JP2005244668A - Communication apparatus and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that missing of packet easily occurs since an error rate is high in a radio section. <P>SOLUTION: A first communication unit 102 receives packets from a wired network 10. An analyzing unit 104 specifies the protocol of a packet, and outputs protocol identification information to a re-transmission time setting unit 107. If the protocol identification information indicates RTP, the unit 107 sets a standard value as the maximum number of times of transmission. If the protocol identification information does not indicate RTP, the unit 107 sets a value smaller than the standard value as the maximum number of times of transmission. In this way, since re-transmission conforming to the RTP is performed many times, the missing of packet can be suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radio communication technique, and more particularly to a method for adjusting the number of times of retransmission of data in a radio section and a communication apparatus using the method.

With the development of infrastructure such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (Fiber To The Home), high-speed communication services of 1 Mbps to 100 Mbps or more have become available. With the establishment of such a communication infrastructure, multimedia services that handle relatively large volumes of content such as VoIP and video streaming are gradually spreading. In general, communication in a network is realized by using various protocols. For this reason, communication packets conforming to various types of protocols are mixed in a single network, and depending on the communication status, services that handle high-real-time data such as VoIP and video streaming are provided with sufficient quality. It may not be done. For this reason, for example, there is one that preferentially transmits VoIP packets (Patent Document 1). Also, there is one that controls the presence / absence of data retransmission processing using real-time data and non-real-time data (Patent Document 2).
JP 2002-125069 A JP-A-7-336366

  The network is constructed by wire or wireless. Since the transmission path characteristics in wireless communication are unstable compared to the transmission path characteristics in wired communication, the communication quality in the wireless network is easily affected by changes in the communication state. For this reason, the data error rate is high in the wireless section, and packet loss and delay often occur. For example, when streaming audio or video, the quality at the time of reproduction deteriorates if many packets are lost or delayed.

  The present invention has been made in view of these points, and an object thereof is to provide a communication method for improving communication quality in a wireless section and an apparatus using the method.

  One embodiment of the present invention is an apparatus that outputs an input from one communication path to the other communication path. In accordance with a series of communication procedures composed of a plurality of layers, this apparatus includes an input unit that receives a packet to be transmitted to a predetermined terminal device, a transmission unit that transmits the packet to the terminal device, and a maximum number of packet retransmissions. A setting unit configured to set a value based on characteristics of a layer higher than the physical layer for physically transmitting the packet to the terminal device, and when the packet needs to be retransmitted, the transmission unit sets the maximum value Retransmission may be performed up to the upper limit.

  According to this aspect, the upper limit value of the number of packet retransmissions in the physical layer can be set based on the characteristics of the higher layer. For example, the “physical layer” may be a wired transmission means or a wireless transmission means. Thereby, it is possible to perform retransmission processing by efficiently using a limited communication band.

  The apparatus may further include an analysis unit that identifies a protocol in a layer higher than the physical layer based on the packet, and the setting unit may set a maximum value according to the protocol.

  The setting unit sets the maximum number of retransmissions of a packet transmitted according to a protocol for transmitting non-real-time data to be smaller than the maximum value of the number of retransmissions of a packet transmitted according to a protocol for transmitting real-time data. It may be set. Thereby, priority is given to retransmission of real-time data.

  The apparatus further includes a monitoring unit that monitors a communication state in the physical layer, and the setting unit determines whether to set a maximum value based on characteristics of a layer higher than the physical layer according to the communication state. Also good. Thereby, a communication band can be used efficiently according to a communication state.

  The monitoring unit monitors the amount of packets to be transmitted through the physical layer, and when the amount of packets exceeds a predetermined amount, the setting unit sets the maximum number of retransmissions as a feature of a layer higher than the physical layer. You may set based on.

  Yet another aspect of the present invention is a method of outputting an input from one communication path to the other communication path. According to this method, a step of receiving a packet to be transmitted to a predetermined terminal device, a step of transmitting the packet to the terminal device, and a maximum value of the number of retransmissions of the packet in accordance with a series of communication procedures including a plurality of layers And setting based on the characteristics of a layer higher than the physical layer for physically transmitting the packet to the terminal device.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, packets can be transmitted efficiently.

