Communication apparatus, communication system and communication control program

Communication equipment, communication system and communication control program

CROSS REFERENCE TO RELATED APPLICATIONS This application is based on the prior Japanese Patent Application No. 2004-129073 filed on April 23, 2004 and claims priority, the entire content of which is incorporated herein by reference.

Technical field

The present invention relates to a communication device, a communication system, and a communication control program that implement media access control (MAC), and more specifically, to a frame aggregation in which a plurality of media access control frames (MAC frames) are included in one physical frame (aggregation).

Background technique

Media Access Control (MAC) is a control that allows multiple communication devices that communicate to decide how to use the media to transmit communication data or management frames when sharing the same media. Due to media access control, even if two or more communication devices simultaneously use the same media to transmit communication data (or management frames), it rarely happens that the receiver's communication device cannot decipher the communication data (conflict ). The basic access method of IEEE802.11 MAC is CSMA/CA (collision avoidance carrier detection multiple access). CSMA/CA is used to reduce the probability of collisions. Media access control is also a technology that controls access to media from a communication device so as to minimize the chance of the phenomenon that the media is not used by any communication device even though there is a communication device with a transmission request.

However, especially in wireless communication, it is difficult to monitor the transmission data at the same time when the communication device transmits data. Therefore, a medium access control (MAC) in which collision detection is not adopted is required. A typical technical standard of wireless LAN IEEE802.11 adopts Collision Avoidance Carrier Sense Multiple Access (CSMA/CA).

The MAC header has a duration value, which is the time required to transmit data or management frames in milliseconds (including the time of the SIFS interval). A communication device that does not have any transmission rights regardless of the sequence determines the virtual busy state of the media and waits for transmission. Thus, the occurrence of conflicts is avoided. In IEEE802.11, the state of the defined media is judged by the combination of virtual carrier detection at the MAC layer and physical carrier detection at the physical layer, thereby controlling media access. CSMA/CA is used to reduce the probability of collisions.

In IEEE802.11 using CSMA/CA, the communication speed is increased by mainly changing the physical layer protocol. For the 2.4GHz band, IEEE802.11 (2Mbps in 1997) has been changed to IEEE802.11b (11Mbps in 1999), and has been changed to IEEE802.11g (54Mbps in 1999). As far as the 5GHz band is concerned, only IEEE802.11a (54Mbps in 1999) currently exists as a standard. In addition, IEEE 802.11 Task Group n (TGn) has been specified to establish standards aimed at further acceleration in the 2.4 GHz and 5 GHz bands.

In addition, several access control technologies for improving the quality of service (QoS) are also known. For example, there is available HCCA (HCF Control Channel Access), which is an extension technique of the conventional polling sequence, and is used as a QoS technique to guarantee parameters such as design bandwidth and delay time. According to HCCA, in order to guarantee parameters such as bandwidth and delay time, scheduling is performed in consideration of the required quality in the polling sequence. Japanese Patent Application KOKAI Publication No. 2002-314546 discloses a method of assigning priority to communication between communication devices in a wireless network while referring to QoS in the IEEE802.11e standard.

Even if the communication speed of the physical layer is increased, there is still a problem that the throughput of communication cannot be significantly improved. That is, when the acceleration of the physical layer is achieved, the format of the PHY (physical) frame is no longer efficient, and the resulting overhead hinders the increase in throughput. In the PHY frame, time parameters related to CSMA/CA are fixedly accompanied by the MAC frame. In addition, each MAC frame requires a PHY frame header and a PHY preamble.

As a method of solving the problem of overhead and improving throughput, the block response (block acknowledgement) mechanism introduced in the recently drafted IEEE802.11e/draft 5.0 (enhancement of QoS in IEEE802.11) can be used. The block response mechanism can continuously transmit multiple MAC frames without any random compensation (with SIFS interval), thereby reducing the amount of compensation to a certain extent. However, the overhead of the physical layer header and preamble cannot be effectively reduced. In addition, according to the aggregation technology introduced in the initial draft of IEEE802.11e, both the amount of compensation and the physical layer overhead can be reduced. However, since under conventional restrictions on the physical layer, the length of the physical layer frame including the MAC frame cannot be increased beyond approximately 4 kbyte, the efficiency improvement is greatly limited. Even if the length of the PHY layer frame can be increased, another problem will occur, that is, a decrease in fault tolerance.

Therefore, it is necessary to solve the overhead associated with the use of an effective frame format to solve the multi-frame transmission, and significantly improve the communication throughput.

On the other hand, according to the conventional HCCA, the quality can be guaranteed for each traffic flow, and the data transmission corresponding to the priority can be realized. In a new communication system in which throughput has been further improved, QoS is best used. For example, QoS is preferably used for frame aggregation designed to improve transmission efficiency by transmitting multiple MAC frames when they are included in one physical (PHY) frame. However, if the conventional frame aggregation technology is simply applied to QoS, such as HCCA, the following problems will arise.

That is, in the conventional frame aggregation technology in which the priority of the frame is not considered, when a series of frames in the transmission queue (TxQ) are aggregation target frames, the FTP (File Transfer Protocol) frame with a relatively low priority may precede High-priority VoIP (Voice over Internet Protocol) frames are extracted and aggregated into transmission aggregation frames. Taking into account the priority of the frame, this will hinder the guarantee of QoS.

In addition, there is a problem in that the program that points out some frames that have led to receiving errors and requests retransmission of partial Ack frames should be used in combination with the ACK program inherent in QoS (for example, the No Ack program). .

Summary of the invention

The present invention has been proposed in consideration of the above circumstances, and an object of the present invention is to provide a communication device, a communication system, and a communication control program that can improve throughput through aggregation of a plurality of communication frames.

A communication device according to an aspect of the present invention includes: a generating device that generates a single physical frame including a plurality of MAC frames; and a transmission device that transmits a physical frame generated by the generating device, the physical frame including variable-length bitmap information and a bitmap Length information of the information, the variable length bitmap information includes bits corresponding to the multiple MAC frames.

Description of the drawings

Fig. 1 is a block diagram showing a communication device according to an embodiment of the present invention; Fig. 2 shows an Ack strategy bitmap with a fixed length; Fig. 3 shows a bitmap information field according to a first embodiment of the present invention; An example of the MAC superframe of the variable-length Ack strategy bitmap; FIG. 5 is an explanatory diagram of receiving buffer management; FIG. 6 is an explanatory diagram of receiving buffer management for each priority according to the second embodiment of the present invention Fig. 7 shows the format of TSPEC; Fig. 8 is an explanatory diagram showing a first example of retransmission control for each priority level; Fig. 9 is an explanatory diagram showing a second retransmission control example for each priority level; Fig. 10 Is an explanatory diagram of an example of retransmission control for each priority according to the third embodiment of the present invention; FIG. 11 shows the sequence of the standard block Ack (immediate block Ack); FIG. 12 shows the QoS control field; The fourth embodiment of the invention is an example of a MAC superframe with a variable length Ack strategy bitmap; Fig. 14 shows a block Ack sequence (immediate block Ack) of aggregated QoS data according to the fourth embodiment of the invention; Fig. 15 shows According to the fourth embodiment of the present invention, an example of aggregation of QoS data and block Ack requests; Fig. 16 shows a block Ack sequence (immediate block Ack) in which QoS data and block Ack requests are aggregated according to the fourth embodiment of the present invention; 17 shows an example of aggregation of QoS data and block Ack requests for multiple TIDs according to the fourth embodiment of the present invention; FIG. 18 shows the fourth embodiment according to the present invention, in which the QoS data and block Ack regarding multiple TIDs are aggregated The requested block Ack sequence;

Figure 19 shows the aggregation of the Ack strategy "No Acknowledgement" and Ack strategy "Block Acknowledgement" frames according to the fourth embodiment of the present invention; Figure 20 shows the MAC frame of the Ack strategy "No Acknowledgement" and Ack strategy "Block Acknowledgement" frames Figure 21 shows a traffic specification (TSPEC) used when setting traffic flows according to the fifth embodiment of the present invention; Figure 22 shows the fifth embodiment of the present invention, where the MPDU length is assumed Is a fixed-length MAC superframe; Figure 23 shows the aggregation of fixed-length MAC frames when mixed with multiple TSIDs according to the fifth embodiment of the present invention; Figure 24 shows the sixth embodiment of the present invention with multiple An example of a MAC super frame of a destination; FIG. 25 shows another example of a MAC super frame with multiple destinations according to the sixth embodiment of the present invention; FIG. 26 shows a seventh embodiment of the present invention, indicating An example of the MAC superframe of the duration of each destination; FIG. 27 shows a modification of the frame of FIG. 26; FIG. 28 shows an explanation of specifying different durations for multiple destinations according to the seventh embodiment of the present invention Figure 29 is a flowchart showing the operation of the receiving terminal according to the seventh embodiment of the present invention; Figure 30 shows a structural example of a wireless communication system to which the present invention is applied; Figure 31 shows another wireless communication system to which the present invention is applied Structure example; Figure 32 shows a sequence of QoS data frames with Ack policy "block confirmation" in IEEE802.11e; Figure 33 shows the eighth embodiment of the present invention, regarding multiple destinations with Ack policy "block confirmation" A data frame aggregation example; FIG. 34 shows a data frame sequence with Ack strategy "block confirmation" for multiple aggregation destinations according to the eighth embodiment of the present invention;

FIG. 35 shows an example of aggregation of data frames and block Ack request frames for multiple destinations according to the eighth embodiment of the present invention; FIG. 36 shows an example of aggregation of data frames and block Ack request frames for multiple destinations according to the eighth embodiment of the present invention. A sequence example of a block Ack request frame; Fig. 37 is an explanatory diagram of retransmission of ACK according to the ninth embodiment of the present invention; Fig. 38 shows an example of aggregation of multiple destinations according to the ninth embodiment of the present invention; Fig. 39 Figure 40 shows another example of ACK retransmission when multiple destinations are aggregated according to the ninth embodiment of the present invention; FIG. 40 shows another example of ACK retransmission when multiple destinations are aggregated according to the ninth embodiment of the present invention; FIG. 41 shows an example of a frame format in the case where the transmission side specifies the time to transmit ACK according to the tenth embodiment of the present invention; FIG. 42 shows the case where the transmission side specifies the time to transmit ACK according to the tenth embodiment of the present invention An example of the frame format below; FIG. 43 shows another example of the frame format in the case where the transmitting party specifies the time to transmit ACK according to the tenth embodiment of the present invention; FIG. 44 shows the tenth embodiment according to the present invention , Another example of the frame format in the case where the transmitting party specifies the time to transmit ACK; FIG. 45 shows the designation of ACK transmission time for multiple destinations according to the tenth embodiment of the present invention; FIG. 46 shows according to the present invention The eleventh embodiment is an example of a MAC superframe for multiple destinations considering QoS; FIG. 47 shows the eleventh embodiment of the present invention regarding simultaneous simulcast of multiple destinations considering QoS; 48 is a block diagram of a communication device (access point) according to the twelfth embodiment of the present invention; FIG. 49 is a block diagram of a communication device (terminal) according to the twelfth embodiment of the present invention; An example of the frame format; Figure 51 shows an example of the first PHY frame format;

