JP5129697B2 - Wireless communication apparatus and packet transmission method - Google Patents

Description

  The present invention relates to a wireless communication apparatus and a packet transmission method for relaying information processing apparatuses and base stations.

  In recent years, communication networks such as the Internet have become broadband, and wireless broadband systems through wireless communication represented by Bluetooth (registered trademark), ZigBee, and the like are also in an expanding trend. As means for executing such wireless communication, CDMA (Code Division Multiple Access) and WiMAX (Worldwide Interoperability for Microwave Access), which are also used in mobile phone networks, can be used.

  CDMA is a scheme in which a plurality of signals are multiplied by different codes, and all signals are combined and transmitted using a single frequency. On the other hand, WiMAX is one of communication systems using an OFDMA (Orthogonal Frequency Division Multiple Access) system (for example, Non-Patent Document 1). The OFDMA system is one of data multiplexing systems. The frequency band is effectively used by superimposing a part of the carrier band so that the phase of the signal wave to be modulated is orthogonal between adjacent carriers, using multiple carrier waves on the unit time axis It is a method.

  When a user performs data transmission / reception with an information processing apparatus such as his / her personal computer using such wireless communication, the user connects a wireless communication apparatus such as a PC card corresponding to the wireless communication to the information processing apparatus. I have to do it. In such a wireless communication device, a packet transmitted from the information processing device is transmitted to the base station as a wireless signal, and a wireless signal received from the base station is converted into a packet and transmitted to the information processing device. Thus, the information processing apparatus can use wireless communication.

  However, since the bandwidth that can be occupied by wireless communication is narrow and resources are limited, the wireless communication apparatus executes packet traffic (throughput) control by a token bucket mechanism in order to effectively use the wireless resource.

  FIG. 10 is an explanatory diagram for explaining traffic control. In FIG. 10, the wireless communication device 10 relays between the information processing device 12 and a base station 14 as a base station, and controls bidirectional packet transmission. Here, a traffic mechanism 16 is provided in each of an upstream transmission path from the information processing apparatus 12 to the base station 14 and a downstream transmission path from the base station 14 to the information processing apparatus 12.

  The traffic mechanism 16 includes a packet buffer 20 that holds an input packet 18 and a token buffer 24 that stores a token 22. The token buffer 24 is replenished with the token 22 at a controlled predetermined cycle. Until a predetermined amount of the token 22 is accumulated in the token buffer 24, the packet 18 in the packet buffer 20 is not output and the state is maintained. When the predetermined amount is accumulated, the packet 18 previously input is changed to the packet buffer 20. 1 is output. At this time, a predetermined amount of tokens 22 is subtracted from the token buffer 24, and the accumulation operation up to the predetermined amount of tokens 22 is repeated.

  Therefore, the throughput of the packet 18 output from the packet buffer 20 is controlled by the replenishment amount (token rate) of the token 22 per unit time. The wireless communication device 10 dynamically changes the token rate according to the traffic control parameter and the wireless communication environment with the base station 14, and traffic is reduced so that the token rate decreases when the traffic is concentrated in wireless communication. When the is low, the token rate is controlled to be high.

  Such token rate control by the token 22 is applied to various technologies. For example, a technique is known that increases the flexibility of traffic control using tokens by connecting token buffers that store tokens in series or in parallel (for example, Patent Document 1).

  In addition, the token upper limit value when the packet is stored in the corresponding queue is set higher than the upper limit value when the packet is not stored in the corresponding queue, and the packet arrives in the queue. Nevertheless, since a packet from another queue is output, a technique for avoiding a situation in which a token that could not be consumed is discarded is also disclosed (for example, Patent Document 2).

Furthermore, a technique is also shown in which the token rate is not updated while the token is not stored in the token buffer, thereby matching the token rate to the network state (for example, Patent Document 3). In addition, the token rate is increased using the reduced token throughput, and the token rate is decreased using the increased token throughput. A technique for updating the token rate is also known (for example, Patent Document 4).
JP 2007-049591 A JP 2007-181085 A JP 2007-189592 A JP 2007-221529 A "Mobile WiMAX? Part I: A Technical Overview and Performance Evaluation" Prepared on Behalf of the WiMAX Forum, February 21, 2006, http://www.intel.com/netcomms/technologies/wimax/WiMAX_Overview_v2.pdf

  When a user attempts to upload a large amount of data from an information processing apparatus to an FTP server on a network under a wireless broadband system to which traffic control using token buckets is applied, the upstream resource is Such temporary traffic concentration of large volumes of data makes it more susceptible to token rates. On the other hand, only the acknowledgment for the transmission data is transmitted to the resources in the downlink direction and is hardly affected by the token rate. Under such circumstances, when an upstream packet is lost on the transmission path, the FTP server recognizes the loss of the packet when a subsequent packet is received, and retransmits the lost packet to the information processing apparatus. Execute the request.

