COMMUNICATION DEVICE, COMMUNICATION DEVICE CONTROL METHOD, AND PROGRAM

Abstract

To suppress a decrease in communication efficiency due to packet retransmission in multi-link communication.SOLUTION: A communication apparatus concurrently transmits packets to a partner apparatus on a plurality of links, determines whether an acknowledgment for a transmitted packet has been received on each of the plurality of links, and if it is determined that an acknowledgment for a first packet transmitted on a first link among the plurality of links has not been received, generates a changed first packet having an increased packet length by reducing a data rate of the first packet, and generating a changed subsequent packet by increasing the packet length of a packet subsequent to a packet transmitted on each of one or more links other than the first link among the plurality of links, and concurrently transmits the changed first packet on the first link and the changed subsequent packet on each of the one or more links other than the first link.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to wireless communication technology. [Background technology]

[0002] The IEEE802.11 series is known as a wireless LAN (Local Area Network) communication standard formulated by the IEEE (Institute of Electrical and Electronics Engineers). The IEEE802.11 series standards include the IEEE802.11a / b / g / n / ac / ax standards. In order to further improve throughput and frequency utilization efficiency, the IEEE is considering formulating the IEEE802.11be standard as a new standard in the IEEE802.11 series. The IEEE802.11be standard considers multi-link communication, in which one AP (access point) establishes multiple links with one STA (station / terminal device) via multiple different frequency channels and communicates in parallel.

[0003] In multi-link communication, if the multiple frequency channels used are sufficiently far apart, the radio signals used on each link do not interfere with each other, making it possible to transmit and receive radio signals at any timing. However, if the frequency channels are close to each other, the radio signals used on each link may interfere with each other. For example, if a device starts a transmission operation on one link while receiving on another link, the radio waves emitted by the device may interfere with the received signal, making it impossible to transmit and receive simultaneously. In this case, the device can use multiple links without causing interference by adjusting the timing of transmission and reception on the multiple links.

[0004] On the other hand, in wireless LAN, wireless communication is transmitted and received in units of packets having a certain period of time. The length of the packet is determined by the amount of data to be transmitted, the wireless modulation method, the coding rate, etc. The combination of the wireless modulation method and the coding rate is indexed in advance as MCS (Modulation and Coding Scheme), and the MCS can be determined based on the communication quality, etc. In general, the higher the MCS, the higher the modulation method is set. Therefore, by increasing the MCS, the data rate becomes higher, and it becomes possible to shorten the packet length for the same amount of data, but on the other hand, there is a contradictory relationship in that the communication distance becomes shorter. Patent Document 1 shows a method for selecting an appropriate modulation method in wireless LAN, thereby reducing reception errors and improving communication throughput. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-88915 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the IEEE802.11be standard, devices that can transmit and receive at any timing over multiple links are called STR (Simultaneous Transmit and Receive) devices, while devices that cannot transmit and receive at any timing over multiple links and must transmit and receive at coordinated timing over multiple links are called Non-STR devices.

[0007] When a non-STR device (transmitter) attempts to simultaneously transmit or receive consecutive packets over multiple links, it determines the amount of data and MCS of the packets to be transmitted in advance in order to transmit and receive simultaneously over multiple links before starting transmission. A series of transmission operations is completed when all multiple packets reach the receiver and an Ack (Acknowledgement) or block Ack, which is a confirmation response (reception response) for each transmitted packet, reaches the transmitter from the receiver. However, if an Ack is not transmitted from the receiver, or if the transmitter is unable to receive an Ack due to interference from jamming waves, the transmitter will determine that the transmission operation for that transmitted packet has not been completed.

[0008] When the sender is sending packets continuously over multiple links and does not receive an Ack over one of the links, the sender must retransmit the packets for which the Ack has not been received. It is desirable to retransmit the packets without reducing communication efficiency.

