JP2004040493A - Packet communication equipment and packet communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packet communication equipment and a packet communication system, capable of surely transmitting a communication packet to a destination terminal, while reducing the load of a network and effectively utilizing a communication band. <P>SOLUTION: A personal computer 10 sequentially transmits packets, providing the sequence numbers (A)-(C). A personal computer 11 detects a loss of the packet and requests retransmission of the packet of the sequence number (B), when it receives the packet of the sequence number (C). The personal computer 10 divides the requested packet and transmits packets of the sequence numbers (B1)and (B2). The personal computer 11 detects the loss and requests the retransmission of the packet of the sequence number (B1), when it receives the packet of the sequence number (B2). The personal computer 10 divides the requested packet and transmits packets of the sequence numbers (B11) and (B12). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a packet communication device, and more particularly to an improvement in a packet retransmission method in a packet communication device.
[0002]
[Prior art]
In recent years, with the development of wireless communication technology, wireless LAN (Local Area Network) systems have shown signs of full-scale spread, and due to their strong cost competitiveness, mobile phones have been expelled in some applications. is there.
Although there are several standards for wireless LAN systems, IEEE 802.11 is currently considered the de facto standard. In particular, devices conforming to IEEE802.11b that communicate using radio waves in the 2.4 GHz band are already widely used, but since the bandwidth is as narrow as 11 Mbps, large-capacity contents such as moving images have recently been distributed. , There is a slight lack of performance.
[0003]
With respect to such a problem, if a device based on IEEE802.11a using a 5.2 GHz band is used, a bandwidth of 56 Mbps, which is at least five times as wide as that of IEEE802.11b, can be secured.
[0004]
[Problems to be solved by the invention]
However, there is a problem that wireless communication is more susceptible to noise and communication packet loss is more likely to occur as compared with wired communication. In such a case, if the packet is to reach the destination terminal, retransmission of the packet must be repeated many times, and the load on the network increases, making it impossible to effectively use the communication band.
[0005]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is possible to reduce a load on a network and effectively use a communication band while ensuring that a communication packet can reach a destination terminal. It is an object to provide a communication device and a packet communication system.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a packet communication device according to the present invention is a packet communication device that transmits a packet to a destination device, and when a retransmission of a packet is requested from the destination device, divides the requested packet. It is characterized by comprising a packet dividing unit for converting a plurality of packets, and a packet transmitting unit for transmitting the plurality of packets to a destination device.
[0007]
By doing so, the expected value of the number of errors per packet can be reduced, so that the packet can be delivered more reliably than when retransmitting without dividing the packet. . Therefore, it is possible to reduce the bandwidth consumption due to the retransmission of the packet and to effectively use the communication bandwidth.
A packet communication device for transmitting a packet to a destination device, wherein the retransmission determination unit determines whether the packet should be retransmitted, and the retransmission determination unit determines that the packet should be retransmitted. In addition, a packet dividing unit that divides a packet to be retransmitted into a plurality of packets by dividing the packet to be retransmitted and a packet transmitting unit that transmits the plurality of packets to a destination device may be provided. Even in this case, the same effect as described above can be obtained.
[0008]
Note that, in this case, an acknowledgment receiving unit that receives an acknowledgment notifying that the packet has been received from the destination device is provided, and the retransmission determination unit determines that the If no acknowledgment is received, it may be determined that the packet should be retransmitted.
Further, the packet division unit of the packet communication device according to the present invention, by dividing a service data unit included in the packet determined to be retransmitted into a plurality of service data units, by adding protocol control information to each of them, It is characterized by a plurality of packets.
[0009]
That is, in general, a packet includes protocol control information (PCI: Protocol Control Information) such as a header and a trailer and a service data unit (SDU: Service Data Unit). Therefore, if only the service data unit is divided and retransmitted as described above, the protocol control information of the original packet is not retransmitted, so that the communication band can be effectively used.
[0010]
If the packet to be retransmitted is equal to or shorter than a predetermined data length, a packet division control unit that causes the packet transmission unit to retransmit the packet without dividing the packet by the packet division unit may be provided. With this configuration, it is possible to avoid a problem that the data length of the service data unit becomes too small, resulting in an increase in communication overhead, which is against the effective use of the communication band.
