JP4619312B2 - Communication system and transmitter - Google Patents

Description

  The present invention relates to a communication system and a transmission device, and more particularly to a technique for suppressing an increase in the amount of communication data passing through a communication section.

  A data amount reduction technique for reducing the amount of communication data passing through a communication section by omitting a part of the communication data is known (for example, ROHC (Robust (Patent Document 1) disclosed in Patent Document 1). Header Compression) technology etc.). In this data amount reduction technique, the transmission device transmits the communication data by omitting a portion that can be predicted by the reception device. When receiving the communication data in which a part is omitted, the receiving device restores the omitted part by prediction, and acquires the communication data before being omitted.

This prediction is performed as follows. That is, the transmitting device transmits communication data without performing omission at first (with an omission rate of 0). Then, the omission rate is increased step by step. On the other hand, the receiving device acquires prediction basic information for prediction from the received communication data while the omission rate of the communication data is low. The receiving device predicts the omitted part based on the basic prediction information thus obtained.
JP-T-2004-533792

  In the above-described prediction process, if an unpredictable change occurs in the configuration of communication data transmitted by the transmission device, the reception device cannot perform prediction, but in reality, the reception device does not have such a change. Prediction may not be possible.

  For example, when the transmitting apparatus is a mobile station apparatus constituting a mobile communication system and the receiving apparatus is the base station apparatus, the receiving apparatus changes when the mobile station apparatus is handed over. Since the new receiving device has not acquired the basic prediction information, the prediction cannot be performed even though there is no unpredictable change in the configuration of the communication data transmitted by the transmitting device.

  In addition, the receiving device may determine that prediction has become impossible when it detects an error in the received communication data, and may abandon the prediction basic information. Even in such a case, although the unpredictable change has not occurred in the configuration of the communication data transmitted by the transmitting apparatus, the prediction cannot be performed.

  In this way, when it becomes impossible to perform prediction in the receiving device, the transmitting device must return the omission rate to 0 and cause the receiving device to acquire prediction basic information again. For this reason, the amount of communication data passing through the communication section increases.

  Accordingly, one of the problems of the present invention is to suppress an increase in the amount of communication data passing through a communication section due to the reception device becoming unpredictable when using a data amount reduction technique. It is an object of the present invention to provide a communication system and a transmission device that can perform the above-described operation.

Communication system according to the present invention for solving the above problems, a mobile station device, a communication system including a receiver of the network side, the mobile station apparatus, abbreviated part content Ministry the data and data transmission means that can be sent in a state, in accordance with data transmitted by said data transmission means, the prediction basic information obtaining means for obtaining a predicted basic information for predicting an abbreviated portion of the data, the Prediction basic information transmission means for transmitting the prediction basic information acquired by the prediction basic information acquisition means to the reception apparatus together with information indicating the mobile station apparatus, and the reception apparatus includes the data transmission means receiving means for sequentially receiving data transmitted by, according to the received Lud over data by the receiving means, the prediction basic information for predicting the omitted portion Prediction basic information generating means for forming, according to the prediction basis information generated by the predicted basic information generating means, wherein the prediction means for predicting an abbreviated portion of the received Lud over data by the receiving means, wherein When the prediction means cannot perform prediction according to the prediction basic information generated by the prediction basic information generation means, the prediction means is based on the prediction basic information transmitted from the prediction basic information transmission means and information indicating the mobile station device. The omitted portion of the data received by the receiving means is predicted .

  According to this, it is possible to suppress an increase in the amount of communication data passing through the communication section due to the prediction failure in the receiving device.

Further, in the communication system, the mobile station device, based on the prediction basic information acquired by the prediction basic information acquisition unit, from the data in a state in which the part transmitted by the data transmission unit is omitted, And further comprising a restoration means for restoring the data acquired by the data acquisition means, wherein the prediction basic information transmission means sends the prediction basic information to the receiving device when the data is restored by the restoration means. It is good also as transmitting .