  FIG. 1 is a configuration diagram of a communication system 50 according to the embodiment. The first terminal device 12 and the first communication device 100 a are connected to the wired network 10. The second terminal device 14 is connected to the second communication device 100b, for example, serially or in parallel. The first communication device 100a and the second communication device 100b form a wireless network 20 to enable the first terminal device 12 and the second terminal device 14 to communicate. The first communication device 100a and the second communication device 100b have the same configuration. Hereinafter, the first communication device 100a and the second communication device 100b are simply referred to as “communication device 100”.

  The communication device 100 transmits a packet received via the wired network 10 to another communication device 100 via the wireless network 20. The communication apparatus 100 can transmit data by selectively using a plurality of modulation schemes such as BPSK resistant to errors and 16QAM capable of transmitting a large amount of data. By changing the modulation method and the coding rate, the transmission rate, that is, the transmission rate can be switched. Hereinafter, changing the modulation method and coding rate is simply expressed as changing the “transmission rate”.

  In general, the data error rate in wireless communication is higher than the data error rate in wired communication. Wireless communication is easily affected by changes in the communication state. For example, when a microwave oven is used in the vicinity, the data error rate is higher than when the microwave oven is not used. Further, as the data transmission rate increases, the data error rate also increases. This is because transmission path characteristics in wireless communication are more susceptible to changes in the communication state due to changes in the surrounding environment than transmission path characteristics in wired communication.

  For example, in an application for streaming audio or video, the quality at the time of reproduction deteriorates if many packets are lost or delayed. In particular, when the number of missing packets increases, the quality of reproduction that is perceived by humans is significantly reduced. If retransmission processing is performed for all packets until they are reliably transmitted, the loss of packets in the wireless section can be prevented, but the communication bandwidth in the wireless section may be compressed and the communication efficiency of the entire network may be reduced. Therefore, the communication apparatus 100 according to the embodiment prevents the packet loss in the wireless section without controlling the communication efficiency of the entire network by controlling the maximum number of retransmissions and the transmission rate.

(About control of the maximum number of retransmissions)
The communication apparatus 100 eliminates the compression of the communication band that accompanies retransmission by providing a difference in the maximum number of retransmissions according to the type of packet. “Maximum number of retransmissions” is the maximum value of the number of times of retransmission of a missing packet in the physical layer. Generally, UDP is used as a lower layer protocol for high real-time protocols used for streaming audio and video, and TCP is used for low real-time protocols such as FTP (File Transfer Protocol) and HTTP (Hyper Text Transfer Protocol). It is a lower layer protocol.

  Since the TCP packet is subjected to retransmission control in the transport layer, the packet is not lost. However, since the UDP packet is not subjected to retransmission control in the transport layer, the packet is lost. Therefore, for example, the communication apparatus 100 sets the maximum number of retransmissions of a UDP packet to be larger than the maximum number of retransmissions of a TCP packet. As a result, loss of UDP packets can be suppressed, and compression of the communication band in the wireless section can be avoided. In other words, since a band that should be used for retransmission of TCP packets can be made free, the communication band is not compressed more than necessary due to retransmission of UDP packets.

  In addition, there is an effect that the retransmission timing is dispersed in time series. For example, when the maximum number of retransmissions of a TCP packet is set to 0, the UDP packet is immediately retransmitted in the wireless section. On the other hand, because TCP packets are retransmitted after being instructed by a higher-level terminal in the wireless section, even if TCP packets and UDP packets are lost at the same time due to deterioration of the communication status, the respective packets are retransmitted. Timing is distributed.

  When streaming audio or video, the quality at the time of reproduction is affected not only by packet loss but also by packet delay, that is, packet arrival time. A TCP packet is reliably transmitted by retransmission control in the transport layer, but since it is a process between terminals, it takes a longer time than a retransmission process in a radio section. For this reason, the communication apparatus 100 uses the maximum number of retransmissions of data (hereinafter simply referred to as “real-time data”) used in an application that performs processing with high real-time characteristics as data used in the application that performs processing with low real-time characteristics. Set more than the maximum number of retransmissions (hereinafter simply referred to as “non-real-time data”). As a result, loss of real-time data can be suppressed and compression of the communication band in the wireless section can be avoided.

