JP4374001B2 - COMMUNICATION DEVICE, COMMUNICATION METHOD, AND COMMUNICATION SYSTEM - Google Patents

Description

  The present invention relates to a communication apparatus, a communication method, and a communication system that perform medium access control based on carrier sense information of a physical layer and carrier sense information of a MAC layer.

  Media access control (MAC) determines how a plurality of communication apparatuses that communicate by sharing the same medium use the medium to transmit communication data. In the medium access control, as a result of two or more communication devices transmitting communication data using the same medium at the same time, the number of events (collisions) in which the communication device on the receiving side cannot separate the communication data is reduced as much as possible. On the other hand, this is a technique for controlling access from a communication device to a medium so that the number of events in which the medium is not used by any communication device despite the presence of a communication device having a transmission request is minimized.

  However, particularly in wireless communication, since it is difficult for a communication apparatus to monitor transmission data while transmitting data, medium access control (MAC) that does not assume collision detection is required. IEEE802.11, which is a typical technical standard for wireless LAN, employs CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance). In CSMA / CA of IEEE802.11, a period (Duration) until a sequence of one or more frame exchanges following the frame ends is set in the header of the MAC frame. During this period, a communication apparatus that is not related to the sequence and has no transmission right waits for transmission by determining the virtual occupation state of the medium. Therefore, the occurrence of a collision is avoided. On the other hand, the communication apparatus having the transmission right in the sequence recognizes that the medium is not used except for the period when the physical medium is actually occupied. IEEE802.11 stipulates that the state of the medium is determined based on the combination of the virtual carrier sense of the MAC layer and the physical carrier sense of the physical layer to control the medium access.

  IEEE802.11, which employs CSMA / CA, has so far attempted to increase the communication speed mainly by changing the physical layer protocol. The 2.4 GHz band is changing from IEEE802.11 (1997, 2 Mbps) to IEEE802.11b (1999, 11 Mbps) and to IEEE802.11g (2003, 54 Mbps). For the 5 GHz band, only IEEE 802.11a (1999, 54 Mbps) exists as a standard so far. And IEEE802.11 TGn (Task Group n) has already been established in order to formulate a standard aiming at further speeding up in both 2.4 GHz band and 5 GHz band.

Furthermore, some access control for improving quality of service (QoS) is also known. For example, there is HCCA (HCF Controlled Access), which is an extension of the conventional polling procedure, as QoS that guarantees parameters such as specified bandwidth and delay time. In HCCA, scheduling in consideration of required quality is performed in a polling procedure so that parameters such as bandwidth and delay time can be guaranteed. Patent Document 2 refers to QoS of the IEEE802.11e standard, and discloses a method of assigning priority to communication between communication devices in a wireless network.
US Pat. No. 5,329,531 JP 2002-314546 A

  If the same frequency band as the existing standard is used to realize higher communication speed, the newly provided communication device can coexist with the communication device that conforms to the existing standard, and the backward compatibility is also achieved. Preferably it is maintained. Therefore, it is considered that the MAC layer protocol should basically conform to CSMA / CA consistent with existing standards. In this case, it is necessary to align time parameters related to CSMA / CA such as a time interval (IFS: Interframe Space) between frames and a back-off period with the existing standards.

  Here, even if the communication speed can be increased with respect to the physical layer, there is a problem that the substantial throughput of communication cannot be improved. That is, when the physical layer is speeded up, the PHY frame format is no longer efficient, and the overhead caused by this is considered to hinder the improvement of the throughput. In the PHY frame, temporal parameters related to CSMA / CA are fixedly attached to the MAC frame. A PHY frame header is required for each MAC frame.

  One method for reducing overhead and improving throughput is Block ACK introduced in the recent draft IEEE802.11e draft 5.0 (IEEE802.11 QoS enhancement). If this is used, a plurality of MAC frames can be continuously transmitted without backoff, so the amount of backoff can be reduced, but the header of the physical layer is not reduced. In addition, according to the aggregation introduced in the early draft IEEE802.11e, both the backoff amount and the physical layer header can be reduced, but the length of the physical layer frame that includes the MAC frame due to the limitations of the conventional physical layer Since it cannot be about 4k bytes or more, there are significant restrictions on improving efficiency. Even if the frame of the physical layer can be lengthened, there arises a problem that error tolerance is lowered.

  The present invention has been made to solve such a problem, and can coexist with an existing apparatus, and further eliminates the overhead associated with transmitting a plurality of frames by improving the efficiency of the frame format. It is an object of the present invention to provide a communication device, a communication method, and a communication system that can improve substantial throughput.

A communication apparatus according to an aspect of the present invention includes a physical frame creation unit that creates one physical frame in which a plurality of MAC frames are aggregated;
It is a communication apparatus comprising: a transmission unit that transmits the physical frame; and a reception unit that receives a delivery confirmation frame responded as an implicit delivery confirmation request to the end of the physical frame.

  A communication apparatus according to still another aspect of the present invention includes a receiving unit that receives one physical frame in which a plurality of MAC frames are aggregated, and an implicit delivery confirmation request at the end of the physical frame received by the receiving unit. In response, the reception status for a plurality of MAC frames in the physical frame is included as a delivery confirmation bitmap, and the sequence number of the first MAC frame that was successfully received in the physical frame is set as the delivery confirmation start sequence number It is a communication apparatus comprising a creation means for creating a delivery confirmation frame and a transmission means for transmitting the delivery confirmation frame.

  According to the present invention, it is possible to provide a communication device, a communication method, and a communication system that can eliminate overhead associated with transmitting a plurality of frames by improving the efficiency of the frame format and improve the substantial throughput of communication.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a communication apparatus according to the first embodiment of the present invention. The communication device 100 is a device that communicates with another communication device via a wireless link, and includes processing units 101, 102, and 103 corresponding to a physical layer, a MAC layer, and a link layer, respectively. These processing units are realized as analog or digital electronic circuits according to mounting, or as firmware executed by a CPU incorporated in an LSI. An antenna 104 is connected to a physical layer processing unit (hereinafter, “processing unit” is omitted) 101. The MAC layer 102 includes an aggregation (aggregation) processing unit 105 for MAC frames. The aggregation processing unit 105 includes a carrier sense control unit 106 and a retransmission control unit 107, and performs transmission / reception of a block ACK (acknowledgment for a plurality of MAC frames) frame and retransmission control based on the block ACK frame, which will be described in detail later. Do.

  The physical layer 101 is configured to be compatible with two types of physical layer protocols. For each protocol processing, the physical layer 101 includes a first type physical layer protocol processing unit 109 and a second type physical layer protocol processing unit 110. In implementation, circuit sharing is often performed between the first-type physical layer protocol processing unit 109 and the second-type physical layer protocol processing unit 110, and therefore they do not necessarily exist independently. .

  In the embodiment of the present invention, the first type physical layer protocol is a protocol defined in IEEE802.11a, and the second type physical layer protocol uses a plurality of antennas on the transmitting side and the receiving side. It is assumed that the protocol is based on (Multiple Input Multiple Output). Even if the frequency band is kept the same, the transmission capacity can be expected to increase almost in proportion to the number of antennas. Therefore, MIMO is one of the technologies that can be used to achieve higher throughput of IEEE802.11. The link layer 103 has a normal link layer function defined by IEEE802. The technology adopted to improve the transmission rate is not limited to MIMO. For example, a method of increasing the frequency occupation band and a combination thereof with MIMO may be used.