The mobile station apparatus according to the present invention, a data transmission means capable of sending the data in a state of short part content Ministry, according Lud over data transmitted by the data transmission means, the omission of the data prediction basic information obtaining means for obtaining a predicted basic information for predicting portion, and transmits the prediction basic information obtained by the predicted basic information acquisition unit to the receiving device together with information indicating the mobile station device Prediction basic information transmission means.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a system configuration of a mobile communication system 1 according to the present embodiment. The mobile communication system 1 is an iBurst (registered trademark) system, and includes a mobile station device 10, a base station device 20, a ROHC server 30, and a packet switch 40, as shown in FIG.

  The mobile station device 10, the base station device 20, the ROHC server 30, and the packet switch 40 are all computers including a CPU and a memory. The CPU is a processing unit for executing a program stored in the memory, and performs processing for controlling each part of each device and realizes functions described later. The memory stores programs and data for carrying out the present embodiment. It also operates as a work memory for the CPU.

  The mobile station device 10 performs wireless communication with the base station device 20. The base station apparatus 20 performs wired communication with the ROHC server 30. The ROHC server 30 performs wired communication with the packet switch 40.

  The mobile station apparatus 10 is connected to the computer 100 for communication. Further, the packet switch 40 is connected to the Internet 101 for communication.

  Particularly in the present embodiment, the computer 100 communicates with a communication device (not shown) connected to the Internet 101 via the mobile communication system 1 via SIP (Session Initiation Protocol) and RTP (Real-time). Packet voice communication (VoIP (Voice over IP) communication) using each protocol of Transport Protocol is performed.

  The mobile communication system 1 includes a plurality of base station devices 20. The mobile station device 10 communicates with any one of the plurality of base station devices 20.

  When the mobile station apparatus 10 is communicating with a certain base station apparatus 20, the mobile station apparatus 10 periodically checks the communication state. Specifically, the S / N ratio (Signal to Noise Ratio) of the radio signal received from the base station apparatus 20 is confirmed. Then, when the communication state deteriorates, that is, when the S / N ratio falls below a predetermined value, it is determined whether or not communication with another base station apparatus 20 is possible. Specifically, whether or not communication with the other base station apparatus 20 is possible by receiving a control signal constantly transmitted by another base station apparatus 20 and confirming its S / N ratio. Determine whether. As a result, when it is determined that communication with another base station device 20 is possible, communication with the base station device 20 in communication is disconnected, and communication with the other base station device 20 is started. Switching the communication partner base station device 20 in this way is called handover. In handover, not only the base station apparatus 20 but also the ROHC server 30 and the packet switch 40 may be switched.

  Further, the mobile station device 10 compresses the packet header when transmitting transmission data (packet) related to packet voice communication. Specifically, the packet header is compressed using a technique called ROHC (Robust Header Compression). In this compression, the mobile station apparatus 10 sequentially transmits each packet in a state where the entire packet is included or a part thereof is omitted. The ROHC server 30 sequentially receives the packets transmitted by the mobile station device 10, and generates prediction basic information (referred to as context) for predicting the omitted portion according to the received packets. Then, the omitted portion of the received packet is predicted according to the generated prediction basic information.

  The basic prediction information will be described. The packet header includes information that does not change during packet voice communication (invariable information: destination address, etc.) and information that can be predicted by the ROHC server 30 (predictable information: RTP sequence) because the contents change according to certain rules. Number, RTP time stamp, and the like) and information unpredictable by the ROHC server 30 (unpredictable information: checksum, etc.). Of these, the basic prediction information includes invariant information and rule information for predicting predictable information.

  The rule information will be described with a specific example. In order to predict the RTP time stamp from the RTP sequence number, it is possible to use an arithmetic sequence having the RTP sequence number as a variable. For this reason, the rule information for predicting the RTP time stamp includes information indicating the tolerance and the first term of the arithmetic sequence.