(About transmission speed control)
Generally, in wireless communication, the data error rate increases as the data transmission rate increases. For this reason, if communication is performed at a low transmission rate, data errors can be suppressed and packet loss can be suppressed, but the transmission rate in the wireless section can be reduced, which can reduce the communication efficiency of the entire network. . Therefore, the communication device 100 switches the transmission rate in the wireless section according to the type of packet. For example, when the packet includes real-time data, the communication apparatus 100 transmits the packet at a transmission rate lower than the standard transmission rate. When the packet includes non-real time data, the communication device 100 transmits the packet at a standard transmission rate. Thereby, lack of real-time data can be suppressed without reducing the communication efficiency of the entire network.

  The communication device 100 efficiently suppresses the loss of real-time data by controlling at least one of the maximum number of transmissions and the transmission rate in the wireless section according to the type of packet.

(Transmission rate is controlled according to packet type)
FIG. 2 is a diagram illustrating communication processing between the first communication device 100a and the second communication device 100b of FIG. 1 using an OSI reference model in a mode in which the transmission rate is controlled according to the type of packet. In this figure, it is assumed that the first communication device 100a is a transmission side and the second communication device 100b is a reception side. The first communication device 100a sets a transmission rate for transmitting packets in the physical layer based on features in a layer higher than the physical layer. Then, the first communication device 100a performs modulation processing so that the packet can be transmitted at the set transmission rate, and wirelessly transmits the packet to the second communication device 100b.

  The communication device 100 controls the transmission rate of the packet so that the user does not feel stress with respect to the processing provided by the application to the user. In this embodiment, the characteristics of the upper layer are used as means for specifying which application is used for which application by which packet. The “feature in the upper layer” may be, for example, a protocol in the upper layer, a data size of a packet generated by a communication procedure in the upper layer, or a predetermined size included in other packets. It may be arbitrary information such as a bit pattern, and it is only necessary to identify what kind of processing the packet is used for. “What process” may be a main process in an application such as streaming playback, or may be an auxiliary process in an application such as user registration.

  In this embodiment, the transmission rate is switched based on whether or not the protocol is used for real-time data transmission. As this real-time data, the case of RTP (Real-time Transport Protocol) is taken as an example. In addition, protocols other than RTP are handled as non-real time data. Of course, in another example, one protocol other than RTP may be selected as real-time data, or a plurality of protocols may be selected. In the case of real-time data, the communication device 100 transmits a packet at a low transmission rate in the wireless section. As a result, the rate of occurrence of errors occurring in the wireless section is reduced, and packet delays and omissions can be suppressed.

(First embodiment)
FIG. 3 is an internal configuration diagram of the communication apparatus 100 according to the first embodiment. Each component of the communication device 100 is, in terms of hardware components, a CPU of any computer, a memory, a program that realizes the components of this figure loaded in the memory, a storage unit such as a hard disk that stores the program, It is realized mainly by a network connection interface, a unit used for wireless communication, etc., but it will be understood by those skilled in the art that there are various modifications in the realization method and apparatus. Each figure to be described below shows functional unit blocks, not hardware unit configurations.

  The first communication unit 102 performs communication by connecting to the network 10 formed by a wire such as 10Base-T or 100Base-T, for example. The first communication unit 102 outputs the packet received from the wired network 10 to the analysis unit 104. As another connection form, you may connect with the 2nd terminal device 14 directly, as demonstrated in FIG.

  The analysis unit 104 specifies the type of data transmitted in the packet based on information identifying a protocol in a predetermined layer included in the packet. Specifically, the analysis unit 104 extracts information for identifying the protocol from the received packet, specifies the protocol based on the extracted information, and identifies the protocol (hereinafter simply referred to as “protocol identification information”). ) To the transmission rate setting unit 106 and the packet is written to the buffer 112. There are various methods for specifying the protocol identification information from the information included in the packet. For example, in the case of a packet conforming to IPv4, the analysis unit 104 may read the information for identifying the protocol from the IP header, or may be included in the IP header. The protocol may be specified based on a protocol in a lower layer such as TCP or UDP and a destination port number included in the TCP header or UDP header.