Fig. 52 shows an example of the format of the second PHY frame; Fig. 53 shows an example of the MAC frame format ; Fig. 54 shows an example of a communication system according to the twelfth embodiment of the present invention; Fig. 55A shows a partial confirmation ( Part Ack) format example, 55B shows a polling (no data) frame format example; Figure 56A shows a data frame format example, 56B shows a data + polling frame format example; Figure 57 shows an example of a MAC super frame; Fig. 58 shows an example of a MAC superframe including partial Ack+[data+polling]+data; Fig. 59 shows an example of a MAC superframe including partial Ack+[polling (no data)]; Fig. 60 shows an example of MAC superframe including [round An example of a MAC super frame of the query (no data)]; Fig. 61A shows an example of a QoS data frame, 61B shows an example of a QoS data + polling frame; Fig. 62 shows an example including a part of Ack+[QoS data+polling]+ An example of a MAC superframe of QoS data; Fig. 63 is a sequence diagram showing an example of PCF frame exchange; Fig. 64 is an explanatory diagram of a CAP/CFP/CF example (CAP generation); Fig. 65 shows an example of a polling sequence (according to (CFP start of beacon) Figure 66 shows an example of a polling sequence (generated according to the CAP of CTS-self, the partial Ack for STA1 and the polling for STA2 overlap together); Figure 67 shows an example of the polling sequence (including legacy STAs); Fig. 68 shows a modification of the sequence example shown in Fig. 65; Fig. 69 shows the case where the format of the MAC superframe header is the same as that of the MPDU; An example of the frame format of the MAC header; FIG. 71 shows an example of the generation of a MAC frame with a contracted MAC header and the process of reproducing the MAC header from the contracted MAC header according to the thirteenth embodiment of the present invention; 72 shows the first example of shrinking MAC header according to the thirteenth embodiment of the present invention; FIG. 73 shows the second example of shrinking MAC header according to the thirteenth embodiment of the present invention; FIG. 74 shows the tenth example of shrinking MAC header according to the present invention. The third embodiment is an example of the generation of a MAC frame with a contracted MAC header and the process of reproducing the MAC header from the contracted MAC header in the case of authentication of a cryptographic message.

detailed description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a block diagram showing the structure of a communication device according to a first embodiment of the present invention. The communication device 100 is a device that communicates with another communication device through a wireless link, and includes processing units 101, 102, and 103 corresponding to a physical (PHY) layer, a MAC layer, and a link layer, respectively. According to implementation requirements, these processing units are implemented as analog or digital electronic circuits, or as firmware to be executed by a CPU included in the LSI, or the like. The antenna 104 is connected to the physical layer processing unit 101. The MAC layer 102 has an aggregation processing device according to the present invention.

The aggregation processing device 105 generates a physical (PYH) frame including a plurality of medium access control (MAC) frames. The media access control frame is, for example, a MAC protocol data unit (MPDU), and may be a MAC service data unit (MSDU) that performs appearance modification and does not include any MAC header. The generated physical frame is processed by the physical layer processing unit 101 and transmitted through the antenna 104. In this specification, this communication system will be referred to as "frame aggregation". Frame aggregation is suitable for the next-generation high-throughput wireless LAN communication (IEEE802.11n standard) currently being standardized.

The basic frame format of a MAC superframe (MAC aggregation frame) has at least one MAC superframe header and at least one MAC superframe payload after the MAC superframe header.

The terminal receiving the MAC superframe judges whether the frame is self-addressed, and performs a cyclic redundancy check (CRC) calculation for each MPDU. After that, check the Ack policy bitmap field in the MAC superframe header. When the flag "1" that requires partial Ack appears, set the corresponding bitmap of the partial Ack frame to the value of "1" or "0" (when the CRC is calculated and received correctly, set "1". When the frame is When receiving error, set "0"). The MPDU whose Ack strategy bitmap is "0" hopes to be transmitted according to the Ack strategy "No Acknowledge", so it is set to a value of "0" regardless of the CRC calculation result.

In the case where the data source receives the partial Ack from the destination terminal, its own cached Ack strategy bitmap information conflicts with the partial Ack bitmap. Although Ack is required, the bit information of some Ack bitmaps is "0". Therefore, the corresponding data frame needs to be retransmitted.

The partial Ack in the frame aggregation will be explained below. The MAC layer of the terminal transmitting the MAC superframe determines each Ack strategy with respect to the data frame from the upper layer. In this case, when the Ack policy is specified in the partial Ack, it means "this data frame is the target of frame aggregation and requires an ACK response from the receiver".

As for the ACK mechanism for frame transmission, three mechanisms "standard acknowledgement" (standard Ack), "No acknowledgement" (No Ack), and "block acknowledgement" (block Ack) have been defined in IEEE802.11e. .

"Standard acknowledgment" is a standard data transmission method supported by IEEE802.11, in which after transmitting a unicast data (or management) frame, the terminal waits for a period of time until it receives an ACK frame from the destination terminal. When a timeout occurs, the random compensation procedure is executed again to retransmit the data frame. The data frame specified in the "standard confirmation" shall be excluded from the frame aggregation target and be transmitted according to the procedures in the existing IEEE802.11 standard.

"No Confirmation" is a data transmission method used when the transmission channel is fairly stable. According to this method, the terminal transmits a new data frame without waiting to receive an ACK frame from the destination terminal.

"Block Acknowledgement" is a data transmission method that continuously transmits unicast data frames every short interframe space (SIFS) (Short Interframe Space interval) in a burst mode. This method is used to use block Ack frames to achieve selective repeated retransmissions.

It should be noted that for various configuration examples of MAC superframe, response control (acknowledgement), retransmission control, QoS and simulcast, refer to the previous Japanese patent application of the applicant according to this application. Description of No. 2004-004847, 2004-063237, 2004-110446.

(First embodiment) The first embodiment relates to a communication device that includes variable-length bitmap information and the data length of the bitmap in the MAC superframe header when aggregating multiple MAC frames (MPDUs) into one physical frame . Specifically, the physical frame has variable-length bitmap information composed of bits corresponding to multiple MAC frames, and length information of the bitmap information.

As shown in Figure 2, when the Ack strategy bitmap 20 is included in the MAC superframe header 21 and transmitted to the MAC superframe, it is necessary to negotiate in advance between the transmitting/receiving terminals, and the receiving side needs to know The length of the Ack strategy bitmap 20. Various methods such as beacon or setting of traffic flow in HCCA of IEEE802.11e are regarded as negotiation methods. It should be noted that the present invention does not limit the length of the Ack strategy bitmap notification through negotiation to a specific method. However, as long as the receiver of the MAC superframe does not know the size information in advance, the Ack strategy bitmap 20 cannot be extracted correctly.

On the other hand, in the first embodiment, variable length bitmap information can be described, and the bitmap information field is defined as shown in FIG. 3. That is, the type of bitmap (Ack strategy bitmap, etc.) is defined by the bitmap ID field 31, for example, the length 32 of the actual bitmap information (bitmap information field 33) is indicated by bytes. Therefore, the Ack strategy bitmap can be hidden in a MAC superframe unit with variable length without any prior negotiation.

Examples of bitmap elements shown in FIG. 3 include "Ack strategy bitmap", "multi-address bitmap", etc., and they can be identified by bitmap ID 31. It should be noted that, needless to say, bitmaps (bitmap IDs) are not limited to them.

When 12 MPDUs are aggregated into a MAC superframe 40 as in the example in Fig. 4, as the Ack strategy bitmap, a bitmap with a size of 2 bytes is required. Therefore, the length of the bitmap information 33 Specify "2" in the field 32. The ID corresponding to the Ack strategy bitmap is specified in the location ID field 31.

(Second embodiment) The communication device according to the second embodiment is a MAC superframe receiving terminal, and uses a timer to manage time in relation to extracting a frame from the receiving buffer and forwarding the frame to each priority of the upper layer Communication equipment. The device is also a MAC superframe transmitting terminal, and each priority of extracting frames from the buffer and forwarding the frames to the upper layer indicates the communication device set by the timer to the receiver.

When multiple MAC frames are aggregated into one physical frame and transmitted according to the HCCA system of IEEE802.11e, each traffic stream (TS) is assigned a sequence number. The sequence number needs to be continuous, and the frame is buffered at the receiver, as shown in Figure 5.

In the example of FIG. 5, there are MAC frames 50, 51, 52 with three priority levels of "high priority", "medium priority" and "low priority" in the MAC superframe, and the header frame 53 is shown. , 54, 55 indicate the condition of retransmission error. When the sequence number is continuously received for each traffic flow, the MAC layer may forward the frame to the upper layer (for example, the network layer). However, in FIG. 5, subsequent frames (sequence number "2" and later) are waiting in the buffer (receive buffer status 56, 57, 58).

In IEEE802.11, when a frame with a sequence number smaller than that of the frame waiting in the receiver's buffer cannot be received, a timeout occurs, and all accumulated frames are forwarded to the upper layer (for example, IP). When the sliding window control is performed on each priority, the sequence number is managed on the transmitting/receiving side according to the priority. Therefore, there is a problem that a traffic flow that is sensitive to delay time and a traffic flow that has a considerable tolerance for delay time are handled in the same way.

In order to solve this problem, in the second embodiment, as shown in FIG. 6, on the MAC superframe receiver side, timers 1, 2, 3 are arranged in buffers 60, 61, 62 for each traffic flow, respectively. , And manage the buffer for each traffic flow according to the operation of the independently working timer. When the timers 1, 2, and 3 expire, the frames stored in the corresponding buffers 60, 61, 62 are released from the buffers and forwarded to the upper layer.

According to the delay limit field 71 of the traffic specification (TSPEC) 70 shown in FIG. 7A, the value (timeout time) set for each timer 1, 2, and 3 can be determined. -The maximum amount of time (microseconds) that is allowed to transmit MPDUs belonging to the TS in the TSPEC, measured between the time when the SAP arrives at the local sublayer and the time when the MSDU transmission or retransmission to the destination is successfully completed. Even before the retransmission upper limit time is reached, frames that exceed the delay limit are discarded on the transmitter (or receiver). The delay limit is set for each priority of the traffic flow (TS) and matched with the values set for timers 1, 2, and 3.

On the other hand, using the reserved field of the TS Info field 72 of TSPEC shown in FIG. 7B, the timeout period of each traffic flow on the MAC superframe receiver can be specified in millisecond units. On the other hand, a new field can be extended to TSPEC, and information for specifying a timeout can be added.

(Third embodiment) The communication device according to the third embodiment aggregates MAC frames with multiple priorities into one physical frame in order to transmit the frame, and then changes to The window size of each priority (the maximum number that can be transmitted at one time) for the communication device to retransmit the MAC superframe.

As shown in FIG. 8, it is assumed that multiple priority MAC frames (MPDUs) are combined into one physical frame and transmitted as one MAC super frame. In the example in FIG. 8, the window size (the number of frames that can be transmitted at one time) of the windows 81, 82, 83 is defined for each priority, and it is assumed that the high priority (for example, VoIP) is "3", and the medium priority ( For example, video) is "3", and low priority (for example, ftp) is "2". It is assumed that a negotiation is made in advance between transmitting/receiving terminals to determine the maximum number of MAC frames that can be aggregated into the MAC superframe 80. For example, it is assumed that the number is 8 (negotiation can be carried out using a beacon, or negotiation can be carried out at the setting time of the traffic flow, and the negotiation method is not specifically specified). Needless to say, the number is variable depending on the situation. In addition, as shown in FIG. 9, a case where the MAC super frame is retransmitted according to the partial Ack 90 is considered. That is, according to the partial Ack Part of the Ack bitmap 91 in 90, because the high-priority first frame and the low-priority second frame were not successfully received, the high-priority sequence number "1" and the low-priority sequence number "2" are Retransmit the target. On the other hand, a medium priority frame can be successfully received without requiring any retransmission. Therefore, the starting point of the windows 82 and 83 is moved, and a new frame can be aggregated corresponding to the window size to generate a MAC super frame 92 to be retransmitted. Here, as described above, the maximum number of MAC frames that can be aggregated is 8. However, the generated MAC super frame 92 as shown in FIG. 9 includes 6 MAC frames, and there is a waste of transmission channels. This is because the window size of each priority is always fixed.