[0011]
In addition, the apparatus further comprises a division number determining unit that determines the number of divisions when the packet division unit divides the packet according to the number of packets obtained by dividing the packet in the past by the packet division unit. . By doing so, the number of packet divisions is determined based on the past history, so that a more appropriate number of divisions can be selected as compared with a case where the number of divisions is fixed. Therefore, the number of packet retransmissions can be reduced, and communication bandwidth can be effectively used.
[0012]
In this case, the division number determination unit may set the number of packets obtained by dividing the packet last by the packet division unit as the division number when the packet division unit divides the packet. With this configuration, the number of divisions can be selected in accordance with a recent communication situation or an error occurrence situation, so that the number of packet retransmissions can be further reduced and communication bandwidth can be effectively used.
[0013]
Further, the division number determination unit may reduce the division number according to the number of packets transmitted after the packet division unit last divided the packet. With this configuration, when it is determined that the communication condition is good, the communication overhead can be reduced by reducing the number of divisions, so that the communication band can be effectively used.
[0014]
A packet communication method according to the present invention is a packet communication method executed by a packet communication device that transmits a packet to a destination device. When a packet retransmission is requested from the destination device, the packet is divided into a plurality of packets. And a packet transmitting step of transmitting the plurality of packets to a destination device.
[0015]
Alternatively, there is provided a packet communication method executed by a packet communication device that transmits a packet to a destination device, wherein a retransmission determination step of determining whether or not the packet should be retransmitted, and the retransmission determination unit retransmits the packet. If it is determined that the packet is to be retransmitted, a packet dividing step of dividing a packet to be retransmitted into a plurality of packets and a packet transmitting step of transmitting the plurality of packets to the destination device are provided.
[0016]
Further, a packet communication program according to the present invention causes a computer to execute the above-described packet communication method. Even in this case, the object of the present invention can be achieved in the same manner as described above.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a packet communication device and a packet communication method according to the present invention will be described with reference to the drawings, taking a wireless LAN system as an example.
[1] System configuration
The wireless LAN system according to the present embodiment is a so-called ad hoc mode wireless LAN system in which communication terminals directly perform wireless communication without going through a so-called access point. FIG. 1 is a system configuration diagram showing a system configuration of a wireless LAN system according to the present embodiment.
[0018]
In FIG. 1, the wireless LAN system 1 includes personal computers 10 and 11, which are two wireless communication terminals. When the personal computers 10 and 11 are within the communication range, the personal computers 10 and 11 directly transmit and receive packets by wireless communication.
For this reason, if electromagnetic noise due to lightning or the like is added while the personal computers 10 and 11 are performing wireless communication with each other, packet loss may occur. Note that a sequence number is assigned to each of the packets transmitted and received by the personal computers 10 and 11.
[0019]
The personal computers 10 and 11 detect packet loss by confirming the sequence numbers assigned to the received packets. As will be described later, each of the personal computers 10 and 11 has an internal buffer for storing the transmitted packet in preparation for retransmission of the packet.
[0020]
[2] Communication sequence
Next, a communication procedure between the personal computers 10 and 11 when a loss of a packet is detected will be described with reference to a case where the personal computer 10 transmits a packet to the personal computer 11 as an example. FIG. 2 is a sequence diagram showing a communication procedure when the personal computer 10 transmits a packet to the personal computer 11, which is executed when the personal computer 11 detects a packet loss. .
[0021]
As shown in FIG. 2, the personal computer 10 first transmits a packet to which the sequence number “A” has been assigned to the personal computer 11.
The packet is normally received by the personal computer 11. Subsequently, the personal computer 10 transmits the packet with the sequence number “B” to the personal computer 11.
[0022]
In FIG. 2, the personal computer 11 cannot receive the packet to which the sequence number “B” has been assigned because a loss has occurred for some reason. Subsequently, the personal computer 10 transmits the packet to which the sequence number “C” has been assigned to the personal computer 11.
[0023]
The packet is normally received by the personal computer 11.
Subsequently, the personal computer 11 compares the sequence number “A” of the previously received packet with the sequence number “C” of the currently received packet. By this comparison, the personal computer 11 detects that the packet with the sequence number “B” has not arrived.