  According to IEEE 802.11e Draft 8.0, Block ACK (Block ACK) is proposed as a technique for improving transmission efficiency of a MAC (Media Access Control) layer. In block ACK, a terminal transmits QoS (Quality of Service) data at a minimum frame interval called SIFS (Short Inter Frame Space) during a certain channel usage period (TXOP: Transmission Opportunity), and then to the receiving terminal. On the other hand, a block ACK request (Block ACK Request) is transmitted at an arbitrary timing in order to request a past reception history situation. On the reception side, based on the start sequence number determined by the block ACK request, the past reception status is converted into a bitmap format and responded as a block ACK (Block ACK).

  2 and 3 show the frame format of the block ACK request and the frame format of the block ACK specified by IEEE802.11e Draft 8.0, respectively. The Frame Control field, Duration field, Receiver Address (destination address), and Transmitter Address (source address) in FIGS. 2 and 3 are MAC headers defined by IEEE 802.11. In the BAR Control (Block ACK Request Control) field, there is a 4-bit TID (Traffic Identifier). Since QoS data exists for each priority (TID) and a sequence number and a fragment number are independently assigned, it is necessary to prepare a reception status in block ACK for each priority. The TID field of BAR Control in the block ACK request is used to specify this priority. Block ACK Starting Sequence Control of the block ACK request in FIG. 2 includes a 4-bit fragment number field and a 12-bit Starting Sequence Number field. The Starting Sequence Number is used for the receiving terminal to go back in the past reception history and create a block ACK based on the relative reception status from the sequence number corresponding to the Starting Sequence Number. The BA Control of the block ACK in FIG. 3 includes a 4-bit TID field, similar to the BAR Control in FIG. Block ACK Starting Sequence Control indicates the start point sequence number of the reception status indicated by the Block ACK Bitmap 30 in the block ACK. According to IEEE802.11e Draft 8.0, the size of the Block ACK Bitmap 30 is a fixed length of 1024 bits, and it is possible to notify a reception history for data of up to 64 MSDU (MAC Service Data Unit). One MSDU can include a maximum of 16 fragmented (divided) MPDUs (MAC Protocol Data Units). Note that an FCS (Frame Check Sequence) for error checking is added to each MAC frame in FIGS. Therefore, the size of the Block ACK Bitmap 30 is 1024 in order to notify the reception history for a maximum of 1024 MPDUs.

  4 and 5 show a sequence example of block ACK transmission in HCCA (Hybrid coordination function Controlled Channel Access). The HC (Hybrid Coordinator) shown in the figure is a QoS access point (QoS-AP) in IEEE802.11e Draft 8.0, which is the main subject of scheduling, and the channel usage period (TXOP) to the QoS terminal (QSTA) ) And downlink (downlink from HC to QSTA) transmission. The TXOP is assigned to the QSTA based on the QoS CF-Poll frame from the HC (QoS Contention Free-Poll: QoS-compliant polling frame transmitted by the HC to permit transmission to the QSTA). In FIG. 4, first, the HC gives a channel use period (TXOP1) by transmitting a QoS CF-Poll frame to QSTA1. QSTA can transmit an arbitrary frame during TXOP, but in the example of FIG. 4, QoS data is transmitted to QSTA2 at SIFS intervals. When the TXOP period of QSTA1 ends, HC is now sending QoS data to QSTA1 in bursts (TXOP2). When the HC channel period ends, the HC gives the channel use period (TXOP3) to QSTA1 again. QSTA1 sends a block ACK request to QSTA2, and requests the relative reception status specified by Block ACK Starting Sequence Control from the destination. FIG. 4 shows an example of an immediate block ACK. In this case, a terminal that has received a block ACK request must respond with a block ACK after the SIFS period. Specifically, QSTA2 must respond with a block ACK 41 after the SIFS period in response to the block ACK request 40 from QSTA1. In TXOP4, QSTA2 must respond with a block ACK 43 after the SIFS period in response to a block ACK request 42 from the HC.

  On the other hand, FIG. 5 shows an example of a delayed block ACK. A terminal that receives a block ACK request first returns an IEEE 802.11 ACK and transmits a block ACK after an arbitrary period. Specifically, QSTA2 that received the block ACK request 50 from QSTA1 first returns IEEE802.11 ACK51, and returns block ACK52 after an arbitrary period. Finally, the data transmission terminal that has received the block ACK returns an ACK, whereby a series of sequences of the delayed block ACK is completed. The QoS data subject to block ACK is notified to the receiving side using the Ack Policy field in the QoS Control field extended for IEEE802.11e Draft 8.0 with respect to the conventional MAC header.

  A processing procedure necessary for creating a block ACK will be described with reference to FIGS. In FIG. 6, after the transmission terminal transmits QoS data in bursts, a block ACK request is transmitted with any Block ACK Starting Sequence Control specified (sequence number “1”, fragment number “0” in the example of FIG. 6). To do. The receiving terminal stores the reception history for each source address and priority (TID), and goes back to the frame corresponding to Block ACK Starting Sequence Control, and the relative reception status from there is 64 MSDU (1024 bits). ) Block ACK bitmap (Block ACK Bitmap). In the example of FIGS. 6 and 7, it is assumed that the transmission side transmits an MSDU with a sequence number “1” (fragmented into three divisions), an MSDU with a sequence number “2” (no fragment), and the like. A bit number 60 in FIG. 6 indicates a relative position from the top of the block ACK bitmap. In the example of the block ACK bitmap 61 in FIG. 6, the MSDU of the sequence number “1” (fragment number 63 is “0”, “1”, “2”) is normally received among the QoS data sent by the transmission side. However, the MSDU (no fragment) with the sequence number “2” indicates that reception failed due to an error or the like. The Block ACK Starting Sequence Control 62 of the block ACK copies and transmits the value specified in the block ACK request. The transmitting terminal in FIG. 7 determines a frame to be retransmitted based on the Block ACK Starting Sequence Control of the block ACK and the contents of the block ACK bitmap. In the example of FIGS. 6 and 7, the sequence number “2” (no fragment) is incorrect, so the corresponding portion of the block ACK bitmap 61 is “0”. As a result, the transmitting terminal determines that it is necessary to retransmit the MSDU (no fragment) with the sequence number “2”.

  As described above, block ACK specified in IEEE802.11e Draft 8.0 has many processes that should be performed on the QoS data reception side, and an immediate block that responds with a block ACK after the SIFS period after receiving the block ACK request. Realization of ACK is generally considered difficult.

  Therefore, the embodiment of the present invention proposes a method for solving such a problem. In the first embodiment of the present invention, when a PSDU in which a plurality of MPDUs are aggregated and a block ACK request is aggregated at the end of the plurality of MPDUs is received, the reception status is reflected back as an immediate block ACK. It is to do.