[0009] The present invention has been made in view of the above-mentioned problems, and has an object to suppress a decrease in communication efficiency caused by packet retransmission in multi-link communication. [Means for solving the problem]

[0010] As one means for achieving the above object, a communication device of the present invention has the following configuration: That is, a communication device capable of continuously transmitting a plurality of packets to a partner device via a plurality of links, the communication device includes a transmitting means for transmitting a packet to the partner device simultaneously via each of the plurality of links, a determining means for determining whether an acknowledgment response to a packet transmitted by the transmitting means has been received via each of the plurality of links, and a generating means for generating a modified packet modified to increase the length of the packet transmitted by the transmitting means, wherein when the determining means determines that an acknowledgment response to a first packet transmitted via a first link among the plurality of links has not been received, the generating means generates a modified first packet modified to increase the packet length by lowering the data rate of the first packet, and generates a modified subsequent packet modified to increase the packet length of a subsequent packet of a packet transmitted via each of one or more other links among the plurality of links other than the first link, and the transmitting means simultaneously transmits the modified first packet via the first link and the modified subsequent packet via each of the one or more other links. Effect of the Invention

[0011] According to the present invention, it is possible to suppress a decrease in communication efficiency caused by packet retransmission in multi-link communication. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Diagram 2] 1A and 1B are diagrams illustrating an example of the configuration of a communication device ((a) hardware configuration, (b) functional configuration). [Diagram 3] 4 shows an example of a timing chart of multi-link communication. [Figure 4] 4 illustrates an example timing diagram for multi-link communication, according to an embodiment. [Diagram 5]4 shows a flow chart of a series of successive transmission processes performed by a sending device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0014] [Wireless communication system configuration] FIG. 1 is a diagram showing an example of the configuration of a wireless communication system according to the present embodiment. An AP (Access Point) 102 is a communication device that has a role of constructing a network 101. The network 101 is a wireless network. An STA (Station / Terminal Device) 103 is a communication device that has a role of participating in the network 101. Each communication device is compatible with the IEEE802.11be (EHT (Extremely / Extreme High Throughput)) standard, and can perform wireless communication conforming to the IEEE802.11be standard via the network 101. Each communication device can communicate in the frequency bands of 2.4 GHz, 5 GHz, and 6 GHz. The frequency bands used by each communication device are not limited to these, and a different frequency band such as the 60 GHz band may be used. Also, each communication device can communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz.

[0015] In addition, the AP 102 and the STA 103 can perform multi-link communication by establishing links and communicating via multiple frequency channels. An AP performing multi-link communication is also called an AP MLD (Multi-Link Device). Here, the frequency channel is a frequency channel defined in the IEEE 802.11 series standard, and refers to a frequency channel capable of performing wireless communication conforming to the IEEE 802.11 series standard. In the IEEE 802.11 series standard, multiple frequency channels are defined for each frequency band, such as the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. In the IEEE 802.11 series standard, the bandwidth of each frequency channel is defined as 20 MHz. Note that a bandwidth of 40 MHz or more may be used in one frequency channel by bonding with adjacent frequency channels.

[0016] For example, the AP 102 can establish a first link 104 via a first frequency channel in the 2.4 GHz band and a second link 105 via a second frequency channel in the 5 GHz band with the STA 103 and communicate via both links. In this case, the AP 102 maintains the second link 105 via the second frequency channel in parallel with the first link 104 via the first frequency channel. In this way, the AP 102 can improve the throughput in communication with the STA 103 by establishing links with the STA 103 via multiple frequency channels.

[0017] In addition, the AP 102 and the STA 103 may establish multiple links in different frequency bands in multi-link communication. For example, the AP 102 and the STA 103 may establish a third link (not shown) in the 6 GHz band in addition to a first link 104 in the 2.4 GHz band and a second link 105 in the 5 GHz band. Alternatively, the AP 102 and the STA 103 may establish links via multiple different channels included in the same frequency band. For example, the AP 102 and the STA 103 may establish a first link 104 via 1ch in the 2.4 GHz band and a second link 105 via 11ch in the 2.4 GHz band.

