JP5127745B2 - Wireless communication system and communication control method - Google Patents

Description

  The present invention relates to a communication control method in a wireless communication system that performs header compression.

  Conventionally, there is ROHC (Robust Header Compression) as a header compression method in a wireless communication environment. In ROHC, in “Unidirectional mode (U-mode)” described in 5.3.1 of Non-Patent Document 1 below and “Bidirectional Optimistic mode (O-mode)” described in 5.4.1, The header compression pattern to be transmitted is changed by autonomous determination on the compression side without depending on the decoding status and status notification from the compression decoding side. In the O-mode of 5.4.1 of the non-patent document 1 and “Bidirectional Reliable mode (R-mode)” described in 5.5.1, the Decompressor receives initial header information, When a ROHC packet including header information for notifying header information change, header compression pattern change, etc. is received, a feedback packet such as ACK, NACK, STATIC NACK for notifying the composite state and mode state on the decompressor side is received. To avoid the occurrence of a deviation in the recognition of the compressed state of each other.

IETF RFC3095, RObust Header Compression (ROHC)

  However, Non-Patent Document 1 stipulates that the header compression pattern on the transmission side in the U mode and O mode of the ROHC header compression method can be changed by autonomous determination on the compression side. No mention of clear standards or methods. For this reason, in the data transfer in the U mode according to the above-described conventional technique or the O mode in which ACK is not taken, even if the receiving side cannot receive the uncompressed full header packet due to packet loss due to line quality degradation or the like, the transmitting side Will change the header compression pattern. In such a case, the receiving side has a problem that a large amount of packets are discarded due to the inability to decode the compressed header.

  In O mode and R mode, data transfer in which the decompressor returns a feedback packet starts when the ACK feedback packet is lost during transmission due to loss of the line due to degradation of the line quality, etc. Header compression is not performed on the Compressor side. In this case, there is a problem that the effect of header compression is reduced.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a communication control method having high durability against communication quality deterioration.

  In order to solve the above-described problems and achieve the object, the present invention includes a plurality of communication devices, adopts ROHC (Robust Header Compression) as a header compression protocol, and the communication device is a ROHC data transmission side device or In a wireless communication system that performs data communication with each other as a ROHC data reception side device, the ROHC data transmission side device holds a predetermined condition for determining reachability of a packet to be transmitted to the ROHC data reception side device, When the header uncompressed ROHC IR (Initiation and Refresh) is transmitted by a PDCP (Packed Data Convergence Protocol) packet and the predetermined condition is not satisfied, the PDCP packet cannot reach the ROHC data receiving side device. It is determined that the header is uncompressed and transmission of ROHC IR is continued. When filled, it is determined that PDCP packet is reachable to the ROHC data receiving-side apparatus starts the transmission by PDCP packets ROHC IR-DYN whose header is compressed, characterized in that.

  According to the present invention, it is possible to determine the reachability of transmission data without adding a special detection method, a control message for notification, or the like.

FIG. 1 is a diagram showing a configuration example of a first embodiment of a wireless communication system according to the present invention. FIG. 2 is a diagram showing a protocol function stack defined by the 3GPP standard. FIG. 3 is a sequence diagram for explaining the operation of the wireless communication system according to the first embodiment. FIG. 4 is a sequence diagram for explaining the operation of the wireless communication system according to the second embodiment. FIG. 5 is a sequence diagram for explaining the operation of the radio communication system according to the third embodiment. FIG. 6 is a sequence diagram for explaining the operation of the wireless communication system according to the fourth embodiment. FIG. 7 is a sequence diagram for explaining the operation of the wireless communication system in the fifth embodiment. FIG. 8 is a sequence diagram for explaining the operation of the wireless communication system according to the sixth embodiment. FIG. 9 is a sequence diagram for explaining the operation of the wireless communication system according to the seventh embodiment.

  Embodiments of a wireless communication system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a first embodiment of a wireless communication system according to the present invention. The wireless communication system of FIG. 1 includes a compressor 1 and a decompressor 2, and transmits and receives data by wireless communication. This wireless communication system employs a communication specification such as 3GPP (3rd Generation Partnership Project) or LTE (Long Term Evolution). Here, the wireless communication system operates in the O mode in the ROHC protocol, the Compressor 1 functions as a ROHC compressed data transmission side device, and the Decompressor 2 functions as a ROHC compressed data reception side device. Note that Compressor 1 and Decompressor 2 are any one of a radio base station, a radio network controller, and a mobile station.