[0024]
Then, the personal computer 11 transmits a packet requesting retransmission to the personal computer 10 by designating the sequence number “B” of the packet not received. Upon receiving the retransmission request, the personal computer 10 divides the packet with the sequence number “B” into two parts, the first half and the second half.
[0025]
In the personal computer 10, the first half is a packet to which the sequence number "B1" is added, and the second half is a packet to which the sequence number "B2" is added. The personal computer 10 first transmits a packet with the sequence number “B1” to the personal computer 11, and then transmits a packet with the sequence number “B2” to the personal computer 11. .
[0026]
In FIG. 2, among the packets retransmitted by the personal computer 10, the packet to which the sequence number “B1” is added does not reach the personal computer 11 due to a loss that has occurred for some reason. On the other hand, the bucket assigned with the sequence number “B2” is normally received by the personal computer 11.
[0027]
When receiving the packet to which the sequence number “B2” is assigned, the personal computer 11 compares the sequence number “B” of the packet requested to be retransmitted with the sequence number “B2” of the packet received this time. When detecting that the packet assigned with the sequence number “B1” has not arrived, the personal computer 11 requests the personal computer 10 to retransmit the packet with the sequence number “B1”.
[0028]
When receiving the retransmission request from the personal computer 11, the personal computer 10 divides the packet given the sequence number "B1" into two parts, a first half and a second half. Then, a sequence number “B11” is assigned to the first half, and a sequence number “B12” is assigned to the second half to make each packet.
[0029]
Then, the personal computer 10 first transmits a packet to which the sequence number “B11” is added, and then transmits a packet to which the sequence number “B12” is added. These packets are all transmitted to the personal computer 11, and are normally received by the personal computer 11 in the example shown in FIG.
[0030]
When receiving the packet with the sequence number “B12”, the personal computer 11 determines that retransmission of the packet with the sequence number “B” is completed, and ends the retransmission processing. When transmitting the packet requested to be retransmitted, the personal computer 10 transmits the packet to which the sequence number “D” is added to the personal computer 11 as the next packet to be transmitted.
[0031]
In FIG. 2, the personal computer 11 normally receives the packet with the sequence number “D”. Also, since the retransmission processing has been completed, the personal computer 11 compares the sequence number “C” of the previously received packet with the sequence number “D” of the currently received packet, and determines It is determined that there is not.
[0032]
[3] Operation of personal computers 10 and 11
Next, the operation of the personal computers 10 and 11 will be described separately for a transmission operation and a reception operation.
[3-1] Transmission operation of personal computers 10 and 11
When there is a service data unit to be transmitted, the personal computers 10 and 11 divide the packet into packets according to the size of the service data unit, and transmit the packets in the order from the beginning to the end of the service data unit. I do. FIG. 3 is a flowchart showing the flow of processing executed when the personal computers 10 and 11 transmit a packet.
[0033]
As shown in FIG. 3, the personal computers 10 and 11 first transmit a packet (step S100). Then, the transmitted packet is stored in the internal buffer in case that there is a request for retransmission of the packet (step S101).
The internal buffer may be, for example, a ring buffer. If there is not enough free space in the ring buffer to store a new packet, packets in the ring buffer may be deleted in order from the oldest packet until the required free space is secured. good.
[0034]
The ring buffer only needs to have a capacity that can store a sufficiently large number of packets. For example, when the data length per packet is fixed, the ring buffer may have a capacity that can store 256 packets. Further, if it is known that retransmission processing is performed by a protocol higher than the protocol that executes the retransmission procedure, the capacity of the internal buffer may be reduced.
[0035]
For example, when the retransmission processing is executed in a MAC (Media Access Control) layer, and TCP (Transmission Control Protocol) is used as a transport layer protocol, the retransmission processing is also performed in TCP. The capacity of the internal buffer prepared for the retransmission processing in the MAC layer may be smaller.
[0036]
Next, the personal computers 10 and 11 confirm whether or not the packet transmission destination has requested retransmission of the packet. Then, if the retransmission of the packet has been requested (step S102: Yes), the packet requested to be retransmitted is read from the internal buffer (step S103). Then, the service data unit included in the read packet is divided into two.
[0037]
Here, the service data unit refers to a portion obtained by removing the protocol control information from the packet. By doing so, it is possible to save the communication band required for retransmitting the protocol control information. Therefore, it is possible to effectively use the communication band. However, it goes without saying that the effects of the present invention can be achieved even if the entire packet including the protocol control information is divided and retransmitted.