[0018] Also, links with the same frequency band and links with different frequency bands may be mixed. For example, the AP 102 and the STA 103 may establish a first link 104 via 1ch in the 2.4GHz band, a second link 105 via 11ch in the 2.4GHz band, and a third link (not shown) via 36ch in the 5GHz band. By establishing multiple connections with the STA 103 using different frequency bands, the AP 102 can communicate with the STA 103 using the other band even when one band is congested, thereby preventing a decrease in throughput in communication with the STA 103.

[0019] In multi-link communication, the multiple links established between the AP 102 and the STA 103 may have at least different frequency channels. Note that in multi-link communication, the channel spacing between the frequency channels of the multiple links established between the AP 102 and the STA 103 may be at least greater than 20 MHz. Note that, in this embodiment, the AP 102 and the STA 103 establish the first link 104 and the second link 105, but three or more links may be established.

[0020] When performing multi-link communication, the AP 102 constructs multiple wireless networks corresponding to the respective links. In this case, the AP 102 has multiple APs internally, and operates to construct a wireless network for each AP. The APs that the AP 102 has internally may be one or more physical APs, or multiple virtual APs configured on one physical AP. When multiple links are established on a frequency channel that belongs to a common frequency band, the multiple links may use a common wireless network.

[0021] When performing multi-link communication, the AP 102 and the STA 103 can divide one piece of data and transmit it to the other device via multiple links. Alternatively, the AP 102 and the STA 103 can transmit the same data via each of multiple links, so that communication via one link can serve as backup communication for communication via the other link.

[0022] Specifically, assume that the AP 102 transmits the same data to the STA 103 via a first link 104 through a first frequency channel and a second link 105 through a second frequency channel. In this case, even if an error occurs in communication via the first link 104, the STA 103 can receive the data transmitted from the AP 102 because the same data is transmitted via the second link 105.

[0023] Alternatively, the AP 102 and the STA 103 may use different links depending on the type of frame or data to be communicated. For example, the AP 102 may transmit a management frame via the first link 104 and transmit a data frame including data via the second link 105. The management frame is a management frame that complies with the IEEE802.11 series standard. Specifically, the management frame refers to a Beacon frame, a Probe Request frame / Response frame, and an Association Request frame / Response frame. In addition to these frames, Disassociation frames, Authentication frames, De-Authentication frames, and Action frames are also called management frames. The Beacon frame is a frame that notifies network information. The Probe Request frame is a frame that requests network information, and the Probe Response frame is a response thereto and provides network information. The Association Request frame is a frame that requests a connection, and the Association Response frame is a response thereto and indicates permission for connection or an error. The Disassociation frame is a frame that cuts off the connection. The Authentication frame is a frame that authenticates the other device, and the De-Authentication frame is a frame that interrupts the authentication of the other device and cuts off the connection. The Action frame is a frame for performing additional functions other than those described above. Alternatively, when transmitting data related to a captured image, for example, the AP 102 may transmit meta-information such as date, parameters at the time of capturing an image (aperture value and shutter speed), and location information via the first link 104, and transmit pixel information via the second link 105.

[0024] Also, the AP 102 and the STA 103 may be capable of performing MIMO (Multiple-Input and Multiple-Output) communication. In this case, the AP 102 and the STA 103 have multiple antennas, and one transmits different signals from each antenna using the same frequency channel. The receiving side simultaneously receives all signals arriving from multiple streams using multiple antennas, and separates and decodes the signals of each stream. In this way, by performing MIMO communication, the AP 102 and the STA 103 can communicate more data in the same time compared to when not performing MIMO communication. Also, the AP 102 and the STA 103 may perform MIMO communication in some links when performing multi-link communication.

[0025] Although the AP 102 and the STA 103 are described as being compatible with the IEEE 802.11be standard, they may also be compatible with at least one of the legacy standards that are standards prior to the IEEE 802.11be standard. The legacy standards are the IEEE 802.11a / b / g / n / ac / ax standards. In this embodiment, at least one of the IEEE 802.11a / b / g / n / ac / ax / be standards is called the IEEE 802.11 series standard. In addition to the IEEE 802.11 series standard, they may also be compatible with other communication standards such as Bluetooth (registered trademark), Near Field Communication (NFC), Ultra Wide Band (UWB), Zigbee, and Multi Band Orthogonal Frequency Division Multiplexing (OFDM) Alliance (MBOA). UWB includes wireless USB, wireless 1394, Winet, and the like. They may also be compatible with a communication standard for wired communication such as a wired LAN.