In order to solve this problem, in this embodiment, the starting point of the sequence number of each priority is moved, and the window size is appropriately changed.

For example, as shown in FIG. 10, only one frame with a high priority can be combined, but there is a margin for the number of frames that can be aggregated into the entire MAC superframe. Thus, the maximum number of frames that can be aggregated is assumed to be the upper limit, and the number of aggregated frames with medium priority is increased as much as possible. In the stage of FIG. 8, the initial value of the transmittable frame with the medium priority is 3 frames. However, since only one frame with a high priority is transmitted, the window size of the medium priority window 100 is enlarged from 3 frames to 5 frames.

Thus, 8 frames corresponding to the maximum number of frames that can be aggregated are aggregated into the MAC superframe 101 generated according to the present embodiment, as shown in FIG. 9, in comparison with the MAC superframe 92 in which 6 frames are aggregated, Can improve transmission efficiency.

As a result of the performed retransmission process, more frames with high priority can be transmitted. Subsequently, the window size of each priority is returned to the initial value again (in this example, the high priority is returned to "3", the medium priority is returned to "2", and the low priority is returned to "2"), and the QoS data is returned to Aggregate into MAC superframes.

(Fourth embodiment) The fourth embodiment relates to the block Ack program. Fig. 11 shows a series of (immediate) standard block Ack. On the other hand, in IEEE802.11, as shown in FIG. 12, the QoS control field 121 is added to the MAC header 120, and the ACK policy 122 is specified, so various acknowledgment modes such as "No Ack" (not required Any Ack transmission), "Block Ack" and "Standard Ack". Here, regarding the QoS data designated by the block Ack, as shown in FIG. 11, after transmitting the data every short interframe space (SIFS), a block Ack request 110 is transmitted. The transmitting terminal receives the block Ack 111 in response to the block Ack request from the destination terminal. The block Ack request 110 and the block Ack 111 need to generate data for each traffic identifier (TID) priority.

[Aggregation example 1 of block ACK] In aggregation example 1 of block Ack, the QoS data frames of the block ACK target to be transmitted at SIFS intervals are aggregated into one physical frame and transmitted.

For example, as shown in FIG. 13, after the MAC superframe header 130, the aggregated ACK policy is block Ack, and is limited to the MAC frame 131 having QoS data of the same destination.

As shown in FIG. 14, a MAC super frame 140 in which QoS data on TID1 is aggregated is first transmitted. Subsequently, after the SIFS period, a MAC super frame 141 in which QoS data on TID2 is aggregated is transmitted. After the SIFS period, a block Ack request 142 for TID1 is transmitted. In addition, after the SIFS period, the block Ack 143 for TID1 is transmitted. After the SIFS for the block Ack 143 of TID1, the block Ack request 144 for TID2 is transmitted. In addition, after the SIFS period, the block Ack 145 for TID2 is transmitted. It should be noted that after sending the QoS data corresponding to the TID, the timing of the transport block Ack request does not need to be particularly limited. That is, in FIG. 14, after the SIFS period after the MAC superframe 140 is transmitted, the block Ack request 142 may be transmitted.

According to the aggregation example 1 of the block Ack, multiple QoS data frames of the block Ack target are aggregated into one MAC super frame and transmitted, so that the transmission efficiency can be improved.

[Aggregation example 2 of block Ack] In aggregation example 2 of block Ack, as shown in FIG. 15, in addition to the aggregation of the QoS data frame 150, the block Ack request frame 151 is also aggregated into one physical frame (MAC superframe )in.

In the case where the maximum aggregation number of MAC superframes is, for example, 8 frames (assuming that the maximum aggregation number is recognized in advance through negotiation), seven QoS data are aggregated, and one block Ack request frame is attached to the aggregate PSDU (PHY Service Data Unit) The tail. According to the MPDU length field 152 of the MAC superframe header, the block Ack request frame 151 is properly processed on the receiving side. Here, the block Ack request cannot be aggregated before the QoS data. This is because, as shown in the block Ack request frame 151, in order to determine the start sequence number of the receiving state target of the QoS data according to the block Ack start sequence control field, it is necessary to perform QoS data processing (error calculation) in advance.

Fig. 16 shows the block Ack sequence of this example. In addition to multiple QoS data frames, block Ack requests are further aggregated into MAC superframes 160 and 161, so that transmission efficiency can be improved.

[Block ACK aggregation example 3] In the block Ack aggregation example 3, the QoS data frame and the corresponding block Ack requests made with respect to multiple TIDs are aggregated into one physical frame and transmitted.

As shown in FIG. 17, the QoS data with the Ack policies "block confirmation" 170, 171 about different TIDs, and the corresponding block Ack requests 172, 173 are aggregated into one physical frame, thereby generating a MAC superframe. As shown in FIG. 18, when the generated MAC super frame is transmitted, the transmission efficiency can be further improved.

[Block Ack aggregation example 4] When the Ack policy "No Acknowledgement" MAC frame that does not require any Ack, and the Ack policy "Block Acknowledgement" MAC frame that requires an acknowledgment corresponding to the MAC frame transmitted in the burst mode are mixed Next, the communication device according to the aggregation example 4 of the block Ack aggregates MAC frames.

As shown in FIG. 19, the MAC superframe of this example has a bitmap ID field 190, a length (bitmap length) field 191, and a variable length bitmap (bitmap information) 192. In the bitmap ID 190, an identifier (ID) indicating that the bitmap type (bitmap element) is a combined strategy of the Ack strategy "No Confirmation" and the Ack strategy "Block Confirmation" is described. In the length field 191, the length of the bitmap information 192 is described in, for example, byte units.

In the bitmap information 192, among a plurality of MAC frames aggregated in the MAC superframe, information on the MAC frame identified as "No Acknowledgement" and the MAC frame for "Block Acknowledgement" is described. For example, in the frame aggregation example shown in Figure 19, a total of 8 MAC frames are aggregated, of which 3 frames (QoS data 1-3) need to be confirmed by block Ack, and 5 frames (Figure 19 only shows QoS data 1, 2) No ACK is required.

In this case, for example, when the bit of the required block Ack is 1, for example, the bitmap information 192 indicates "11100000" and is set on the transmitting side (note that, needless to say, the bit may be a negative logical value) . The receiving terminal generates a block Ack according to the bitmap information 192, and returns the ACK to the transmitting terminal.

For example, as shown in FIG. 20, assuming that the MAC super frame 2002 is transmitted from the transmitting terminal, after the MAC super frame 2002, the block Ack request 2003 is transmitted from the transmitting terminal. According to the bitmap information 2001 included in the MAC super frame 2002, the receiving terminal judges that the first three MAC frames in the MAC super frame 2002 require the block Ack in the MAC super frame 2002, and the remaining 5 MAC frames do not require any ACK. In response to the block Ack request 2003 from the transmitting terminal, the receiving terminal returns the block Ack 2004 information.

According to the aggregation example 4 of the block Ack, the transmission efficiency can be improved by the aggregation of MAC frames with different Ack strategies. It should be noted that the bitmap information does not have to have a variable length as in this example, it can have a fixed length. In this case, no length information is required.

It should be noted that the aggregation example 4 of the block Ack can be realized by the aggregation of QoS data and the frame requested by the block Ack, or by the aggregation of the QoS data and the frame requested by the block Ack for each of the multiple TIDs. In this case, it is possible to support the transmission of both "No Confirmation" and "Block Confirmation" Ack strategies at the same time.

(Fifth embodiment) When the MSDU size of the traffic flow is fixed in order to aggregate multiple MPDUs into one physical frame, the communication device according to the fifth embodiment includes information indicating the number of MPDUs in the MAC superframe header.

In IEEE802.11e, when communicating using HCCA, a QoS station (QSTA) sets a traffic flow in a QoS access point (also called a hybrid coordinator: HC). Fig. 21 shows the TSPEC 210 used when setting the traffic flow. TSPEC has a nominal MSDU size field 211. The nominal MSDU size field 211 is 2 bytes long, and contains an unsigned integer that specifies the nominal size of the MSDU belonging to the TS in bytes according to the traffic specification. If the fixed subfield is set to 1, the size of the MSDU is fixed and indicated by the size subfield 212. If the fixed subfield is set to 0, the size of the MSDU may not be fixed.

When the size of the MAC protocol data unit (MPDU) aggregated into the MAC superframe has a variable length, the MPDU length field for identifying each segment is necessary. When it is informed in advance that the MSDU has a fixed length when setting the traffic flow, the MPDU length field can be omitted, and the number of aggregated MPDUs can be set instead. Therefore, the size of the MAC superframe header in which the MPDU length field is stored can be reduced.

Fig. 22 shows a MAC superframe in which the MPDU length is a fixed length according to the fifth embodiment. According to the field indicating the number of aggregated MPDUs (the aggregated number field in FIG. 22) 221 in the MAC superframe header 220, MPDUs 1, 2, 3... can be extracted. It should be noted that in the example of FIG. 22, the frames with the equivalent TSID 222 can be aggregated into one MAC superframe.

In the MPDU, the MAC header (including the QoS control field in IEEE802.11e) and the FCS (Frame Check Sequence) are added to the MSDU. The receiving terminal of the MAC super frame first calculates the error of the MAC super frame header (using the header CRC 223). When the frame can be received correctly, the TSID of the MPDU aggregated in the MAC superframe header is determined according to the TSID field 222. When the TSID information is obtained, the fixed length of the MSDU is detected from the setting of the traffic flow. On the other hand, the length of each MPDU corresponds to the sum of the nominal MSDU length (fixed) and the MAC header length including the QoS control field and the FCS length. The receiving terminal judges each receiving state of the MPDU, generates a partial Ack according to the result, and returns an acknowledgement to the transmitting terminal of the MAC superframe.

For example, in the case where the transmission control protocol (TCP) is used by an application such as the file transfer protocol (FTP), the length of the data frame is sometimes shortened at the end of the communication (for example, the end of the file download). When a fixed-length nominal MSDU length is specified on the traffic flow, the last frame cannot be transmitted/received in the MAC layer. In this case, when the MSDU is generated, the bit string of "0" is filled to the rear to realize a fixed-length MSDU. The receiver uses the length field of the IP header in the upper layer from the MAC to extract the payload with the correct length. Since the MSDU has a fixed length specified when establishing a traffic flow, it can correctly communicate in the MAC layer.

In addition, when multiple traffic flows are established, and all the nominal MSDU length fields corresponding to each traffic flow are designated as fixed lengths, multiple MPDUs with different traffic flow identifiers (TSID) are aggregated to form one MAC super frame, and the MAC super frame can be transmitted as a physical frame.

Another communication device according to this embodiment aggregates MAC frames designated as fixed lengths among a plurality of traffic flows into one physical frame, and combines information indicating a traffic flow identifier and information indicating each traffic flow. Information on the number of aggregated MPDUs is included in the header in order to communicate the information to the communication device.

Figure 23 shows the aggregation of fixed-length MAC frames when multiple TSIDs are mixed. In this example, a field (the number of TSIDs) 231 indicating the number of aggregated TSIDs is added to the MAC superframe header 230. The MAC superframe header 230 has a variable length field 232, which has a pair of TSIDs, and a field indicating the number of aggregated MPDUs relative to the TSID according to the number of TSIDs.