  FIG. 2 is a diagram showing a protocol function stack defined by the 3GPP standard. Compressor 1 and Decompressor 2 have the same protocol function stack. Compressor 1 includes RLC layer 3, PDCP layer 4, and ROHC layer 5, and Decompressor 2 includes RLC layer 6, PDCP layer 7, and ROHC layer 8. The ROHC packet is set and transmitted in the data part of the PDCP packet, and the PDCP packet is transmitted using, for example, one of the RLC connections with data bidirectionality set between the radio base station and the mobile station. It is transmitted as the data part of the packet.

  Next, communication control operations in the radio communication system configured as described above will be described. FIG. 3 is a sequence diagram for explaining the operation of the wireless communication system according to the present embodiment. Compressor 1 first sets uncompressed ROHC IR (Initiation and Refresh) in the data part of the PDCP packet, and uses the already set RLC connection (in this case, RLC connection # 0), to The packet is set in the data part of the RLC packet and transmitted. Also, a timer (time T1) is started at the transmission timing (step S1).

  Here, it is assumed that the transmission path quality is degraded. In this case, the PDCP packet including the ROHC IR transmitted in step S1 does not reach Decompressor 2, and even if Decompressor 2 transmits the PDCP packet, it does not reach Compressor 1 (step S2). On the other hand, when the time T1 elapses from step S1 and the timer times out, the Compressor 1 determines that it is a timing at which ROHC IR DYN (Initiation and Refresh DYNamic), which is a compression header, can be transmitted according to the conventional specification. However, since the PDCP packet is not received at all by the RLC connection # 0 from the Decompressor 2 during the T1 time, the Compressor 1 determines that the PDCP packet transmitted by the Compressor 1 is not normally received by the Decompressor 2, and thereafter, the ROHC The IR packet is continuously transmitted (step S3, step S4).

  As the transmission of the ROHC IR packet continues, the transmission path quality and the like improve. For example, it is assumed that the PDCP packet transmitted by Compressor 1 reaches Decompressor 2 in Step S4 and Decompressor 2 transmits the PDCP packet (Step S5). Compressor 1 determines that the PDCP packet can reach the opposite side by receiving the PDCP packet, and transmits the ROHC IR-DYN packet in which the fixed information is deleted and the header is compressed by the PDCP packet (step S1). S6).

  As described above, in this embodiment, in addition to the conventional timeout control on the transmission side, the compressed header is transmitted by confirming the reception of the packet from the opposite side. This makes it possible to determine the reachability of transmission data without adding a special detection method, a control message for notification, or the like. In addition, the sending side can avoid sending compressed headers even though packet loss has occurred, so it is possible to avoid the occurrence of packet discards due to inability to decode the compressed headers on the receiving side. High performance ROHC header compression can be realized.

Embodiment 2. FIG.
In the first embodiment, the transmission status is determined based on the reception status of the PDCP packet on the transmission side. In the present embodiment, a case will be described in which the transmission status is determined based on the reception status of the PDCP packet on the receiving side.

  The wireless communication system in the present embodiment is the same as the wireless communication system of FIG. 1, and includes Compressor 1B instead of Compressor 1 and Decompressor 2B instead of Decompressor 2 (not shown). Compressor 1B sets a sequence number (hereinafter also referred to as “SN”) in a “sequence number” field defined in the PDCP packet when transmitting the PDCP packet, and Decompressor 2B determines that the PDCP packet itself is based on the sequence number. Is continuously received. When the Decompressor 2B determines that the PDCP packet is not continuously received, the Decompressor 2B turns on the “reception loss occurrence flag” defined in the PDCP packet to indicate that the packet to be received has been lost. Send. The Compressor 1B switches the header compression mode based on the “reception loss occurrence flag”.

  Next, communication control operations in the radio communication system configured as described above will be described. FIG. 4 is a sequence diagram for explaining the operation of the radio communication system according to the present embodiment.

  The Compressor 1B first sets uncompressed ROHC IR (Initiation and Refresh) in the data part of the PDCP packet, and sets a sequence number in the PDCP packet. Then, using the RLC connection that has already been set (here, RLC connection # 0), the PDCP packet is set in the data part of the RLC packet and transmitted. Also, a timer (time T2) is started at the transmission timing (step S11).

