JP4823754B2 - Transmitting apparatus and transmitting method - Google Patents

Description

  The present invention relates to a transmission apparatus and a transmission method, and more particularly to a technique for maintaining real-time communication.

  In a communication system that performs real-time communication such as voice communication and streaming communication, a predetermined amount of communication data obtained by adding a certain amount of communication control data to a certain amount of communication content data is transmitted predetermined one by one Some are sent sequentially at intervals.

Patent Document 1 discloses a technique for transmitting a packet having a certain amount of data.
JP 2002-77251 A

  By the way, if the throughput is remarkably reduced due to a wireless environment deteriorated by adaptive modulation and a communication rate is lowered, it becomes difficult to maintain communication in the communication system. This is because, when the throughput is reduced, the time required for transmission of communication data increases, so that the arrival delay of communication data gradually becomes significant.

  Accordingly, one of the objects of the present invention is to provide a transmission apparatus and a transmission method capable of maintaining real-time communication even when the throughput is significantly reduced.

  A transmitting apparatus according to the present invention for solving the above-described problems includes an acquisition unit that sequentially acquires communication content data for each predetermined amount of data, communication control data is added to the communication content data acquired by the acquisition unit, and communication data As a transmission means, a detection means for detecting a decrease in throughput, and a control means for controlling the predetermined data amount according to the detection result of the detection means.

  According to this, even if the throughput is significantly reduced, the amount of communication data to be transmitted can be reduced by increasing the predetermined data amount and the reduction in throughput can be suppressed, so that communication can be maintained.

  If throughput is increased and the number of transmissions is increased by lowering the predetermined data amount, data can be transmitted at a finer frequency in communications (such as voice communication) where communication content data is constantly generated. become.

  Further, in the transmission device, communication control data control means for controlling the data amount of the communication control data based on a mutual relationship between communication control data added to communication content data sequentially acquired by the acquisition means, In addition, when the control unit is unable to control the predetermined data amount as a result of detection by the detection unit, the control unit causes the communication control data control unit to control the data amount of the communication control data. The amount of communication data may be controlled.

  According to this, even if the throughput is significantly reduced, it is possible to reduce the data amount of the communication data transmitted by the data amount control processing (for example, packet header compression processing) of the communication control data and suppress the decrease in the throughput. Because it can, communication can be maintained.

  The transmission apparatus may further include a communication rate acquisition unit that acquires a communication rate, and the detection unit detects a decrease in throughput based on the communication rate acquired by the communication rate acquisition unit. Good.

  According to this, it is possible to detect a decrease in throughput based on the communication rate.

  The transmission method according to the present invention includes an acquisition step of sequentially acquiring communication content data by a predetermined amount of data, and a transmission step of adding communication control data to the communication content data acquired in the acquisition step and transmitting the communication content data. A transmission method including: a detection step of detecting a decrease in throughput; and a control step of controlling the predetermined data amount according to a detection result in the detection step.

  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. As shown in the figure, the mobile communication system 1 includes a mobile station device 10, a base station device 20, and a communication device 30.

  The mobile station device 10, the base station device 20, and the communication device 30 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 and the base station device 20 perform wireless communication. The base station device 20 and the communication device 30 perform wired communication via a network (not shown). In the present embodiment, in particular, the mobile station device 10 uses the SIP (Session Initiation Protocol) and RTP (Real-time Transport Protocol) protocols to communicate with the communication device 30 via the base station device 20. Communication (VoIP (Voice over IP) communication) is performed.

  FIG. 2 is a functional block diagram illustrating functions of the mobile station apparatus 10 as a transmission apparatus that transmits communication data related to packet voice communication. In the present embodiment, the mobile station device 10 is described as an example, but it is preferable that the base station device 20 and the communication device 30 have the same function.

  The audio data acquisition unit 11 includes sound collection means such as a microphone. This sound collection means converts sounds such as words uttered by humans into electrical signals. The audio data acquisition unit 11 acquires audio data as communication content data by sampling the electrical signal obtained by the sound collection means at a predetermined sampling period. Then, the acquired data are sequentially written in the audio data buffer 12 which is a first-in first-out storage unit. This sampling period differs depending on the codec provided in the sound collecting means.