  Since the prediction basic information is such, it is necessary for the ROHC server 30 to receive a plurality of transmission data in order to generate the prediction basic information. When the prediction basic information is generated, the ROHC server 30 can make a prediction. For this reason, for a while after the start of communication, the mobile station apparatus 10 transmits each transmission data in a state including the entire transmission data, and gradually increases the omission rate.

  By the way, the mobile station apparatus 10 performs a handover as described above. As described above, the communication partner ROHC server 30 may change before and after the handover. In this case, the new ROHC server 30 does not have prediction basic information. Therefore, the mobile station device 10 generates and holds the basic prediction information by itself and transmits it to the new ROHC server 30. As a result, the mobile station apparatus 10 can sequentially transmit each transmission data while maintaining the omission rate up to that point immediately after the handover.

  Below, the process demonstrated above is demonstrated in detail, referring the functional block of the mobile station apparatus 10 and the ROHC server 30. FIG.

  FIG. 2 is a diagram illustrating functional blocks of the mobile station device 10 and the ROHC server 30. As shown in the figure, the mobile station apparatus 10 functionally includes a compressor 11, a decompressor 12, a prediction basic information storage unit 13, a prediction basic information transmission unit 14, and a handover execution determination unit 15. The ROHC server 30 is functionally configured to include a decompressor 31, a prediction basic information storage unit 32, and a prediction basic information reception unit 33.

  The compressor 11 includes a transmission data acquisition unit 110 and a transmission data transmission unit 111 internally. The transmission data acquisition unit 110 sequentially receives packets related to packet voice communication from the computer 100. The transmission data transmission unit 111 compresses the packet header by ROHC for each packet sequentially acquired by the transmission data acquisition unit 110 and sequentially transmits the packets. The packet transmitted in this way is called a ROHC packet.

  The decompressor 31 includes a transmission data receiving unit 310, a prediction unit 311, and a prediction basic information generation unit 312 internally. The transmission data receiving unit 310 receives the ROHC packet transmitted by the compressor 11. The prediction basic information generation unit 312 generates prediction basic information as described above based on the sequentially received ROHC packets, and associates the prediction basic information with information indicating the mobile station apparatus 10 that is the transmission source of the ROHC packet. The information is stored in the information storage unit 32.

  The prediction unit 311 determines whether or not the packet header is omitted for the ROHC packets sequentially received by the transmission data reception unit 310. When the prediction unit 311 determines that the packet header is omitted, the prediction unit 311 stores the prediction basic information stored in the prediction basic information storage unit 32 in association with the information indicating the mobile station device 10 that is the transmission source of the ROHC packet. Based on this, the omitted packet header is predicted, the packet including the complete packet header is restored, and is transferred to the packet switch 40.

  The decompressor 12 is configured to include a prediction basic information generation unit 121 internally. The prediction basic information generation unit 121 acquires the ROHC packets that are transmitted sequentially by the transmission data transmission unit 111. Then, the basic prediction information is generated in the same manner as the processing of the basic prediction information generation unit 312 and is stored in the basic prediction information storage unit 13. Thereby, in principle, the same basic prediction information stored in the basic prediction information storage unit 32 is stored in the basic prediction information storage unit 13.

  The handover execution determining unit 15 determines whether or not the mobile station apparatus 10 performs a handover. If it is determined that the handover is to be performed, it is further determined whether or not the ROHC server 30 of the communication partner is changed by the handover. When it is determined that the communication partner ROHC server 30 is changed, the handover execution determination unit 15 generates ROHC server information indicating the ROHC server 30 as a new communication partner and outputs the ROHC server information to the prediction basic information transmission unit 14. .

  The prediction basic information transmission part 14 will read the prediction basic information memorize | stored in the prediction basic information storage part 13, if the input of ROHC server information is received. Then, the read prediction basic information is transmitted to the ROHC server 30 indicated by the ROHC server information.