  The transmission rate setting unit 106 sets the transmission rate in the wireless section based on the protocol identification information supplied from the analysis unit 104. Then, the transmission rate setting unit 106 instructs the modulation unit 108 to perform modulation processing on the packet for transmission at the set transmission rate. Although details will be described later, a plurality of transmission rates are prepared in advance according to the modulation capability of the modulation unit 108, and the transmission rate setting unit 106 selects a transmission rate according to the protocol identification information from among them.

  In the present embodiment, when the protocol identification information received from the analysis unit 104 is other than RTP, the transmission rate setting unit 106 selects the highest transmission rate that can be obtained in communication with the receiving-side communication apparatus 100 in the wireless section. This transmission rate is hereinafter referred to as “standard transmission rate”. When the protocol identification information received from the analysis unit 104 is RTP, the transmission rate setting unit 106 selects a transmission rate lower than the standard transmission rate. As a result, the possibility that an error will occur for an RTP packet in the radio section can be made lower than the possibility that an error will occur for a packet of another protocol. That is, delays and omissions in the radio section of RTP packets can be suppressed.

  Second communication unit 120 includes modulation unit 108, RF unit 110, buffer 112, transmission control unit 114, retransmission instruction unit 116, and demodulation unit 118.

  The RF unit 110 performs frequency conversion processing, amplification processing, AD or DA conversion processing between a baseband signal and a radio frequency signal processed by a modulation unit 108 and a demodulation unit 118 described later. The RF unit 110 transmits and receives radio waves via the antenna 122.

  The buffer 112 stores the packet supplied from the analysis unit 104. The transmission control unit 114 reads the packet from the buffer 112 and supplies the packet to the modulation unit 108. In addition, when receiving a retransmission instruction from the retransmission instruction unit 116, the transmission control unit 114 reads a packet to be retransmitted from the buffer 112 and instructs the transmission rate setting unit 106 to determine the transmission rate of the packet.

  For example, the modulation unit 108 uses a modulation scheme such as BPSK (Binary Phase Shift Keying), π / 4 shift QPSK (Quadrature Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation), Mps, 5 ps, Mps, 5 ps. Data can be transmitted selectively using a plurality of transmission speeds such as 11 Mbps, 12 Mbps, and 18 Mbps. In response to an instruction from the transmission rate setting unit 106, the modulation unit 108 performs modulation processing so that data can be transmitted at a designated transmission rate.

  The demodulator 118 performs a demodulation process on the received signal converted into the baseband by the RF unit 110. The demodulator 118 changes the demodulation process according to the modulation method of the received signal. Demodulation section 118 outputs the demodulated packet to first communication section 102. The first communication unit 102 outputs the packet received from the demodulation unit 118 to the wired network 10. Demodulation section 118 outputs a reception notification obtained by demodulation to retransmission instruction section 116. “Reception notification” is information indicating that the receiving-side communication device 100 created in a layer lower than the transport layer has received a packet. If the reception notification for the transmitted packet does not return within a predetermined period, the retransmission instruction unit 116 instructs the transmission control unit 114 to retransmit the packet.

  When receiving a retransmission instruction from the retransmission instruction unit 116, the transmission control unit 114 reads the packet to be retransmitted from the buffer 112 and notifies the transmission rate setting unit 106 that the packet is to be retransmitted. The transmission rate setting unit 106 receives the notification from the transmission control unit 114 and determines the transmission rate at the time of retransmission. For example, the analysis unit 104 may store the packet and the protocol identification information of the packet in the buffer 112 in association with each other so that the transmission rate at the time of retransmission can be determined for each packet. Then, the transmission control unit 114 outputs protocol identification information to the transmission rate setting unit 106 together with the retransmission notification. Thereby, the transmission rate setting unit 106 can determine the transmission rate at the time of retransmission based on the protocol identification information.

  FIG. 4 is a flowchart of a process for transmitting one packet in the communication apparatus 100 of FIG. The first communication unit 102 in FIG. 3 receives a packet from the wired network 10 (S10). The analysis unit 104 in FIG. 2 specifies the protocol of the packet (S12), and determines whether it is RTP (S14). In the case of RTP (Y in S14), the transmission speed setting unit 106 in FIG. 2 sets the transmission speed to a low speed (S16). If it is not RTP (N in S14), the transmission rate setting unit 106 sets the transmission rate to the standard transmission rate (S18). 2 performs a modulation process so that a packet can be transmitted at the transmission rate set by the transmission rate setting unit 106 (S20). Then, the packet is transmitted via the RF unit 110 of FIG. 2 and the antenna 122 of FIG. 2 (S22), and the process of transmitting one packet is completed. The communication device 100 performs this process for each received packet.

