection unit 22, the data invalidation unit 23 is configured to display the end position indicated by the latest end pointer information transmitted before the slot in which the error is detected, and the slot. Data between the head position indicated by the most recent head pointer information transmitted later is invalidated as a packet having an error. Note that the invalidation of a packet here means that a higher-level application using the received packet can recognize that the packet is a meaningless data string.

For example, the data invalidation means 23 invalidates the packet by performing the settings shown in the following (1) to (3) on the packet.
(1) If a packet error can be indicated by a standard or the like, it is used. For example, when the packet is an MPEG-2TS packet, the value of the transport error indicator is set to “1”.
(2) If an invalid packet is defined by a standard or the like, it is used. For example, when the packet is an MPEG-2 TS packet, the PID (packet identifier) is replaced with “0x1FFF” (indicating a null packet).
(3) Replace with null data. For example, all values are set to “1” or “0”.

  The data invalidation means 23 overwrites the synchronization pattern from the beginning of the packet when invalidating the packet according to (1) to (3). This synchronization pattern is information added to the TMCC (see FIG. 7). Thus, when invalidating a packet, by overwriting the synchronization pattern added to the TMCC, the correct synchronization pattern is set even if an error is detected in the slot. Packet synchronization can be performed reliably.

  Here, with reference to FIG. 9 (refer to FIG. 4 as appropriate), the range of packets to be invalidated by the data invalidation means 23 will be described. FIG. 9 is an explanatory diagram for explaining a range in which a packet is invalidated. FIG. 9 shows an example in which a packet is arranged in each slot as described in FIG. Further, here, slot #N indicates a slot in which an error is detected (error detection slot) or a slot in which an error cannot be corrected (error correction impossible slot).

As shown in FIG. 9, when an error is detected in the slot #N, the data invalidation means 23 starts from the data immediately after the end pointer of the slot # (N−1) which is the previous slot. The data just before the head pointer of a certain slot # (N + 1) is invalidated.
Thereby, for example, the case of FIG. 9 (a), the slot # (N-1) and the packet across the slot #N, the packet _{P 1} in the slot #N, Slot #N and slot # (N + 1) And the packet straddling both are invalidated. In addition, in the case of FIG. 9 (b), the packet was astride the slot #N, Slot #N and slot # (N + 1) and packet _{P 2} that across the is invalidated and slot # (N-1) . In addition, in the case of FIG. 9 (c), the slot # (N-1) and the packet _{P 3} which astride the slot #N, is invalidated and the packet across the slot #N and slot # (N + 1) . Further, in the case of FIG. 9D, the packet P ₄ extending from slot # (N−1) to slot # (N + 1) is invalidated.

Here, when there is no tail pointer in the previous slot (when the tail pointer information is “0xFFFF”), the data invalidating means 23 sequentially searches the slots in which the tail pointer is present in the forward direction. The data immediately after the last pointer is the beginning of the invalidation range. If there is no head pointer in the subsequent slot (when the head pointer information is “0xFFFF”), the data invalidation means 23 sequentially searches the slot in which the head pointer exists in the backward direction. The data immediately before the start pointer is the end of the invalidation range. Note that the data invalidation means 23 stores data and pointer information for each slot in a storage means (not shown) for a predetermined search range in order to search for pointer information. This search range is, for example, 10 slots.
Returning to FIG. 4, the description of the configuration of the data receiving device 2 will be continued.

The packet extraction unit 24 extracts a packet from the data for each slot based on the pointer information (head pointer information) output from the frame decoding unit 21.
Here, the packet extraction unit 24 extracts the packet by sequentially reading data from the pointer indicated by the head pointer information for each slot including the packet invalidated by the data invalidation unit 23.

By configuring the data receiving device 2 in this way, the data receiving device 2 can easily identify the range of packets that may have transmission errors. Furthermore, when invalidating a packet that may have a transmission error, the data receiving device 2 can notify an upper application that the packet is invalid by using an error indicator or the like.
Here, the data receiving apparatus 2 is configured to include the demodulating means 20, but the demodulating means 20 may be provided outside as a demodulating apparatus. In this case, the frame decoding means 21 inputs a demodulated signal from the demodulating device.

  The data receiving apparatus 2 can be configured by a general computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. (not shown). It can be operated by a data receiving program that functions as each means.

[Operation of data receiver]
Next, the operation of the data receiving apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flowchart showing the operation of the data receiving apparatus according to the embodiment of the present invention.

First, the data receiving apparatus 2 demodulates the input digital modulation signal by the demodulation means 20 (step S21).
Then, the data receiving device 2 detects the frame synchronization signal from the demodulated signal demodulated in step S21 by the frame decoding means 21, and decodes it for each transmission frame (step S22). At this time, the slot extracting means 21a extracts slot data from the demodulated signal. Further, the pointer information extraction unit 21b extracts pointer information (first pointer information and end pointer information) from the TMCC of the demodulated signal, and the synchronization pattern extraction unit 21c extracts a synchronization pattern from the TMCC.
The various information such as the pointer information is stored in a storage means (not shown) for a predetermined slot search range, although not shown as steps.