[0026] Specific examples of the AP 102 include, but are not limited to, a WLAN router and a PC. The AP 102 may be any communication device capable of performing multi-link communication with other communication devices. The AP 102 may also be an information processing device such as a wireless chip capable of performing wireless communication conforming to the IEEE802.11be standard. Specific examples of the STA 103 include, but are not limited to, a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, and the like. The STA 103 may also be any communication device capable of performing multi-link communication with other communication devices. The STA 103 may also be an information processing device such as a wireless chip capable of performing wireless communication conforming to the IEEE802.11be standard. The communication system in FIG. 1 is configured with one AP and one STA, but the number of APs and STAs is not limited to this. The information processing device such as a wireless chip may have an antenna for transmitting the generated signal.

[0027] In this embodiment, the AP 102 is an access point and the STA 103 is a station, but this is not limiting, and both the AP 102 and the STA 103 may be stations. In this case, the AP 102 is a station, but can operate as a device having a role of constructing a wireless network for establishing a link with the STA 103.

[0028] [Communication device configuration] Fig. 2 shows an example of the configuration of a communication device (AP, STA). Fig. 2(a) shows an example of the hardware configuration of a communication device, and Fig. 2(b) shows an example of the functional configuration of a communication device. First, the hardware configuration of a communication device will be described with reference to Fig. 2(a). Note that, although the description will be given here using AP102 as an example, the same description can be applied to the case of STA103, and in that case, the communication partner device of STA103 can be AP102.

[0029] The storage unit 201 is configured with one or more memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and stores various information such as computer programs for performing various operations described below and communication parameters for wireless communication. Note that, in addition to memories such as ROM and RAM, storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, and DVDs may be used as the storage unit 201. Furthermore, the storage unit 201 may include multiple memories.

[0030] The control unit 202 is configured with one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and controls the entire AP 102 by executing a computer program stored in the storage unit 201. The control unit 202 may control the entire AP 102 in cooperation with the computer program stored in the storage unit 201 and an OS (Operating System). The control unit 202 also generates data and signals (wireless frames) to be transmitted in communication with other communication devices. The control unit 202 may also include multiple processors, such as multi-core processors, and the entire AP 102 may be controlled by the multiple processors.

[0031] Furthermore, the control unit 202 controls the functional unit 203 to execute predetermined processes such as wireless communication, imaging, printing, projection, etc. The functional unit 203 is hardware that enables the AP 102 to execute predetermined processes.

[0032] The input unit 204 receives various operations from the user. The output unit 205 outputs various types of information to the user via a monitor screen or a speaker. Here, the output by the output unit 205 may be a display on a monitor screen, a voice output by a speaker, a vibration output, or the like. Note that both the input unit 204 and the output unit 205 may be realized by a single module, such as a touch panel. Also, the input unit 204 and the output unit 205 may be integrated with the AP 102, or may be separate from it.

[0033] The communication unit 206 controls wireless communication conforming to the IEEE802.11be standard. The communication unit 206 may control wireless communication conforming to other IEEE802.11 series standards in addition to the IEEE802.11be standard, or control wired communication such as a wired LAN. The communication unit 206 controls the antenna 207 to transmit and receive signals for wireless communication generated by the control unit 202. The AP 102 may have a plurality of communication units 206. When establishing multiple links in multi-link communication, the AP 102 having a plurality of communication units 206 can establish at least one link per communication unit 206. Alternatively, the AP 102 may establish multiple links using one communication unit 206. In this case, the communication unit 206 executes communication via the multiple links by switching frequency channels that operate in a time-division manner. Note that, when the AP 102 supports the NFC standard, the Bluetooth standard, or the like in addition to the IEEE802.11be standard, it may control wireless communication conforming to these communication standards. In addition, when the AP 102 can perform wireless communication conforming to a plurality of communication standards, it may be configured to have a communication unit and an antenna corresponding to each communication standard separately. The AP 102 communicates data such as image data, document data, and video data with the STA 103 via the communication unit 206. The antenna 207 may be configured as a separate unit from the communication unit 206, or may be configured together with the communication unit 206 as a single module.