  Here, it is assumed that the transmission path quality is degraded. In this case, the PDCP packet including the ROHC IR transmitted in step S11 does not reach the Decompressor 2B. On the other hand, the Compressor 1B increments the sequence number and continuously transmits the ROHC IR packet using the PDCP packet including SN = “1” (step S12). Here, for example, it is assumed that the transmission path quality is improved and the PDCP packet in step S12 arrives. The Decompressor 2B checks the SN included in the PDCP packet to be received. In this case, the Decompressor 2B receives the PDCP packet with SN = “1” in a state where SN = “0”. The Decompressor 2B determines that the loss of the PDCP packet to be received has occurred due to the fact that the sequence numbers are not continuous, and transmits the reception loss occurrence flag in the PDCP packet turned ON in RLC connection # 0 (step S13). .

  On the other hand, when the time T2 elapses from step S11 and the timer times out, the Compressor 1B determines that it is a timing at which ROHC IR DYN (Initiation and Refresh DYNamic), which is a compression header, can be transmitted according to the conventional specification. However, since the PDCP packet whose “reception loss occurrence flag” is ON is received from the Decompressor 2 through the RLC connection # 0 during the T2 time, the Compressor 1B does not normally receive the PDCP packet transmitted by the Compressor 1B. After that, the ROHC IR packet is continuously transmitted (step S14). At this time, SN = “2” is set as the sequence number.

  The Decompressor 2B determines that the packet loss has been resolved by receiving the recently received PDCP packet with SN = “2” and SN = “2”, and in the RLC connection # 0, the “reception loss occurrence flag” A PDCP packet in which is turned OFF is transmitted (step S15). The Compressor 1B determines that the PDCP packet can reach the opposite side by receiving the PDCP packet whose “reception loss occurrence flag” is OFF, and deletes the fixed information and performs the header compression on the ROHC IR-DYN packet. Is transmitted by the PDCP packet (step S16). At this time, SN = “3” is set as the sequence number.

  As described above, in this embodiment, transmission is performed including an identifier on the transmission side, and the reception side determines whether or not packets can be continuously received based on the identifier, and packet loss is determined based on the determination result. It was decided to send it including information indicating. Thereby, the same effect as Embodiment 1 is acquired.

Embodiment 3 FIG.
In the second embodiment, a packet including an identifier is transmitted on the transmission side, the identifier included in the packet received on the reception side is checked, and the transmission status is determined based on whether or not the identifier is continuous. In this embodiment, a case will be described in which a transmission status is determined by another method using the identifier.

  The wireless communication system according to the present embodiment is the same as the wireless communication system of FIG. 1, and includes Compressor 1C instead of Compressor 1 and Decompressor 2C instead of Decompressor 2 (not shown). Compressor 1C sets a sequence number (hereinafter also referred to as “SN”) defined in the PDCP packet when transmitting the PDCP packet, and the Decompressor 2C determines whether the sequence number is lost within a predetermined time by the timer monitoring. Judge whether. If the Decompressor 2C determines that the PDCP packet has not been continuously received, the Decompressor 2C indicates that the reception status has deteriorated, so that the “health check state” defined in the PDCP packet is set to FAIL. To do. The Compressor 1C switches the header compression mode based on the “health check state”.

  Next, communication control operations in the radio communication system configured as described above will be described. FIG. 5 is a sequence diagram for explaining the operation of the radio communication system according to the present embodiment.

  Compressor 1C first sets uncompressed ROHC IR (Initiation and Refresh) in the data part of the PDCP packet, and sets a sequence number in the PDCP packet. Then, using the RLC connection that has already been set (here, RLC connection # 0), the PDCP packet is set in the data part of the RLC packet and transmitted. Also, a timer (time T3) is started at the transmission timing (step S21).

  Here, it is assumed that the transmission path quality is degraded. In this case, the PDCP packet including the ROHC IR transmitted in step S21 does not reach the Decompressor 2C. On the other hand, the Compressor 1C increments the sequence number and continuously transmits the ROHC IR packet using the PDCP packet including SN = “1” (step S22). Here, for example, it is assumed that the transmission path quality is improved and the PDCP packet in step S22 has arrived. By the way, the Decompressor 2C checks the SN included in the received PDCP packet in units of a fixed monitoring time. Here, for example, it is assumed that a PDCP packet with SN = "1" is received without receiving a PDCP packet with SN = "0" during a certain monitoring time (time T4). In this case, the Decompressor 2C determines that the loss of the PDCP packet to be received has occurred due to a missing sequence number, and transmits the “health check state” in the PDCP packet as FAIL in RLC connection # 0 ( Step S23).

