JP2012165141A - Communication device, control method and program therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that communication delay is larger than necessary when the frequency of occurrence of missing frames is low, although throughput does not decrease significantly without reordering, and that the buffer size increases.SOLUTION: The communication device comprises a reception unit which receives a plurality of frames, a calculation unit which calculates the loss rate of received frame based on the sequence number included in a frame received by the reception unit, a determination unit which determines that the received frame is reordered if the loss rate calculated by the calculation unit is equal to or above a threshold otherwise determines that the received frame is not reordered, and a reordering unit which reorders the received frame if a determination is made that the received frame is reordered by the determination unit.

Description

  The present invention relates to a communication device that performs reorder processing of a received frame, a control method for the communication device, and a program.

  The IEEE802.11n standard supports aggregation in which a plurality of frames are aggregated (concatenated) and transmitted in order to achieve high speed. In an A-MPDU (aggregation MPDU) that aggregates frames in units of MPDU (MAC protocol data unit), Block Ack is used for confirmation response instead of conventional Ack. Block Ack acknowledges each aggregated MPDU subframe. If reception of some of the MPDU subframes fails at the same time, a retransmission request is made by notifying the MPDU subframes that have failed to be received with Block Ack. Therefore, when the A-MPDU is transmitted, the arrival order of MPDU subframes may frequently differ. At this time, if communication is performed using TCP or the like, there is a possibility that the frame that has been lost in the middle will be retransmitted at the TCP layer, and the throughput will be reduced.

  With a rate control algorithm in a version of TCP, a single packet loss does not affect the overall throughput, but the continuous packet loss reacts sensitively as the network is congested and increases the throughput. Deteriorate.

  In the case of a wireless section, packet loss does not always occur due to congestion, and there are cases where it is better to perform retransmission and reorder as much as possible in the lower network layer than to stop data transmission in the upper network layer.

  There is reordering as a technique for rearranging the order of frames after waiting for a missing frame when such frames do not arrive in order. If reordering is performed in the data link layer, frames are notified in order to the TCP layer, so that a reduction in throughput can be prevented. Therefore, reordering is widely performed in wireless communication.

  However, when the reordering process is performed, it is necessary to always hold frames in the middle until they are arranged in order, so that the necessary buffer becomes larger accordingly. There is also a problem that communication delay increases.

  In TCP data communication, even if data does not arrive in order, the data is awaited for a certain period or a certain number of frames without being retransmitted. For this reason, when there are few frame skips in the lower layer, the throughput does not decrease much even if the frame is not reordered in the lower layer.

  Patent Document 1 discloses that when receiving sound information, reception is performed without reordering when reproducing in real time, and reordering is performed when reproducing after reception.

  In Patent Document 2, the efficiency of a buffer necessary for reordering is improved. It is disclosed that the reordering buffer is ranked based on the QoS information, and when the memory release becomes necessary, the memory of the reordering buffer is released according to the rank.

  Patent Documents 3 and 4 disclose that the relay apparatus performs control necessary for reordering.

Japanese Patent Laid-Open No. 2003-101662 JP 2006-33019 JP 2007-81678 A JP 2007-300502

  The reordering in these prior arts has been performed regardless of the frequency at which frame skipping occurs in the lower layer. Therefore, in an environment with few frame skips, the required buffer size increases or the communication delay increases more than necessary even though the throughput does not decrease much even if reordering is not performed. There are challenges.

  In view of the above problems, an object of the present invention is to reduce the buffer size required for reordering when the occurrence frequency of frame dropout is low.

A communication device according to the present invention that achieves the above object is as follows.
Receiving means for receiving a plurality of frames;
Calculating means for calculating a loss rate of the received frame based on a sequence number included in the received frame received by the receiving means;
Determination means for determining that the received frame is to be reordered when the loss rate calculated by the calculation means is equal to or greater than a threshold, and for determining that the received frame is not to be reordered when the loss rate is less than the threshold. When,
Reordering means for reordering the received frame when it is determined by the determining means to reorder the received frame;
It is characterized by providing.

  According to the present invention, it is possible to reduce the buffer size required for reordering when the frequency of frame dropouts is low. Further, since unnecessary reordering can be suppressed, communication delay can be reduced.