[0034] The antenna 207 is an antenna capable of communication in various frequency bands. In this embodiment, the AP 102 has one antenna, but may have a different antenna for each frequency band. In addition, when the AP 102 has multiple antennas, it may have a communication unit 206 corresponding to each antenna.

[0035] Next, the software functional configuration of the communication device will be described with reference to Fig. 2(b). Note that, although the AP 102 will be described as an example here, the same description can be applied to the STA 103 as well.

[0036] The transmitting unit 211 performs a transmitting process via the communicating unit 206 (FIG. 2(a)). The receiving unit 212 performs a receiving process via the communicating unit 206. The connection control unit 213 performs control for establishing a connection with a partner device by transmitting and receiving various frames via the transmitting unit 211 and the receiving unit 212. The Ack determining unit 214 determines whether the receiving unit 212 has received an Ack (acknowledgement response / receipt response) from the partner device in response to the transmitted data. The packet length changing unit 215 changes the packet length of a packet transmitted via the transmitting unit 211, and performs control for generating a changed packet.

[0037] [Transmitting and receiving operations in multi-link communication] Next, the transmission and reception operations in multi-link communication will be described. First, with reference to Fig. 3, the operation when Ack is normally received on the transmitting side will be described. Fig. 3 shows an example of a timing chart of multi-link communication. It is assumed that AP102 (transmitting side (Tx)) and STA103 (receiving side (Rx)) are connected by multi-link communication using a first link 104 and a second link 105. Note that the operation in Fig. 3 can be similarly applied when the transmitting side is STA103 and the receiving side is AP102.

[0038] In this example, it is assumed that the first link 104 and the second link 105 use frequencies that are relatively close to each other. As a result, in the STA 103, a signal transmitted from one link causes radio interference in the other link, so there is a restriction that while one link is transmitting, the other link cannot receive. In other words, the STA 103 is the Non-STR (Simultaneous Transmit and Receive) device described above. In order to perform multi-link communication with the Non-STR device STA 103, it is necessary to adjust one link so that the other link does not enter a receiving state while transmitting. Specifically, the AP 102 and the STA 103 need to synchronize the timing of transmissions in multiple links.

[0039] On the other hand, IEEE802.11e, which has been standardized as a mechanism for realizing QoS (Quality of Service) control, specifies the Enhanced Distributed Channel Access (EDCA) method, which prioritizes transmission of frames with a higher priority. In the EDCA method, packets are transmitted according to an access category (AC) as a priority set according to a traffic type. In the EDCA method, a parameter called TXOP Limit is set as one of the parameters for QoS control set for each priority. The TXOP Limit may be held in advance in each device, or may be acquired (and updated) by a received predetermined frame. The TXOP Limit indicates the upper limit of the period (TXOP (Transmission Opportunity)) during which continuous transmission is possible after the transmission right is acquired (secured). The TXOP Limit is specified for each access category (AC). For example, when TXOP limit=0, transmission of only one packet is permitted, and when the value is other than 0, continuous transmission of multiple packets is permitted.