  On the other hand, when time T3 elapses from step S21 and the timer times out, the Compressor 1C determines that it is a timing at which ROHC IR DYN (Initiation and Refresh DYNamic), which is a compression header, can be transmitted according to the conventional specification. However, since the PDCP packet whose “health check state” is FAIL is received from the Decompressor 2C through the RLC connection # 0 during the time T3, the Compressor 1C does not normally receive the PDCP packet transmitted by the Compressor 1C at the Decompressor 2C. Thereafter, the ROHC IR packet is continuously transmitted (step S24, step S25). At this time, “2” is set as the sequence number in step S24, and “3” is set as the sequence number in step S25.

  The Decompressor 2C monitors the new monitoring time (time T5) with a timer and checks the sequence number of the PDCP packet received during that time. Here, since the PDCP packets with SN = “2” and “3” are received, there is no omission, and the Decompressor 2C determines that the packet loss has been resolved, and sets “health check state” in RLC connection # 0. The PDCP packet set is transmitted (step S26). The Compressor 1C determines that the PDCP packet can reach the opposite side by receiving the PDCP packet whose “health check state” is OK, and deletes the fixed information and performs the header compression on the ROHC IR-DYN packet. Transmission is performed using a PDCP packet (step S27).

  As described above, in the present embodiment, the transmitting side transmits a packet including an identifier, and the receiving side determines whether or not the packet can be received without omission based on the identifier. It was decided to send including information indicating the reception status. Thereby, the same effect as in the first and second embodiments can be obtained. In addition, compared with the method of the second embodiment, it is possible to determine missing packets (continuity in a broad sense) during a certain monitoring time, so that a more realistic transmission situation can be grasped.

Embodiment 4 FIG.
In the second and third embodiments, a packet including an identifier is transmitted on the transmitting side, an identifier included in a packet received on the receiving side is checked, and a transmission status is determined based on whether the identifier is continuous. did. In this embodiment, a case will be described in which a transmission status is determined using an existing mechanism in a lower layer.

  The wireless communication system according to the present embodiment is the same as the wireless communication system of FIG. 1, and includes Compressor 1D instead of Compressor 1 and Decompressor 2D instead of Decompressor 2 (not shown). The Compressor 1D transmits a PDCP packet using the AM mode of the RLC that is a lower layer, and the Decompressor 2D returns a reception status by a delivery confirmation in the AM mode. The Compressor 1D switches the header compression mode based on the presence / absence of the delivery confirmation.

  Next, communication control operations in the radio communication system configured as described above will be described. FIG. 6 is a sequence diagram for explaining the operation of the wireless communication system in the present embodiment.

  Compressor 1D first sets ROHC IR (Initiation and Refresh) in the PDCP layer in the data portion of the PDCP packet, and outputs it to the RLC layer. At that timing, a timer (time T6) is started (step S31). Next, the Compressor 1D uses the RLC connection that has already been set in the RLC layer (here, RLC connection # 0) to set the PDCP packet in the data part of the RLC packet and transmit it in the AM mode. (Step S32, “RLC AM Data”).

  Here, it is assumed that the transmission path quality is degraded. In this case, the PDCP packet (RLC AM Data) including the ROHC IR transmitted in step S32 does not reach the Decompressor 2D. On the other hand, when the time T6 elapses from step S31 and time-out occurs, the Compressor 1D determines that it is a timing at which ROHC IR DYN (Initiation and Refresh DYNamic), which is a compression header, can be transmitted according to the conventional specification. However, during the time T6, since the delivery confirmation in the RLC layer is not received from the Decompressor 2D in the RLC connection # 0, the Compressor 1D determines that the PDCP packet transmitted by itself does not reach the Decompressor 2D. Continuously transmit the ROHC IR packet. That is, as described above, Compressor 1D outputs ROHC IR from the PDCP layer (step S33), and transmits RLC AM Data from the RLC layer (step S34). Also, a new timer (time T7) is set.