  As described above, since data flows smoothly in the downlink direction, the retransmission request is immediately transmitted to the information processing apparatus, and the information processing apparatus quickly retransmits the packet for which the retransmission request has been made (retransmission packet). However, the upstream token rate is limited, and packets that have not been transmitted remain in the FIFO (First In First Out) format packet buffer. Are not sent to the FTP server.

  As described above, while the retransmission packet stays in the packet buffer, the FTP server that does not recognize the state executes a further retransmission request for the retransmission packet that has not yet arrived. Then, the information processing apparatus repeats transmission of the retransmission packet in response to the retransmission request, and the retransmission packet is accumulated in the packet buffer. The occupation of the packet buffer for such retransmission packets increases the risk of overflow.

  In addition, even after the first retransmission packet normally reaches the FTP server, the retransmission packet stored in the packet buffer is repeatedly sent to the FTP server, and the FTP server does not receive the meaningless packet many times. In other words, wireless resources are wasted due to unnecessary traffic.

  In this way, when a large amount of data is transmitted, or when the uplink throughput is limited to a low level due to traffic control, if there is a retransmission request for an uplink packet, a plurality of retransmission packets may Unnecessary duplicate transmission can occur.

  Such a phenomenon depends not only on the token rate but also on the TCP (Transmission Control Protocol) window size, which is the amount of data that can be transmitted without waiting for an acknowledgment from the FTP server. This is because if the TCP window size is large, a large amount of packets are accumulated in the packet buffer before the first confirmation response, and it takes a long time until the retransmission packet is normally transmitted from the packet buffer. Therefore, when the token rate is low and the TCP window size is large, the greatest damage is caused to the performance of the wireless communication.

  In view of such problems, the present invention reduces wireless traffic and can perform efficient wireless communication regardless of the token rate and TCP window size, and a wireless communication apparatus and a packet transmission method The purpose is to provide.

  In order to solve the above problems, a typical configuration of the present invention is a wireless communication device that relays wireless communication from any one of an information processing device and a base station to another device. A transmission buffer that temporarily holds a plurality of packets to be transmitted from the side to the other apparatus side in FIFO format, and wireless communication that sequentially transmits the packets in the transmission buffer to the other apparatus side and receives an acknowledgment for the packet , A traffic control unit for controlling traffic of packets transmitted from the transmission buffer to the other device side, and a buffer input for determining whether or not the packet input from the one device side to the transmission buffer is a retransmission packet A packet that discards the input packet if the input packet is a retransmission packet and the packet exists in the transmission buffer; Characterized by comprising a preparative discarding unit. Here, the reason why “one device” or “other device” is used is that the positional relationship between the information processing device and the base station can be mutually replaced. This is because it includes indirect transmission / reception directly with a device or another device or through one or more relay devices.

  In the present invention, when retransmission packets are duplicated in the transmission buffer, it is determined that the duplication is caused by retention of retransmission packets, and subsequent retransmission packets are discarded to avoid duplicate transmission of retransmission packets. With this configuration, it is possible to prevent the transmission buffer from being occupied by retransmission packets, avoid overflow, and suppress unnecessary consumption of radio resources due to unnecessary traffic, without modification on the base station side or information processing device side. it can. Thus, efficient wireless communication can be performed regardless of the token rate and TCP window size.

  An acknowledgment determination unit that determines whether or not a packet received from another device is an acknowledgment, and a buffer output that determines whether or not a packet output from the transmission buffer to the other device is a retransmission packet If the packet to be output is a retransmission packet, the determination unit may further include a packet maintaining unit that maintains the packet in the transmission buffer until there is an acknowledgment for the packet.

  The other device side that is the communication destination keeps requesting retransmission of the packet until the missing packet arrives, so a new normal packet is not input to the transmission buffer for transmission to the other device side, Normal packets are not stored after the retransmission packet. However, after the retransmission packet is transmitted, the packet is not transmitted from the transmission buffer until the acknowledgment (ACK) is received. Here, if the retransmission packet is lost again, there is no subsequent packet, so that the other device side cannot recognize the loss of the retransmission packet, and the retransmission of the retransmission packet only by the retransmission timeout of one device side. Is carried out. In the present invention, the retransmission packet is not deleted from the transmission buffer until an acknowledgment is received, and the retransmission packet is maintained at the head, so that the retransmission packet is transmitted according to the token rate without waiting for timeout. The retransmission process can be performed smoothly.