The terminal receiving the MAC superframe detects the number of aggregate TSIDs and the number of MPDUs according to the MAC superframe header 230. Regarding the length of the MPDU with a fixed length, the total value of the MPDU length (which is the fixed MSDU length, the sum of the MAC header and the FCS) is calculated for each traffic flow in the same manner as described above. When the length of the data frame from the upper layer is shortened as in the above-mentioned FTP application, "0" is padded to the back of the MSDU, and a fixed length can be set. Even in this case, since the field value indicating the length of the IP data message of the IP header cannot be rewritten, the data payload of the upper layer is not affected. It should be noted that as far as the format of the MAC superframe is concerned, the MPDU length field of the MAC superframe header can be used to aggregate MPDUs with different lengths. As in this embodiment, MPDUs with a fixed length are aggregated, and information indicating the number of MPDUs can be added to the MAC superframe header. The format to be adopted by the MAC superframe header is based on the assumption that the transmitter/receiver is negotiated in advance (a specific negotiation method different from the target of this embodiment).

The following sixth to eleventh embodiments involve aggregation of multiple MAC frames, where multiple destinations are targets, and simultaneous simulcast transmission is performed.

In general, the transmission of one MAC frame to a destination terminal in the MAC layer of the wireless LAN is called "unicast", and the transmission of one MAC frame to which multiple destinations are receiving targets is called "multicast". ". On the other hand, in the description of the embodiment of the present invention, a transmission in which a plurality of MAC frames are aggregated into one physical frame, and a plurality of destinations are reception targets will be referred to as "simultaneous simulcast."

Here, consider a case where MAC frames with multiple destinations are simply aggregated into one physical frame, and simulcast from the AP to each STA at the same time. In this case, in the case of simultaneous simulcast MAC superframes, partial Ack frames from each receiving terminal collide, so that communication cannot be performed correctly. According to the definition of IEEE802.11, the STA that receives the unicast data frame does not confirm the channel status and returns an ACK frame immediately after the SIFS interval has passed. Therefore, the possibility of collision of ACK frames from multiple STAs is extremely high.

In order to solve this problem, in the communication system according to the embodiment of the present invention, multiple destination MAC superframes are simultaneously simulcast from AP to STA. When each STA transmits an ACK frame to the AP, the transmission timing should preferably be shifted in order to avoid collision with an ACK frame from another STA (this will be referred to as a bad time ACK).

When the other terminal returns to the partial Ack at a bad time, each terminal appropriately sets the NAV and stops the transmission of data frames and the like. It should be noted that the NAV duration is determined by the number of remaining terminals×(SIFS+ACK transmission time). In this embodiment of the present invention, it is assumed that the transmission rate of the ACK from each STA is equal. However, if the ACK transmission rate of each STA is different, it is better to calculate the corresponding ACK transmission time.

(Sixth embodiment) When aggregating MAC frames for multiple destinations into one physical frame to transmit the frame, the communication device according to the sixth embodiment adds information indicating the ordinal number corresponding to the destination of the MAC frame The front part of each MAC frame.

When MAC frames for multiple destinations are aggregated into one physical frame and transmitted, information (multiple access bitmap) indicating the division of each destination is considered to be added to the MAC superframe header. However, in this embodiment, as shown in FIG. 24, an additional field 240 with a size of about 1 byte is added to the front of each MAC protocol data unit (MPDU) instead of the multiple access bitmap. Each added field 240 describes information indicating the ordinal number of the destination corresponding to the MPDU (referred to as a POS (location) field).

When constructing a physical frame including multiple media access control frames with different destinations, the multiple access bitmap indicates that it is related to the position of the frame whose destination has changed compared with the destination of the previous MPDU in the physical frame. Information. Specifically, this information contains bits corresponding to aggregated MAC frames and indicates multiple destination divisions.

The example in FIG. 24 shows a case where 8 MPDUs are aggregated, but the number is not fixed. For example, in the example of FIG. 24, four MAC frames for the destination (DEST) "α" from the head are aggregated, and the information "1" indicating the first destination is added to each front part. In the POS field. The information "2" indicating the second destination is described in the POS field at the front of the subsequent MAC frame to the destination β. Here, if the values of all POS fields are "1", it means that only MAC frames for one destination are aggregated in the MAC superframe.

When the MAC superframe header has an MPDU length field, the length of each MAC frame is described in this field, and the data frames aggregated in the MAC superframe payload can be cut according to the length. On the other hand, in this example in which a POS field is added to the front of the MPDU, a value equal to (POS field (one byte at this time) + MPDU length) is described in the MPDU length field. In this embodiment, the FCS field is calculated in all fields of the POS field, the MAC header and the frame body field. Therefore, the error of the POS field relative to the MAC header or the MAC frame body can be detected.

According to the multiple access bitmap in the MAC superframe header, it is possible to determine the existence of MPDUs for multiple destinations, but a format can be set independently of the multiple access bitmap. For example, as shown in FIG. 25, a destination number field 251 indicating the number of aggregation destinations is added to the MAC superframe header 250. When the value of field 251 is 1, there is only one type of address in the MAC superframe. The subsequent destination field 252 and the POS field 253 indicate the destination address and the ordinal number of the destination. For example, in FIG. 25, it is assumed that the MPDU for the destination "α" and the MPDU for the destination "β" are aggregated. The value "2" is described in the number of destinations field 251 in order to indicate that there are two destinations. The destination field 252 and the POS field have a fixed length of 6 bytes (for MAC address) and 1 byte, respectively. In the example of FIG. 25, the MAC address of the destination α is described in the destination 1 field, and the information indicating the ordinal number of the destination α is described in the POS1 field. The MAC address of the destination β is described in the destination 2 field, and the information indicating the ordinal number of the destination β (2 in this example) is described in the POS2 field.

It should be noted that, assuming that the destination field 252 in the MAC superframe header 250 is described according to the order of aggregated MAC frames, the POS field 253 is not required.

(Seventh embodiment) When aggregating MAC frames for multiple destinations into one physical frame in order to transmit the frame, the communication device according to the seventh embodiment includes the duration of the ground channel usage for the multiple destinations in the MAC super In the frame header.

In this embodiment, when simulcasting MAC superframes to multiple destinations at the same time, the confirmation frame from each destination does not have to be equal to the duration value in the MAC header.

The seventh embodiment deals with the case where each ACK has a variable length. As shown in FIG. 26, the channel usage duration (duration 1, duration 2) regarding each destination is described in the MAC superframe header 260. Usually in the IEEE802.11 standard, it is described in the duration field of the unicast data MAC frame (short interframe space (SIFS) time + ACK transmission time). The calculation of the duration value of the data frame is based on the rules for determining the data rate of the control frame in the transmission frame exchange sequence. It should be noted that, as shown in FIG. 27, a MAC superframe header 270 may be constituted. In this case, no multiple access bitmap is included, and the channel usage duration is specified together with the destination. When it is assumed that MPDUs are aggregated for each destination in the MAC superframe, the destination field in the MAC superframe header 270 is not particularly required.

The size of the partial Ack response to the MAC superframe increases in proportion to the number of aggregated MPDUs. For example, when the number of MPDUs aggregated in the MAC superframe is 8, the size of the partial Ack bitmap of the partial Ack response is 1 byte. However, when the number of aggregated MPDUs is 9 or more (within 16), the partial Ack bitmap requires a size of 2 bytes. That is, the MAC superframe transmitting terminal can estimate each transmission time of the difference-time ACK from the destination according to the information indicating the number of MPDUs to be aggregated and transmitted for each destination.

For example, as shown in FIG. 28, consider the case where 16 MPDUs are aggregated and delivered to two destinations DEST1 and DEST2 (13 MPDUs for DEST1 and 3 MPDUs for DEST2). Since the length of the partial Ack response generated by each destination is different, the corresponding duration values 280 and 281 are determined. In the case where 13 MPDUs are aggregated and delivered to DEST1, the size of the partial Ack bitmap is 2 bytes. When 3 MPDUs are aggregated and delivered to DEST2, the size is 1 byte.

In the example of FIG. 28, after receiving the simultaneous simulcast MAC superframe, after the SIFS interval, the terminal of DEST1 returns the partial Ack 282. Next there is the address of the terminal of DEST2. After waiting for a duration of 1 (until the transmission of the partial Ack of DEST1 ends) + the value of the SIFS time, the terminal transmits its own partial Ack 283. After completing the transmission of the partial Ack 282, DEST1 sets a network allocation vector (NAV) 284 corresponding to the sum of the remaining duration values. Its purpose is to set the NAV of the sum value of the duration field of the MAC superframe header on the terminal that does not exist in the MAC superframe. In the example of FIG. 28, the sum of the settings of terminals (other STAs) other than DEST1 and DEST2 and the value of the duration of the MAC superframe header (the value obtained by adding the values of duration 1 and duration 2 ) Corresponding to NAV 285.

Fig. 29 is a flowchart showing the operation of the receiving terminal. After receiving the MAC superframe with multiple destinations (step S1), the receiving terminal calculates the error of the MAC superframe header (step S2). When there is an error as a result of the error calculation, the MAC superframe is discarded (step S3). After the channel becomes idle, the duration carrier detection of the extended interframe space (EIFS) is performed (step S4).

When there is no error in the header, an error is checked for each MAC frame (step S5). Subsequently, the number (M) of destinations of the MAC frames aggregated in the MAC superframe and the ordinal number (N-th) of the MAC address of the own terminal that exist are checked (step S9).

For example, the MAC frames for the receiving terminal corresponding to DEST1 are first aggregated (N=1), in a sequence similar to the usual frame aggregation, after the SIFS interval (step S15), the receiving terminal transmits a partial Ack frame (or in IEEE802 The block Ack defined in .11e) (step S16). After that, the terminal sets the NAV corresponding to the total duration of the value of duration 2-M, and stops the transmission of the data frame, and at the same time, another terminal (DEST2, other STA) returns to the partial Ack (step S17).

After DEST1 transmits the partial Ack (step S11), after the SIFS interval has elapsed (step S12), the next aggregated DEST2 transmits the partial Ack (step S13). In addition, after its own terminal transmits the partial Ack, the NAV corresponding to the total duration of the value of duration N+1-M is set (step S14).

In the case where the MAC frame whose terminal is the destination does not exist in the MAC superframe, the NAV corresponding to the total duration of the value of duration 1-M is set (step S7).

Figures 30 and 31 show examples of the configuration of a wireless communication system to which the present invention is applied. The communication system in which multiple MAC frames are aggregated into one physical frame is suitable for downlink and uplink transmission between AP (or IEEE802.11e hybrid coordinator: HC) and STA, and STAs are based on independent basic Ad hoc communication of service set (IBSS) and direct link establishment (DLS) communication between QSTA and QSTA according to IEEE802.11e.

(Eighth Embodiment) The eighth embodiment relates to block Ack in the case where simulcast is performed. The communication device according to the eighth embodiment aggregates MAC frames with Ack policy "block acknowledgment" for multiple destinations into one physical frame to transmit the frame, transmits a block Ack request to each destination, and receives the block Ack. Another communication device according to this embodiment aggregates MAC frames with Ack policy "block acknowledgment" for multiple destinations and block Ack frames into one physical frame to transmit the frame, and receive the frames from multiple destinations. Block Ack of the land.

As shown in FIG. 32, in IEEE802.11e, a QoS data frame with an Ack policy "block acknowledgment" is transmitted every SIFS interval.

In this embodiment, QoS data frames for multiple destinations are aggregated into one physical frame, thereby improving transmission efficiency. As shown in FIG. 33, information indicating the existence of multiple destinations is added to the MAC superframe header, and the QoS data frame is divided for each destination and aggregated into the payload part. At this time, the MAC superframe can be constructed as shown in the above-mentioned Figs. 24 and 25. There are no special restrictions, as long as the receiving terminal of the MAC superframe can determine the existence and relative positions of multiple destinations. In the example of FIG. 33, a multiple address bitmap 331 is used.