[0040] In FIG. 3, during the period of the TXOP acquired by the first link 104 and the second link 105 on the transmitting side (AP 102), data 1 and data 3 (data may correspond to (QoS) data packets; the same applies below) of the same packet length are started to be transmitted at the same timing. Note that the TXOP is acquired (secured) when, for example, the transmitting side transmits a predetermined frame based on CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) and correctly receives a response frame from the receiving side. When the data 1 and data 3 are received by the receiving side (STA 103), the receiving side issues and transmits Ack1 and Ack3 for the data 1 and data 3 after the SIFS (Short Inter Frame Sequence) time has elapsed. The transmitting side receives Ack1 and Ack3 after the SIFS time has elapsed since transmitting the data 1 and data 3. Furthermore, after the SIFS time has elapsed since the transmitting side received Ack1 and Ack3, the transmitting side again starts transmitting data 2 and data 4 of the same packet length at the same timing on the first link 104 and the second link 105. The transmitting side is able to receive Ack2 and Ack4 for data 2 and data 4, and data transmission is normally completed during the TXOP.

[0041] However, if the transmitting side does not normally receive an Ack for the data after transmitting the data (data packet), it can be determined that the data transmission did not end normally. For example, in FIG. 3, assume that the receiving side does not normally receive Data 3 in the second link 105, and is therefore unable to issue and transmit Ack 3.

[0042] There are two main reasons why the receiving side may not receive data 3 correctly. The first reason is that there is a change in the communication path of the wireless signal between the transmitting side and the receiving side, causing a decrease in the signal strength of the signal that reaches the receiving side. For example, the signal strength may decrease if the transmitting side moves or if an obstacle appears in the communication path. The second reason is that interference waves cause the signal-to-noise (SN) ratio of the signal to deteriorate. Receiving interference waves from other wireless devices or devices that generate radio waves (not shown) may cause the SN ratio to decrease.

[0043] If the receiver is unable to receive the data correctly due to at least one of these two reasons or other reasons and does not issue an Ack, it is highly likely that the receiver will not be able to receive it correctly again even if the sender resends the same data (packet) in the same format. When the sender resends a packet that was not received correctly by the receiver, there are two methods that can be considered to increase the chances of the retransmission being successful.

[0044] The first method is to lower the MCS (Modulation and Coding Scheme). As described above, MCS is an index of the combination of the wireless modulation method and the coding rate. Lowering the MCS means that the packet length will be longer for the same amount of data. If the cause of the failure in transmission is a change in the communication environment, there is a high possibility that the transmission will fail again even if it is retransmitted with the same MCS. In order to increase the probability of successful transmission, it is considered effective to lower the MCS and increase the reach of the wireless signal. On the other hand, lowering the MCS means that the packet length will be longer for the same amount of data. If the packet length of only one link is increased, the extended packet length will overlap when the Ack is received on the other link, which may result in a state in which communication cannot be performed correctly on the other link.

[0045] The second method is to stop continuous packet transmission on the link where the packet transmission has failed and wait until the continuous packet transmission on the other links is completed. This can avoid affecting the communication on other links, but communication efficiency / space utilization efficiency may decrease by not transmitting during the period when TXOP is reserved.

[0046] Therefore, in this embodiment, the packet length of a packet to be transmitted is adjusted as described below. Fig. 4 shows an example of a timing chart of multi-link communication according to this embodiment. As in Fig. 3, it is assumed that AP 102 (receiving side (Rx)) and STA 103 (transmitting side (Tx)) are connected by multi-link communication using a first link 104 and a second link 105. It is assumed that the transmitting side cannot receive Ack3 on the second link 105 (failed to transmit data 3) after transmitting data 1 and data 3 on the first link 104 and the second link 105.

[0047] The transmitting side that could not receive Ack3 retransmits Data 3 with a lower MCS (Low MCS) on the second link 105, and at the same time, on the first link 104 where the transmission did not fail, increases the packet length to the same as the packet length of the data on the second link 105. A method called padding, which adds dummy data, is generally used to increase the packet length. This increases the probability of successful retransmission on the second link 105, and makes it possible to maintain multi-link communication with the STA 103, which is a Non-STR device. As a result, the success rate of successive packet transmissions can be increased, and as a result, a decrease in spatial utilization efficiency can be avoided.

[0048] As a result of making the packet length longer, it may happen that transmission and reception continues beyond the previously acquired TXOP period. However, since the wireless LAN uses the CSMA / CA method, if transmission and reception are continuing when the TXOP period ends, other wireless LAN devices will not start transmission by detecting the wireless signal of transmission and reception. Therefore, it is expected that transmission and reception operations can be completed normally even if continuous transmission exceeds the TXOP period.