  The packet maintaining unit may delete the packet from the transmission buffer when the number of transmissions of the maintained packet to another device reaches a predetermined number.

  If the retransmission packet cannot be received on the network side for some reason, even if the retransmission packet is transmitted normally, the possibility that the retransmission packet will arrive is low. At this time, if retransmission packets can be transmitted without limitation, only the retransmission processing occupies radio resources. In the present invention, it is possible to release radio resources at an appropriate timing after an appropriate number of transmissions by limiting the number of retransmission packet transmissions.

  Another typical configuration of the present invention is a packet transmission in which a wireless communication device that relays wireless communication from any one of an information processing device and a base station to another device and a wireless communication device having a transmission buffer transmits the packet. In this method, it is determined whether or not a packet input to the transmission buffer from one device side is a retransmission packet, and the input packet is a retransmission packet and the same packet exists in the transmission buffer. For example, the input packet is discarded, the non-discarded packet is temporarily stored in the buffer in FIFO format, and the stored packet is sequentially transmitted to other devices while controlling the traffic, and the transmitted packet is confirmed. A response is received.

  The above-described components based on the technical idea of the wireless communication apparatus and the description thereof can be applied to the packet transmission method.

  As described above, according to the present invention, it is possible to reduce useless traffic and perform efficient wireless communication regardless of the token rate and TCP window size.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Wireless communication system 100)
FIG. 1 is an explanatory diagram showing a schematic connection relationship of the wireless communication system 100. The wireless communication system 100 includes an information processing apparatus 110, a wireless communication apparatus 120, a base station 130, a communication network 140 including an ISDN (Integrated Services Digital Network) line, the Internet, a dedicated line, and the like, and a relay server 150. And an external server 160.

  The information processing apparatus 110 includes a personal computer, a notebook personal computer, an in-vehicle module, a car navigation system, a PDA (Personal Digital Assistant), a digital camera, a music player, a portable TV, a game device, a DVD player, a remote controller, a mobile phone, and a PHS (PHS). It is composed of various electronic devices such as Personal Handy phone System) terminals and functions as an input / output interface for users.

  The wireless communication device 120 has a wireless function and is electrically connected to a PCMCIA (Personal Computer Memory Card International Association) slot or USB (Universal Serial Bus) provided in the information processing device 110 to connect the information processing device 110 and the base station. 130 is relayed. In the present embodiment, the wireless communication device 120 performs wireless communication with the base station 130. However, wireless communication devices do not pass through a base station such as an access point in wireless LAN or WiMAX, or an ad hoc network. This embodiment also includes a form of direct communication connection. Further, in the present embodiment, the term “network” refers to all elements that can be a communication target of the wireless communication apparatus 120 via wireless communication, including the base station 130 and the external server 160.

  The base station 130 establishes wireless communication with the wireless communication device 120, a mobile terminal such as a mobile phone and a PHS terminal, and provides a call function, a Web browsing function, a mail transmission / reception function, and the like, and thus serves as a network-side interface.

  The relay server 150 uses the information processing apparatus 110 of the user to access the external server 160 and the like through the wireless communication apparatus 120, and between the wireless communication apparatus 120 and the base station 130, and the base station 130. Communication path between the information processing apparatus 110 and the external server 160 is established.

  The external server 160 is various servers connected to the communication network 140 such as an FTP server provided by a service provider, and uploads data (packets) from the information processing apparatus 110 and downloads data to the information processing apparatus 110. Carry out.

  The wireless communication device 120 in the wireless communication system 100 performs traffic control as described later. However, if retransmission packets of data stay in the packet buffer, there is a risk of overflow and unnecessary traffic. Such a phenomenon is likely to occur not only when the token rate is low but also when the TCP window size is large. The object of the present embodiment is to reduce such useless traffic and to perform efficient wireless communication regardless of the size of the token rate or TCP window size. Hereinafter, the wireless communication apparatus 120 that exhibits such an effect will be described in detail.

(Wireless communication device 120)
FIG. 2 is a functional block diagram illustrating a hardware configuration of the wireless communication device 120. The wireless communication device 120 includes a transmission buffer 210, a transmission token buffer 212, a reception buffer 214, a reception token buffer 216, a traffic control unit 218, a wireless communication unit 220, an antenna unit 222, and a buffer input determination unit 224. A packet discard unit 226, an acknowledgment response determination unit 228, a buffer output determination unit 230, and a packet maintenance unit 232.