In addition, as shown in FIG. 34, the block Ack target QoS data frames for multiple destinations are aggregated into one physical frame and transmitted as a MAC super frame 340, so the transmission efficiency can be improved. FIG. 34 shows that in response to the block Ack requests 341, 342 after the MAC superframe 340, the block Ack 343, 344 is transmitted from the corresponding destination (QSTA1, QSTA2).

In addition, as shown in FIG. 35, it is preferable to aggregate not only the QoS data frames, but also the block Ack requests 350, 351. In this case, divide frames and requests for each destination, aggregate them, and describe the frame size of each frame (QoS data, block Ack request). Therefore, the MPDU is appropriately cut off, and the block Ack can be transmitted at a different time. In the example of Figure 36, three data frames for QSTA1, a block Ack request for QSTA1, three data frames for QSTA2, and a MAC superframe 360 for the block Ack request for QSTA2 are generated as a physical frame. Simultaneous broadcast from HC to QSTA1 and 2. The blocks Ack361 and 362 from the corresponding QSTAs are received at a time difference, so the transmission efficiency of the entire system is improved.

(Ninth embodiment) When multiple MAC frames for a certain destination are aggregated into one physical frame and transmitted, but after the SIFS interval, the terminal of the destination cannot transmit ACK, according to the ninth embodiment The communication device can transmit the ACK frame again within the NAV duration set in advance to be slightly longer.

When multiple MAC frames for a certain destination are aggregated into one physical frame and transmitted, when the terminal of the destination cannot transmit ACK after the SIFS interval, another communication device according to this embodiment can The MAC frame for another destination is aggregated into one physical frame in order to transmit the frame, and the ACK frame is transmitted at a poor time.

In addition, when multiple MAC frames for multiple destinations are aggregated into one physical frame and transmitted, when no ACK can be transmitted after the SIFS interval after the MAC superframe is received by the first aggregation destination, according to this Another communication device of the embodiment sequentially transmits ACK frames from the first destination within a NAV duration set in advance to be slightly longer.

In the ninth embodiment, in the case of a turbo code that requires more time in the decoding process or a low-density parity check (LDPC) code is used in the communication device, the short-frame interval determined in IEEE802.11 is solved. Issues that cannot be processed in time within the SIFS. After multiple MAC frames are aggregated into one physical frame and transmitted to a certain destination, after the SIFS interval, the destination terminal must return an ACK, but for the decoding process in some cases, no ACK can be transmitted.

In this case, as shown in FIG. 37, the value of the duration set for terminals other than the destination terminal is set to be slightly longer, and therefore the destination terminal is given an opportunity to transmit the ACK frame again. Terminals other than the destination terminal set a network allocation vector (NAV) 370 of a certain duration and stop transmission. Therefore, even when the destination terminal transmits an ACK frame, any collision does not occur. In the case where it is assumed that a certain destination performs an encoding process that usually requires a long processing time, and the ACK cannot be returned after the SIFS interval, another terminal is notified of the result in the basic service set (BSS) in advance. In the example of FIG. 37, only MAC frames that are aggregated to one destination are aggregated. Receiving terminals other than the destination terminal set a duration NAV that is twice the sum of the SIFS interval and the ACK transmission time, for example. Here, the double value is not particularly fixed, and a period of time duration can be notified between wireless terminals. The MAC superframe transmitting terminal may describe an appropriate value in the duration field of the MPDU.

In the state of FIG. 37 (that is, in the state where only MAC frames of one destination are aggregated in the MAC superframe), it is generally considered that a longer decoding time is required. In this case, when frames to multiple destinations are aggregated as shown in FIG. 38 (for example, frames sent to DEST2, DEST3), after the SIFS interval, the possibility that the first destination terminal can transmit ACK increases . This is based on the assumption that the encoding process is performed in symbol units, and generally less processing time can be used to transmit ACK, as long as the entire MAC superframe is guaranteed to be used for the frame to the first destination (in the example of FIG. 38, Three MPDU) decoding time.

Now, consider a case in which when MAC frames for multiple destinations are aggregated into one physical frame and transmitted, after the SIFS interval, the first destination cannot transmit any ACK. In this case, the terminal does not need to notify the other terminal in advance of the information indicating that no ACK can be transmitted in the SIFS interval. As shown in FIG. 39, the terminals DEST2, DEST3, and other STAs other than the first aggregated terminal set NAV390, 391, and 392 larger than usual. The NAV set to be slightly larger corresponds to (SIFS + ACK transmission time of the first destination). In the example of FIG. 39, since another terminal has extended many NAVs in advance, after the SIFS interval after the MAC superframe has been received, no ACK can be returned, the first destination can transmit the ACK 393 again. It is to be noted that, in the example of FIG. 39, after all other terminals finish transmitting ACK, the first destination transmits ACK. However, as shown in FIG. 40, the ACKs 400, 401, 402 may be transmitted sequentially starting from the first destination.

(Tenth Embodiment) The tenth embodiment relates to the designation of the transmission timing of ACK. The communication device according to the tenth embodiment aggregates MAC frames for multiple destinations into one physical frame to transmit the frame, and includes information specifying the time to transmit ACK in the MAC superframe with respect to each destination terminal In the header.

Instead of calculating the timing for transmitting the ACK at the receiving terminal of the MAC superframe, this embodiment specifies the time for transmitting the ACK in advance on the MAC superframe transmitter. Figures 41-44 show the frame format when the transmitter specifies the timing for transmitting ACK.

41 and 42 show an example in which time designation information of ACK transmission timing is included in MAC superframe headers 410, 420. The ACK transmission start time indicates the timing at which each destination should transmit the ACK. Specifically, after receiving the MAC superframe, ACK is transmitted after SIFS+N (microseconds), and the value of N is described in the ACK transmission start time. In this case, for the ACK transmission start time 1 of the first destination, "0" is designated. On the other hand, a specified method of returning an ACK after receiving the MAC superframe N microseconds can be performed. Using the size of the indication part Ack, the physical transmission rate and the ordinal number of the destination, the transmission side calculates the second destination and subsequent ACK transmission timing. The transmission end time indicates the predetermined time to end the transmission of all ACKs. This is information indicating the time (in microseconds) required from the receipt of the MAC superframe to the transmission of all ACKs. It should be noted that if the MPDUs are aggregated in the order of destinations, the destination field of the MAC superframe header 420 of FIG. 41 is not required, but this field is necessary for another case (the case where the order of the aggregated MPDUs is not consistent) information.

FIG. 43 shows that the ACK transmission start time 430 and the transmission end time 431 are added to the front part of the MPDU aggregated in the MAC superframe. In this case, the value of the MPDU length field is increased by the field lengths of the ACK transmission start time 430 and the transmission end time 431. The FCS is calculated in the ACK transmission start time 430 and the ACK transmission end time 431 and all fields of the MPDU. FIG. 44 shows that the ACK transmission start time 440 is added to the front part of the MPDU aggregated in the MAC superframe, and a transmission end time 442 is added to the MAC superframe header 441. In FIG. 43, the FCS calculation in the MAC superframe payload is performed with respect to the target including the time field, the end field, the MAC header, and the MAC frame payload. In Figure 44, the calculation target of FCS includes time field, MAC header and MAC frame payload.

As shown in FIG. 45, the receiving terminal of DEST1 starts transmission of ACK (partial Ack) at the ACK transmission start time 450, and sets the NAV 453 after transmitting the ACK until the transmission end time 452. The receiving terminal of DEST2 starts transmission of ACK (partial Ack) at the ACK transmission start time 451. The transmission end time of the ACK 456 is consistent with the transmission end time 452, and NAV is not set. Another terminal (other STA) that is not the target of frame reception sets the NAV 454 until the transmission end time 452.

(Eleventh embodiment) The communication device cluster indication according to the eleventh embodiment, for each priority, MAC frames that require and do not require ACK for multiple destinations, aggregate the frames into one physical frame, And transmit the frame. Each destination terminal transmits ACK at short notice.

As shown in FIG. 46, the MAC superframe header 460 includes both the multiple access bitmap 461 and the Ack policy bitmap 462. Each receiving terminal can appropriately set NAV according to the multiple access bitmap 461, and calculate the transmission timing of ACK. On the other hand, according to the Ack strategy bitmap 462, when all MPDUs to a certain destination have an Ack strategy of "No acknowledgment", the destination does not transmit any ACK, and ACK control is performed in a manner that the subsequent destination terminal transmits ACK.

For example, as shown in FIG. 47, since all MPDUs to DEST2 have an Ack policy of "No Acknowledgement", DEST3 can transmit ACK 471 immediately after the transmission of ACK 470 is ended. The terminal of DEST2 sets NAV 472 until the transmission of all ACKs ends. It should be noted that the header structure of the MAC superframe shown in FIG. 46 is only an example. When the above header formats are appropriately combined, or the ACK transmission timing is specified, efficiency can be improved.

(Twelfth Embodiment) FIG. 48 is a block diagram showing the structure of a communication device (access point) according to a twelfth embodiment of the present invention. The communication device 100A is a device that communicates with another communication device through a wireless link, and includes processing units 101A, 102A, and 103A corresponding to a physical (PHY) layer, a MAC layer, and a link layer, respectively. According to implementation requirements, these processing units are implemented as analog or digital electronic circuits, or as firmware to be executed by a CPU included in the LSI, or the like. The antenna 104A is connected to a physical layer processing unit 101A ("processing unit" will be omitted below). The MAC layer 102A has an aggregation processing device 105A according to the present invention. The aggregation processing device 105A includes a carrier detection control device 106A, a medium access control device 108A, a polling/data transmission schedule control device 1051, and a retransmission control device 107A. The physical layer 101A is configured to be able to handle two physical layer protocols. In order to process the corresponding protocol, the physical layer 101A has a first type of physical layer protocol processing device 109A and a second type of physical layer protocol processing device 110A. It should be noted that in this implementation, the first type of physical layer protocol processing device 109A and the second type of physical layer protocol processing device 110A usually share a circuit, so they do not need to exist independently.

In this embodiment of the present invention, the first physical layer protocol is defined by IEEE802.11a, and the second physical layer protocol is assumed to be a so-called multiple-input multiple-output (MIMO) adoption using multiple antennas on the transmitting side and the receiving side. Agreement. Even when the frequency bands are kept equal, an increase in transmission capacity that is basically proportional to the number of antennas can be predicted. Therefore, MIMO is one of the effective technologies targeting the higher throughput of IEEE802.11. It is assumed that the link layer 103A has a normal link layer function defined by IEEE802. The technology used to increase the transmission rate is not limited to MIMO. For example, a method of increasing the frequency band occupancy rate, or a combination of this method and MIMO may also be used.

FIG. 49 is a block diagram showing the structure of a communication device (terminal) according to the present embodiment. The main difference from the communication device (access point) 100A shown in FIG. 48 is that the MAC layer 102 of the access point 100A has polling/data transmission schedule control means 1051 capable of performing polling control, while the MAC layer of the terminal 100S The layer 102S has a data transmission schedule control device 1052 without polling control. The other structural components are similar to those of the access point 100A, and the tail of the reference number is changed to "S".

FIG. 50 shows an example of a frame format used by the communication device according to this embodiment. The frame format 200 schematically represents the frame structure associated with the physical layer and the MAC layer. More specifically, the format is assumed to be a format that conforms to IEEE802.11, or an extended version thereof. It should be noted that IEEE802.11 frames are roughly divided into three categories: control frames; management frames; and data frames; in the present invention, it is assumed that this embodiment is mainly applied to data frames and control frames, but it is not necessary to exclude management frames. application. As shown in FIG. 50, the frame format 200 includes a PHY header 201, a MAC superframe header 202, a MAC superframe payload 203, and a PHY trailer 204. The MAC superframe header 202 and the MAC superframe payload 203 correspond to the PHY payload described later.