  According to the specification of IEEE802.11, when the frame size is larger than a predetermined threshold value, fragmentation (division) processing is performed. A fragment number is assigned to the fragmented MPDU. The fragment number in the MAC header is a value indicating the relative position of the MPDU in the MSDU, and usually takes a continuous value starting from 0. The receiving terminal assembles the original MSDU based on the fragment number and sequence number.

  Generally, in the MAC transmission procedure of IEEE802.11 and IEEE802.11e Draft 8.0, since fragmented MPDUs are transmitted at SIFS intervals, overhead corresponding to the frame interval (SIFS) occurs and transmission efficiency decreases. Therefore, in order to realize high throughput, it is desirable not to fragment. According to this embodiment on the assumption that no fragmentation is performed, the number of bits of the Block ACK Bitmap 80 can be compressed to a maximum of 64 MPDUs as shown in FIG. That is, the size of the block ACK Bitmap 80 corresponds to the maximum number of MSDUs when one MPDU corresponds to one MSDU, and is suppressed to 64 bits, that is, 1/16 of the conventional one.

  Hereinafter, the block ACK frame as shown in FIG. 8 is referred to as “compressed block ACK (compression delivery confirmation)”. When performing block ACK transmission using the compressed block ACK between the transmitting and receiving terminals, negotiation may be performed in advance. As a specific negotiation method, for example, it is conceivable to extend the block ACK setting procedure described in IEEE802.11e Draft 8.0. That is, it is requested to use the compressed block ACK by the ADDBA request, and the use of the compressed block ACK is permitted or rejected by the ADDBA response. There may be a restriction that all data, block ACK requests, and (compressed) block ACK frames must be responded with a compressed block ACK, or a normal block ACK and a compressed block. It may be acceptable to mix ACKs and respond. Further, information that requests or allows a compressed block ACK instead of a normal block ACK may be added to the block ACK request. The method of requesting or allowing a compressed block ACK with a block ACK request can be applied with or without a prior block ACK setting procedure.

  Also, in order to achieve high throughput at the MAC level, a method is conceivable in which individual MPDUs are aggregated into one PSDU and transmitted at a time. 9 and 10 show examples of aggregation of a plurality of MPDUs. In the example of FIG. 9, a field indicating the length of the MPDU and a CRC (Cyclic Redundancy Check) for the length information of the MPDU exist at the head of each MPDU in the PSDU. The MPDU length information and CRC will be collectively referred to as “MPDU separation field”. Note that the MPDU separation field may include other additional information, a reserved area, an area for adjusting byte alignment (for example, aligning with 4 byte alignment), and the like. If the MPDU separation field is not an error, the terminal that has received PSDU as shown in FIG. 9 cuts out the subsequent MPDU and calculates the FCS (Frame Check Sequence) of the MPDU. If the MPDU separation field is incorrect, the length of the subsequent MPDU is unknown, so the CRC of the MPDU separation field is continuously calculated (scanned) in appropriate bytes. For the MPDU separation with the correct CRC calculation result, the FCS for the subsequent MPDU is calculated to determine whether or not the reception was successful.

  On the other hand, in the aggregate example of FIG. 10, length information for a plurality of MPDUs exists as a header at the beginning of the PSDU, and a CRC for the plurality of length information is added. Hereinafter, this header is referred to as a “MAC super frame header”. The terminal that receives the PSDU of FIG. 10 performs CRC calculation of the MAC super frame header, and if it is an error, determines that all MPDUs are incorrect. If the MAC super frame header is normally received, the FCS is calculated for each aggregated MPDU, and it is determined whether or not the MAC super frame header is normally received.

  Further, in the examples of FIGS. 9 and 10, block ACK request frames 90 and 101 are aggregated at the end of the PSDU in which a plurality of MPDUs are aggregated. In the example of FIGS. 9 and 10, the maximum number of MPDUs that can be aggregated is 8. However, this number is not limited to 8, and it goes without saying that any number may be taken. The maximum number that can be aggregated must be determined in advance, or some kind of negotiation must be performed between the transmitting and receiving terminals, but a specific procedure method will not be described in detail.

  With reference to FIG. 11 thru | or FIG. 13, the basic concept which concerns on embodiment of this invention is demonstrated. Here, it is assumed that the transmitting terminal transmits MPDUs having sequence numbers “1” to “7” assigned continuously. The transmitting terminal aggregates a plurality of MPDUs (QoS data) into one PSDU by one of the methods shown in FIG. 9 or FIG. 10, and aggregates a block ACK request 111 for the plurality of MPDUs at the end thereof. The value of Block ACK Starting Sequence Control in the block ACK request 111 is the same as the sequence number described in the MAC header of the first MPDU aggregated in PSDU. Here, the transmitting terminal has a main queue for storing MAC frames of various destinations and priorities, and a sub-queue for retransmitting the aggregated MPDU. In the example of FIG. 11, copies of MPDUs with sequence numbers “1” to “7” are stored in the subqueue in preparation for retransmission. A terminal that receives a PSDU in which multiple MPDUs are aggregated performs error calculation of multiple MPDUs by the above-described method. For example, in the example of FIG. 11, the MPDUs with sequence numbers “2” and “5” in the PSDU are errors as a result of the FCS calculation. In the embodiment of the present invention, the PSDU receiving terminal creates a reception status at that time as a Block ACK Bitmap 112. That is, in the example of FIG. 11, 1 is normal reception and 0 is reception failure, and is represented by a bitmap configuration such as 1011011. Here, it goes without saying that the positive logic and the negative logic may be used interchangeably. If the last MPDU aggregated in PSDU has been successfully received, a compressed block ACK 113 as shown in FIG. 12 is created for the data transmission terminal using the Block ACK Bitmap 112 created at that time. To do.

  When the number of aggregated MPDUs is smaller than the maximum number that can be aggregated in one PSDU, the Block ACK Bitmap 112 is padded with 0. In the example of FIG. 11, assuming that the maximum number that can be aggregated is 64 MPDU, a bitmap configuration represented by 10110110000. Alternatively, the bitmap length of the Block ACK Bitmap 112 may be made variable on the receiving terminal side according to the number of MPDUs aggregated in the PSDU. When variable, information indicating the bitmap length may be added to the BA control field of the block ACK in FIG. As the value of Block ACK Starting Sequence Control of the compressed block ACK 113, the value of the block ACK request 111 is copied. In FIG. 12, the data transmitting terminal that has received the block ACK compares the value indicated by the Block ACK Starting Sequence Control of the compressed block ACK 113 with the sequence number of the transmitted MPDU, and from the information in the Block ACK Bitmap 112, An MPDU that can be transmitted is detected, and an MPDU that needs to be retransmitted is determined. In the example of FIG. 12, since the Block ACK Bitmap 112 of the sequence numbers “2” and “5” is 0, it is determined that these two frames are MPDUs that need to be retransmitted.

  After determining the MPDU to be retransmitted, if it is within the range allowed by the buffer capacity on the receiving terminal side, a new MAC frame 120 is newly taken out from the main queue, sequence number assignment and aggregation to PSDU are performed. At this time, the MPDUs in the subqueue that have been successfully transmitted continuously from the head of the queue can be deleted. The number of newly added MPDUs 120 is realized by using a technique called sliding window control, for example. At the end of the PSDU that aggregates a plurality of MPDUs including the retransmission portion 121, a block ACK request 122 is aggregated for them.