  The transmission buffer (transmission packet buffer) 210 is composed of a FIFO memory, for example, a shift register, and temporarily holds a plurality of packets transmitted from the information processing apparatus 110 to the base station 130 (external server 160). The packet 250 input to the transmission buffer 210 is automatically transmitted in order from the packet input first according to the token rate, and is deleted from the transmission buffer 210. Therefore, the packet 250 inputted later is maintained in the transmission buffer 210 unless the packet 250 inputted before that is sent out.

  The transmission token buffer 212 controls the transmission timing of the packet 250 in the transmission buffer 210. Specifically, when the token 252 transmitted from the traffic control unit 218 (described later) is replenished in the transmission token buffer 212 at a predetermined cycle and a predetermined amount of the token 252 is accumulated in the transmission token buffer 212, the transmission buffer 210 Output of the packet 250 is permitted. At this time, a predetermined amount of tokens 252 is subtracted from the transmission token buffer 212. Thereafter, such an accumulation operation up to a predetermined amount of tokens 252 is repeated, and a packet 250 from the transmission buffer 210 is sent out each time.

  Similarly to the transmission buffer 210, the reception buffer (reception packet buffer) 214 is configured by a FIFO memory, and temporarily holds a plurality of packets transmitted from the base station 130 (external server 160) to the information processing apparatus 110.

  Similar to the transmission token buffer 212, the reception token buffer 216 controls the transmission timing of the packet 250 in the reception buffer 214 to the information processing apparatus 110. Specifically, when the token 252 transmitted from the traffic control unit 218, which will be described later, is replenished to the reception token buffer 216 at a predetermined cycle, and the token 252 is accumulated in the reception token buffer 216, a predetermined amount is stored. The output of the packet 250 is permitted. At this time, a predetermined amount of tokens 252 is subtracted from the reception token buffer 216.

  The traffic control unit 218 controls the traffic of the packet 250 transmitted from the transmission buffer 210 to the base station 130 and the packet 250 transmitted from the reception buffer 214 to the information processing apparatus 110. Such traffic control is performed by controlling the transmission amount (token rate) of a token per unit time to the transmission token buffer 212 and the reception token buffer 216.

  The wireless communication unit 220 establishes wireless communication such as CDMA or WiMAX in a common link layer, sequentially transmits the packets 250 of the transmission buffer 210 to the base station 130, and sends an acknowledgment (ACK) to the packets 250 as the base station 130. (External server 160). It is also possible to simply receive the packet 250 transmitted from the base station 130.

  The antenna unit 222 performs wireless communication with the base station 130 by converting the electric signal in the wireless communication unit 220 into an electromagnetic wave or converting the electromagnetic wave into an electric signal.

  The buffer input determination unit 224 determines whether or not the packet 250 input from the information processing apparatus 110 to the transmission buffer 210 is a retransmission packet. The determination of whether or not the packet is a retransmission packet may be performed with reference to a retransmission packet flag in a header or the like, may be performed with reference to a packet identifier or a packet number, and the transmission buffer may be determined within a predetermined period. It may be performed by matching with all packets 250 input to 210.

  When the buffer input determining unit 224 determines that the input packet 250 is a retransmission packet, the packet discarding unit 226 further matches the input packet 250 among the packets stored in the transmission buffer 210. It is determined whether or not the packet 250 exists, and if it exists, the input packet 250 is discarded.

  In the present embodiment, when retransmission packets overlap in the transmission buffer 210, it is determined that the overlap is due to retention of retransmission packets, and subsequent retransmission packets are discarded to avoid redundant transmission of retransmission packets. With this configuration, it is possible to prevent the transmission buffer 210 from being occupied by retransmission packets without changing the network side or the information processing apparatus 110, avoid overflow, and suppress unnecessary consumption of radio resources due to unnecessary traffic. it can. Thus, efficient wireless communication can be performed regardless of the token rate and TCP window size.

  The confirmation response determination unit 228 determines whether or not the packet received from the base station 130 (external server 160) is a confirmation response.

  The buffer output determination unit 230 determines whether or not the packet output from the transmission buffer 210 to the base station 130 is a retransmission packet.

  When the buffer output determining unit 230 determines that the output packet 250 is a retransmission packet, the packet maintaining unit 232 retransmits the packet until the confirmation response determining unit 228 determines that there is an acknowledgment for the retransmitted packet. The packet is maintained at the head of the transmission buffer 210.

  The external server 160 keeps requesting retransmission of the packet until the missing packet arrives, so that no new normal packet is input to the transmission buffer 210 for transmission to the external server 160, and the normal packet is transmitted after the retransmission packet. Packets are not accumulated. However, after the retransmission packet is transmitted, the packet is not transmitted from the transmission buffer 210 until the confirmation response is received.