[0038]
Further, the method of division is not limited to two, whether in service data units or the whole packet, and may be divided into three or more. In addition, it is not always necessary to perform equal division.
Furthermore, if the data length of the service data unit is too small, it may be contrary to the effective use of the bandwidth, so a condition for not dividing the service data unit may be set. For example, if the service data unit is equal to or less than a predetermined data length, the division may not be performed, or if the service data unit after division is equal to or less than the predetermined data length, the division may not be performed.
[0039]
After the division of the service data unit, the personal computers 10 and 11 add protocol control information to the division. Then, a new sequence number is assigned to the packet created in this way, and the packet is transmitted (step S100). Also, if No in step S102, the process proceeds to step S100. If there is a packet to be transmitted, it is transmitted.
[0040]
[3-2] Reception operation of personal computers 10 and 11
Next, the receiving operation of the personal computers 10 and 11 will be described. FIG. 4 is a flowchart showing a flow of processing executed when the personal computers 10 and 11 receive a packet. As shown in FIG. 4, upon receiving a packet (step S200), the personal computers 10 and 11 check the sequence number of the received packet (step S201).
[0041]
Then, the sequence number of the previously received packet is compared with the sequence number of the currently received packet, and if it is determined that there is a packet that has not been reached (step S202: Yes), the transmission source of the currently received packet is The retransmission of the packet is requested by designating the sequence number of the packet determined to have been reached (step S203).
[0042]
After the processing in step S203, or in the case of No in step S202, the personal computers 10 and 11 proceed to step S200 to receive the next packet.
[4] Packet format
Next, a format of a packet transmitted and received by the personal computers 10 and 11 will be described. FIG. 5 is a diagram showing a format of a packet transmitted and received by the personal computers 10 and 11.
[0043]
As can be seen from FIG. 5, the packets 2 transmitted and received by the personal computers 10 and 11 are composed of a packet control field 20, a source address field 21, a destination address field 22, a sequence number # 1 field 23, and a sequence number # 2 field. 24, a sequence number # 3 field 25, a data field 26, and an FCS field 27.
[0044]
The packet control field 20 is composed of a plurality of bit-assigned flags. For example, a certain flag indicates whether or not the packet is a divided packet by turning on / off a bit.
Further, there may be a flag indicating whether or not the packet is a retransmission packet, or a flag indicating whether or not there is a subsequent divided packet when the packet is a divided packet. Further, there is a flag indicating whether or not the data stored in the data field 26 has been encrypted by WEP (Wired Equivalent Privacy) processing.
[0045]
The source address field 21 stores the address assigned to the terminal that transmits the packet, and the destination address field 22 stores the address assigned to the terminal that is the destination of the packet. The sequence number # 1 field 23 is a field in which a sequence number used when performing normal communication is stored.
[0046]
The sequence number # 2 field 24 is a field used when retransmitting a packet transmitted and received in normal communication. For example, in FIG. 2 described above, the sequence number “B1” is used as the sequence number of the retransmission packet. The sequence number # 2 field 24 is a field for storing a portion of "1" in the sequence number "B1".
[0047]
The sequence number # 3 field 25 is a field used when the retransmission packet is further retransmitted. For example, in FIG. 2 described above, the sequence number “B12” is used as the sequence number of the retransmission packet. In the sequence number # 3 field 25, the part of "2" in the sequence number "B12" is stored.
[0048]
In the present embodiment, the above three fields are used as fields for storing sequence numbers. Therefore, if a packet (hereinafter, referred to as “re-retransmission packet”) is lost when retransmitting the retransmission packet, the packet is not divided when retransmitting the retransmission packet, and the retransmission packet is left as it is. resend.
[0049]
The data field 26 is a field corresponding to a service data unit, and fields other than the data field 26 correspond to protocol control information. This service data unit (data field 26) may be a division of the service data unit received from the upper layer.
The FCS field 27 is a field for storing an FCS (Frame Check Sequence). For example, a 32-bit CRC (Cyclic Redundancy Check) may be used for one entire packet.