  FIG. 13 shows a basic sequence example based on the above contents. Within a given TXOP period, multiple QoS data are aggregated into one physical frame, and a block ACK request is aggregated at the end of the PSDU. Prompt. On the data receiving side, the reception status of a plurality of MPDUs in the PSDU is calculated excluding the block ACK request portion, and the information is directly associated with the Block ACK Bitmap and a compressed block ACK is returned. Specifically, for example, in TXOP period 1, QSTA1 aggregates a plurality of QoS data to one PSDU 130, and aggregates a block ACK request 131 at the end of the PSDU 130, so that the receiving side can immediately Prompt transmission of block ACK. QSTA2 on the data receiving side calculates the reception status of a plurality of MPDUs in PSDU 130 excluding the part of block ACK request 131, and returns the compressed block ACK 132 in correspondence with the block ACK bitmap as it is.

  Unlike the conventional method, since the past reception history is not searched based on the Block ACK Starting Sequence Control of the block ACK request, the search processing with a relatively large load is reduced, and SIFS is limited in a limited period of time. It becomes easier to return partial responses. In general, since the search time and the circuit scale are in a trade-off relationship, it can be said that the circuit scale can be reduced when the allowable maximum processing delay is the same.

  Next, an example of retransmission control when an error occurs in reception will be described.

  First, retransmission control example 1 will be described with reference to FIGS. 14 to 16. In this example, it is assumed that the data transmission terminal aggregates MPDUs with sequence numbers “1” to “7” into one PSDU and aggregates and transmits a block ACK request at the end of the PSDU. As shown in the example of FIG. 14, if the block ACK request portion 140 is an error as a result of the FCS calculation, the receiving terminal cannot return the compressed block ACK. Therefore, in the embodiment of the present invention, even if a terminal that has received a PSDU in which a plurality of MPDUs are aggregated cannot return a compressed block ACK, the reception status of the plurality of MPDUs at that time is expressed as one Block ACK Bitmap. It shall be remembered. In the example of FIG. 14, bitmap information 141 of 1011011 is stored on the receiving side. On the receiving side, the sequence number of the MPDU that was normally received last by the terminal is also stored. In FIG. 14, this corresponds to the MPDU with the sequence number “7”. It is desirable to store the bitmap information 141 for one compressed block ACK and the sequence number of the last received MPDU for each data transmission terminal and priority.

If a compressed block ACK is not received from a destination after a PSDU that has aggregated multiple MPDUs and a certain period of time has passed, the transmitting terminal uses the sequence number of the first MPDU among the aggregated MPDUs. The block ACK request is retransmitted as the value of Block ACK Starting Sequence Control. Normally, the block ACK request aggregated to the immediately preceding PSDU may be retransmitted as it is. However, when the block ACK request is omitted and the previous PSDU is not aggregated as in the second embodiment, it is necessary to newly configure the block ACK request in this way. In the case of FIG. 14, Block ACK Starting Sequence Control describes “1” that is the first MPDU among the MPDUs having the sequence numbers “1” to “7” transmitted last time. This block ACK request 142 basically does not aggregate with other frames. The terminal that has received the block ACK request 142 to which no other MPDU is aggregated compares the value of Block ACK Starting Sequence Control in the block ACK request 142 with the sequence number of the MPDU that has been normally received last by the terminal. If the value of Block ACK Starting Sequence Control is equal to the sequence number of the last received MPDU or older (previous) number, it was held for sending one compressed block ACK, The bitmap information 141 is used as it is as Block ACK Bitmap information, and after the SIFS period, it responds reflectively with a compressed block ACK 150 as shown in FIG. In the example of FIG. 15, the reception status 1011011 of a plurality of MPDUs in the PSDU received last time is directly used as a Block ACK Bitmap, and a compressed block ACK 150 is returned to the transmitting terminal. The value of Block ACK Starting Sequence Control of the compressed block ACK 150 is copied from the value of Block ACK Starting Sequence Control of the block ACK request 142.
There is a case where the Block ACK Starting Sequence Control assumed when the bitmap information 141 is created and the Block ACK Starting Sequence Control of the block ACK request 142 are different. This is because, for example, the aggregated top MPDU is broken and the block ACK request is broken, and the bitmap information 141 is created assuming that the sequence number of the first MPDU that the receiving side has successfully received is the top. It happens in some cases. The bitmap information 141 is converted so that the sequence number of the starting point of the bitmap information 141 is consistent with the latter. Alternatively, the bitmap information 141 is left as it is, and the Block ACK Starting Sequence Control of the responding block ACK is set to a value assumed when the bitmap information 141 is created (that is, a value different from the block ACK request). Note that the receiving side may store the leading sequence number assumed when the bitmap information 141 is generated. Even if not stored, for example, if there is a sequence number of the last successfully received MPDU and bitmap information 141, the top sequence number can be calculated backward.

  FIG. 16 shows a sequence example when a block ACK request is retransmitted in the above control example. HC sends QoS CF-Poll to QSTA1 and gives TXOP period 1. In FIG. 16, QSTA1 aggregates a plurality of QoS data frames and one block ACK request into one physical frame 160 and transmits them to QSTA2 within the range of the TXOP period, but there is an error in the block ACK request portion 161. This indicates that the compressed block ACK cannot be received. After that, when the TXOP period 2 of QSTA2 ends and the HC grants TXOP period 3 to QSTA1 again, QSTA1 retransmits the block ACK request 162 and receives a compressed block ACK 163 from QSTA2, thereby a series of frame sequences. Exit.