(Second Embodiment)
FIG. 5 is an internal configuration diagram of the communication apparatus 100 according to the second embodiment. The communication device 100 according to the second embodiment lowers the transmission rate when retransmission occurs in a radio section. The configurations denoted by the same reference numerals as those already described in this figure have substantially the same functions and operations. In the following, the points of difference in function and operation from the configuration already described will be mainly described.

  When receiving a packet from the wired network 10, the first communication unit 102 stores the packet in the buffer 112. The transmission control unit 114 reads a packet from the buffer 112 and outputs it to the modulation unit 108. Then, the packet is modulated by the modulation unit 108 and transmitted via the RF unit 110 and the antenna 122. When receiving a retransmission instruction from the retransmission instruction unit 116, the transmission control unit 114 instructs the transmission rate setting unit 106 to switch the transmission rate.

  At the time of retransmission, the transmission rate setting unit 106 sets a transmission rate lower than the transmission rate at the time of transmitting the packet for the first time. Further, the transmission rate setting unit 106 may gradually decrease the transmission rate as the number of retransmissions increases. Thereby, in the wireless section where the communication state is likely to change, the transmission rate according to the communication state at that time is appropriately set. For example, when the initial transmission rate is 24 Mbps, the transmission rate setting unit 106 lowers the transmission rate at the time of retransmission stepwise, such as 18 Mbps, 12 Mbps, and 9 Mbps.

  FIG. 6 is a flowchart of a process for transmitting one packet in the communication apparatus 100 of FIG. The first communication unit 102 in FIG. 5 receives a packet from the wired network 10 (S10). The transmission rate setting unit 106 in FIG. 5 sets the transmission rate to the standard transmission rate (S18), and the modulation unit 108 performs modulation processing so that packets can be transmitted at the set transmission rate (S20). The RF unit 110 in FIG. 5 and the antenna 122 in FIG. 5 transmit the modulated packet (S22). 5 receives a retransmission instruction from the retransmission instruction unit 116 in FIG. 5 (Y in S30), the transmission control unit 114 instructs the transmission rate setting unit 106 to switch the transmission rate. The transmission rate setting unit 106 sets a lower transmission rate than before retransmission (S26). If a retransmission instruction has not been accepted (N in S30), the transmission process for one packet is terminated.

(Third embodiment)
FIG. 7 is an internal configuration diagram of the communication apparatus 100 according to the third embodiment. The third embodiment is a combination of the first embodiment and the second embodiment, and the communication apparatus 100 determines the packet based on the type of packet and the number of retransmissions in the radio section. The transmission speed is switched.

  That is, the transmission rate setting unit 106 in FIG. 1 determines the transmission rate of a packet in the wireless section based on the protocol of the packet. When retransmission occurs in the wireless section, the transmission rate setting unit 106 switches the transmission rate stepwise to a lower direction.

  FIG. 8 is a flowchart of a process for transmitting one packet in the communication apparatus 100 of FIG. The first communication unit 102 in FIG. 3 receives a packet from the wired network 10 (S10). The analysis unit 104 in FIG. 2 specifies the protocol of the packet (S12), and determines whether it is RTP (S14). In the case of RTP (Y in S14), the transmission speed setting unit 106 in FIG. 2 sets the transmission speed to a low speed (S16). If it is not RTP (N in S14), the transmission rate setting unit 106 sets the transmission rate to the standard transmission rate (S18). 2 performs a modulation process so that a packet can be transmitted at the transmission rate set by the transmission rate setting unit 106 (S20). Then, the packet is transmitted via the communication device 100 of FIG. 2 and the antenna 122 of FIG. 2 (S22). When receiving a retransmission instruction from the retransmission instruction unit 116 in FIG. 2 (Y in S24), the transmission control unit 114 in FIG. 2 requests the transmission rate setting unit 106 to determine the transmission rate at the time of retransmission. Then, the transmission speed setting unit 106 further sets the transmission speed to a low speed (S26). If no retransmission instruction is accepted in step 24 (N in S24), the process of transmitting one packet is terminated. The communication device 100 performs this process for each received packet.