1 is a configuration diagram of a wireless LAN terminal according to a first embodiment. FIG. 3 is a configuration diagram of a reception frame according to the first embodiment. FIG. 3 is a configuration diagram of a reorder buffer according to the first embodiment. 6 is a flowchart of received frame processing according to the first embodiment. 5 is a flowchart of a reorder determination unit according to the first embodiment. FIG. 5 is a configuration diagram of a wireless LAN terminal according to a second embodiment. 10 is a flowchart of received frame processing according to the second embodiment. 10 is a flowchart of a reorder determining unit according to the second embodiment. FIG. 6 is a configuration diagram of a wireless LAN terminal according to a third embodiment. 10 is a flowchart of received frame processing according to the third embodiment. 10 is a flowchart of a TCP retransmission rate measurement unit according to the third embodiment. The flowchart of the reorder judgment part of 3rd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a configuration of a wireless LAN terminal (communication device) to which the first embodiment can be applied. In the present embodiment, the present invention is applied to the wireless LAN terminal 101 of FIG. The wireless LAN terminal 101 is a terminal capable of wireless LAN communication in accordance with the IEEE802.11n standard. The wireless LAN terminal 101 includes a TCP / IP processing unit 102, a wireless LAN control unit 103, a TCP / IP notification unit 104, a wireless LAN error rate measurement unit 105, a reorder determination unit 106, and a reorder control unit 107. Prepare.

  The TCP / IP processing unit 102 includes a control program that processes protocols such as TCP, UDP, and IP. The wireless LAN control unit 103 includes a wireless LAN chip and an antenna for performing wireless LAN communication, and a control program thereof. When a frame is transmitted from another terminal (not shown) to the wireless LAN terminal 101, the wireless LAN control unit 103 receives the frame, and a reception process is first performed. The TCP / IP notification unit 104 notifies the TCP / IP processing unit 102 of the frame when the frame received by the wireless LAN control unit 103 is IP data to be processed by the TCP / IP processing unit 102. Is a control program.

  The wireless LAN error rate measuring unit 105 is a program for calculating an error rate that has occurred on the wireless LAN. The wireless LAN error rate measuring unit 105 measures an error rate (loss rate) of a received frame from the last 100 received frames by counting as an error when a missing frame occurs.

  The reorder determination unit 106 is a program that determines whether or not to perform reordering when a frame is missing. The reorder control unit 107 is a program that performs processing to arrange the order of frames when a missing frame occurs in a received frame, and includes a reorder buffer that is necessary for performing reordering.

  FIG. 2A shows a configuration example of a frame received by the wireless LAN terminal 101. In the present embodiment, when simply referred to as a frame, it refers to a frame shown in FIG. 2 (a) and is distinguished from an A-MPDU frame. On the other hand, the A-MPDU frame is represented as a frame in which a plurality of frames shown in FIG. When the wireless LAN terminal 101 receives an A-MPDU frame, the wireless LAN control unit 103 divides the A-MPDU frame into a plurality of frames. FIG. 2 (b) shows details of the MPDU header. FIG. 2 (c) shows details of sequence control. Each frame is transmitted so that the sequence numbers of the sequence control (FIG. 2 (c)) in the MPDU header (FIG. 2 (b)) are consecutive. For this reason, when an A-MPDU frame is received and a gap occurs in the middle of the frame, the received frame sequence numbers do not become continuous, and the gap occurs. In addition, even when a frame that has been lost in the middle due to Block Ack or the like is retransmitted and received by the wireless LAN terminal 101, the sequence number does not become consecutive, and a frame with a sequence number smaller than the sequence number of the frames received so far Will be received. In the present embodiment and the following embodiments, the description will be made assuming that no fragmentation is performed in order to simplify the description.

  FIG. 3A shows a configuration example of the reorder buffer. The data in the reorder buffer shown in FIG. 3A is stored by the reorder control unit 107 for reordering. The area 301 is an area for storing the sequence number last notified to the TCP / IP processing unit 102, and is used to detect that a frame has been lost or that the arrangement of frames has been aligned. The Each of the area 302, the area 303, and the area 304 stores a frame sequence number and a pointer to the frame. This is used to store the sequence number of a previously received frame and a pointer to the frame when a missing frame occurs. In FIG. 3 (a), three frame regions are shown, but the number of regions is not limited. Each area may be a statically secured area, but dynamically securing the area leads to more efficient use of the buffer.