Next, retransmission control example 2 will be described with reference to FIGS. As shown in FIG. 17, it is assumed that the transmitting terminal aggregates and transmits MPDUs with sequence numbers “1” to “7” and a block ACK request to one PSDU. When the receiving side finds that the sequence number “2”, “5”, and block ACK request error check result indicate that these could not be received normally, the reception status of multiple MPDUs in the PSDU received at that time Is stored as bitmap information (in the example of FIG. 17, the bitmap is 1011011) and the sequence number of the last received MPDU (sequence number “7” in the example of FIG. 17) is also stored. Same as above.
In the example of FIG. 17, the data receiving terminal cannot respond with the compressed block ACK. Therefore, if the transmitting terminal cannot receive the compressed block ACK even after a predetermined time has elapsed, it retransmits the block ACK request. As described above, the Block ACK Starting Sequence Control value of the block ACK request describes the sequence number (“1” in the example of FIG. 17) of the head MPDU that has been aggregated. Here, even if the block ACK request is transmitted, if the compressed block ACK is not returned, the retransmission of the data is given up. According to IEEE802.11e Draft 8.0, a delay limit (Delay Bound) is defined in QoS data according to priority, and this value is mutually recognized between transmitting and receiving terminals through negotiation. A MAC frame exceeding the Delay Bound is discarded at the transmitting terminal (or receiving terminal), assuming that the QoS quality cannot be satisfied. In the example of FIG. 17, when all MAC frames with sequence numbers “1” to “7” that are aggregated and transmitted by the transmitting terminal exceed the Delay Bound and are discarded, a new frame is aggregated as the next transmission sequence. Will be gated.
In the example of FIG. 18, MPDU 180 and block ACK request 181 with sequence numbers “8” to “14” are aggregated and transmitted as one PSDU as a new data frame. The value of Block ACK Starting Sequence Control of the block ACK request 181 aggregated at the end of the PSDU describes the sequence number “8” of the first MPDU. If the PSDU that aggregates the multiple MPDUs (sequence numbers “8” to “14”) 180 and the block ACK request 181 becomes an error due to a collision or the like, the receiving terminal side does not update the reception status at all. It remains in a state of not performing. If the transmitting terminal cannot receive the compressed block ACK even after a certain period of time, the transmitting terminal retransmits the block ACK request 181 whose Block ACK Starting Sequence Control is “8”. When the receiving terminal receives the retransmitted block ACK request 181, the value of the Block ACK Starting Sequence Control of the frame 181 is “8”, which is higher than the sequence number “7” of the last MPDU received by itself. It turns out that it is a large value. In the example of FIG. 18, since the bitmap information for one compressed block ACK is for the MPDUs with sequence numbers “1” to “7”, the reception status indicated by the Block ACK Starting Sequence Control is not recorded at all. Is the situation. Here, as shown in FIG. 19, the MPDU reception status (1011011 in the example of FIG. 18) of the sequence numbers “1” to “7” stored so far is cleared to 0, and Block ACK Bitmap 190 is set. A compressed block ACK 190 with all 0s is transmitted. That is, the Block ACK Bitmap 190 indicates that there is no normally received MAC frame.

  A terminal that has aggregated and transmitted a plurality of MPDUs having sequence numbers “8” to “14” receives the compressed block ACK 191 from the destination terminal in FIG. 19 and the block ACK bitmap 190 is all 0, the sequence number All MPDUs 192 of “8” to “14” are to be retransmitted. In the example of FIG. 19, the MPDU 192 to be retransmitted with the sequence numbers “8” to “14” and the block ACK request (Block ACK Starting Sequence Control is “8”) 193 are aggregated into one PSDU and transmitted. ing. In the receiving terminal, if any one of the MPDUs 192 aggregated in the PSDU except for the block ACK request 193 can be normally received, the reception status bitmap and the sequence number of the last successfully received MPDU are received. Update.

  According to the first embodiment of the present invention described above, it is possible to reduce the bitmap information included in the block ACK and improve the MAC efficiency on the assumption that the MSDU is not fragmented. In this embodiment, an example of realizing an immediate block ACK that responds with a block ACK after a SIFS period after receiving a block ACK request is shown. Specifically, a plurality of MPDUs are aggregated and the end of the plurality of MPDUs When a PSDU in which a block ACK request is aggregated is received, the reception status can be reflected back as an immediate block ACK. However, compressing the bitmap information on the assumption that there is no fragment can be similarly applied to the case of the delayed block ACK.

  Also, in this embodiment, an example in which one block ACK request and one block ACK are included in one PSDU has been shown, but it is extended to include a plurality of block ACK requests and a plurality of block ACKs in one PSDU. You can also. For example, when a plurality of MPDUs having the same destination but different TIDs are aggregated into one PSDU, a block ACK request may be associated with each TID included in the PSDU. If some TIDs do not require an ACK immediately or no ACK at all, the number of TIDs may be greater than the number of block ACK requests. A block ACK in response to this is also generated and transmitted for each block ACK request. The responding block ACK is naturally aggregated into one PSDU, but can be transmitted as an individual PSDU. Further, when a plurality of destination MPDUs are aggregated to one PSDU, a block ACK request may be associated with each destination included in the PSDU. The response block ACK is individually transmitted from each receiving side apparatus corresponding to the destination. It is assumed that the response of the block ACK transmitted by each receiving side apparatus is scheduled so as not to collide with each other. It is also possible to combine multiple TIDs and multiple destinations.

  The same applies to normal CSMA / CA that is not scheduled by HC.

(Second embodiment)
In the first embodiment of the present invention, when a plurality of MPDUs are aggregated into one PSDU, the block ACK request is always aggregated at the end of the PSDU. In this case, when the terminal that has received the PSDU performs an error check on the aggregated MPDUs and confirms the presence of a block ACK request therein, the compressed block ACK is reflected back. In contrast, in the second embodiment of the present invention, when a plurality of MPDUs are aggregated, a physical frame is transmitted without a block ACK request being aggregated at the end of the PSDU.
FIG. 20 and FIG. 21 show PSDU frame configuration examples in which multiple MPDUs are aggregated in the second embodiment of the present invention. In FIG. 20, information (MPDU length) 201 indicating the length of the MPDU and a CRC 202 for the length information are added to the head of the plurality of MPDUs. The MPDU length 201 and the CRC 202 are collectively referred to as “MPDU separation” 203 as in the first embodiment. As can be seen from FIG. 20, in the second embodiment, there is no block ACK request at the end of the PSDU in which a plurality of MPDUs are aggregated. Each MPDU is considered to have been successfully received if the CRC calculation of the MPDU separation 203 is correct and the FCS calculation result of the MPDU indicated by the MPDU length 201 is normal. FIG. 21 is a diagram in which length information of a plurality of MPDUs is added to the head of an aggregated MPDU group as a header, and this header is referred to as a “MAC super frame header” 210 as in the first embodiment. The MAC super frame header 210 includes a header CRC 211. If the result of the CRC calculation of the MAC super frame header 210 is an error, all MPDUs are regarded as an error. The MPDU length information specifies the length from the MAC header to FCS in bytes. In the second embodiment, as shown in FIGS. 20 and 21, the physical (PHY) header (200 in FIG. 20, 212 in FIG. 21) and the physical (PHY) trailer (204 in FIG. 20, 213 in FIG. 21) are provided. A terminal that receives a physical frame in which a plurality of MPDUs are aggregated within the sandwiched PSDU responds reflexively with the reception status at that time as a compressed block ACK.