The PHY header 201 is processed by the physical layer 101 of the receiving communication device (access point, or terminal). That is, the physical layer 101 performs frame header detection, carrier detection, timing synchronization establishment, automatic gain control (AGC) of the amplifier, tracking of the transmitter carrier frequency (automatic frequency control), transmission channel estimation, etc. The physical layer 101 also detects the modulation scheme and coding rate, transmission rate, and data length of the PHY payload after the PHY header 201.

Fig. 51 shows an example of the format of the first PHY frame. When the communication device according to the present invention communicates with an existing communication device, the first type of PHY frame is used, and the first type of PHY frame is processed by the first type of physical layer protocol processing device 109 of the physical layer 101 (here adopted in accordance with IEEE802.11a Communication). As shown in FIG. 51, the first type of PHY frame, that is, the first type of PLCP frame includes a physical layer convergence protocol (PLCP) 301, a PLCP long preamble 302, a signal field 303, and a data field 304. The signal field 303 corresponds to the PLCP header 305 and has a transmission rate field 306 and a data length field 307 as shown in the figure. It should be noted that, needless to say, the first type of PHY frame is not limited to the PYH frame defined by IEEE802.11a.

Fig. 52 shows an example of the format of the second PHY frame. The second type of PHY frame, that is, the second type of PLCP frame has a first header part 401 for the first physical layer protocol, and a second header part 402 for the second physical layer protocol. The first header part 401 and the second header part 402 are arranged in time series and correspond to the PHY header 201 shown in FIG. 50.

In addition, the second type of PHY frame has a PHY payload 403 after the second header part 402, and tail bits and padding bits 404. The PHY payload 403 corresponds to the MAC superframe header 202 and the MAC superframe payload 203 shown, and corresponds to the PLCP service data unit (PSDU) in the format of the physical layer. The tail bits and padding bits 404 correspond to the PHY tail 204 of FIG. 50.

The first header part 401 for the first physical layer protocol contains a PLCP short preamble 405, a PLCP long preamble 406, and a signal field 407. The signal field 407 corresponds to all or part of the PLCP header, so that at least the transmission rate field 408 and the data length field 409 are set with valid values in order to perform physical carrier detection. In the signal field 407, the information content, modulation scheme, etc. are the same as those of the PLCP header 305 of the first type PHY frame shown in FIG. 51.

The second header part 402 for the second physical layer protocol includes a MIMO signal field 411, a PLCP long synchronization code 410 for MIMO, and a MIMO service field 412. The MIMO signal field 411 has a transmission rate field 413 and a data length field 414 as shown in the figure, and is referred to in the physical carrier detection. When a receiving communication device capable of interpreting MIMO of the second physical protocol obtains transmission channel information necessary for decoding processing, the PLCP long preamble 410 for MIMO is used.

Since the second type of PHY frame is formed into the format shown in Figure 52, existing communication devices that can only work according to the first type of physical layer protocol can at least interpret the first signal field 407. According to the signal field 407, perform the correct operation. Carrier detection at the physical layer. Therefore, the same physical layer carrier detection information can be shared between existing communication devices and communication devices that can work according to the second physical layer protocol in addition to the first physical layer protocol. It should be noted that the existing communication equipment cannot share the carrier detection information of the MAC layer, but with partial Ack, this will not cause any problems.

Information indicating the media occupation duration of the PHY payload (hereinafter referred to as "physical occupation duration") and signal strength are used together as carrier detection information of the physical layer when the PHY payload is transmitted on the physical medium. Once the physical carrier detection and the physical occupation duration of the PHY payload are known, the receiving communication device considers the physical medium to be occupied for this duration (PHY is busy). In addition, when the signal strength exceeds a certain threshold, the physical medium is also considered to be occupied for a certain duration. According to the transmission rate (408 or 413) and data length (409 or 414) of the PHY payload detected in the receiving communication device, the physical occupancy duration of the PYH payload can be calculated. Specifically, the value of the data length field represented by the octet length is divided by the value of the transmission rate field. This also applies to the first PHY frame shown in Figure 51.

It should be noted that when the maximum data length of the PHY payload allowed by the first physical layer protocol (4096 octets in IEEE802.11a) is actually smaller than the maximum PYH payload allowed by the second physical layer protocol When the data length is used, the physical occupancy duration of the PHY payload is an appropriate way to intentionally set the transmission rate field 408 and the data length field 409 falsely. Thus, the carrier detection information of the physical layer can be shared.

Here, the description with reference to FIG. 50 is returned. A MAC super frame is composed of a single PHY frame including multiple MAC frames. In the frame format 200 shown in the figure, the MAC superframe header 202 has fixed 8 MAC frame data length fields 1-8. It should be noted that in this embodiment, it is assumed that the MAC superframe header 202 has a fixed length. However, when the information indicating the number of MAC frames is added, the MAC superframe header 202 may have a variable length.

For example, when only 4 MAC frames 1-4 are included in the MAC superframe payload 203, a value of 0 is buried in the MAC frame data corresponding to the MAC frames 5-8 that do not exist in the same payload 203 Length field 5-8. In addition, during transmission control described later, for example, MAC frames 1 and 3 need to be returned, but MAC frames 2 and 4 need not be returned. In this case, the MAC frame data length can be set to 0 to specify the MAC frame that is not the retransmission target. For example, the MAC frame data length 1>0, the MAC frame data length 2=0, the MAC frame data length 3>0, MAC frame data length 4=0.

It should be noted that, in order to indicate that the MAC frame does not exist, a method other than the method in which the data length of the MAC frame is set to 0 can also be used. For example, a maximum of 8 MAC frames can be included in the MAC superframe payload, MAC frames 1-4 exist in the MAC superframe, and MAC frames 5-8 do not exist. In this case, the existence of the frame can be indicated by an 8-bit bitmap. The bitmap is part of the MAC superframe header (not shown).

The HCS 205 is a header check sequence and is added to the header 202 in such a way that the error in the MAC superframe header 202 can be detected. When the receiving communication device detects an error in the MAC superframe header 202 according to the HCS 205, it is considered that all the MAC frames included in the MAC superframe payload 203 are damaged.

In order to prevent buffer overflow in the receiving communication device, the number of MAC frames included in the MAC superframe payload 203 is preferably dynamically limited (sliding window control).

Fig. 53 shows an example of the format of the MAC frame. One MAC frame included in the MAC superframe payload 203 of FIG. 50 includes a MAC header 500, a frame body 501, and a frame check sequence (FCS) 502. The MAC header 500 includes a frame control field 503, a duration field 504, address fields 505-507, and a sequence control field 508. The frame body 501 has a variable length in the length range of 0 to 2312 octets, and is the payload of the MAC frame corresponding to the MAC protocol data unit (MPDU).

Regarding the acceleration of the physical layer through the second physical layer protocol (for example, MIMO in this embodiment), in this embodiment, multiple MAC frames are included in one PHY frame as a MAC superframe, so this format is Effectively constitute. Thus, the overhead of the entire PHY frame attributable to the format, namely PLCP header, various inter-frame spacing (IFS), random compensation, etc., is avoided, and the communication throughput can be significantly improved.

Fig. 54 shows an example of a communication system according to the twelfth embodiment of the present invention. In this communication system, the communication device 1 (access point) and the communication device 2-4 (terminal) communicate via a wireless link. The illustrated communication device 1 has the structure shown in FIG. 48. The communication devices 2, 3 (terminals) have the structure shown in FIG. 49. On the other hand, the communication device 4 (legacy terminal) only includes the first type of physical layer protocol processing device 109S, and does not include the second type of processing layer protocol processing device 110S. Thus, the device corresponds to an existing communication terminal that does not transmit any MAC superframe.

Fig. 55A shows an example of the format of a partial acknowledgment (partial Ack) frame. A value indicating that the frame is a partial Ack is entered in the type/subcategory field of the frame control field 550. The value of the confirmation state indicating whether the data frame constituting the confirmation target is successfully received by the receiving terminal or the access point is input to the partial Ack bitmap 551. Part Ack is used to implement selective repetitive retransmission control (so-called selective repetition). The PHY feedback information 552 may be included in the partial Ack frame in order to return physical layer level information. Information (bits) (not shown) that enables possible polling of partial Ack can be given.

Fig. 55B shows an example of the format of a polling (no data) frame. The value indicating that the frame is a polling frame that does not include any data (referred to as "polling (no data)") is input into the type/subtype field of the frame control field 553. When the access point grants the transmission right to the terminal, a polling (no data) frame is used. The access point is assumed to comply with IEEE802.11e "Media Access Control (MAC) Quality of Service (QoS) Management" (current draft specification), or its extended version, or may not comply with the specification. It should be noted that in IEEE802.11e, a physical access point is distinguished from a logical entity called a hybrid coordinator for schedule management, but the embodiments of the present invention can be implemented without distinguishing them in particular.

Fig. 56A shows an example of the format of a data frame. The value indicating that the frame is a data frame is entered in the type/subtype field of the frame control field 560. User data (usually, the link layer requests the MAC layer to transmit the data) enters the MAC payload (or MAC service data unit (MSDU)) 561.

Fig. 56B shows an example of the format of the data+polling frame. The value indicating that the frame is a polling frame including data (referred to as "data+polling") is entered in the type/subtype field of the frame control field. The data+polling frame is used in the case where the access point needs to allocate transmission rights to the terminal, and the access point transmits user data 562 to the terminal.

These frames (MAC frames) may be transmitted/received as a single MAC frame that is not aggregated, or may sometimes be aggregated into a single physical frame together with other MAC frames and transmitted/received as a MAC superframe.

It should be noted that the conventional communication device 4 (legacy terminal) can only transmit/receive a single MAC frame, and the communication device 1 (access point) and communication devices 2, 3 (MIMO processing terminals) are assumed to be capable of transmitting/receiving a single MAC frame. MAC frame or MAC super frame.

Fig. 57 shows that in the case where multiple MAC frames shown in Fig. 50 are aggregated into a single physical frame, all MAC frames (MAC frames 1-4) of the basic aggregate frame format are data formats. The frame of FIG. 57 is used to transmit/receive user data between the terminal and the access point, or between the terminals.

Figure 58 shows the case where MAC frame 1 in the aggregate frame format is a partial Ack frame, MAC frame 2 is a data + polling frame, and MAC frames 3 and 4 are data frames. When the access point confirms with the terminal (partial Ack), assigns the transmission right to the terminal, and transmits user data to the terminal, the frame of FIG. 58 is used. Here, the terminal as the confirmation target, the terminal to be given the transmission right and the terminal as the data transmission target are generally the same, but it is not prohibited to be different from each other.

Fig. 59 shows a case where MAC frame 1 in the aggregate frame format is a partial Ack frame, and MAC frame 2 is a polling (no data) frame. The frame of FIG. 59 is used when the access point confirms the terminal and grants the transmission right to the terminal. Here, the terminal as the confirmation target and the terminal to which the transmission right is granted are usually the same, and they may not be different from each other.

Fig. 60 shows a case where MAC frame 1 in the aggregate frame format is a polling (no data) frame. The frame of FIG. 60 is used when the access point grants the transmission right to the terminal.

It should be noted that the combination of multiple MAC frames and one aggregated frame is not limited to the above method, and various other combinations are also possible.