[0049] Also, since the transmitting side, first link 104, correctly receives Ack1 following Data 1, there is no need to change the MCS, but since the packet length of Data 2 is lengthened following the change in second link 105, the MCS may be lowered to match the longer packet length. In Fig. 4, padding is used for Data 2 to make the packet length the same as that of Data 3, but by lowering the MCS and keeping the padding to a minimum, it is expected that the probability of successful transmission of Data 2 will be increased.

[0050] Furthermore, when transmitting three or more consecutive packets, the transmitting side may limit the change in packet length of the retransmitted data to only the last packet of the consecutive packets within the TXOP period. If the packet length is changed for packets other than the last packet, the possibility arises that the transmission is stopped at the timing when the TXOP period ends, and the possibility of wireless communication collision increases. Furthermore, in order to prepare a means for avoiding such collision, more complicated processing is required. In order to simplify the processing, it may be effective to limit the change in packet length to the last packet of the consecutive packets.

[0051] The data (data packet) continuously transmitted by the transmitting side may be a combination of multiple frames by frame aggregation, and the Ack received (sent by the receiving side) in this case will be a block Ack. Even if the transmitting side is unable to receive the block Ack normally, it can expect the same effect as above by carrying out the same process as in the case of the Ack described above.

[0052] [Processing flow on the sending side] Fig. 5 shows a flowchart of a series of continuous transmission processes executed by a transmitting device according to this embodiment. Here, the transmitting device is AP102, the receiving device is STA103, and STA103 is a Non-STR device. The flowchart shown in Fig. 5 can be realized by the control unit 202 of AP102 executing a control program stored in the storage unit 201, and performing calculations and processing of information and control of each hardware. Note that the same explanation can be applied even if the transmitting device is STA103.

[0053] First, in S501, the connection control unit 213 of the AP 102 establishes a multi-link connection using multiple links with the STA 103. Here, since the STA 103 is a non-STR device, in order to simultaneously transmit and receive via multiple links, the timing of transmission and reception on each link must match. This is the same whether the AP 102 transmits or the STA 103 transmits.

[0054] In S502, the transmitting unit 211 of the AP 102 secures (acquires) a TXOP for a period during which multiple packets ((QoS) data packets) can be transmitted simultaneously and consecutively through multiple links. Based on the acquired TXOP, the transmitting unit 211 of the AP 102 transmits data packets of the same packet length simultaneously to the STA 103, one for each of the multiple links, in S503. The transmitting unit 211 checks whether the transmitted packet is the last packet of a series of consecutive transmissions. If the transmitted packet is the last packet (Yes in S504), the process ends. If it is not the last packet (No in S504), the Ack determining unit 214 of the AP 102 determines whether the receiving unit 212 has received an Ack from the receiving side on all links through which transmission has been performed (S505).

[0055] If Ack has been received on all links (Yes in S505), the process returns to S503. On the other hand, if Ack has not been received on one or more links (No in S505), there is a high possibility that the transmission will fail again even if the same MCS is used for retransmission on the link on which Ack has not been received. Therefore, AP102 changes the packet length so that the packet lengths are equal for all links, including the link on which Ack has been correctly received (S506). That is, AP102 lowers the MCS for the link on which Ack has not been received, and reconstructs the retransmitted packet with a higher probability of successful transmission. AP102 also changes the packet length of the subsequent packets to be transmitted on one or more links other than the link on which Ack has not been correctly received.

[0056] Specifically, the packet length modification unit 215 generates a modified retransmission packet in which the packet length is increased by lowering the data rate of the packet to be retransmitted on the link on which the Ack has not been received. The packet length modification unit 215 also generates a modified subsequent packet in which the packet length of the packet subsequent to the packet already transmitted on the link on which the Ack has been received is increased. The transmitted packet may be a packet transmitted simultaneously with the packet transmitted on the link on which the Ack has not been received. The packet length modification unit 215 generates the modified subsequent packet such that the difference between the packet length of the modified subsequent packet and the packet length of the retransmission packet is equal to or less than a predetermined value (if possible, the same). As described above, this may be achieved by adding dummy data, lowering the data rate, or a combination of these.