  Here, if the retransmission packet is lost again, there is no subsequent packet. Therefore, the external server 160 cannot recognize the loss of the retransmission packet, and further retransmission of the retransmission packet is performed only by the retransmission timeout of the information processing apparatus 110. Carried out. In the present embodiment, the retransmission packet is not deleted from the transmission buffer 210 until an acknowledgment is received, and the retransmission packet is maintained at the head, so that the retransmission packet is transmitted according to the token rate without waiting for timeout. It is possible to smoothly perform further retransmission processing.

  Further, the packet maintaining unit 232 may delete the packet from the transmission buffer 210 when the number of transmissions of the maintained packet to the base station 130 reaches a predetermined number.

  If the retransmission packet cannot be received on the network side for some reason, even if the retransmission packet is transmitted normally, the possibility that the retransmission packet will arrive is low. At this time, if retransmission packets can be transmitted without limitation, only the retransmission processing occupies radio resources.

  For example, when browsing a WEB site operated by another external server 160 during uploading to an FTP server that is the external server 160, transmission to a WEB site having a different transmission system regardless of transmission restrictions to the FTP server. A packet is generated. At this time, if retransmission packets to the FTP server continue to remain in the transmission buffer 210 by the packet maintaining unit 232, transmission packets to the WEB site are accumulated in the transmission buffer 210, which may cause an overflow.

  Therefore, in the present embodiment, by limiting the number of retransmission packet transmissions to a predetermined number, it is possible to release radio resources at an appropriate timing after an appropriate number of transmissions. The predetermined number of times can be the number of times that the packet discarding unit 226 has discarded the retransmission packet, that is, the number of times that the information processing apparatus 110 has actually retransmitted. With such a configuration, the number of transmissions corresponding to the actual number of retransmissions of the information processing apparatus 110 can be secured without occupying the transmission buffer 210. In addition, the range that does not affect other transmission systems and applications, and the number of times that it can be determined that an abnormality has occurred in the network can be set to a predetermined number.

  Further, the packet maintaining unit 232 may delete a packet from the transmission buffer 210 when a predetermined number of packets 250 are accumulated in the subsequent stage of the maintained packet in the transmission buffer 210. With this configuration, it is possible to maintain and retransmit the retransmission packet by the packet maintaining unit 232 while a new packet is not accumulated in the subsequent stage, that is, until a different transmission system is used. When detected, the maintenance of the retransmission packet is stopped, and the radio resource can be released to the new packet 250.

  As described above, according to the wireless communication apparatus 120 described above, it is possible to reduce unnecessary traffic and perform efficient wireless communication regardless of the token rate and the TCP window size.

(Packet transmission method)
Next, a packet transmission method that is connected to the information processing apparatus 110, relays wireless communication with the base station 130 by the information processing apparatus 110, and the wireless communication apparatus 120 including the transmission buffer 210 transmits the packet 250 to the external server 160. Will be explained. Here, the packet transmission method will be described by dividing it into upstream packet transmission processing, traffic control processing thereof, and downstream packet reception processing.

  3 is a flowchart showing an upstream packet transmission process in the packet transmission method, FIG. 4 is a flowchart showing a traffic control process in the packet transmission method, and FIG. 5 is a downlink direction in the packet transmission method. It is the flowchart which showed the packet reception process. These three processes are performed in parallel.

  Referring to FIG. 3, first, the retransmission counter is reset (S300). Such a retransmission counter is used to limit the number of retransmissions of a retransmission packet in a traffic control process (FIG. 4) described later. When the packet 250 is input from the information processing apparatus 110 (S302), the wireless communication apparatus 120 checks whether or not the traffic control is valid (S304), and if invalid (NO in S304), The data is transmitted to the base station 130 without being stored in the transmission buffer 210 (S306).

  When the traffic control is valid (YES in S304), the buffer input determination unit 224 determines whether or not the packet input from the information processing apparatus 110 to the transmission buffer 210 is a retransmission packet (S308). If so (YES in S308), the retransmission counter is incremented (added by 1) (S310). Subsequently, the packet discarding unit 226 determines whether or not the retransmission packet exists in the transmission buffer 210 (S312). If the packet is present (YES in S312), the packet discarding unit 226 discards the packet (S314), Return to the standby state (S302).

  If the packet input to the transmission buffer 210 is not a retransmission packet (NO in S308), or is a retransmission packet but does not exist in the transmission buffer 210 (NO in S312), the packet is input to the transmission buffer 210. Then, the process returns to the packet waiting state (S302).

  In FIG. 4, the traffic control unit 218 determines whether or not it is time to add a token to the transmission token buffer 212 according to a predetermined token rate (S330). It adds to the buffer 212 (S332). Then, it is determined whether there is a packet 250 to be transmitted to the transmission buffer 210 (S334). If there is no packet (NO in S334), the process returns to the transmission packet waiting state.