  When receiving the basic prediction information from the mobile station device 10, the basic prediction information receiving unit 33 associates the information indicating the mobile station device 10 with the basic prediction information and stores the information in the basic prediction information storage unit 32. As a result, when the prediction unit 311 subsequently receives a ROHC packet from the mobile station device 10, the prediction unit 311 predicts the omitted packet header based on the prediction basic information received from the mobile station device 10.

  Note that the basic prediction information stored in the basic prediction information storage unit 32 in this way is sequentially updated by the basic prediction information generation unit 312 based on newly received ROHC packets.

  The processing described above will be described again in more detail with reference to the processing flow of the mobile station apparatus 10.

  FIG. 3 is a diagram illustrating a processing flow of the mobile station apparatus 10. As shown in the figure, when receiving a packet from the computer 100 (S1), the mobile station apparatus 10 performs processing related to compression of the packet header (S2). Then, assuming that the ROHC server 30 of the communication partner has received a packet to be transmitted by the mobile station device 10, the basic prediction information for the ROHC server 30 is generated (S3). The mobile station device 10 further tries to restore the packet to be transmitted using the basic prediction information (S4). As a result, when the restoration cannot be performed, the basic prediction information is discarded (S5), the transmission of the ROHC packet is stopped, and the reception from the computer 100 is again waited. For packets received after waiting, ROHC packets are generated for a predetermined time without compressing the packet header in the process of S2. That is, the ROHC packet is generated by returning to the omission rate 0 state.

  On the other hand, if restoration is possible in S4, it is determined whether or not handover is performed (S6). When the handover is not performed, the ROHC packet is transmitted to the Internet 101 (S7). On the other hand, when the handover is performed, the basic prediction information generated in S3 is transmitted to the ROHC server 30 that is the handover destination (S8). Thereafter, the ROHC packet is transmitted to the Internet 101 (S7).

  Next, a more detailed description will be given again with reference to a processing sequence between the mobile station device 10 and the ROHC server 30.

  FIG. 4 is a diagram showing a processing sequence between the mobile station device 10 and the ROHC server 30. As shown in the figure, when the compressor 11 transmits a ROHC packet, the decompressor 12 receives this and generates basic prediction information. The ROHC server 30 also receives this, generates basic prediction information, restores the packet header, and transfers it to the packet switch 40 (S10).

  Here, it is assumed that the mobile station apparatus 10 is handed over (S11). Then, the mobile station apparatus 10 transmits the generated prediction basic information to the ROHC server 30 after the handover (S12). On the other hand, the mobile station device 10 disconnects communication with the ROHC server 30 before the handover (S13). Thereafter, the ROHC packet is transmitted to the ROHC server 30 after the handover (S14).

  As described above, according to the mobile communication system 1, it is possible to suppress an increase in the amount of communication data (ROHC packet) passing through the communication section due to the fact that the ROHC server 30 cannot perform prediction. Can do.

  Moreover, since the prediction basic information can be transmitted when the ROHC server 30 is changed, the change in the ROHC server 30 makes it impossible for the receiving apparatus (new ROHC server 30) to predict, and the amount of communication data passing through the communication section is reduced. It can suppress that it increases.

  The present invention is not limited to the above embodiment. For example, the present invention can be applied not only at the time of handover but also when the ROHC server 30 cannot restore a packet. This example will be described below.

  FIG. 5 is a diagram showing a processing sequence between the mobile station apparatus 10 and the ROHC server 30 according to the modification of the above embodiment. As shown in the figure, when the compressor 11 transmits a ROHC packet, the decompressor 12 receives this and generates basic prediction information. The ROHC server 30 also receives this, generates basic prediction information, restores the packet header, and transfers it to the packet switch 40 (S20, S21).

  Here, it is assumed that the ROHC server 30 has failed to restore the ROHC packet received in S21 (S22). As an example of this, there is a case where an unrecoverable error is detected as a result of an error check using CRC (cyclic redundancy code).