  FIG. 3 (b) shows an example of a reorder buffer when data is specifically stored. FIG. 3B shows an example in which frames from sequence number 1000 to sequence number 1005 are transmitted from the terminal, and frames having sequence number 1001 and sequence number 1004 are received and received. Since the sequence number 1001 has been received and received, the sequence number finally notified to the TCP / IP processing unit 102 is 1000, and each of the frames of the sequence number 1002, the sequence number 1003, and the sequence number 1005 received subsequently is received. A sequence number and a pointer to a frame are stored as a pair.

  When the wireless LAN control unit 103 receives the frame having the sequence number 1001 from the state of FIG. 3B, the frames from the sequence number 1001 to the sequence number 1003 are prepared. Therefore, the frames of sequence number 1000, sequence number 1001, sequence number 1002, and sequence number 1003 are rearranged by the reorder control unit 107, and the TCP / IP notification unit 104 sends the frame to the TCP / IP processing unit 102. Notify and request processing. The sequence number finally notified to the TCP / IP processing unit 102 is the sequence number 1003, and the sequence number 1002 and the sequence number 1003 are deleted from the reorder buffer.

  On the other hand, when the wireless LAN control unit 103 receives the frame having the sequence number 1004 from the state of FIG. 3B, the frame having the sequence number 1001 is still missing. Therefore, the reorder control unit 107 adds the frame having the sequence number 1004 to the reorder buffer. The TCP / IP notification unit 104 does not notify the TCP / IP processing unit 102 until the frame having the sequence number 1001 is received.

  With reference to the flowchart of FIG. 4, a procedure of processing when the wireless LAN terminal 101 receives a frame in this embodiment will be described. Each process of S401, S402, S403, S405, and S406 in FIG. 4 is executed by the wireless LAN error rate measuring unit 105. Each process of S404 and S411 is executed by the TCP / IP notification unit 104. The process of S407 is executed by the reorder determining unit 106. Each process of S408, S409, and S410 is executed by the reorder control unit 107.

  When a frame is transmitted from a terminal (not shown) to the wireless LAN terminal 101, first, the wireless LAN control unit 103 receives the frame. When receiving the frame, the wireless LAN control unit 103 passes the received frame to the wireless LAN error rate measurement unit 105. Also, when the wireless LAN control unit 103 receives an A-MPDU frame, the wireless LAN control unit 103 divides the A-MPDU frame into a plurality of frames, and then each frame is subjected to a wireless LAN error rate one by one. It passes to the measurement part 105 and requests a process.

  In S401, when the frame is passed, the wireless LAN error rate measurement unit 105 acquires the sequence number from the sequence control of the MPDU header, and finally notifies the TCP / IP processing unit 102 of the acquired sequence number. Compare with the sequence number. At this time, if the acquired sequence number is one greater than the sequence number last notified to the TCP / IP processing unit 102, the sequence number is determined to be in order, and the process proceeds to S402. If it is determined that the acquired sequence number is 2 or more than the sequence number last notified to the TCP / IP processing unit 102, it is determined that a frame has dropped out and the process proceeds to S405. If the acquired sequence number is smaller than the sequence number last notified to the TCP / IP processing unit 102, it is determined that the retransmission frame has arrived and the process proceeds to S408.

  In S402, when the received frames arrive in order, the wireless LAN error measuring unit 105 counts the received frames as being normally received packets.

  In S405, the wireless LAN error measurement unit 105 counts as an error when a missing frame occurs.

  On the other hand, the wireless LAN error measurement unit 105 does not count when it is determined as a retransmission frame.

  In S403 and S406, the wireless LAN error rate measuring unit 105 calculates the wireless LAN error rate in each case from the latest 100 received frames that were counted as normal or error last.

  The frame determined to be in order in S402 is notified to the TCP / IP processing unit 102 by the TCP / IP notification unit 104 in S404 after the wireless LAN error rate is calculated in S403 and received in the upper layer of the network. Request processing of the frame. At this time, the received frame may be passed to the TCP / IP processing unit 102 after performing some MAC processing. For example, if the received frame is an A-MSDU (MAC service data unit) frame, the A-MSDU frame may be divided into a plurality of MSDUs and passed to the TCP / IP processing unit 102.