  When there is a packet in the transmission buffer 210 (YES in S334), the transmission token buffer 212 determines whether or not the token 252 has reached a predetermined amount (S336), and if it has not yet reached (NO in S336), the token Wait for 252 to accumulate.

  If the token 252 has reached the predetermined amount (YES in S336), the buffer output determining unit 230 acquires one packet from the top of the transmission buffer 210 (S338), and determines whether or not it is a retransmission packet. (S340). If the packet is a retransmission packet (YES in S340), the retransmission counter is decremented (reduced by 1) (S342).

  Subsequently, it is determined whether or not the decremented retransmission counter is a value greater than 0, that is, whether or not the number of retransmissions of the retransmission packet still remains by the packet maintaining unit 232 (S344). If it remains (YES in S344) ), The packet is transmitted and the packet is maintained at the head of the transmission buffer 210 (S364). If not, that is, if the retransmission counter is 0 (NO in S344), only the packet transmission process is performed (S348), and finally a predetermined amount of tokens is subtracted from the transmission token buffer 212 (S350). The process waits for the token addition timing again (S330).

  In FIG. 5, when the packet 250 is received from the base station 130 to the wireless communication device 120 (S360), the wireless communication device 120 checks whether or not the traffic control is valid (S362). The packet 250 is transmitted to the information processing apparatus 110 without being stored in the reception buffer 214 (S364).

  If the traffic control is valid (YES in S362), it is determined whether or not the retransmission packet is maintained by the packet maintaining unit 232 (S366). If the retransmission counter is not yet 0 (YES in S366), the confirmation response determination unit 228 determines whether or not the packet is an acknowledgment for the retransmission packet (S368). If it is an acknowledgment for the retransmitted packet (YES in S368), the packet maintained by the packet maintaining unit 232 is deleted (S370). The last received packet is input to the reception buffer 214 to be transmitted to the information processing apparatus 110 (S372).

  According to the packet transmission method described above, it is possible to reduce useless traffic and perform efficient wireless communication regardless of the token rate and the TCP window size. Subsequently, the effects of the wireless communication device 120 and the packet transmission method described above are confirmed.

  FIG. 6 is a sequence diagram showing normal packet transmission as a comparative example. In FIG. 6, eight squares indicate the internal state of the transmission buffer 210 of the wireless communication apparatus 120. Here, a case where the window size of the transmission buffer 210 is 8 packets is shown. Here, “Seg (segment)” is used as a symbol of the packet, but the segment is a transmission unit in the transport layer, which is the fourth layer of the OSI reference model, and the above-described packet (network layer, which is the third layer). Transmission unit). Further, in order to facilitate understanding, the wireless communication apparatus 120 and the external server 160 are described as directly communicating with each other in the same figure, but it goes without saying that the communication is via the base station 130 or the communication network 140.

  When data to be transmitted to the external server 160 occurs in the information processing apparatus 110, a packet obtained by dividing the data to be transmitted is transmitted to the wireless communication apparatus 120. Since the window size is 8, the transmission buffer 210 of the wireless communication apparatus 120 inputs and accumulates 8 packets, that is, Seg1 to Seg8 (S400). Then, the transmission buffer 210 once stops the input of the packet from the information processing apparatus 110 when its own storage area is filled.

  Here, when the transmission token buffer 212 reaches a predetermined amount, one packet Seg1 is transmitted from the transmission buffer 210 (S402), and an acknowledgment (ACK transmission) is made from the external server 160 to the packet Seg1 (S404). ). The information processing apparatus 110 receives the confirmation response of the packet Seg1, recognizes that the storage area in the transmission buffer 210 has become empty, and transmits the subsequent packet Seg9 to the wireless communication apparatus 120 (S406).

  Subsequently, in the wireless communication device 120, when the transmission token buffer 212 reaches a predetermined amount, the packet Seg2 is transmitted (S408). Here, it is assumed that the packet Seg2 is lost (lost). Since the external server 160 has not acquired the packet Seg2, it cannot react at all, but recognizes the lack of the packet Seg2 by receiving the subsequent packet Seg3 from the wireless communication device 120 (S410).

  The external server 160 requests the information processing apparatus 110 to retransmit the packet Seg2 in order to supplement the missing packet Seg2 (S412), and the information processing apparatus 110 immediately retransmits the packet Seg2 that has been requested to be retransmitted (S414). . However, the token rate in the upstream direction is limited, and there are packets Seg4 to Seg9 that have not been transmitted yet in the transmission buffer 210. Therefore, unless the output of the remaining packets Seg4 to Seg9 is completed, the packet Seg2 It is not sent to the external server 160.