[0050]
[5] Effects of the present embodiment
As described above, according to the present embodiment, the packet is divided and retransmitted, so that the packet can easily reach the destination terminal normally. That is, for one packet, if the error occurrence probability is the same, the smaller the size of the packet, the easier it is to reach the destination terminal normally. Therefore, the communication packet can more reliably reach the destination terminal.
[0051]
Further, according to the present embodiment, even if an error occurs, less data needs to be retransmitted, so that it is necessary to retransmit the packet as compared with the case of retransmitting without dividing the packet. Requires less bandwidth. Therefore, the communication band can be effectively used. In particular, the higher the probability of occurrence of an error, such as when the radio wave condition is not favorable, the higher the effect of the wireless LAN system according to the present embodiment can be.
[0052]
[6] Modifications
As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments, and the following modified examples can be implemented.
(1) In the above embodiment, the personal computer 11, which is the communication terminal receiving the packet, detects the packet loss by checking the sequence number assigned to the packet. The following may be used.
[0053]
That is, every time the receiving communication terminal receives a packet, it may return an acknowledgment (ACK: Acknowledgement), and the transmitting communication terminal may confirm the delivery of the packet by the ACK. In this case, if the communication terminal on the transmitting side does not receive the corresponding ACK within a predetermined time after transmitting the packet, it determines that a packet loss has occurred and executes a retransmission process.
[0054]
FIG. 6 is a sequence diagram showing a communication procedure when the communication terminal 30 transmits a packet to the communication terminal 31 and which is executed when the communication terminal 30 detects a packet loss. As shown in FIG. 6, the communication terminal 30 first transmits a packet to which the sequence number “X” has been assigned to the communication terminal 31. On the other hand, the communication terminal 31 normally receives the packet and returns an ACK to the communication terminal 30.
[0055]
In this modification, in order to clearly show the correspondence between a packet and ACK, the communication terminal 31 assigns a sequence number of the corresponding packet to ACK. For example, for the ACK corresponding to the packet to which the sequence number X is assigned, the communication terminal 31 assigns the sequence number X.
Subsequently, the communication terminal 30 transmits the packet to which the sequence number “Y” is added to the communication terminal 31. In FIG. 6, the packet given the sequence number “Y” does not reach the communication terminal 31 due to a loss generated for some reason. The communication terminal 30 further transmits a packet to which the sequence number “Z” has been added.
[0056]
The communication terminal 31 normally receives the packet, and compares the sequence number “X” of the previously received packet with the sequence number “Z” of the currently received packet. When the communication terminal 31 detects that the packet with the sequence number “Y” has not arrived by this comparison, it specifies the sequence number “Y” and requests the communication terminal 30 to retransmit.
[0057]
When receiving the retransmission request, the communication terminal 30 reads out the packet with the sequence number “Y” from the internal buffer, divides the packet into two parts, the first half and the second half, and respectively reads the sequence number “Y1”, This is a packet to which “Y2” is added. Then, the communication terminal 30 first transmits a packet of the sequence number “Y1”.
[0058]
When receiving the ACK corresponding to the packet, the communication terminal 30 transmits the packet with the sequence number “Y2”. Upon receiving the ACK for the packet, communication terminal 30 ends the retransmission processing. Then, the communication terminal 30 transmits the packet with the sequence number “Z”, and upon receiving the ACK for the packet, ends the series of procedures.
[0059]
As described above, even in a communication system that performs delivery confirmation using ACK, by applying the present invention, it is possible to reduce bandwidth consumption related to retransmission processing and effectively use a communication bandwidth. The same applies to the point that the communication packet can be more easily delivered to the destination terminal.
(2) In the above embodiment, a case has been described where the personal computer 10 divides the packet into two when retransmitting the packet. However, the following may be used instead. That is, the number of packet divisions (referred to as “the number of packets obtained by division” in this specification) is not limited to 2, and the packet may be divided into N and retransmitted. Here, the division number N is a number of 2 or more.
[0060]
Further, the number of packet divisions may be dynamically changed. For example, it is assumed that the final division number when the retransmission processing is executed last is recorded, and when the retransmission processing is next executed, the packet is divided according to the recorded division number and retransmitted. Is also good.
Taking the case where the retransmission processing executed last in FIG. 2 as an example, the packet of sequence number "B11" or "B12" is divided into two packets after dividing the packet of sequence number "B" by (2). , Ie, a packet obtained by dividing 2 × 2 = 4, 4 is recorded as the final division number. Then, when performing retransmission processing next, the packet may be immediately divided into four parts and retransmitted.