  Next, the received frame counted as an error in S405 will be described. After the wireless LAN error rate is calculated by the wireless LAN error rate measuring unit 105 in S406, S407 is performed. The processing of S407 is performed by the reorder determining unit 106, and details are shown in FIG. The flowchart of FIG. 5 shows details of the processing of the reorder determining unit 106.

  The reorder determining unit 106 determines whether or not to reorder based on the wireless LAN error rate measured by the wireless LAN error rate measuring unit 105. As the wireless LAN error rate, the wireless LAN error rate calculated last in S403 or S406 is used.

  In S501, the reorder determining unit 106 determines whether or not the wireless LAN error rate is 5% or higher (threshold or higher). If it is determined that the wireless LAN error rate is 5% or more (above the threshold) (S501; YES), the process proceeds to S502. On the other hand, if it is determined that the wireless LAN error rate is less than 5% (less than the threshold) (S501; NO), the process proceeds to S503. In S502, the reorder determining unit 106 determines to reorder. On the other hand, in S503, the reorder determining unit 106 determines not to reorder. Although the threshold is 5% as a reference, the threshold is not necessarily limited to 5%, and an arbitrary predetermined value may be set as the threshold.

  If it is determined to reorder in S502, it corresponds to Yes in S407 in the flowchart of FIG. 4, and the process proceeds to S409. In S409, the reorder control unit 107 stores the received frame determined to be reordered in the reorder buffer. The frame is delivered to the TCP / IP processing unit 102 after the frame order is aligned. For this reason, the frames are held in the reorder buffer until the frames are arranged.

  On the other hand, if it is determined not to reorder in S503, it corresponds to No in S407 in the flowchart of FIG. 4, and the process proceeds to S404.

  In S404, the TCP / IP notification unit 102 notifies the TCP / IP processing unit 102 of the received frame. That is, processing of the frame is performed in the upper layer of the network with the frame missing.

  Next, the processing in S408 for processing the received frame determined as the retransmission frame in S401 will be described.

  In S408, when the received frame is a retransmission frame, the reorder control unit 107 determines whether or not missing frames are prepared from the sequence numbers of the received frames stored in the reorder buffer. If it is determined that the missing frames are aligned (S408; YES), the process proceeds to S410. If it is determined that the missing frames are not complete (S408; NO), the process proceeds to S409.

  In S409, the reorder control unit 107 stores the retransmission frame in the reorder buffer. Then, the retransmission frame is not notified to the TCP / IP processing unit 102 until the missing frames are arranged.

  If it is determined in S410 that the missing frames are complete in S408, the reorder control unit 106 performs reordering and rearranges the received frames stored in the reorder buffer according to the sequence number.

  In S411, the TCP / IP notification unit 104 notifies the TCP / IP processing unit 102 of the received frame group reordered in the order of the sequence numbers. After each process of S404, S409, and S411, the process of the flowchart of FIG. 4 ends.

  According to the present embodiment, it is possible to control whether or not the reorder processing is performed according to the error rate at the wireless LAN level. Thereby, when there are few missing frames, the communication delay can be reduced. At the same time, if the reorder buffer area is dynamically secured as necessary, the buffer size required for reordering can be reduced. On the other hand, if there is a possibility that the TCP throughput is greatly deteriorated due to frequent frame loss (at the wireless LAN level), reorder processing is performed in the MAC layer to reduce the TCP throughput. Can be prevented.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows the configuration of a wireless LAN terminal 601 to which this embodiment can be applied. The wireless LAN terminal 601 includes a TCP / IP processing unit 602, a wireless LAN control unit 603, a TCP / IP notification unit 604, an application processing unit 605, a wireless LAN error rate measurement unit 606, a reorder determination unit 607, A reorder control unit 608 and a protocol identification unit 609 are provided. A wireless LAN terminal 601 in FIG. 6 is obtained by adding an application processing unit 605 and a protocol identification unit 609 to the configuration of the wireless LAN terminal 101 described in FIG. Therefore, the description of the same part as in FIG. 1 is omitted. The application processing unit 605 is an application program that operates by performing TCP or UDP communication via the TCP / IP processing unit 602. Examples of the application include an application that transmits image data and a status management application that responds to an inquiry about the state of the wireless LAN terminal 601.

  The protocol identification unit 609 is a program for identifying whether or not the received frame is a designated protocol. Only frames of the protocol identified by the protocol identification unit 609 are included in the reorder target. The protocol is specified by the application processing unit 605 specifying a port number.