  Thus, while the packet Seg2 stays in the transmission buffer 210, even if the external server 160 that does not recognize the state receives the continuing packet Seg4 (S416), it is possible to further increase the number of retransmission packets that have not yet arrived. A retransmission request is executed (S418). Then, the information processing apparatus 110 repeats transmission of the packet Seg2 in response to the retransmission request (S420), and the packet Seg2 is accumulated in the transmission buffer 210 in vain.

  When transmission up to the packet Seg9 stored in the transmission buffer 210 is completed (S440), the packet Seg2 for which retransmission has been requested finally moves to the top of the transmission buffer 210, and the packet Seg2 is transmitted to the external server 160 at the next transmission timing. (S442). The external server 160 supplemented with the packet Seg2 performs an acknowledgment up to the packet Seg9 that has already been received (S444).

  However, even after the desired packet Seg2 successfully reaches the external server 160, the retransmitted packet Seg2 stored in the transmission buffer 210 is repeatedly sent to the external server 160 (S446), and the external server 160 does not make sense. The packet must be received and discarded many times (S448), and the unnecessary traffic consumes radio resources. At this time, although the transfer rate of wireless communication is secured, the effective rate falls.

  FIG. 7 is a sequence diagram illustrating packet transmission according to the present embodiment. The transmission of the packet 250 in FIG. 7 is substantially the same as the process in FIG. 6 until the middle of the process, so the same reference numerals are given and the description is omitted.

  In the present embodiment, the information processing apparatus 110 retransmits the packet Seg2 in response to the retransmission request from the external server 160 (S420). If the retransmission packet is duplicated in the transmission buffer 210, the packet discarding unit 226 However, it is determined that the retransmission packet Seg2 is accumulated, the packet Seg2 is discarded (S500), and duplicate transmission of the retransmission packet is avoided.

  With the configuration of the packet discarding unit 226, duplication of the subsequent retransmission packet Seg2 is avoided, the occupation of the transmission buffer 210 by the retransmission packet is prevented, an overflow is avoided, and the retransmission packet Seg2 is transmitted to the external server 160. After receiving unnecessary confirmation response (S502) of the packet Seg9 from the external server 160, the subsequent packets Seg10 to 17 can be quickly stored in the transmission buffer 210. .

  FIG. 8 is a sequence diagram showing another example of packet transmission according to this embodiment. The packet transmission in FIG. 8 is substantially the same as the process in FIG. 7 until the middle of the process, and therefore the same reference numerals are given and the description thereof is omitted. Here, a further problem that occurs when the present embodiment is applied will be described.

  In FIG. 8, the external server 160 continues to request retransmission of the packet 250 until the missing packet Seg2 arrives (S412, S418,..., S504). Therefore, as shown in FIG. 8, a new normal packet 250 is not input to the transmission buffer 210 for transmission to the external server 160, and the normal packet 250 is not accumulated after the retransmission packet. However, after the retransmission packet is transmitted, the packet is not transmitted from the transmission buffer 210 until the confirmation response is received.

  At this time, if the retransmission packet is further lost at the transmission timing of the retransmission packet (S510), since there is no subsequent packet 250, the external server 160 cannot recognize the loss of the retransmission packet, and the information processing apparatus 110 Further retransmission of the retransmission packet is performed only by timeout (S512) due to RTO (Retransmit Time Out) (S514). In this RTO, if the retransmission request continues in accordance with the standard, the time interval gradually increases by a factor of two, and depending on the setting of the RTO, it takes a long time to retransmit the packet Seg2.

  FIG. 9 is a sequence diagram illustrating another example of packet transmission according to this embodiment. The transmission of the packet 250 in FIG. 9 is substantially the same as the process of FIG. 8 until the middle of the process, so the same reference numerals are given and the description is omitted.

  In FIG. 9, at the retransmission packet transmission timing, the packet maintaining unit 232 receives the fact that the packet is the retransmission packet Seg2, and maintains the retransmission packet in the transmission buffer 210 until there is an acknowledgment of the retransmission packet Seg2 ( S520). Therefore, even if the retransmitted packet Seg2 does not reach the external server 160 (S510), it is possible to smoothly perform further retransmission processing of the retransmitted packet Seg2 without waiting for a timeout due to RTO at the next packet transmission timing. It becomes possible.

  When the external server 160 normally receives the packet Seg2 (S524), a confirmation response of the packet Seg9 is returned (S444). Upon receiving this confirmation response, the packet maintaining unit 232 receives the packet Seg2 maintained from the transmission buffer 210. Is deleted.