(Mode for controlling the maximum number of retransmissions according to the type of packet)
FIG. 9 is a diagram illustrating communication processing between the first communication device 100a and the second communication device 100b of FIG. 1 using an OSI reference model in a form in which the maximum number of retransmissions is controlled according to the type of packet. In this figure, it is assumed that the first communication device 100a is a transmission side and the second communication device 100b is a reception side. The first communication device 100a sets the maximum number of retransmissions based on features in a layer higher than the physical layer. Then, the first communication device 100a performs retransmission with the maximum number of retransmissions set for each packet as an upper limit.

  As described above, the communication apparatus 100 controls the maximum number of packet retransmissions so that the user does not feel stress with respect to the processing provided by the application to the user. In this embodiment, the characteristics of the upper layer are used as means for specifying which application is used for which application by which packet. In the present embodiment, the maximum number of retransmissions is set based on whether the protocol is used for transmitting real-time data or the protocol used for transmitting non-real-time data.

(Fourth embodiment)
FIG. 10 is an internal configuration diagram of the communication apparatus 100 according to the fourth embodiment. The analysis unit 104 analyzes the packet received from the first communication unit 102 and outputs protocol identification information to the retransmission number setting unit 107. The analysis unit 104 stores the packet in the buffer 112. The transmission control unit 114 reads the packet from the buffer 112 and outputs it to the modulation unit 108. Modulation section 108 performs a predetermined modulation process on the packet and outputs the result to RF section 110. The packet is DA-converted by the RF unit 110 and transmitted from the antenna 122. In addition, the RF unit 110 performs AD conversion on the radio wave received by the antenna 122 and outputs the result to the demodulation unit 118. Demodulation section 118 outputs the packet obtained by demodulation to first communication section 102. Demodulation section 118 also outputs a reception notification to retransmission instruction section 116.

  The retransmission number setting unit 107 sets the maximum number of retransmissions for each packet based on the protocol identification information. When the protocol identification information indicates RTP, the retransmission number setting unit 107 sets a standard maximum number of retransmissions for the packet. The “standard maximum number of retransmissions” may be registered in advance as a default value, or may be changed according to a communication state or a congestion state in the physical layer. When the protocol identification information indicates other than RTP, the retransmission count setting unit 107 sets a value smaller than the standard maximum retransmission count for the packet as the maximum retransmission count. In another example, when the protocol identification information indicates other than RTP, the retransmission number setting unit 107 may not perform retransmission for the packet, that is, may set the maximum number of retransmissions to zero. Based on the protocol identification information, the retransmission number setting unit 107 may perform setting so that a difference occurs in the maximum number of retransmissions for packets conforming to each protocol.

  The retransmission instruction unit 116 identifies a packet to be retransmitted based on the reception notification. The retransmission instruction unit 116 may specify a packet to be retransmitted using a known technique. Then, the retransmission instruction unit 116 determines whether or not the number of retransmissions of the identified packet is less than the maximum number of retransmissions set in the retransmission number setting unit 107. If the number of retransmissions is less than the maximum number of retransmissions, retransmission instruction unit 116 instructs transmission control unit 114 to retransmit the packet. When the number of retransmissions is equal to or greater than the maximum number of retransmissions, retransmission instruction unit 116 does not instruct transmission control unit 114 to retransmit the packet. As a result, the communication apparatus 100 can limit the number of retransmissions according to the type of packet.

  FIG. 11 is a flowchart of a process for transmitting one packet in the communication apparatus 100 of FIG. The first communication unit 102 in FIG. 10 receives a packet from the wired network 10 (S10). The analysis unit 104 in FIG. 10 specifies the protocol of the packet (S12). The retransmission number setting unit 107 in FIG. 10 determines whether or not the packet is RTP (S50). In the case of RTP (S50Y), the retransmission number setting unit 107 sets the maximum number of retransmissions of the packet as a standard (S54). In cases other than RTP (N in S50), the retransmission number setting unit 107 sets the maximum number of retransmissions of the packet to be less than the standard (S52). The second communication unit 120 in FIG. 10 transmits the packet (S22).