Fig. 61A shows an example of the format of a QoS data frame having a QoS control field in the MAC header. The value indicating that the frame is a QoS data frame is entered in the type/subtype field of the frame control field 610. User data (usually, the link layer requests the MAC layer to transmit the data) enters the MAC payload (or MAC service data unit (MSDU)) 611.

Fig. 61B shows an example of the format of a QoS data+polling frame with a QoS control field in the MAC header. The value indicating that the frame is QoS data+polling frame enters the type/subtype field of the frame control field 612. The QoS data+polling frame is used when the access point needs to give the terminal the transmission right, and the access point transmits user data 613 to the terminal.

The QoS data frame shown in Fig. 61A and the QoS data+polling frame shown in Fig. 61B are the QoS extensions of the data frame of Fig. 56A and the data+polling frame of Fig. 56B, and comply with IEEE802.11e or as an extension thereof, Use these frames.

Figure 62 shows the case where the aggregated MAC frame is partial Ack, QoS data + polling, and 2 QoS data frames. The frame of FIG. 62 is used to transmit/receive user data between the terminal and the access point or between the terminals. In addition, the aforementioned data frame in the aggregate frame format can be replaced with a QoS data frame, or another combination including QoS data frames is also possible.

Fig. 63 shows an example of a frame change sequence when the point coordination function (pointcoordicate furnction: PCF) defined in IEEE802.11-1999 is used. In IEEE802.11, in the contention period 630, the terminal and the access point use the distributed coordination function (DCF) of the CSMA/CA base station to compete for the media fairly. In the contention-free period 631, the access point (or a logical entity called the point coordinator in the access point) controls all media access through polling. The access point periodically transmits beacon frames 632. The contention-free period 631 starts from the contention-free repetition interval (integer multiples of the beacon transmission interval) 633 and ends with the contention-free end (CF-End) frame 634 transmitted by the access point, or with the CF_Max_Duration 635 The past and the end. Terminals other than the access point set NAV 636 in the contention-free period 631 and consider that the media is busy at the MAC layer. This prohibits active transmission that does not rely on polling.

During the CF time (631), the access point can transmit MAC frames, such as polling, data, data+Ack, data+polling, data+Ack+polling. The polled terminal can transmit data, data + Ack, etc. Terminals that are not polled cannot transmit any data, but can transmit Ack about data transmitted from the access point. Assume that the terminal responds in the SIFS cycle and the access point works. When the expected response is not returned in the SIFS, the access point may initiate a sequence of frames that will be scheduled after the next PIFS.

According to the capability information field included in the beacon or probe response frame, it can be determined whether the access point has a point coordination function (PCF). Among the terminals desiring to be polling targets, its own terminal can receive a poll of an access point with a polling function, and the terminal transmits an association request frame including a capability information field indicating registration to the polling schedule.

IEEE802.11e extends the method in which access points perform medium access control through polling (HCF controlled channel access: HCCA, hybrid coordination function: HCF). As shown in Figure 64, the main difference from IEEE802.11 is that the access point (hybrid coordinator) can start a controlled access period (CAP) 641 for polling control at any time in the contention period 640, 642, 643. That is, after confirming the idle state of the media in the PIFS cycle, the access point can start any frame sequence determined according to the specification. The terminal constituting the polling target is given the transmission right for the transmission opportunity (TXOP) period specified by the QoS control field of the polling frame. In the TXOP period, the terminal can continuously transmit/receive multiple MAC frames at SIFS intervals. When the terminal transmits a null data frame, it can return the transmission right to the access point before ending the designated TXOP.

As another difference in IEEE802.11e, it is determined that the terminal that wants to poll should request the setting of the traffic flow from the access point. When the traffic flow is set, the access point controls the media access of the terminal in such a way to satisfy QoS requirements such as band and delay. That is, the data transmission from the access point to the terminal is scheduled in such a way that if the specified QoS requirements are met, the MSDU that meets the specified traffic classifier (TCLAS) is transmitted. In terms of data transmission from the terminal to the access point, the access point polls the terminal in a manner that meets the specified QoS requirements.

In the IEEE802.11-1999, or IEEE802.11e specification, the MAC frame used for polling control or the MAC frame allowed to be changed by the polling control is a single MAC frame that has a one-to-one correspondence with the physical frame. This is not a MAC superframe in which multiple MAC frames are aggregated into one physical frame. However, when multiple MAC frames are aggregated into a single physical frame, the overhead associated with each physical frame (preamble, physical header, inter-interval (IFS), random compensation, etc.) can be reduced, and the MAC can be improved The transmission efficiency of the layer. The polling sequence involving aggregated MAC frames will be explained below.

Fig. 65 shows an example of a polling sequence in the case of extending PCF with frame aggregation. The contention-free period is initiated by the beacon frame 650. The time (timing) of transmitting the beacon frame 650 is determined by the polling/data transmission schedule control device 1051 of the access point. Before sending the beacon 650, continuing the PIFS period requires the media to be idle. This is confirmed by the carrier detection control device 106A. After confirmation, the media access control device 108A transmits the beacon frame 650 to the physical layer. The beacon frame 650 must be able to be received by all communication devices including the communication device 4 (legacy of STA3) which is assumed to be a terminal compliant with IEEE802.11a. Then, the frame is formed as a first type (IEEE802.11a) physical frame by the first type physical layer protocol processing device 109A that controls the transmission/reception of IEEE802.11a, and is transmitted.

Next, examples of symbols in the sequence diagram will be explained.

· F{BC(beacon)}: It represents the beacon MAC frame for the broadcast address, which is transmitted as a single MAC frame that is not a MAC superframe.

SF{STA1(poll(no data))}: It represents a polled (no data) MAC frame for STA1, which is transmitted as a MAC superframe.

SF{STA1(pack), STA2(poll(no data))}: It represents the MAC frame obtained by the partial Ack aggregated to STA1, and the MAC superframe obtained by the polling (no data) MAC frame to STA2 The transmitted frame.

After the SIFS elapses after transmitting the beacon frame, the access point transmits a polling (no data) frame 651 to STA1 in order to give the transmission right to STA1. At this time, the grant of the transmission right to the STA1 is determined by the polling/data transmission schedule control device 1051 of the access point. In this example, the polling (no data) frame 651 is transmitted as a MAC super frame ("SF" in the figure is an abbreviation of "super frame").

The MAC super frame is formed into a second type physical frame by the second type physical layer protocol processing device 110A that controls the transmission/reception of MIMO, and is transmitted. However, since only one MAC frame is needed here, the frame can be transmitted as a normal MAC frame. In this case, the frame may be formed as a physical frame of IEEE802.11a by the first physical layer protocol processing device 109A that controls transmission/reception of IEEE802.11a, and transmitted.

When the polling frame 651 is transmitted from the access point in the form of the second physical frame, the terminal (STA1) can estimate the state of the MIMO channel between the access point and the terminal based on the MIMO PLCP long preamble (FIG. 52). Usually, the channel state is detected and appropriate control is performed on the transmitting side (for example, power loading, bit loading, and their combination, where power or information is not evenly distributed, but is appropriately tilted/distributed to multiple One MIMO stream or multiple OFDM sub-carriers). It is known that the capacity of the transmission channel increases as a result. With simpler control, for example, information about the received power measured by the terminal, it is possible to control the appropriate transmission rate (modulation system, coding rate, etc.) during transmission.

In addition, parameters in the case where the access point transmits the frame, such as information on the transmission power or antenna gain, are included in the PHY feedback information 5000 (see FIG. 50) of the MAC superframe header, so the estimation of the channel state can be corrected. That is, it is possible to prevent the channel estimation result from being interpreted incorrectly based on the difference in transmit power or antenna gain between the access point and the terminal. For example, although the transmission power of the access point is greater than the transmission power of the terminal, the terminals assume that the transmission power is the same as each other. When the terminal estimates the channel, it misunderstands the channel state. When the maximum rate that is considered possible under the misunderstood channel state is selected, and the terminal transmits a frame to the access point, the access point may not receive the frame. Therefore, the physical layer reception status data (channel estimation information, error correction amount, received power) based on the immediately preceding transmission from the same terminal to the access point is included in the PHY feedback information 5000, which is appropriate for the terminal side. Control is useful.

Return to the description of Figure 65. The terminal (STA1) receiving the polling from the access point aggregates multiple data frames for the access point into a single MAC super frame 652 and transmits the frame. The data frame to be transmitted is selected by the data transmission schedule control means 1052 shown in FIG. 49. When it is not necessary to pay attention to QoS, etc., the data frames in the head of the queue can be simply selected sequentially as the transmission target. When QoS is required, a data frame with a high priority, or a data frame at the timing of periodically transmitting the frame is selected as the transmission target first. Data frames with multiple priorities can be included in a single MAC superframe.

When receiving a poll for its own terminal, the media access control device 108S of the terminal shown in FIG. 49 performs control in a manner of transmitting a MAC superframe after SIFS. The MAC super frame is configured to include the data frame selected by the data transmission schedule control means 1052 as described above. The MAC super frame is formed into a second type physical frame by the second type physical layer control processing device 110S that controls transmission/reception of MIMO, and is transmitted.

When receiving a frame, the access point first uses the second physical layer control processing device 110A (FIG. 48) that controls MIMO transmission/reception to receive the physical layer 101A, extracts the MAC superframe, and transmits the frame to the MAC layer 102A . In this case, the information of the reception status in the physical layer 101A can be forwarded to the MAC layer 102A as additional information.

The retransmission control device 107A of the access point determines whether each data frame included in the MAC superframe is successfully received according to the FCS, and generates a partial Ack frame including confirmation information (partial Ack bitmap). In addition, the information of the reception status of the physical layer 101A may be included in the PHY feedback information of the partial Ack frame. The polling/data transmission schedule control device 1051 confirms that there is no data to be transmitted in the terminal (STA1), and judges that the transmission right should continue to be granted to the terminal. In this case, a partial Ack frame and a polling (no data) frame for the terminal (STA1) are aggregated, thereby generating a MAC super frame 653. The media access control device 108A controls the access to the media in such a way that the MAC superframe 653 thus generated is transmitted after the SIFS. The MAC super frame 653 is formed into a second type physical frame by the second type physical layer protocol processing device 110A that controls the transmission/reception of MIMO, and is transmitted.

When receiving the frame 653, the terminal first uses the second physical layer control processing device 110S (FIG. 49) that controls MIMO transmission/reception to receive the physical layer 101S, extracts the MAC superframe, and transmits the frame to the MAC layer 102S. In this case, the information of the reception status in the physical layer 101S can be forwarded to the MAC layer 102S as additional information.

Partial Ack and polling (no data) are included in the MAC superframe 653. Since the terminal (STA1) is polled, the terminal can aggregate multiple data frames for the access point into a single MAC super frame and transmit the frame. The data frame to be transmitted is selected by the retransmission control means 107S and the data transmission schedule control means 1052 shown in FIG. 49. That is, the MAC frame to be retransmitted is identified by the partial Ack. In addition, the data transmission schedule control means 1052 considers the priority of the newly transmitted MAC frame and the MAC frame to be retransmitted, and selects the actual MAC frame to be transmitted. Simply put, a frame with a high priority can be transmitted first. On the other hand, for example, even when the priority assigned to the MAC frame is low, the remaining time of the timeout for discarding the MAC frame is short, it can also be considered as having a high priority, but before the allowed MAC frame is obtained until the timeout period The way of transmitting frames with low priority is controlled. When data frames with multiple priorities are included in a single MAC superframe, there is no problem.