  The RTP packet generator 13 sequentially acquires audio data from the audio data buffer 12 by a predetermined amount of data at predetermined time intervals.

  The amount of audio data to be extracted from the audio data buffer 12 by the RTP packet generator 13 and its time interval vary depending on the type of codec provided in the sound collection means. In a specific codec example (G.729), for example, as shown in Table 1, there are three types of data amounts of audio data that the RTP packet generator 13 should extract from the audio data buffer 12. Three more types are added depending on the presence or absence of header compression, and the amount of RTP packet data is six. The RTP packet generation unit 13 selects one of six types according to control by the throughput decrease detection unit 15 to be described later, and the audio data corresponding to the selected type (hereinafter referred to as a selected data amount). The data is sequentially acquired at the transmission interval according to the selected type (hereinafter referred to as the selected transmission interval).

  When header compression is not performed, the RTP packet generation unit 13 adds communication control data including an RTP packet header, a UDP header, an IP header, and a PPP header to the acquired audio data of the selected data amount, thereby Are generated sequentially. Then, the generated RTP packets are sequentially output to the wireless transmission unit 14 at selected transmission intervals.

  On the other hand, when performing header compression, the RTP packet generator 13 performs header compression using a technique called ROHC (Robust Header Compression). This will be specifically described below.

  The RTP packet generator 13 controls the data amount of the communication control data based on the relationship between the communication control data added to the sequentially acquired audio data. More specifically, the RTP packet generation unit 13 compresses the data amount of the communication control data by omitting a portion of the communication control data that can be predicted by the receiving device (for example, the base station device 20). To do. Then, RTP packets (referred to as ROHC packets) formed by adding communication control data with a part omitted are sequentially generated.

  In this way, the receiving device that has received the ROHC packet in which a part of the communication control data is omitted, omits the communication control data based on the communication control data included in the ROHC packet received in the past and the above mutual relationship. Predict the part. Header compression is thus achieved.

  Specifically, the processing related to the ROHC is realized by a compression function called a ROHC compressor. Since most of the communication control data is omitted from the ROHC packet, the data amount is smaller than that of the RTP packet that is not the ROHC packet. The RTP packet generation unit 13 sequentially outputs the generated ROHC packets to the wireless transmission unit 14 at selected transmission intervals.

  The wireless transmission unit 14 includes an antenna, converts RTP packets (including ROHC packets) input from the RTP packet generation unit 13 into wireless signals, and sequentially transmits them to the wireless section. The radio signal transmitted in this way is received by the base station device 20 and transferred to the communication device 30.

  By the way, the throughput of the wireless section changes as appropriate according to the communication state (wireless quality) of the wireless section. For example, in a situation where the radio quality is poor and retransmission control occurs frequently, the throughput decreases. In addition, when adaptive modulation control (link adaptation) is performed, the communication rate is set according to the S / N ratio (Signal per Noise Ratio) of the radio signal received by the base station apparatus 20. Be controlled. The throughput also decreases when the communication rate decreases due to this control.

  The throughput decrease detection unit 15 detects such a decrease in throughput. Specifically, it is preferable to acquire the communication rate of the wireless section and detect a decrease in throughput based on the acquired communication rate.

  The throughput decrease detection unit 15 controls the data amount of the RTP packet generated by the RTP packet generation unit 13 in accordance with the detection result of the throughput decrease acquired in this way. Specifically, the throughput decrease detection unit 15 controls the amount of audio data acquired by the RTP packet generation unit 13 according to the detection result of the throughput decrease. Further, the throughput decrease detection unit 15 determines whether or not to cause the RTP packet generation unit 13 to perform the data amount control of the communication control data according to the detection result of the throughput decrease. Based on these controls or determinations, the RTP packet generator 13 decides what should be selected among the data amounts of the six types of RTP packets, and instructs the RTP packet generator 13 to select the determined data amount. To do.