(Fifth embodiment)
FIG. 12 is an internal configuration diagram of the communication apparatus 100 according to the fifth embodiment. The communication device 100 according to the fifth embodiment monitors the communication state in the wireless section, and performs processing for setting different maximum retransmission counts for real-time data and non-real-time data when communication is congested. The communication apparatus 100 is obtained by adding a monitoring unit 130 that monitors the state of the buffer 112 to the communication apparatus 100 described with reference to FIG.

  The monitoring unit 130 monitors communication congestion in the wireless section based on the amount of packets held in the buffer 112, the free capacity of the buffer 112, and the like. In the present embodiment, the monitoring unit 130 notifies the retransmission number setting unit 107 when the free capacity of the buffer 112 becomes smaller than a predetermined value. Upon receiving this notification, the retransmission number setting unit 107 starts a process of setting the maximum number of retransmissions according to the type of packet.

  In another example, the monitoring unit 130 notifies the retransmission capacity setting unit 107 in steps of the free capacity of the buffer 112, and the retransmission number setting unit 107 increases the maximum retransmission in stages according to the free capacity of the buffer 112. The number of times may be set. For example, the retransmission number setting unit 107 may gradually decrease the maximum number of retransmissions as the free capacity of the buffer 112 decreases. Also in this case, the maximum number of retransmissions of non-real time data is set to be smaller than the maximum number of retransmissions of real time data. That is, when real-time data and non-real-time data are transmitted through the radio section at the same time, the maximum number of retransmissions of non-real-time data is reduced first. As a result, the process of setting the maximum number of retransmissions according to the type of packet can be selectively performed according to the communication state, so that efficient control according to the communication state is possible.

  When only real-time data or non-real-time data is transmitted at the same time, the retransmission number setting unit 107 may select a packet that lowers the number of retransmissions preferentially based on the size of each packet. For example, when a packet including video data and a packet including audio data that are handled as real-time data at the same time are transmitted, the retransmission number setting unit 107 sets the maximum number of retransmissions of a packet including video data to a packet including audio data. May be lower than the maximum number of retransmissions. That is, the retransmission number setting unit 107 first lowers the maximum number of retransmissions of a packet including video data. The retransmission number setting unit 107 may specify a packet including video data and a packet including audio data based on, for example, the data size of the packet. In general, a packet including video data has a larger data size than a packet including audio data. Therefore, the retransmission count setting unit 107 may hold a data size threshold value that is determined in advance as video data, and perform the determination according to whether the threshold value is exceeded or not exceeded.

  FIG. 13 is a flowchart of a process for transmitting one packet in the communication apparatus 100 of FIG. The first communication unit 102 in FIG. 12 receives a packet from the wired network 10 (S10). The analysis unit 104 in FIG. 12 specifies the protocol of the packet (S12). The monitoring unit 130 in FIG. 12 monitors the state of the buffer 112 in FIG. 12 (S60), and determines whether the free capacity is less than a predetermined capacity (S62). When the free capacity of the buffer 112 is smaller than the predetermined capacity (Y in S62), the retransmission number setting unit 107 in FIG. 12 determines whether or not the specified protocol is RTP (S50). In the case of RTP (Y in S50), the retransmission number setting unit 107 sets the maximum number of retransmissions of the packet to a standard number (S54). If it is not RTP (N in S50), the retransmission number setting unit 107 sets the maximum number of retransmissions of the packet to a number smaller than the standard (S52). If the free capacity of the buffer 112 is larger than the predetermined capacity in Step 62 (N in S62), the retransmission number setting unit 107 sets the maximum number of retransmissions for each packet to the standard number regardless of the protocol (S54). . The second communication unit 120 in FIG. 12 transmits the packet (S22).

(Sixth embodiment)
The mode for controlling the transmission rate according to the type of packet has been described by taking the first to third embodiments as an example. Further, the mode of controlling the maximum number of retransmissions according to the type of packet has been described by taking the fourth and fifth embodiments as examples. The communication device 100 according to the sixth embodiment controls the transmission rate and the maximum number of retransmissions according to the type of packet. That is, the communication device 100 may be configured by combining the first to fifth embodiments.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there. Examples of such modifications are as follows.