[0057] In this way, AP 102 changes the packet length so that the packet lengths are equal on all links, including the links on which Ack was correctly received (S506). At the next transmission start timing, transmitter 211 simultaneously transmits the retransmitted packet and the changed subsequent packet on each of the multiple links (S503).

[0058] In this flowchart, the packet length is changed for packets that are not the final packet as determined in S504, but as described above, control may be performed so that the packet length is changed only for the final packet.

[0059] According to the embodiment described above, it is possible to reduce the possibility of failure in retransmission of data in multi-link communication, and not only to prevent a decrease in communication efficiency but also to reduce power consumption of the communication device.

[0060] [Other embodiments] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0061] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0062] 101 network, 102 AP (access point), 103 STA (station / terminal device), 104 first link, 105 second link

Claims

1. A communication device capable of continuously transmitting a plurality of packets to a destination device via a plurality of links, a transmitting means for simultaneously transmitting a packet to the other device via each of the plurality of links; a determination means for determining whether an acknowledgment for a packet transmitted by the transmission means has been received in each of the plurality of links; a generating means for generating a modified packet by modifying the packet to be transmitted by the transmitting means so as to increase the length of the packet; When the determining means determines that an acknowledgment response to a first packet transmitted on a first link among the plurality of links has not been received, the generating means generates a modified first packet modified to increase a packet length by lowering a data rate of the first packet, and generates modified subsequent packets modified to increase a packet length of a subsequent packet of the packet transmitted through each of one or more links other than the first link among the plurality of links; a first packet transmitted via the first link and a subsequent packet transmitted via each of the one or more other links, the first packet being modified at the same time;

2. 2. The communication device according to claim 1, wherein the generating means generates the changed subsequent packet such that a difference between the packet length of the changed subsequent packet and the packet length of the first packet is equal to or smaller than a predetermined value.

3. 3. The communication device according to claim 1, wherein the generating means generates the changed subsequent packet by adding dummy data to the subsequent packet.

4. 4. The communication device according to claim 1, wherein the generating means generates the changed subsequent packet by lowering a data rate of the subsequent packet and increasing a packet length of the subsequent packet.

5. The communication device is a communication device conforming to the IEEE 802.11 series standard, 5. The communication device according to claim 1, wherein the transmitting means transmits packets simultaneously through each of the plurality of links during a TXOP (Transmission Opportunity) period.

6. 6. The communication device according to claim 5, wherein the first packet is a last packet transmitted by the transmitting means to the other device during the TXOP period.

7. 7. The communication device according to claim 5, wherein at least one of the communication device and the counterpart device is a Non-STR (Simultaneous Transmit and Receive) device.

8. The communication device according to any one of claims 5 to 7, characterized in that the communication device is an access point.

9. The communication device according to claim 5, wherein the communication device is a terminal device.

10. A method for controlling a communication device capable of continuously transmitting a plurality of packets to a partner device via a plurality of links, comprising the steps of: a first transmission step of simultaneously transmitting a packet to the other device through each of the plurality of links; a determining step of determining whether an acknowledgment for the packet transmitted in the first transmitting step has been received in each of the plurality of links; a generating step of generating a modified first packet in which a packet length of the first packet is increased by lowering a data rate of the first packet when it is determined in the determining step that an acknowledgment response to the first packet transmitted through a first link among the plurality of links has not been received, and generating a modified subsequent packet in which a packet length of a subsequent packet of the packet transmitted through each of one or more other links among the plurality of links other than the first link is increased; a second transmitting step of simultaneously transmitting the modified first packet over the first link and the modified subsequent packets over each of the one or more other links; A control method comprising the steps of:

11. A program for causing a computer to function as the communication device according to any one of claims 1 to 9.

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