  Here, for example, it is assumed that the transmission path quality is improved and the RLC AM Data in step S34 reaches the Decompressor 2D. In this case, the Decompressor 2D transmits RLC AM Stat as a delivery confirmation for the RLC AM Data in the RLC connection # 0 (step S35). The Compressor 1D determines that the PDCP packet previously transmitted by being included in the RLC AM Data has reached the Decompressor 2D by receiving the RLC AM Stat in the RLC layer during the timer time T7. Accordingly, the Compressor 1D outputs the ROHC IR-DYN packet in which the fixed information is deleted and the header is compressed in the PDCP layer to the RLC layer by the PDCP packet (step S36), and the PDCP packet is transmitted to the RLC packet data in the RLC layer. And using the already set RLC connection (RLC connection # 0) (step S37).

  As described above, in the present embodiment, the transmitting side transmits a packet in the RLC AM mode, and determines the data reachability (and the line quality) to the opposite side based on the presence or absence of the RLC data delivery confirmation from the receiving side. It was decided to. Thereby, the same effect as Embodiment 1 is acquired.

Embodiment 5 FIG.
In the first to fourth embodiments, the case has been described where it is assumed that the PDCP packet from the transmission side does not arrive. In this embodiment, a case will be described in which it is assumed that a PDCP packet from the receiving side does not arrive.

  The wireless communication system in the present embodiment is the same as the wireless communication system of FIG. 1, and includes a Compressor 1E instead of the Compressor 1 and a Decompressor 2E instead of the Decompressor 2 (not shown). The Compressor 1E transmits a PDCP packet, and the Decompressor 2E returns a reception status by a Feedback packet, stores information about transmission by the Feedback packet, and retransmits the transmission packet when a transmission packet is generated. The Compressor 1E switches the header compression mode based on the content of the Feedback packet.

  Next, communication control operations in the radio communication system configured as described above will be described. FIG. 7 is a sequence diagram for explaining the operation of the wireless communication system according to the present embodiment.

  When a user packet is generated in an upper layer such as IP (Internet Protocol), UDP (User Datagram Protocol), or RTP (Real-time Transport Protocol) in the ROHC layer (step S41), the Compressor 1E performs uncompressed header processing. ROHC IR (Initiation and Refresh) is set in the data part of the PDCP packet, and the PDCP packet is set in the data part of the RLC packet by using the already set RLC connection (here, RLC connection # 0). (Step S42).

  Since the Decompressor 2E normally receives the PDCP packet and can decode the ROHC IR, the Decompressor 2E transmits the ROHC Feedback (here, ACK) to the Compressor 1E using the RLC connection # 0 (Step S43). In contrast, information (transmission information) indicating that the ROHC Feedback (ACK) has been transmitted is stored in its own memory (not shown). Here, it is assumed that the ROHC Feedback packet has been lost due to temporary quality degradation.

  Thereafter, the Decompressor 2E detects that a user packet directed to the Compressor 1E has occurred in an upper layer such as IP, UDP, RTP (step S44). The Decompressor 2E generates a ROHC packet of the user packet in the ROHC layer. Further, the Decompressor 2E reads the transmission information from the memory, and from the transmission information, “recognizes that the ROHC Feedback (ACK) has already been transmitted to the Compressor 1E. Therefore, the ROHC obtained by adding the Feedback (ACK) to the generated ROHC packet. A packet is generated and transmitted as described above (step S45).

  The compressor 1E extracts the user packet from the received ROHC packet and transmits it to the upper layer. In addition, it is confirmed that Feedback is set in the ROHC packet and that it is ACK (positive Feedback) (step S46). In this case, since the feedback (ACK) in step S43 has not reached the Compressor 1E, the Compressor 1E recognizes that the ACK of the ROHC IR packet transmitted in Step S42 has been obtained for the first time. Therefore, when receiving the user packet from the upper layer (step S47), the Compressor 1E transmits the ROHC IR-DYN packet in which the fixed information is deleted and the header is compressed (step S48).

  As described above, in the present embodiment, when transmitting a Feedback packet on the receiving side, the transmission information of the packet is stored, and then the packet is generated on the same transmitting side. Thereby, the reachability of the Feedback packet can be improved, and the reachability of the transmission data can be determined without adding a special detection method, a control message for notification, and the like, as in the first embodiment. . In addition, the sending side can avoid sending compressed headers even though packet loss has occurred, so it is possible to avoid the occurrence of packet discards due to inability to decode the compressed headers on the receiving side. High performance ROHC header compression can be realized.