  The transmission rate setting unit 106 in FIG. 3 selects a transmission rate lower than the standard transmission rate in the case of RTP. However, the transmission rate setting unit 106 holds a table in which the protocol identification information and the transmission rate are associated with each other and refers to the table. The transmission speed may be set. That is, a transmission rate can be set for each protocol by providing a table in which protocol identification information handled as real-time data is associated with a transmission rate. Similarly, the retransmission number setting unit 107 in FIG. 10 may hold a table in which protocol identification information handled as real-time data is associated with the maximum number of retransmissions.

It is a block diagram of the communication system which concerns on embodiment. FIG. 2 is a diagram showing communication processing between the first communication device and the second communication device in FIG. 1 using an OSI reference model in a mode in which the transmission rate is controlled according to the type of packet. It is an internal block diagram of the communication apparatus which concerns on 1st Embodiment. It is a flowchart of the process which transmits one packet in the communication apparatus of FIG. It is an internal block diagram of the communication apparatus which concerns on 2nd Embodiment. It is a flowchart of the process which transmits one packet in the communication apparatus of FIG. It is an internal block diagram of the communication apparatus which concerns on 3rd Embodiment. It is a flowchart of the process which transmits one packet in the communication apparatus of FIG. FIG. 3 is a diagram showing communication processing between the first communication device and the second communication device in FIG. 1 using an OSI reference model in a form in which the maximum number of retransmissions is controlled according to the type of packet. It is an internal block diagram of the communication apparatus which concerns on 4th Embodiment. 11 is a flowchart of processing for transmitting one packet in the communication apparatus of FIG. 10. It is an internal block diagram of the communication apparatus which concerns on 5th Embodiment. 13 is a flowchart of processing for transmitting one packet in the communication apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Wired network, 20 Wireless network, 50 Communication system, 100 Communication apparatus, 102 1st communication part, 104 Analysis part, 106 Transmission rate setting part, 107 Retransmission number setting part, 108 Modulation part, 110 RF part, 112 Buffer, 114 Transmission control unit, 116 retransmission instruction unit, 118 demodulation unit, 120 second communication unit, 122 antenna, 130 monitoring unit.

Claims (7)

In accordance with a series of communication procedures composed of a plurality of layers, an input unit that receives a packet to be transmitted to a predetermined terminal device;
A transmission unit for transmitting the packet to the terminal device;
A setting unit that sets a maximum value of the number of retransmissions of the packet based on characteristics of a layer higher than a physical layer for physically transmitting the packet to the terminal device;
When the packet needs to be retransmitted, the transmission unit retransmits the set maximum value as an upper limit. An analysis unit that identifies a protocol in a layer higher than the physical layer based on the packet;
The communication device according to claim 1, wherein the setting unit sets the maximum value according to the protocol.   The setting unit determines a maximum value of the number of retransmissions of a packet transmitted according to a protocol for transmitting non-real-time data, from a maximum value of the number of retransmissions of a packet transmitted according to a protocol for transmitting real-time data. The communication apparatus according to claim 2, wherein the communication apparatus is set to a small number. A monitoring unit for monitoring a communication state in the physical layer;
The said setting part determines whether the said maximum value is set based on the characteristic of a layer higher than the said physical layer according to the said communication state. Communication equipment.   The monitoring unit monitors the amount of packets to be transmitted through the physical layer, and when the amount of packets exceeds a predetermined amount, the setting unit sets the maximum number of retransmissions to the physical layer. The communication apparatus according to claim 4, wherein the communication apparatus is set based on characteristics of a higher layer. Receiving a packet to be transmitted to a predetermined terminal device according to a series of communication procedures including a plurality of layers;
Transmitting the packet to the terminal device;
Setting a maximum value of the number of retransmissions of the packet based on characteristics of a layer higher than a physical layer for physically transmitting the packet to the terminal device;
A communication method comprising: Receiving a packet to be transmitted to a predetermined terminal device from a predetermined input device in accordance with a series of communication procedures including a plurality of layers;
Setting a maximum value of the number of retransmissions of the packet based on characteristics of a layer higher than a physical layer for physically transmitting the packet to the terminal device;
A program to make a computer realize.

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