  For example, in the case of an image data transmission application that requires throughput, the application processing unit 605 specifies a port number used by the image data transmission application. On the other hand, if the application does not require much throughput, such as an application that manages the status of the wireless LAN terminal 601, the application processing unit 605 does not specify a port number. Alternatively, if the application receives streaming in real time by UDP, the port number is not specified to reduce the communication delay.

  Processing when the wireless LAN terminal 601 receives a frame will be described with reference to the flowchart of FIG. Each process of S701 to S706 is the same as each process of S401 to S406 in FIG. Further, the processes of S709 to S712 are the same as the processes of S409, S408, S410, and S411, respectively. Description of the same processing as in FIG. 4 is omitted. The difference from the processing in FIG. 4 is the processing in S707 and S708. The process of S707 is performed by the protocol identification unit 609. The processing in S708 is performed by the reorder determining unit 607.

  If it is determined in S701 that there is a missing frame, the process proceeds to S705 and S706 as in the first embodiment. In S706, the wireless LAN error measurement unit 105 calculates a wireless LAN error rate. Thereafter, in S707, the protocol identification unit 609 identifies the protocol (data type). The protocol identification unit 609 identifies whether the received frame is data of a port number designated in advance, and notifies the reorder determination unit 607 of the result. In S708, the reorder determining unit 607 determines whether or not to include the received frame as a reorder target. FIG. 8 shows the processing of S708 of the reordering determination unit 607 in the second embodiment.

  A detailed process of the reorder determination unit 607 will be described with reference to the flowchart of FIG. First, in S801, the reorder determining unit 607 determines whether or not the wireless LAN error rate calculated by the wireless LAN error rate measuring unit 606 is 5% or more. When it is determined that the wireless LAN error rate is 5% or more (S801; YES), the process proceeds to S802. On the other hand, if it is determined that the wireless LAN error rate is less than 5% (S801; NO), the process proceeds to S804. In S802, the reorder determining unit 607 determines whether or not the port number has been designated as a reorder target in advance from the result identified by the protocol identifying unit 609. If it is determined that the port number has been designated as a reorder target in advance (S802; YES), the process proceeds to S803. On the other hand, if it is determined that the port number is not designated as a reorder target in advance (S802; NO), the process proceeds to S804. In S804, the reorder determining unit 607 determines not to reorder. In S805, the reorder determining unit 607 determines that reordering is to be performed. The process ends here.

  As described above, the reorder determining unit 607 determines whether or not to reorder in the process of S708 of the flowchart of FIG. 7 according to the process of the flowchart of FIG. According to the present embodiment, it is possible to specify whether or not to perform reordering for each application or protocol. For example, in the case of an application that requires throughput by TCP, by performing reordering, it is possible to reduce a decrease in throughput even when a frame dropout occurs at the wireless LAN level. On the other hand, when audio or video streaming is received by UDP, it is possible to specify that reordering is not performed in order to reduce communication delay.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIGS. FIG. 9 shows the configuration of a wireless LAN terminal 901 to which this embodiment can be applied. The wireless LAN terminal 901 includes a TCP / IP processing unit 902, a wireless LAN control unit 903, a TCP / IP notification unit 904, an application processing unit 905, a wireless LAN error rate measurement unit 906, a reorder determination unit 907, A reorder control unit 908, a protocol identification unit 909, and a TCP retransmission rate measurement unit 910 are provided. The wireless LAN terminal 901 in FIG. 9 is obtained by adding a TCP retransmission rate measurement unit 910 to the wireless LAN terminal 601 in FIG. Therefore, the description of the same part as in FIG. 6 is omitted.

  The TCP retransmission rate measurement unit 910 is a program for calculating a frame retransmission rate generated in TCP from received TCP data (retransmission rate calculation processing). The TCP retransmission rate measurement unit 910 holds the largest TCP sequence number of the received TCP data as a reference TCP sequence number. When TCP data larger than the reference TCP sequence number is received, it is counted as not being retransmitted. On the other hand, when TCP data smaller than the reference TCP sequence number is received, it is counted as retransmission. If it is not TCP data, it is not counted. TCP retransmission rate measuring section 910 measures the TCP retransmission rate from the last received 100 pieces of TCP data. The reference TCP sequence number is updated each time TCP data having a larger TCP sequence number is received.