[0061]
By doing so, the expected value of the number of bit errors is reduced in accordance with the probability of occurrence of an error that varies from time to time, such as the surrounding electromagnetic wave condition, so that the packet can be transmitted to the destination terminal more quickly.
Further, when the error occurrence probability decreases, the number of divisions can be reduced to reduce the overhead such as the packet header. As a specific method for reducing the overhead, for example, there is a method that utilizes the number of packets that can be transmitted without requiring retransmission processing.
[0062]
That is, after the retransmission processing is completed, each time a packet can be delivered without the need for the retransmission processing, the recorded division number may be reduced by one. Note that the reduction width is not limited to one and may be two or more, or may be reduced by one each time all of a plurality of continuous packets can be delivered.
[0063]
In any case, the number of divisions must not be less than two. In this way, when the error occurrence probability decreases, the overhead required for the retransmission processing can be reduced, and the communication band can be effectively used.
In addition, as a method of determining the number of divisions, as described above, in addition to recording the number of divisions at the time of performing the last retransmission processing, the final number of divisions is recorded each time the retransmission processing is performed. Statistics may be taken and the most frequent division number may be selected.
[0064]
Alternatively, if the last retransmission processing is successfully completed, the size of the packet at that time is recorded, and in the next retransmission processing, the packet is immediately divided into the recorded size. good. In addition, instead of the number of divisions, statistics of the packet size may be obtained, and the most suitable packet size may be determined according to the statistics to divide the packet.
[0065]
Regardless of the method employed, if the number of divisions is increased as the error occurrence probability is higher, and if the number of divisions is decreased as the error occurrence probability is lower, the communication The overhead can be reduced, and the communication band can be used more effectively.
When the number of divisions is dynamically changed, a packet format different from the packet format described in the above embodiment may be employed, and the number of divisions may be stored in the packet header. Further, a flag indicating the last packet in a series of divided packets may be provided in the packet header. This is useful as information when the receiving terminal assembles the divided packets.
[0066]
(3) In the above embodiment, the case of the ad hoc mode in which the wireless communication terminals directly communicate with each other has been described as an example, but the following may be used instead.
That is, it may be an infrastructure mode in which communication is performed via a so-called access point. In this case, the retransmission processing may be performed between the wireless communication terminals or between the wireless communication terminal and the access point. In any case, the effects of the present invention can be achieved.
[0067]
(4) Although not explicitly stated in the above embodiment, the present invention may be applied to a so-called MAC layer protocol, and may be replaced with a basic OSI (Open System Interconnection) instead of the MAC layer protocol. It may be applied to a transport layer protocol in a reference model (Basic Reference Model). Regardless of which layer the target protocol belongs to, the effect can be obtained by applying the present invention.
[0068]
(5) In the above-described embodiment, the case where the present invention is applied exclusively to wireless communication has been described. However, the present invention is not limited to wireless communication, and can be applied to wired communication to achieve the effect. . For example, assuming a packet switched network, packet loss may occur due to network congestion. Even in such a case, by applying the present invention, it is possible to execute the retransmission processing while suppressing the bandwidth consumption, so that not only can the packets be delivered more reliably, but also it is difficult to cause network congestion. You can also.
[0069]
(6) In the above embodiment, a case has been described where a personal computer is exclusively used as a communication terminal. However, the present invention is not limited to this. The effect can be achieved. Further, the present invention can provide effects irrespective of whether the communication system is the pre-duplex system or the half-duplex system.
[0070]
【The invention's effect】
As described above, according to the present invention, a packet that has not been delivered to the destination terminal is divided and retransmitted, so that the expected value of the number of errors in the packet can be reduced in comparison with the case where the packet is not divided. Therefore, the packet can be more reliably delivered to the destination terminal.
[0071]
Further, as described above, since only the retransmission packet that has not been transmitted to the destination terminal among the retransmission packets is retransmitted, the bandwidth consumption required for retransmitting the packet can be reduced in comparison with the case where the packet is not divided. Therefore, the communication band can be effectively used.
Also, when retransmitting a retransmitted packet that has not been transmitted to the destination terminal, the retransmitted packet is divided and retransmitted, so that the retransmitted packet can be transmitted to the destination terminal more reliably as described above.