A basic transmission / reception sequence according to the second embodiment of the present invention will be described with reference to FIGS. In FIG. 22, the transmitting terminal aggregates and continuously transmits MPDUs having sequence numbers “1” to “8” assigned to one PSDU. Similar to the first embodiment described above, the transmitting terminal has a subqueue for retransmission, and stores copies of MPDUs with sequence numbers “1” to “8” in FIG. 22 in the subqueue. In the example of FIG. 22, the receiving terminal that has received the PSDU in which a plurality of MPDUs are aggregated calculates the reception status of each MPDU, converts it to Block ACK Bitmap 220, and transmits the compressed block ACK in a reflective manner. Unlike the first embodiment, since the block ACK request is not aggregated, if any one of the MPDUs in the PSDU can be normally received, the compressed block ACK is returned when the PSDU ends. The example of FIG. 22 shows a case where MPDUs with sequence numbers “2”, “5”, and “7” are erroneous as a result of FCS calculation. The receiving terminal uses the sequence number of the head MPDU that has been successfully received in the PSDU as the value of Block ACK Starting Sequence Control of the compressed block ACK. The Block ACK Bitmap 220 is created from the relative positional relationship from the MPDU that can be received first. In FIG. 22, the bitmap configuration of the reception status can be shown as 10110101. The Block ACK Starting Sequence Control of the compressed block ACK is “1”. As in the first embodiment described above, when the maximum number of MPDUs that can be aggregated in one PSDU is not reached, padding or the like is performed with 0 in the second half of the bitmap field. Alternatively, the bitmap length of the Block ACK Bitmap 220 may be made variable on the receiving terminal side according to the number of MPDUs aggregated in the PSDU. In FIG. 23, when receiving the compressed block ACK 230 from the destination, the data transmitting terminal first confirms Block ACK Starting Sequence Control of the frame 230. In the example of FIG. 23, since it is equal to the sequence number “1” of the first MPDU transmitted by the transmitting terminal, the transmission status of the MPDU transmitted by the terminal is determined from the Block ACK Bitmap 231 of the compressed block ACK 230. The block ACK bitmap 231 in FIG. 23 has a configuration indicated by 10110101. As a result, the transmitting terminal detects that the MPDUs having the sequence numbers “2”, “5”, and “7” cannot be transmitted correctly. Therefore, the MPDUs with sequence numbers “2”, “5”, and “7” are to be retransmitted and re-aggregated at the time of retransmission, and the buffer capacity on the receiving side permits as in the first embodiment of the present invention. Within range, a new frame 232 is aggregated and transmitted together. Even when a PSDU including a plurality of MPDUs including the retransmission frame 233 is transmitted, a block ACK request is not aggregated at the end.
As shown in FIG. 24, QSTA1 given the TXOP period 1 from the HC transmits a physical frame 240 in which a plurality of QoS data is aggregated to QSTA2, and the QSTA2 receiving the frame 240 receives the SIFS period. After that, the compressed block ACK 241 is returned. The downlink transmission from HC to QSTA1 is performed in the same procedure. That is, in the HC TXOP period 2, a physical frame 242 in which a plurality of QoS data is aggregated is transmitted to QSTA1, and a compressed block ACK 243 is received from QSTA1, thereby completing a series of transmission sequences.

  According to the second embodiment of the present invention, since the block ACK request is not aggregated in the PSDU, the MAC efficiency can be improved. It is also possible to reduce the processing load of receiving a block ACK request frame on the receiving side.

Next, with reference to FIG. 25 and FIG. 26, a description will be given of an example of retransmission control in the case where frame errors continuously occur from the top of the PSDU in which multiple MPDUs are aggregated. As shown in FIG. 25, MPDUs with sequence numbers “1” to “8” are aggregated and transmitted, and MPDUs with sequence numbers “1”, “2”, “5”, and “7” are FCS on the receiving terminal side. Assume that the result of the calculation is an error. Unlike the first embodiment, since the block ACK request is not aggregated in the PSDU in the second embodiment, it is not possible to determine which sequence number is the head of the PSDU. In particular, as shown in FIG. 20, when an MPDU separation field is added to the head of a plurality of MPDUs, it is not known how many MPDUs are aggregated in the PSDU, and therefore Block ACK Starting Sequence Control is estimated. I can't. Therefore, in the second embodiment of the present invention, a terminal that has received a PSDU obtained by aggregating a plurality of MPDUs uses the block ACK of the compressed block ACK as the sequence number of the first MPDU that has been normally received in the PSDU. A reception status bitmap is constructed from the value of Starting Sequence Control and the relative positional relationship from the MPDU. That is, as shown in FIG. 25, since the first MPDU successfully received on the data receiving terminal side is a frame of sequence number “3”, Block ACK Starting Sequence Control of the compressed block ACK is set to “3”. And Furthermore, the Block ACK Bitmap 250 is created from the relative positional relationship from the MPDU with the sequence number “3” in the PSDU. In the example of FIG. 25, a bitmap like 110101 is created. As already discussed, if the maximum number of MPDUs that can be aggregated in one PSDU is not reached, the second half 251 of the bitmap is padded with zeros. Alternatively, the bitmap length of the Block ACK Bitmap 250 may be made variable on the receiving terminal side according to the number of MPDUs aggregated in the PSDU. If a compressed block ACK 252 is received after a plurality of MPDUs are aggregated and transmitted, the sequence number of the MPDU transmitted by the terminal is compared with Block ACK Starting Sequence Control.
As in the example of FIG. 26, when MPDUs having sequence numbers “1” to “8” are transmitted and the value of Block ACK Starting Sequence Control of the compressed block ACK 252 from the destination terminal is “3”, Block ACK All MPDUs with sequence numbers prior to Starting Sequence Control are considered errors. That is, it is determined that the MPDUs with sequence numbers “1” and “2” are errors. Also, starting from the value “3” of Block ACK Starting Sequence Control, it is determined from the relative positional relationship of the bitmap that an error has occurred in the MPDUs of sequence numbers “5” and “7”. The transmitting terminal aggregates the MPDU 260 that needs to be retransmitted by receiving such a compressed block ACK 252 and, if there is room in the buffer capacity on the receiving side, newly aggregates and transmits the frame. .

  With reference to FIG. 27, a case where the transmitting terminal retransmits the block ACK request will be described. As described in the first embodiment, when the compressed block ACK from the destination is not received, the transmitting terminal retransmits the block ACK request. In the second embodiment of the present invention, when one piece of QoS data is aggregated, a block ACK request is not included at the end. This is only the case when the message cannot be received. In the example of FIG. 27, MPDUs with sequence numbers “1”, “2”, “5”, and “7” are aggregated as retransmissions 260 and transmitted. At this time, the Block ACK Starting Sequence Control of the block ACK request 270 copies the value of the sequence number of the first MPDU of the PSDU transmitted last time. In FIG. 27, the Block ACK Starting Sequence Control of the block ACK request 270 is “1”. The terminal that has received the block ACK request 270 stores the reception status of a plurality of MPDUs in the PSDU that was last received last time as one compressed block ACK, and the sequence number of the MPDU that was normally received last by the receiving terminal. If the value of the Block ACK Starting Sequence Control in the block ACK request 270 is smaller than that, the stored bitmap information is converted into the Block ACK Bitmap as it is, and the compressed block ACK is reflected back. At this time, the value of Block ACK Starting Sequence Control of the compressed block ACK is not copied from the block ACK request, but describes the sequence number of the first MPDU that can be normally received in the previously received PSDU. This is because the MPDU corresponding to the Block ACK Starting Sequence Control indicated by the block ACK request is not necessarily received normally. Alternatively, Block ACK Starting Sequence Control may be copied from the block ACK request, and the bitmap information may be converted to the content that the part older than the first sequence number of the stored bitmap information could not be received normally.