  A more specific example will be described. In the adaptive modulation scheme, one modulation scheme is selected from the nine types of modulation schemes shown in Table 2 according to the S / N ratio. In Table 2, BPSK is an abbreviation for Binary Phase Shift Keying (two-phase phase shift keying), QPSK is an abbreviation for Quadrature Phase Shift Keying (four-phase phase shift keying), and 8PSK is 8 Phase Shift Keying (eight). QAM is an abbreviation of Quadrature Amplitude Modulation (Quadrature Amplitude Modulation).

  As shown in Table 2, the communication rate differs for each modulation method. The throughput decrease detection unit 15 compares the smaller communication rate of the downlink communication rate and the uplink communication rate corresponding to the modulation method selected by the adaptive modulation method with the total throughput shown in Table 1. Then, the RTP packet generator 13 determines that the RTP packet data amount corresponding to the maximum total throughput not exceeding the communication rate should be selected. By doing so, even if the throughput (communication rate) is significantly reduced, the total throughput can be reduced and the reduction in throughput can be suppressed, so that communication can be maintained.

  The processing described above will be described again in more detail with reference to the processing sequence between the mobile station device 10 and the base station device 20.

  3 and 4 are diagrams illustrating a processing sequence between the mobile station apparatus 10 and the base station apparatus 20.

  As shown in FIG. 3, the mobile station apparatus 10 first receives an instruction to start packet voice communication from the user. Specifically, a SIP INVITE signal is received from an upper layer (S1). The SIP INVITE signal includes information indicating a codec. Upon receiving the SIP INVITE signal, the mobile station apparatus 10 acquires information indicating the codec from the received SIP INVITE signal (S2).

  Here, assuming that the codec is G.729, the mobile station apparatus 10 selects one of the RTP packet data amounts shown in Table 1 and starts transmission (S3).

  In this case, the mobile station apparatus 10 preferentially selects the one that does not use header compression. This is because the processing load on the mobile station device 10 and the communication partner increases when processing for header compression is performed. In addition, a transmission interval that is as short as possible is preferentially selected. This is because the shorter the transmission interval, the faster the acquired voice data can be transmitted as an RTP packet.

  While performing the transmission by S3, the mobile station apparatus 10 calculates a throughput regularly (S4).

  Here, it is assumed that the radio quality is deteriorated and the modulation method is changed (S5). Then, the throughput decreases, and the mobile station apparatus 10 detects that the throughput has decreased. Here, if it is detected that the throughput has dropped to 25 kbps, the mobile station device 10 corresponds to the maximum total throughput that does not exceed 25 kbps among the RTP packet data amounts shown in Table 1 according to the detection result. Select the RTP packet data amount (62 bytes). Then, acquisition of audio data is started at a data amount (20 bytes) and a time interval (20 ms) of audio data corresponding to the RTP packet data amount (62 bytes) (S6). As a result, the total throughput is 24.8 kbps, which is below 25 kbps.

  Next, it is assumed that the radio quality further deteriorates and the modulation method is changed (S7 in FIG. 4). Then, the throughput further decreases, and the mobile station apparatus 10 detects that the throughput has further decreased. Here, if it is detected that the throughput has dropped to 11 kbps, the mobile station device 10 corresponds to the maximum total throughput that does not exceed 11 kbps among the RTP packet data amounts shown in Table 1 according to the detection result. Select the RTP packet data amount (13 bytes).

  Since this RTP packet data amount is realized when header compression processing is performed by ROHC, the mobile station device 10 and the base station device 20 perform processing as a ROHC compressor and a ROHC decompressor, respectively, by a conventionally known method. Is started (S8, S9).

In addition, the mobile station apparatus 10 starts acquiring voice data at a voice data volume (10 bytes) and a time interval (10 ms) corresponding to the RTP packet data volume (13 bytes). Then, the ROHC compressor compresses the data amount of the RTP packet by omitting the communication control data (S10), generates an RTP packet (ROHC packet), and starts transmission (S11). As a result of this process, the total throughput is 10.4.
It will be kbps and will be below 11 kbps.