  If the restoration fails, the ROHC server 30 transmits error information to the mobile station device 10 (S23). When receiving this error information, the mobile station apparatus 10 transmits the stored prediction basic information to the ROHC server 30 (S24) and indicates that the transmission of the prediction basic information to the compressor 11 is completed. Prediction basic information transmission completion information is output (S25). Upon receiving the error information, the compressor 11 usually starts transmission of the ROHC packet with the omission rate lowered. When the prediction basic information transmission completion information is input, while maintaining the omission rate until then, The ROHC packet is transmitted (S26). The ROHC server 30 restores the ROHC packet transmitted in S26 based on the prediction basic information received from the mobile station device 10.

  As shown in the present modification, according to the mobile communication system 1, even when restoration by the ROHC server 30 fails, it is possible to transmit the ROHC packet while maintaining the omission rate so far. .

It is a figure which shows the system configuration | structure of the mobile communication system concerning embodiment of this invention. It is a figure which shows the functional block of the mobile station apparatus and ROHC server concerning embodiment of this invention. It is a figure which shows the processing flow of the mobile station apparatus concerning embodiment of this invention. It is a figure which shows the process sequence between the mobile station apparatus and ROHC server concerning embodiment of this invention. It is a figure which shows the process sequence between the mobile station apparatus and ROHC server concerning the modification of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Mobile communication system, 10 Mobile station apparatus, 11 Compressor, 12 Decompressor, 13 Prediction basic information storage part, 14 Prediction basic information transmission part, 15 Handover execution determination part, 20 Base station apparatus, 30 ROHC server, 31 Decompressor 32, basic prediction information storage unit, 33 basic prediction information reception unit, 40 packet switch, 100 computer, 101 Internet, 110 transmission data acquisition unit, 111 transmission data transmission unit, 121 prediction basic information generation unit, 310 transmission data reception unit, 311 Prediction unit, 312 Prediction basic information generation unit.

Claims (3)

A communication system including a mobile station device and a network-side receiving device,
The mobile station apparatus,
And data transmission means for the data can be sent in a state of short part fraction Ministry,
Prediction basic information acquisition means for acquiring prediction basic information for predicting an omitted portion of the data according to data transmitted by the data transmission means;
Prediction basic information transmission means for transmitting the prediction basic information acquired by the prediction basic information acquisition means to the receiving device together with information indicating the mobile station device;
Including
The receiving device is:
Receiving means for sequentially receiving data transmitted by the data transmitting means;
According to the received Lud over data by the receiving means, the predicted basic information generating means for generating a predicted basic information for predicting the omitted portions,
According to the prediction basic information generated by the predicted basic information generating means, prediction means for predicting an abbreviated portion of Lud over data received by the receiving means,
Including
The prediction means is based on prediction basic information transmitted from the prediction basic information transmission means and information indicating the mobile station device when prediction according to the prediction basic information generated in the prediction basic information generation means cannot be performed. Predicting omitted portions of data received by the receiving means,
A communication system characterized by the above. The communication system according to claim 1,
The mobile station apparatus is acquired by the data acquisition means from the data in a state in which the portion transmitted by the data transmission means is omitted, based on the prediction basic information acquired by the prediction basic information acquisition means. And further comprising a restoring means for restoring the data,
The prediction basic information transmission means transmits the prediction basic information to the receiving device when the data is restored by the restoration means.
A communication system characterized by the above. And data transmission means for the data can be sent in a state of short part fraction Ministry,
Prediction basic information obtaining means according Lud over data transmitted, acquires predicted basic information for predicting the omitted portion of the data by the data transmission means,
Prediction basic information transmission means for transmitting the prediction basic information acquired by the prediction basic information acquisition means to the receiving device together with information indicating the mobile station device ;
A mobile station apparatus comprising:

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