  At this time, the packet maintaining unit 232 sets an upper limit on the number of transmissions of the maintained packet to the external server 160, and deletes the packet from the transmission buffer 210 when the number of transmissions reaches a predetermined number. Here, by limiting the number of retransmission packet transmissions, it becomes possible to release radio resources at an appropriate timing after an appropriate number of transmissions.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above-described embodiment, an example in which the information processing apparatus 110 and the wireless communication apparatus 120 are connected by USB has been described. However, the present invention is not limited to this, and the information processing apparatus 110 and the wireless communication apparatus 120 may be connected. They can also be connected by short-range wireless communication or infrared communication such as Bluetooth (registered trademark) or IrDA (Infrared Data Association).

  Further, when the information processing apparatus 110 and the wireless communication apparatus 120 are connected by Bluetooth (registered trademark) or IrDA in this way, a packet error may occur because this connection is also wireless communication. Therefore, an event similar to a packet error that occurs between the base station 130 and the wireless communication device 120 may occur.

  Furthermore, in the above-described embodiment, transmission of a packet from the information processing apparatus side to the base station side has been described. However, in the case of connection by Bluetooth or the like, the reverse direction (direction from the base station side to the information processing apparatus side) It can also be applied to the transmission of packets. That is, even if the information processing apparatus 110 and the base station 130 (external server 160) are replaced in the configurations shown in FIGS.

  Each step in the packet transmission method of the present specification does not necessarily have to be processed in time series in the order described as a flowchart or sequence diagram, and may include processing in parallel or by a subroutine.

  INDUSTRIAL APPLICABILITY The present invention can be used for a wireless communication apparatus and a packet transmission method that relay information processing apparatuses and base stations.

It is explanatory drawing which showed the rough connection relation of the radio | wireless communications system. It is the functional block diagram which showed the hardware constitutions of the radio | wireless communication apparatus. It is the flowchart which showed the packet transmission process of the uplink direction in the packet transmission method. It is the flowchart which showed the traffic control processing in the packet transmission method. It is the flowchart which showed the packet reception process of the downlink direction in the packet transmission method. It is a sequence diagram which shows normal packet transmission as a comparative example. It is a sequence diagram which shows packet transmission of this embodiment. It is a sequence diagram which shows the other example of the packet transmission of this embodiment. It is a sequence diagram which shows the other example of the packet transmission of this embodiment. It is explanatory drawing for demonstrating the traffic control in a prior art.

Explanation of symbols

110 ... information processing device 120 ... wireless communication device 130 ... base station 210 ... transmission buffer 214 ... reception buffer 218 ... traffic control unit 220 ... wireless communication unit 224 ... buffer input determination unit 226 ... packet discarding unit 228 ... confirmation response determination unit 230 ... buffer output determination unit 232 ... packet maintenance unit 250 ... packet 252 ... token

Claims (4)

A wireless communication device that relays wireless communication from any one of an information processing device and a base station to another device,
A transmission buffer that temporarily holds a plurality of packets to be transmitted from the one apparatus side to the other apparatus side in a FIFO format;
A wireless communication unit that sequentially transmits packets in the transmission buffer to the other device side, and receives an acknowledgment for the packet;
A traffic control unit for controlling traffic of packets transmitted from the transmission buffer to the other device side;
A buffer input determination unit that determines whether or not a packet input from the one device side to the transmission buffer is a retransmission packet;
A packet discard unit that discards the input packet if the input packet is a retransmission packet and the packet exists in the transmission buffer;
A wireless communication apparatus comprising: An acknowledgment determination unit that determines whether or not the packet received from the other apparatus side is an acknowledgment;
A buffer output determination unit that determines whether or not a packet to be output from the transmission buffer to the other device side is a retransmission packet;
If the packet to be output is a retransmission packet, a packet maintaining unit that maintains the packet in the transmission buffer until there is an acknowledgment for the packet;
The wireless communication apparatus according to claim 1, further comprising:   The wireless communication apparatus according to claim 2, wherein the packet maintaining unit deletes the packet from the transmission buffer when the number of transmissions of the maintained packet to another apparatus reaches a predetermined number. A packet transmission method in which a wireless communication device that relays wireless communication from any one of an information processing device and a base station to another device and has a transmission buffer transmits a packet,
Determining whether the packet input from the one device side to the transmission buffer is a retransmission packet;
If the input packet is a retransmission packet, and the packet exists in the transmission buffer, the input packet is discarded,
Temporarily holding the undiscarded packets in the buffer in FIFO format;
Sequentially send the held packets to other devices while controlling traffic,
A packet transmission method comprising receiving an acknowledgment for the transmitted packet.

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