Embodiment 6 FIG.
In the fifth embodiment, when a feedback packet is transmitted on the receiving side, the transmission information is stored, and when the user packet is generated, the content of the feedback packet is added and retransmitted. In this embodiment, a case where the number of times is limited in retransmission will be described.

  The wireless communication system according to the present embodiment is the same as the wireless communication system according to the fifth embodiment, and includes Compressor 1F instead of Compressor 1E, and Decompressor 2F instead of Decompressor 2E (not shown). The Decompressor 2F holds the maximum number of transmissions when retransmitting the Feedback packet, and retransmits the maximum number of times. The Compressor 1F switches the header compression mode based on the presence / absence of the delivery confirmation. In the present embodiment, the maximum number of transmissions “1” is set in the memory of the Decompressor 2F.

  Next, communication control operations in the radio communication system configured as described above will be described. FIG. 8 is a sequence diagram for explaining the operation of the wireless communication system in the present embodiment.

  As described above, the processes of steps S41 to S44 are performed. The Decompressor 2F receives the user packet in step S44 and generates a ROHC packet of the user packet in the ROHC layer. Further, the Decompressor 2F reads the transmission information from the memory, and acquires information indicating that the ROHC Feedback (ACK) has been transmitted to the Compressor 1F in the transmission information. Therefore, the Feedback 2 (ACK) is added to the generated ROHC packet. A ROHC packet is generated and transmitted as described above. Further, the Decompressor 2F adds, for example, to the transmission information that the number of times of retransmission is one (step S51).

  The compressor 1F extracts the user packet from the received ROHC packet and outputs it to the upper layer. Also, it is confirmed that Feedback (ACK) is set in the ROHC packet. In this case, since the feedback (ACK) in step S43 has not reached Compressor 1F, Compressor 1F recognizes that the ACK of the ROHC IR packet transmitted in step S42 has been obtained (step S52).

  On the other hand, when a user packet from an upper layer is subsequently generated (Step S53), the Decompressor 2F generates a ROHC packet of the user packet in the ROHC layer. Also, the Decompressor 2F reads the transmission information from the memory, and recognizes from the transmission information that the ROHC Feedback (ACK) has been transmitted to the Compressor 1F, and the number of retransmission results is “1”. Further, the maximum number of transmissions is read from the memory, and it is recognized that the number of times is “one time”. Therefore, the Decompressor 2F determines that the actual number of retransmissions has reached the maximum number of transmissions, and transmits the ROHC packet without sharing the ROHC Feedback (ACK) (step S54). Also, the transmission information and the actual number of retransmissions are initialized. The compressor 1F extracts the user packet from the received ROHC packet and transmits it to the upper layer (step S55).

  As described above, in the present embodiment, the maximum number of transmissions is set when the feedback packet is retransmitted on the receiving side. Thereby, in addition to the effect of Embodiment 5, the amount of control data transferred together with the user data packet can be suppressed. Accordingly, ROHC header compression with high durability and reduced transfer data amount can be realized.

Embodiment 7 FIG.
In the fifth embodiment, when a feedback packet is transmitted on the receiving side, the transmission information is stored, and when the user packet is generated, the content of the feedback packet is added and retransmitted. In this embodiment, a case where the time for performing retransmission is limited will be described.

  The wireless communication system according to the present embodiment is the same as the wireless communication system according to the fifth embodiment, and includes Compressor 1G instead of Compressor 1E, and Decompressor 2G instead of Decompressor 2E (not shown). The Decompressor 2G performs timer monitoring when retransmitting the Feedback packet, and retransmits the monitoring time as a limit. The Compressor 1G switches the header compression mode based on the presence / absence of the delivery confirmation. In the present embodiment, time T8 is set as the monitoring time.

  Next, communication control operations in the radio communication system configured as described above will be described. FIG. 9 is a sequence diagram for explaining the operation of the radio communication system according to the present embodiment.

  As described above, the processes of steps S41 to S44 are performed. The Decompressor 2G receives the user packet in step S44 and generates a ROHC packet of the user packet in the ROHC layer. In addition, the Decompressor 2G reads the transmission information from the memory, and acquires information indicating that the ROHC Feedback (ACK) has been transmitted to the Compressor 1G in the transmission information. Therefore, the Feedback (ACK) is added to the generated ROHC packet. A ROHC packet is generated and transmitted as described above. In addition, the Decompressor 2G stores the fact in the transmission information as described above. Furthermore, the Decompressor 2G starts timer monitoring for transmission information for the Compressor 1G (step S61).