  A processing procedure when the wireless LAN terminal 901 receives a frame will be described with reference to the flowchart of FIG. Each process of S1001 to S1007 is the same as each process of S701 to S707 in FIG. Further, the processes of S1010 to S1013 are the same as the processes of S709 to S712. Explanation of the same processing as in FIG. 7 is omitted. The difference from the processing in FIG. 7 is the processing of S1008 and S1009. The processing in S1008 is performed by the TCP retransmission rate measurement unit 910. The processing of S1009 is performed by the reorder determining unit 907.

  If it is determined in S1001 that there is a missing frame, wireless LAN error rate calculation processing and protocol identification processing are performed by S1005, S1006, and S1007, as in the second embodiment. Thereafter, in S1008, the TCP retransmission rate measurement unit 910 measures the TCP retransmission occurrence rate. Detailed processing of S1008 will be described with reference to the flowchart of FIG.

  In step S1101, the TCP retransmission rate measurement unit 910 determines whether the received frame is data of the TCP protocol. When it is determined that the received frame is TCP protocol data (S1101; YES), the process proceeds to S1102. On the other hand, if it is determined that the received frame is not data of the TCP protocol (S1101; NO), the process is terminated without updating the TCP retransmission rate.

  In S1102, the TCP retransmission rate measurement unit 910 compares the TCP sequence number of the received frame with the reference TCP sequence number. If it is determined that the TCP sequence number of the received frame is larger than the reference TCP sequence number (S1102; YES), the process proceeds to S1103. On the other hand, when it is determined that the TCP sequence number of the received frame is equal to or less than the reference TCP sequence number (S1102; NO), the process proceeds to S1104.

  In S1103, TCP retransmission rate measurement section 910 counts the received frame as not being retransmitted. Also, the TCP retransmission rate measurement unit 910 updates the reference TCP sequence number. In S1104, TCP retransmission rate measurement section 910 counts the received frame as being retransmitted. After counting whether or not it is retransmission in S1103 and S1104, the process proceeds to S1105.

  In S1105, the TCP retransmission rate measurement unit 910 recalculates the TCP retransmission rate. The TCP retransmission rate is calculated by calculating the frequency of occurrence of retransmissions from the last 100 received TCP data. Thus, the process of S1008 ends.

  After measuring the TCP retransmission rate in S1008, in S1009, the reorder determining unit 907 determines whether or not to include the received frame as a reorder target. The processing of S1009 by the reorder determining unit 907 in the third embodiment will be described with reference to the flowchart of FIG.

  First, in S1201, the reorder determining unit 907 determines whether or not the wireless LAN error rate calculated by the wireless LAN error rate measuring unit 906 is 5% or more. When it is determined that the wireless LAN error rate is 5% or more (S1202; YES), the process proceeds to S1202. On the other hand, if it is determined that the wireless LAN error rate is less than 5% (S1202; NO), the process proceeds to S1205, and it is determined not to reorder.

  In step S1202, the reorder determining unit 907 determines whether or not the port number is designated as a reorder target in advance based on the result identified by the protocol identifying unit 909. When it is determined that the port number has been designated as a reorder target in advance (S1202; YES), the process proceeds to S1203. On the other hand, if it is determined that the port number is not a port number designated in advance as a reorder target (S1202; NO), the process proceeds to S1205, and it is determined not to reorder.

  In S1203, the reorder determining unit 907 determines whether or not the TCP retransmission rate calculated by the TCP retransmission rate measuring unit 910 is 3% or more (a threshold value or more) (retransmission rate determination process). If it is determined that the TCP retransmission rate is 3% or more (greater than or equal to the threshold) (S1203; YES), the process proceeds to S1204. On the other hand, if it is determined that the TCP retransmission rate is less than 3% (less than the threshold) (S1203; YES), the process proceeds to S1205. In S1204, the reorder determining unit 907 determines to perform reordering. In step S1205, the reorder determining unit 907 determines not to perform reordering. The process ends here. Although the threshold is 3% as a reference, it is not necessarily limited to 3%, and an arbitrary predetermined value may be set as the threshold.

  As described above, the reorder determining unit 907 determines whether or not to reorder in the process of S1109 of the flowchart of FIG. 11 according to the process of the flowchart of FIG. The subsequent processing is the same as in the second embodiment.