  When the base station apparatus 20 receives the ROHC packet thus transmitted, the base station apparatus 20 decompresses the RTP packet by supplementing the communication control data by the ROHC decompressor (S12), and transfers the packet to the communication apparatus 30.

  As described above, according to the present invention, even if the throughput is significantly reduced, the amount of communication data to be transmitted can be reduced and the reduction in throughput can be suppressed, so that communication can be maintained.

  Specifically, by increasing the predetermined data amount, the data amount of communication data to be transmitted can be reduced and the decrease in throughput can be suppressed, so that communication can be maintained.

  Furthermore, if the number of transmissions is increased by lowering the predetermined data amount when the throughput increases, data can be transmitted at a finer frequency in communications (such as voice communication) in which communication content data is constantly generated. become.

  In addition, since the amount of communication data transmitted by the data amount control process of communication control data can be reduced and the decrease in throughput can be suppressed, communication can be maintained even if the throughput is significantly decreased.

  Further, a decrease in throughput can be detected based on the communication rate.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, an example in which the present invention is applied to a mobile communication system has been described. However, the present invention can be applied to any other communication system that performs real-time communication.

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 concerning embodiment of this invention. It is a figure which shows the process sequence between the mobile station apparatus and base station apparatus concerning embodiment of this invention. It is a figure which shows the process sequence between the mobile station apparatus and base station apparatus concerning embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Mobile communication system, 10 Mobile station apparatus, 11 Voice data acquisition part, 12 Voice data buffer, 13 Packet generation part, 14 Wireless transmission part, 15 Throughput fall detection part, 20 Base station apparatus, 30 Communication apparatus

Claims (7)

Acquisition means for sequentially acquiring communication content data by a predetermined amount of data;
Against the communication content data acquired by the acquisition unit, a transmission unit adds the communication control data, or perform additional although compressing the communication control data, and sequentially transmits the obtained data as the communication data,
Detection means for detecting a decrease in throughput;
In accordance with the communication rate when the decrease in throughput is detected, the transmission means selects either the addition of the communication control data to the communication content data or the addition of a compressed version of the communication control data And control means for transmitting the communication data ;
A transmission apparatus comprising: The control means adds the communication control data to the communication content data and compresses the communication control data so that the communication rate in the transmission means does not exceed the communication rate when the decrease in throughput is detected. The transmission apparatus according to claim 1, wherein any one of additions of selected ones is selected. The predetermined data amount has a plurality of types,
The control means further selects any one of a plurality of types of the predetermined data amount so that the communication rate in the transmission means does not exceed the communication rate when the decrease in the throughput is detected. The transmission device according to claim 2 . A set of the predetermined data amount, the number of transmissions of the communication content data per unit time, and whether or not the communication control data is compressed is defined corresponding to each of a plurality of communication rates,
4. The transmission apparatus according to claim 3, wherein the control unit selects a pair corresponding to a communication rate that does not exceed a communication rate when a decrease in the throughput is detected . The control means, when there are a plurality of pairs corresponding to a communication rate that does not exceed the communication rate when the decrease in the throughput is detected, preferentially selects a pair without compression of the communication control data. The transmission device according to claim 4, wherein the transmission device is characterized. When there are a plurality of sets corresponding to a communication rate that does not exceed the communication rate when the throughput decrease is detected, the control unit preferentially selects a set having a large number of transmissions per unit time of the communication content data. The transmission device according to claim 4, wherein the transmission device is selected. An acquisition step of sequentially acquiring communication content data by a predetermined amount of data;
A transmission step of adding the communication control data to the communication content data acquired in the acquisition step or adding the compressed communication control data and transmitting the obtained data;
A transmission method including:
A detection step for detecting a decrease in throughput;
Depending on the communication rate when a decrease in throughput is detected, either the addition of the communication control data or the addition of a compressed version of the communication control data is executed in the transmission step in the transmission step. A control step to select whether to
The transmission method characterized by further including.

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