[0072]
Also, when retransmitting a packet, the number of packet divisions is dynamically optimized, so that the retransmitted packet can be delivered to the destination terminal more quickly. In addition, since communication overhead required for retransmission can be reduced, effective use of a communication band can be achieved.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a system configuration of a wireless LAN system according to an embodiment of the present invention.
FIG. 2 is a communication procedure when the personal computer 10 transmits a packet to the personal computer 11 in the wireless LAN system 1 according to the present embodiment, and the personal computer 11 detects a packet loss. FIG. 6 is a sequence diagram showing a communication procedure executed in the first embodiment.
FIG. 3 is a flowchart showing a flow of processing executed when the personal computers 10 and 11 transmit packets in the wireless LAN system 1 according to the present embodiment.
FIG. 4 is a flowchart showing a flow of processing executed when the personal computers 10 and 11 receive a packet in the wireless LAN system 1 according to the present embodiment.
FIG. 5 is a diagram showing a format of a packet transmitted and received by the personal computers 10 and 11 in the wireless LAN system 1 according to the present embodiment.
FIG. 6 is a communication procedure when the communication terminal 30 transmits a packet to the communication terminal 31 in the communication system according to the modified example (1), which is executed when the communication terminal 30 detects a packet loss. It is a sequence diagram showing a communication procedure.
[Explanation of symbols]
1. Wireless LAN system
2 ………… Packet
10, 11 ... personal computer
20: Packet control field
21 ... source address field
22 destination address field
23: Sequence number # 1 field
24 ............. Sequence number # 2 field
25 Sequence number # 3 field
26 Data field
27 ……… FCS field
30, 31 ... communication terminal

Claims (11)

A packet communication device for transmitting a packet to a destination device,
A packet dividing means for dividing the requested packet into a plurality of packets when requested to retransmit the packet from the destination device;
A packet transmission device for transmitting the plurality of packets to a destination device. A packet communication device for transmitting a packet to a destination device,
Retransmission determination means for determining whether to retransmit the packet,
When the retransmission determination unit determines that the packet should be retransmitted, a packet division unit that divides the packet to be retransmitted into a plurality of packets,
A packet transmission device for transmitting the plurality of packets to a destination device. An acknowledgment receiving unit that receives an acknowledgment notifying that the packet has been received from the destination device,
The method according to claim 2, wherein the retransmission determination unit determines that the packet should be retransmitted if an acknowledgment relating to the packet is not received within a predetermined time after transmitting the packet. A packet communication device according to claim 1. The packet division unit divides a service data unit included in a packet determined to be retransmitted into a plurality of service data units, and assigns protocol control information to each of the plurality of service data units, thereby forming the plurality of packets. The packet communication device according to claim 1 or 2. 3. The apparatus according to claim 1, further comprising a packet division control unit configured to cause the packet transmission unit to retransmit the packet if the packet to be retransmitted is shorter than a predetermined data length without causing the packet division unit to divide the packet. 2. The packet communication device according to 1. 2. The apparatus according to claim 1, further comprising: a division number determining unit that determines the number of divisions when the packet division unit divides the packet according to the number of packets obtained by dividing the packet in the past. The packet communication device according to claim 1 or 2. 7. The method according to claim 6, wherein the division number determination unit sets the number of packets obtained by dividing the packet last by the packet division unit as the division number when the packet division unit divides the packet. A packet communication device according to claim 1. 8. The packet communication device according to claim 6, wherein the division number determining unit reduces the division number in accordance with the number of packets transmitted after the packet division unit last divides the packet. . A packet communication method executed by a packet communication device that transmits a packet to a destination device,
When a packet retransmission is requested from the destination device, a packet division step of dividing the requested packet into a plurality of packets,
A packet transmission step of transmitting the plurality of packets to a destination device. A packet communication method executed by a packet communication device that transmits a packet to a destination device,
A retransmission determination step of determining whether to retransmit the packet;
A packet division step of dividing the packet to be retransmitted into a plurality of packets when the retransmission determination unit determines that the packet should be retransmitted;
A packet transmission step of transmitting the plurality of packets to the destination device. A packet communication program for causing a computer to execute the packet communication method according to claim 9 or 10.

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