  According to the present embodiment, it is possible to determine whether or not to implement reordering according to the TCP retransmission rate. Even when a packet dropout occurs at the wireless LAN level, the throughput may not be significantly reduced unless retransmission occurs at the TCP level. In such a case, reordering is not performed due to buffer utilization efficiency or communication delay.

  In addition, when there are few packet drops at the wireless LAN level and retransmissions occur frequently at the TCP level, there is a possibility that a loss has occurred in another part of the network instead of wireless LAN communication. There is sex. Even in such a case, a decrease in throughput may be unavoidable even if reordering is performed.

  According to the present embodiment, when packet loss occurs at the wireless LAN level and TCP throughput is likely to be greatly reduced, reordering can be performed to reduce the reduction in throughput. On the other hand, if this is not the case, it is possible to prevent the buffer from being used unnecessarily and the communication delay from being increased without performing reordering.

<About each embodiment>
The present invention is not limited to the embodiments described above, and can be implemented in various forms. For example, in each process of S408, S710, and S1011, after the missing frames are prepared, the reorder control unit performs reordering and notifies the TCP / IP processing unit. Here, when the missing frame is not received for a certain period of time, reordering may be performed with a part of the frame missing and notified to the TCP / IP processing unit.

  In the third embodiment, it is determined whether or not to reorder from the TCP retransmission rate in S1203, but whether or not to reorder regardless of the TCP retransmission rate if the received frame is UDP protocol data. May be determined. That is, in the TCP protocol, whether or not to reorder is determined based on the wireless LAN error rate, the protocol type, and the TCP retransmission rate as in the third embodiment. On the other hand, in the UDP protocol, the application method may be changed according to the protocol so as to determine whether or not to reorder based on the wireless LAN error rate and the protocol type as in the second embodiment.

  Further, in TCP, a specific application or port number may determine whether to reorder based on the TCP retransmission rate, and another application or port number may not consider the TCP retransmission rate.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (7)

Receiving means for receiving a plurality of frames;
Calculating means for calculating a loss rate of the received frame based on a sequence number included in the received frame received by the receiving means;
Determination means for determining that the received frame is to be reordered when the loss rate calculated by the calculation means is equal to or greater than a threshold value, and for determining that the received frame is not to be reordered when the loss rate is less than the threshold value. When,
Reordering means for reordering the received frame when it is determined by the determining means to reorder the received frame;
A communication apparatus comprising: A specifying means for specifying the data type;
An identification unit for identifying whether or not the received frame received by the receiving unit is the data type designated by the designation unit;
The determining means determines to reorder the received frame when the loss rate calculated by the calculating means is equal to or greater than a threshold and the identifying means identifies the received frame as the data type. The communication apparatus according to claim 1, wherein: Based on the sequence number of the received frame, retransmission rate calculating means for calculating a retransmission rate that is the frequency of occurrence of frame retransmission;
Retransmission rate determining means for determining whether the retransmission rate is equal to or higher than a threshold; and
The determining means is such that the loss rate calculated by the calculating means is equal to or greater than a threshold, the identifying means identifies the received frame as the data type, and the retransmission rate determining means determines the retransmission rate to be a threshold. The communication apparatus according to claim 2, wherein if it is determined as above, it is determined to reorder the received frame.   4. The communication apparatus according to claim 2, wherein the data type is TCP protocol data.   If it is determined by the determining means that the received frame is reordered, the received frame is notified to the upper layer of the network after the received frame is reordered, and the determined means is determined not to reorder the received frame. 5. The communication apparatus according to claim 1, further comprising notification means for notifying the received frame to the upper layer of the network without reordering the received frame. A control method for a communication device comprising a receiving means, a calculating means, a judging means, and a reordering means,
A receiving step in which the receiving means receives a plurality of frames;
The calculating means calculates a loss rate of the received frame based on a sequence number included in the received frame received by the receiving step;
The determining means determines that the received frame is reordered when the loss rate calculated by the calculating step is equal to or greater than a threshold value, and does not reorder the received frame when the loss rate is less than the threshold value. A determination process for determining
A reordering step of reordering the received frame when the reordering means determines that the received frame is reordered by the determining step;
A method for controlling a communication apparatus, comprising:   A program for causing a computer to execute each step of the communication device control method according to claim 6.

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