  FIG. 28 shows a basic frame exchange sequence including a retransmission process according to the second embodiment of the present invention. Here, the data transmission terminal aggregates and transmits MPDUs having sequence numbers “1” to “8” to one PSDU 280. When the PSDU 280 is received on the receiving side, if the MPDUs with sequence numbers “1”, “2”, “5”, and “7” are in error, the compressed block ACK 281 is transmitted with a bitmap configuration such as 11010100. On the transmission side, it is determined from the contents of the compressed block ACK 281 that the MPDUs with sequence numbers “1”, “2”, “5”, and “7” have not been transmitted normally, and the MPDUs to be retransmitted are Aggregate and retransmit PSDU 282. When the retransmitted PSDU 282 cannot be received at all on the receiving side due to a collision or the like, the transmitting terminal retransmits the block ACK request 283 with Block ACK Starting Sequence Control set to “1” after a certain time. The terminal that has received the block ACK request 283 has a Block ACK Starting Sequence Control value of “1”, but among the plurality of MPDUs in the PSDU that was previously received by the receiving terminal, the first sequence number is “3”. Therefore, the value of Block ACK Starting Sequence Control of the compressed block ACK 284 is set to “3”, and the stored reception status bitmap is returned as Block ACK Bitmap. When the transmitting terminal receives the compressed block ACK 284, all the MPDUs having sequence numbers before the Block ACK Starting Sequence Control of the compressed block ACK 284 in the previously transmitted MPDU 282 are regarded as errors, and An erroneous MPDU is also detected from the positional relationship. That is, in the example of FIG. 28, since all the retransmitted MPDUs 282 are incorrect, as a result, all MPDUs with sequence numbers “1”, “2”, “5”, and “7” are to be retransmitted. The aggregated MPDU 285 is retransmitted. Thereafter, by receiving the compressed block ACK 286 from the destination, it is considered that a series of frame exchange sequences has been completed.

  FIG. 29 shows buffer management at a data transmission terminal including retransmission. A MAC frame is extracted from a main queue including MAC frames having various destinations and priorities, and consecutive sequence numbers “1” to “8” are assigned and stored in a sub-queue 290 for retransmission. Then, a copy of the MPDU with sequence numbers “1” to “8” is taken out, aggregated into one PSDU and transmitted, and then the sequence number of the MPDU transmitted by the transmitting terminal is stored. In the example of FIG. 29, information “1”, “2”, “3”, “4”, “5”, “6”, “7”, “8” is stored on the transmission side. When a compressed block ACK 291 with Block ACK Starting Sequence Control “3” is received from the destination terminal, both MPDUs with sequence numbers “1” and “2” before that are regarded as errors. At the same time, MPDUs with sequence numbers “5” and “7” are also regarded as errors from the relative positional relationship of the Block ACK Bitmap. From the retransmission subqueue 290, if the transmission has succeeded continuously from the head, the MPDU can be deleted from the front. In the example of FIG. 29, since it is determined that the MPDU with the sequence number “1” is incorrect, no frame can be deleted from the subqueue. Here, it is desirable to give some identification information indicating successful transmission to the MAC frame successfully transmitted in the sub-queue 290 and store it in the sub-queue as it is. This is because, when the compressed block ACK is received in the next sequence, it becomes difficult to distinguish between MPDUs that have been successfully transmitted and MPDUs that have not been transmitted normally, from the relative positional relationship of the bitmap. Because it is. Here, it is not always necessary to store the entity of the successfully transmitted MPDU. The state for each sequence number is important. After that, the transmitting terminal retransmits the MPDUs with sequence numbers “1”, “2”, “5”, and “7”, and except that the MPDU with the sequence number “7” has been received successfully on the receiving side. , Block ACK Starting Sequence Control “1” compressed block ACK 292 is returned. The transmitting terminal continuously deletes MPDUs having sequence numbers “6” from the top of the subqueue 290 in order to determine that MPDUs having sequence numbers “1”, “2”, and “5” have been normally transmitted. . As a result, the MPDU with the sequence number “7” is stored at the head of the sub-queue 290.

  Since the block ACK request can be deleted from the PSDU according to the second embodiment of the present invention described above, the MAC efficiency is improved. Also, on the premise that MSDU fragmentation is not performed, the bitmap information included in the block ACK can be reduced, and the MAC efficiency can be improved. Furthermore, an immediate block ACK that responds with a block ACK after the SIFS period after receiving the block ACK request can be realized. The method of improving the MAC efficiency by deleting the block ACK request from PSDU can also be applied to the case of delayed block ACK.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The block diagram which shows the structure of the communication apparatus which concerns on 1st embodiment of this invention. The figure which shows the frame format of the block ACK request stipulated in IEEE802.11e Draft 8.0 The figure which shows the frame format of the block ACK specified by IEEE802.11e Draft 8.0 Diagram showing block ACK sequence (immediate type) Diagram showing block ACK sequence (delay type) Diagram for explaining conventional block ACK creation procedure Diagram for explaining conventional block ACK creation procedure The figure which shows the format of compressed block ACK Diagram showing an example of a format for aggregating multiple MPDUs Figure showing another example of a format for aggregating multiple MPDUs The figure for demonstrating the compressed block ACK immediate response which concerns on 1st embodiment The figure for demonstrating the compressed block ACK immediate response which concerns on 1st embodiment The figure for demonstrating the compressed block ACK immediate response which concerns on 1st embodiment The figure for demonstrating the resending control example 1 which concerns on 1st embodiment. The figure for demonstrating the resending control example 1 which concerns on 1st embodiment. The figure for demonstrating the resending control example 1 which concerns on 1st embodiment. The figure for demonstrating the resending control example 2 which concerns on 1st embodiment. The figure for demonstrating the resending control example 2 which concerns on 1st embodiment. The figure for demonstrating the resending control example 2 which concerns on 1st embodiment. The figure which shows an example of the format which aggregates several MPDU which concerns on 2nd embodiment The figure which shows another example of the format which aggregates several MPDU which concerns on 2nd embodiment. The figure for demonstrating an example of the resending procedure at the time of the block ACK request | requirement omission concerning 2nd embodiment The figure for demonstrating an example of the resending procedure at the time of the block ACK request | requirement omission concerning 2nd embodiment The figure for demonstrating an example of the resending procedure at the time of the block ACK request | requirement omission concerning 2nd embodiment The figure for demonstrating another example of the resending procedure at the time of the block ACK request | requirement omission concerning 2nd embodiment The figure for demonstrating another example of the resending procedure at the time of the block ACK request | requirement omission concerning 2nd embodiment The figure for demonstrating another example of the resending procedure at the time of the block ACK request | requirement omission concerning 2nd embodiment The figure for demonstrating another example of the resending procedure at the time of the block ACK request | requirement omission concerning 2nd embodiment Diagram showing buffer management at data transmission terminal including retransmission

Explanation of symbols

100: Communication device;
101 ... Physical layer (PHY);
102 ... MAC (medium access control) layer;
103 ... link layer;
104: antenna;
105 ... aggregation processing unit;
106: Carrier sense control unit;
107 ... retransmission control unit;
109 ... The first type physical layer protocol processing unit;
110 ... Second-type physical layer protocol processing unit

Claims (10)