When receiving a poll for its own terminal, the media access control device 108S of the terminal shown in FIG. 49 performs control in a manner of transmitting a MAC super frame 654 after SIFS. The MAC super frame 654 is configured to include the data frame selected by the data transmission schedule control means 1052 as described above. In addition, the information of the reception status in the physical layer may be included in the PHY feedback information 5000 of the MAC superframe 654. The MAC super frame 654 is formed into a second type of physical frame by the second type of physical protocol processing device 110S that controls the transmission/reception of MIMO.

During transmission, the information about the channel state obtained from the received physical frame, the PHY feedback information from the access point included in the received partial Ack frame, and the correct reception rate obtained from the partial Ack bitmap are considered, and Transmission control can be performed on modulation system, coding rate, power bit loading, etc.

In the case where there is a tendency that the second half of the MAC frame is not successfully received in the partial Ack bitmap, there is a possibility that the time required for the transmission of the MAC superframe is longer than the channel lifetime. Thus, the maximum length of the MAC superframe to be transmitted can be controlled to be limited. As for the physical frame containing the MAC superframe, it is adaptively added not only to the header of the frame, but also to the middle of the frame based on the information (known information, such as midamble) that can estimate the channel. Therefore, the channel estimation can be corrected before the channel state changes greatly.

In the following, another example of the polling sequence will be explained mainly in terms of differences from the example of FIG. 65.

When a frame that requires a response is received, the retransmission control device 107A of the access point generates a partial Ack frame. Here, the polling/data transmission schedule control device 1051 determines that priority should be given to the allocation of the transmission right to the terminal STA2 instead of the polling and partial Ack transmission to the terminal STA1. It is assumed that a partial Ack frame has been formed for STA2 according to the previous frame change for the terminal STA2, and there is no frame to be transmitted to the terminal STA2. In this case, the partial Ack frames and polling (no data) frames for the terminal (STA2) are aggregated to form a MAC super frame. The media access control device 108A controls the access to the media by transmitting the MAC superframe constructed in this way after the SIFS. The MAC super frame is formed into a second type physical frame by the second type physical layer protocol processing device 110A that controls transmission/reception of MIMO, and is transmitted.

The terminal STA2 receiving the MAC superframe selects the data frame to be transmitted to form the MAC superframe, and transmits the frame to the access point after the SIFS in the same manner as described above.

Although not shown in FIG. 65, when the access point transmits the CF-End frame 634 as shown in FIG. 63, or before the CF_Max_Duration 635 elapses, the contention-free period for performing polling control ends.

The other sequence example shown in FIG. 66 is different from the polling sequence in which the CF period is initiated by the beacon frame as shown in FIG. 65 in that the access point transmits CTS-self 660 to itself, thereby generating the CAP period. When the time indicated by TXOP elapses, the CAP period ends. The difference in this example is that a MAC superframe 661 of SF{STA1(pack), STA2(poll(no data))} transmits a partial Ack frame to the terminal STA1, and also transmits a poll (no data) to the terminal STA2. frame. In the case where all data frames from the terminal STA1 are received by the access point and retransmission from the terminal STA1 is not required, the MAC superframe is valid.

Fig. 67 shows a polling sequence in which the access point polls the terminal STA3 (legacy). The terminal STA3 is a legacy terminal on which only the first physical layer protocol (for example, IEEE802.11a) is installed, and the access point including the polling control frame exchanges frames with the terminal STA3 that complies with the first physical layer protocol. Assuming that the terminal STA3 cannot process the MAC super frame, the MAC frame is transmitted/received separately without any aggregation.

In FIG. 67, when the terminal STA3 continuously transmits MAC frames, it follows the block Ack frame change procedure defined by IEEE80211e. That is, every SIFS interval, the QoS data frames 670 and 671 are continuously and burst-transmitted in the form of independent physical frames. The block Ack request frame 672 and the block Ack frame 673 realize confirmation.

Since no MAC superframe is used for the legacy terminal STA3 in terms of polling, data, response frames, etc. (aggregation is prohibited), access points can coexist and work when the network has the legacy terminal STA3. It should be noted that with some frame exchange, the access point can detect in advance whether the polling target terminal is a legacy terminal that does not correspond to MAC aggregation.

FIG. 68 shows a modification of the sequence example shown in FIG. 65. In the case that the MAC superframe transmits a polling frame, not only a polling (no data) frame with no task data is allowed, but also a polling (data) frame with data is allowed.

The above-described embodiment of the present invention may be modified. This means that the MAC superframe header is formatted in the same way as in the MPDU. Fig. 69 shows an example of the MAC superframe header 1900 having the same format as the MPDU. For example, a value indicating the MAC superframe header is newly defined and assigned to the type/subtype area included in the frame control field. Based on this value, the MAC layer of the receiving communication device determines whether to perform the processing of the MAC super frame or the processing of the normal MAC frame. According to the method of calculating the duration of another MAC frame included in the MAC superframe, the value of the duration 504 is set. The value of the address 1 field 505 (receiver address) is set to be equal to the value of address 1 of another MAC frame included in the corresponding MAC superframe. Thus, the address specifying the receiving communication device is set in the address 1 field 505.

Since the MAC superframe header 1900 is not segmented or retransmitted, the value of the sequence control field 508 does not have any special meaning. Therefore, when a MAC superframe is allocated as a control frame, the sequence control field 508 is preferably omitted.

When the type is defined as management or data, the sequence control field 508 needs to be arranged, and the value needs to be processed and consistent with the retransmission control of the embodiment of the present invention. For example, the sequence numbers of the MAC frames constituting the retransmission target in a series of retransmission control of the MAC superframe are assumed to adopt continuous values. Therefore, when the sequence number is set to a discontinuous value, a series of retransmission control of the MAC superframe is immediately ended, and it is necessary to start another sequence of retransmission control. Thus, the discontinuity of the serial number is avoided. On the other hand, if the sequence number becomes discontinuous, then a series of retransmission control needs to be continued. As an example of solving this problem, when window control at the time of retransmission is performed as described in another embodiment of the present invention, it may be allocated to the MAC frame that is the retransmission target in a series of retransmission control. The value of the largest serial number is known. Therefore, there is a method of continuously assigning values in such a manner that the serial number indicates a value exceeding the maximum value. The continuous value needs to be assigned to the value including the MAC frame as the retransmission target. However, a method in which the sequence number of the MAC frame that is the target of the retransmission is ignored during the execution of the retransmission control so that the value is not continuous is also possible.

The length of each MAC frame included in the MAC superframe is set to the portion 1901 corresponding to the payload as shown in FIG. 69. The segment number used to process the segment may be included in the payload 1901.

FCS 502 corresponds to HCS 205 in Figure 50, and FCS 502 can be used in the same way as in normal MPDUs. For example, the CRC value calculated for the entire MAC superframe header is set in FCS 502. In the case where the receiving communication device recognizes that the MAC superframe header 1900 is damaged according to the FCS 502 accompanying the MAC superframe header 1900, the header is processed in the same manner as when the HCS 205 detects an error. The receiving communication device that detects the damage discards the entire MAC superframe.

(Thirteenth embodiment) The thirteenth embodiment removes redundant elements from the MAC headers of multiple MAC frames included in a single physical frame, further improving efficiency.

The MAC header with extra elements removed will be referred to as a shrinked MAC header. Fig. 70 shows an example of a MAC superframe structure including a MAC frame with a contracted MAC header. In this example, MAC frame 1 has a normal MAC header, but MAC frames 2, 3, and 4 have contracted MAC frames.

Figure 71 shows one of the process of generating a MAC frame with a contracted MAC header from a MAC frame with a normal MAC header on the transmitting side, and a process of reproducing a MAC frame with a normal MAC header from a MAC with a contracted MAC header on the receiving side example.

As shown in FIG. 70, it is assumed that the MAC superframe has at least one MAC frame with a normal MAC header. For example, suppose that a wired terminal with an address SA aggregates multiple MAC frames transmitted to a terminal with an address RA into a single MAC superframe through an access point with an address TA. In this case, the address SA, the address TA (BSSID), and the address RA are common to all MAC frames and are included in the MAC header as address information. In the transmitting access point, the addresses SA, TA, and RA are only left in the MAC header of a single MAC frame 1, and the addresses SA, TA, and RA are omitted from the MAC headers of other MAC frames 2, 3, and 4. Since the addresses SA, TA, and RA of MAC frames 2, 3, and 4 are the same, even in this case, the receiving terminal can reproduce the MAC headers of MAC 2, 3, and 4 based on the MAC header of MAC frame 1 (Figure 72). This is the transmitter process of "removing the MAC header information included in the MAC super frame and reproducible from another MAC frame" in FIG. 72, and "reproducing the MAC header information included in the MAC super frame and can be reproduced from another MAC frame". An example of the receiver process of reproducing the MAC header information. Also consider the case where the value of the duration field is equal in the MAC header of all MAC frames included in a single MAC superframe. In this case, in addition to the address, the duration field is also the erasure and reproduction target (Figure 73).

When it is determined that the MAC frame with the normal MAC header is indeed the MAC frame 1 of the header, the MAC frame with the normal MAC header is implicitly identified on the transmitting side and the receiving side. On the other hand, in a case where a MAC frame with multiple destinations is included in a single MAC superframe, the transmitting STA may include header MAC frame information indicating each destination to the receiving STA in the MAC superframe. This can be indicated by bitmap information (multiple access bitmap) included in the MAC frame header. Here, it is assumed that the header MAC frame of each destination has a normal MAC header. In addition, when multiple attributes, such as QoS attributes (TID, TSID, etc.) are included in a single MAC superframe, the transmitting STA may include a MAC frame whose attributes change according to which the receiving SAT can recognize. Here, the first MAC frame of the MAC frame group with the same attributes is assumed to have a normal MAC header.

Fig. 74 shows an example of the generation of a MAC frame with a contracted MAC header, and the reproduction process of the MAC header from the contracted MAC header in the case of authentication of a cryptographic message. The user data cryptographic message authentication system (temporary key integrity protocol: TKIP and CTR (counter) with CBC (Cipher Block Chain) MAC defined in the IEEE802.11i draft (security enhancement) that defines the security extension of IEEE802.11 Mode) Protocol: CCMP), not only the payload part of the MAC frame, but also part of the MAC header information is the target of security protection. The MAC header is not the target of encryption (secrecy), but a part of the information (including address information, etc.) included in the MAC frame is the calculation target of the message verification code used to detect changes. Thus, there is a correlation between the security processing of the transmitting STA and the receiving STA and the shrinking and reproduction processing procedure of the MAC header.

In the transmitting STA, a set of plaintext MAC header and MAC payload is first generated. The set of plaintext MAC header and MAC payload are forwarded to the encrypted message verification code (integrity check value: ICV) distribution process. Therefore, the MAC payload is encrypted and the ICV is assigned to the MAC payload. The FCS is calculated and assigned to the entire MAC header and MAC payload (encrypted MAC payload + ICV). After that, the shrinking process of the MAC header is performed, and the frames are aggregated into the MAC superframe and transmitted.

In the receiving STA, a process of reproducing the normal MAC header from the first contracted MAC header is performed. Subsequently, FCS is calculated with respect to the entire MAC header and MAC payload (encrypted MAC payload + ICV) and compared with the FCS assigned to the MAC frame. When they are consistent with each other, it is judged that the reception is successful. When they are inconsistent, it is judged to be damaged. Subsequently, the encrypted MAC payload is decrypted, and the ICV is calculated relative to a portion of the MAC header and MAC frame. When they are consistent with each other, it is judged that there is no change. When they are inconsistent, it is judged that there is a change.

Those skilled in the art can easily think of other advantages and modifications. Therefore, the present invention is not limited to the specific details and typical embodiments shown and described herein. Therefore, various modifications can be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.