Thereafter, the data receiving apparatus 2 performs error detection of the slot by the error detection means 22 using the error detection code added to the slot (step S23).
If no slot error is detected (No in step S23), the data reception device 2 proceeds to step S26.
On the other hand, when an error in the slot is detected (Yes in step S23), the data receiving apparatus 2 indicates the latest end pointer information transmitted before the slot in which the error is detected by the data invalidating unit 23. The data between the end position and the start position indicated by the most recent start pointer information transmitted after the slot is invalidated as an erroneous packet (step S24).

Further, the data receiving apparatus 2 overwrites the synchronization pattern extracted in step S22 from the beginning of the invalidated packet by the data invalidating means 23 (step S25).
Then, the data receiving device 2 extracts a packet from the data for each slot based on the head pointer information extracted in step S22 by the packet extracting unit 24 (step S26).

  With the above operation, the data receiving device 2 can easily identify the position of the packet in the slot even if the data stream to be transmitted is of indefinite length. The invalidation of the packet in the slot and the packet across the slot can be executed at high speed and accurately, and thus hierarchical modulation is also possible.

The configuration and operation of the data transmission device and the data reception device according to the embodiment of the present invention have been described above, but the present invention is not limited to this embodiment.
For example, here, the slot and the TMCC corresponding to the slot are transmitted as a transmission frame, but the TMCC control information may be transmitted several frames ahead of the slot from the data transmission apparatus. Good. As a result, the data receiving apparatus can analyze the slot configuration and the like in advance based on the TMCC control information, thereby speeding up the reception process.

It is explanatory drawing for demonstrating the structure of the transmission frame of the transmission signal which the data transmitter which concerns on embodiment of this invention transmits. It is a block diagram which shows the structure of the data transmitter which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the data transmitter which concerns on embodiment of this invention. It is a block diagram which shows the structure of the data receiver which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the data receiver which concerns on embodiment of this invention. It is a schematic diagram which shows the example of arrangement | positioning of the slot and packet for demonstrating pointer information. It is a block diagram which shows the structural example of TMCC. It is explanatory drawing for demonstrating the setting example of the pointer information of TMCC in a certain slot. It is explanatory drawing for demonstrating the range which invalidates a packet.

Explanation of symbols

1 Data transmission device 10 Packet placement means (data structure placement means)
DESCRIPTION OF SYMBOLS 11 Pointer information production | generation means 12 Error detection code addition means 13 Frame formation means 13a Slot configuration means 13b Pointer information addition means 13c Synchronization pattern addition means 14 Modulation means 2 Data receiving device 20 Demodulation means 21 Frame decoding means 21a Slot extraction means (data area) Extraction means)
21b Pointer information extraction means 21c Synchronization pattern extraction means 22 Error detection means 23 Data invalidation means 24 Packet extraction means (data structure extraction means)

Claims (5)

Transmits continuous transmission data in a data structure as a transmission frame having one or more data areas independent of the structure of the data structure and a control area to which control information for the data area is added as a frame structure. A data transmission device for
Data structure arrangement means for arranging a data structure of the transmission data for each data area;
Error detection code addition means for adding an error detection code to each data area arranged by the data structure arrangement means;
In the data area in which the data structure is arranged, the first pointer information specifying the first position of the first data structure arranged from the first data of the data structure and the last data arranged up to the last data of the data structure Pointer information generating means for generating tail pointer information for specifying the tail position of the structure;
The control area and the data area are configured as the predetermined frame structure, and the framing means for adding the start pointer information and the end pointer information to the control area,
A data transmission device comprising:   The framing means, when configuring the control area and the data area, frames the control area into an area where modulation is performed using a modulation scheme having a transmission error resistance higher than that of the data area. The data transmission device according to claim 1.   The pointer information generating means, when there is no data structure arranged from the top data of the data structure in the data area, as a value larger than the maximum position pointing in the data area or smaller than the minimum position When the head pointer information is generated and there is no data structure arranged up to the end data of the data structure in the data area, the value is larger than the maximum position indicating the data area or smaller than the minimum position. The data transmission device according to claim 1 or 2, wherein tail pointer information is generated.   The said framing means adds the predetermined synchronization pattern for synchronizing the said data structure between transmission / reception to the said control area, The Claim 1 characterized by the above-mentioned. Data transmission device. Transmits continuous transmission data in a data structure as a transmission frame having one or more data areas independent of the structure of the data structure and a control area to which control information for the data area is added as a frame structure. In order to
Data structure arrangement means for arranging a data structure of the transmission data for each data area;
Error detection code addition means for adding an error detection code to each data area arranged by the data structure arrangement means;
In the data area in which the data structure is arranged, the first pointer information specifying the first position of the first data structure arranged from the first data of the data structure and the last data arranged up to the last data of the data structure Pointer information generating means for generating tail pointer information for specifying the tail position of the structure;
A framing means for configuring the control area and the data area as the predetermined frame structure, and adding the head pointer information and the tail pointer information to the control area,
A data transmission program characterized in that it functions as

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