Receiving means for receiving a physical frame having a first data frame and a second data frame each having a sequence number and an FCS (Frame Check Sequence) ;
Creating means for creating a first delivery confirmation frame including a start point sequence number and a bitmap indicating a reception state of at least one of the first data frame and the second data frame ;
Transmission means for transmitting the first delivery confirmation frame to a communication device that is a transmission source of the physical frame after a minimum frame interval has elapsed since the reception of the physical frame by the reception means;
The physical frame is
(A) To perform byte alignment, the first data frame, first information about the length of the first data frame, a first error detection code for detecting an error in the first information, and A first field having a first field of
(B) To perform byte alignment with the second data frame, second information about the length of the second data frame, a second error detection code for detecting an error in the second information, and A second field having a second field,
The creation means has correctly received the first data frame when no error is detected in the first information by the first error detection code and no error is detected by FCS of the first data frame. age,
When an error is detected in the first information by the first error detection code or when an error is detected by FCS of the first data frame, reception of the first data frame has failed,
When no error is detected in the second information by the second error detection code and no error is detected by FCS of the second data frame, the second data frame is correctly received;
When an error is detected in the second information by the second error detection code or when an error is detected by FCS of the second data frame, reception of the second data frame has failed,
The receiving means is configured to change the first number according to the sequence number added to the first data frame and the sequence number added to the second data frame, the start point sequence number, and the bitmap . communication apparatus characterized by receiving at least one again of the data frame and the second data frame. Receiving means for receiving a physical frame having a first data frame and a second data frame each having a sequence number and an FCS (Frame Check Sequence) ;
Creating means for creating a first delivery confirmation frame including a start point sequence number and a bitmap indicating a reception state of at least one of the first data frame and the second data frame ;
A transmission unit that transmits the first delivery confirmation frame to a communication device that is a transmission source of the physical frame after a SIFS period has elapsed since the reception unit received the physical frame;
The physical frame is
(A) To perform byte alignment, the first data frame, first information about the length of the first data frame, a first error detection code for detecting an error in the first information, and A first field having a first field of
(B) To perform byte alignment with the second data frame, second information about the length of the second data frame, a second error detection code for detecting an error in the second information, and A second field having a second field,
The creation means has correctly received the first data frame when no error is detected in the first information by the first error detection code and no error is detected by FCS of the first data frame. age,
When an error is detected in the first information by the first error detection code or when an error is detected by FCS of the first data frame, reception of the first data frame has failed,
When no error is detected in the second information by the second error detection code and no error is detected by FCS of the second data frame, the second data frame is correctly received;
When an error is detected in the second information by the second error detection code or when an error is detected by FCS of the second data frame, reception of the second data frame has failed,
The receiving means is configured to change the first number according to the sequence number added to the first data frame and the sequence number added to the second data frame, the start point sequence number, and the bitmap . A communication apparatus, wherein at least one of a data frame and the second data frame is received again. Each of the first data frame and the second data frame includes a transmission source address indicating a communication device that is a transmission source of the data frame, a destination address indicating a communication device that is a destination of the data frame, and a priority identifier. (TID: Traffic Identifier :)
The creation unit creates the first delivery confirmation frame using a sequence number, a source address, a destination address, and a priority identifier included in a correctly received data frame. The communication device according to claim 1 or 2. Said creation means, wherein the first said start sequence number of the acknowledgment frame, the first data frame and the claims 1 to 3, characterized in that either the sequence number of the second data frame The communication device according to any one of the above. Storage means for storing a bitmap included in the first delivery confirmation frame;
When the receiving means receives the delivery confirmation request frame, the creating means creates a second delivery confirmation frame by the bitmap stored in the storage means,
The communication apparatus according to claim 4 , wherein the transmission unit transmits the second delivery confirmation frame. When the start sequence number of the delivery confirmation request frame is larger than the sequence number of the data frame received before receiving the delivery confirmation request frame, the creation means indicates that there is no data frame successfully received. 3 Create a delivery confirmation frame,
The communication apparatus according to claim 5 , wherein the transmission unit transmits the third delivery confirmation frame. If the start sequence number of the delivery confirmation request frame is equal to or less than the sequence number corresponding to the last bit of the bitmap stored in the storage means, the creation means includes at least a part of the bitmap. 4 Create a delivery confirmation frame,
The communication device according to claim 5 , wherein the transmission unit transmits the fourth delivery confirmation frame. An antenna,
The receiving means receives the physical frame via the antenna;
The communication apparatus according to claim 1, wherein the transmission unit transmits the first delivery confirmation frame via the antenna. Each receiving a physical frame having a first data frame and the second data frame with a sequence number and FCS (Frame Check Sequence),
Creating a first delivery confirmation frame including a start point sequence number and a bitmap indicating a reception state of at least one of the first data frame and the second data frame;
After a minimum frame interval has elapsed since receiving the physical frame, the first delivery confirmation frame is transmitted to the communication device that is the transmission source of the physical frame ,
The physical frame is
(A) To perform byte alignment, the first data frame, first information about the length of the first data frame, a first error detection code for detecting an error in the first information, and A first field having a first field of
(B) To perform byte alignment with the second data frame, second information about the length of the second data frame, a second error detection code for detecting an error in the second information, and A second field having a second field,
In creating the first delivery confirmation frame,
When no error is detected in the first information by the first error detection code and no error is detected by FCS of the first data frame, the first data frame is correctly received;
When an error is detected in the first information by the first error detection code or when an error is detected by FCS of the first data frame, reception of the first data frame has failed,
When no error is detected in the second information by the second error detection code and no error is detected by FCS of the second data frame, the second data frame is correctly received;
When an error is detected in the second information by the second error detection code or when an error is detected by FCS of the second data frame, reception of the second data frame has failed,
According to the sequence number added to the first data frame and the sequence number added to the second data frame, the starting sequence number, and the bitmap, the first data frame and the first data frame A communication method comprising receiving at least one of the two data frames again . Each receiving a physical frame having a first data frame and the second data frame with a sequence number and FCS (Frame Check Sequence),
Creating a first delivery confirmation frame including a start point sequence number and a bitmap indicating a reception state of at least one of the first data frame and the second data frame;
After the SIFS period has elapsed since the physical frame was received, the first delivery confirmation frame is transmitted to the communication device that is the transmission source of the physical frame ,
The physical frame is
(A) To perform byte alignment, the first data frame, first information about the length of the first data frame, a first error detection code for detecting an error in the first information, and A first field having a first field of
(B) To perform byte alignment with the second data frame, second information about the length of the second data frame, a second error detection code for detecting an error in the second information, and A second field having a second field,
In creating the first delivery confirmation frame,
When no error is detected in the first information by the first error detection code and no error is detected by FCS of the first data frame, the first data frame is correctly received;
When an error is detected in the first information by the first error detection code or when an error is detected by FCS of the first data frame, reception of the first data frame has failed,
When no error is detected in the second information by the second error detection code and no error is detected by FCS of the second data frame, the second data frame is correctly received;
When an error is detected in the second information by the second error detection code or when an error is detected by FCS of the second data frame, reception of the second data frame has failed,
According to the sequence number added to the first data frame and the sequence number added to the second data frame, the starting sequence number, and the bitmap, the first data frame and the first data frame A communication method comprising receiving at least one of the two data frames again .

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