  The Compressor 1G extracts the user packet from the received ROHC packet and outputs it to the upper layer. Further, it is confirmed that Feedback (ACK) is set in the ROHC packet, and it is recognized that the ACK of the ROHC IR packet transmitted in step S42 is obtained (step S62).

  On the other hand, when the Decompressor 2G is notified by the timer that the monitoring time (time T8) has elapsed, it initializes transmission information for the Compressor 1G. Thereafter, when a user packet is generated from an upper layer (Step S63), the Decompressor 2G generates a ROHC packet of the user packet in the ROHC layer. Here, the Decompressor 2G refers to the transmission information in the memory, but the transmission information for the Compressor 1G is initialized when the monitoring time (time T8) has elapsed. Therefore, the Decompressor 2G determines that there is no information to be shared, and transmits the ROHC packet without sharing the ROHC Feedback (ACK) (step S64). The Compressor 1G extracts the user packet from the received ROHC packet and transmits it to the upper layer (step S65).

  As described above, in the present embodiment, the timer monitoring is performed when the feedback packet is retransmitted on the receiving side. As a result, the same effect as in the sixth embodiment can be obtained.

  As described above, the communication control method according to the present invention is useful for a communication system that performs header compression, and is particularly suitable for a communication system that employs ROHC as a header compression protocol.

1,1B, 1C, 1D, 1E, 1F, 1G Compressor
2, 2B, 2C, 2D, 2E, 2F, 2G Decompressor
3, 6 RLC layer 4, 7 PDCP layer 5, 8 ROHC layer

Claims (2)

In a wireless communication system comprising a plurality of communication devices, adopting ROHC (Robust Header Compression) as a header compression protocol, and wherein the communication device performs data communication with each other as a ROHC data transmission side device or a ROHC data reception side device,
The ROHC data transmission side device
Holding a predetermined condition for judging the reachability of the packet to be transmitted to the ROHC data receiving side device;
Sends uncompressed ROHC IR (Initiation and Refresh) by PDCP (Packed Data Convergence Protocol) packet,
If the predetermined condition is not satisfied, it is determined that the PDCP packet is unreachable to the ROHC data receiving side device, and the transmission of the header uncompressed ROHC IR is continued.
If the predetermined condition is satisfied, it is determined that PDCP packet is reachable to the ROHC data receiving-side apparatus starts the transmission by PDCP packets ROHC IR-DYN whose header is compressed,
The predetermined condition is
The ROHC data transmission side device receives a PDCP packet from the ROHC data reception side device within a predetermined time, and the PDHC packet from the ROHC data reception side device includes at least the ROHC data reception side device, Including a PDCP packet transmitted independently of the PDCP packet transmitted by the ROHC data transmission side device;
A wireless communication system. A communication control method in a wireless communication system comprising a plurality of communication devices, adopting ROHC (Robust Header Compression) as a header compression protocol, wherein the communication devices perform data communication with each other as a ROHC data transmission side device or ROHC data reception side device Because
A condition holding step in which the ROHC data transmission side apparatus holds a predetermined condition for determining reachability of the packet to be transmitted to the ROHC data reception side apparatus;
The ROHC data transmission side device transmits an uncompressed ROHC IR (Initiation and Refresh) by a PDCP (Packed Data Convergence Protocol) packet;
When the ROHC data transmission side device does not satisfy the predetermined condition, the ROHC data transmission side device determines that the PDCP packet cannot reach the ROHC data reception side device, and continues to transmit the header-uncompressed ROHC IR. A compressed header continuous transmission step;
When the ROHC data transmission side apparatus satisfies the predetermined condition, the ROHC data transmission side apparatus determines that the PDCP packet can reach the ROHC data reception side apparatus, and the header-compressed ROHC IR-DYN PDCP packet A compressed header transmission step for starting transmission;
Only including,
The predetermined condition is
The ROHC data transmission side device receives a PDCP packet from the ROHC data reception side device within a predetermined time, and the PDHC packet from the ROHC data reception side device includes at least the ROHC data reception side device, Including a PDCP packet transmitted independently of the PDCP packet transmitted by the ROHC data transmission side device;
A communication control method characterized by the above.

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