JP2011050091A - Wireless communication system, wireless communication device, wireless communication method, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To favorably perform access control based on CSMA using an RTS/CTS method together. <P>SOLUTION: In a wireless communication system, when the RTS/CTS procedure is combinedly used, CTS information is transmitted in response to the reception of RTS information, and data are transmitted in response to the reception of CTS. A CTS transmitting station measures the quality of an RTS receive signal, and thereby determines a transmission rate at which it can receive the signal and reports the determination to a station as the destination of the CTS. The station as the destination of the CTS transmits data in response to the CTS information. As the transmission rate for the data, a transmission rate indicated in the RATE field in the CTS is applied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program that perform communication between a plurality of wireless stations such as a wireless LAN (Local Area Network) or a PAN (Personal Area Network). In particular, the present invention relates to a radio communication system, a radio communication apparatus and a radio communication method, and a computer program that perform random access based on carrier detection by CSMA (Carrier Sense Multiple Access with Collision Avidity).

  More particularly, the present invention relates to a radio communication system, a radio communication apparatus and a radio communication method, and a computer program for performing access control based on CSMA using both RTS / CTS schemes in order to maintain communication quality. The present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program that provide a flexible transmission / reception procedure by multiplexing a plurality of types of frames such as CTS, DATA, and ACK and reduce overhead.

  A wireless network has attracted attention as a communication system that releases users from cable wiring between devices in a wired manner. According to the wireless network, since most of the wired cables can be omitted in a work space such as an office, a communication terminal such as a personal computer (PC) can be moved relatively easily. In recent years, the demand for wireless LAN systems has increased remarkably with the increase in speed and cost. Particularly recently, introduction of a personal area network (PAN) has been studied in order to construct a small-scale wireless network between a plurality of electronic devices existing around a person and perform information communication. For example, different radio communication systems and radio communication apparatuses are defined using frequency bands that do not require a license from a supervisory agency, such as 2.4 GHz band and 5 GHz band.

  As a standard for wireless networks, IEEE (The Institute of Electrical and Electronics Engineers) 802.11 (for example, refer to Non-Patent Document 1), HiperLAN / 2 (for example, Non-Patent Document 2 or Non-Patent Document) 3), IEEE802.15.3, Bluetooth communication, and the like. As for the IEEE802.11 standard, there are various wireless communication systems such as the IEEE802.11a standard, the IEEE802.11b standard, etc., depending on the wireless communication system and the frequency band to be used.

  In order to configure a local area network using wireless technology, a single device serving as a control station called an “access point” or “coordinator” is provided in the area, and is under the overall control of this control station. A method of forming a network is generally used.

  In a wireless network in which an access point is arranged, when information is transmitted from a certain communication device, a bandwidth necessary for the information transmission is first reserved in the access point so that there is no collision with information transmission in another communication device. In this way, an access control method based on bandwidth reservation that uses a transmission line is widely adopted. That is, by arranging access points, synchronous wireless communication is performed in which communication devices in a wireless network are synchronized with each other.

  However, when asynchronous communication is performed between the communication device on the transmission side and the reception side in a wireless communication system in which an access point exists, wireless communication via the access point is always required. There is a problem that the efficiency is halved.

  On the other hand, as another method of configuring a wireless network, “ad-hoc communication” in which terminals perform wireless communication directly and asynchronously has been devised. In particular, in a small-scale wireless network composed of a relatively small number of clients located in the vicinity, ad hoc communication that allows arbitrary terminals to perform direct or random wireless communication without using a specific access point Is considered appropriate.

  Since an ad hoc wireless communication system does not have a central control station, it is suitable for configuring a home network made up of household electrical devices, for example. In an ad hoc network, the routing is automatically changed even if one unit fails or power is turned off, so the network is unlikely to fail. The high data rate can be maintained by hopping packets between mobile stations multiple times. There is a feature that data can be transmitted relatively far. Various development cases are known for ad hoc systems (for example, see Non-Patent Document 5).

  For example, an IEEE802.11 wireless LAN system is provided with an ad hoc mode that operates in a peer-to-peer manner in a distributed manner without providing a control station.

  On the other hand, it is known that a hidden terminal problem generally occurs in a wireless LAN network in an ad hoc environment. A hidden terminal is a communication station that can be heard from one communication station that is a communication partner but cannot be heard from the other communication station when communicating between specific communication stations. Since terminals cannot negotiate with each other, there is a possibility that transmission operations may collide.

  As a methodology for solving such a hidden terminal problem, CSMA / CA by the RTS / CTS procedure is known.

  Here, CSMA (Carrier Sense Multiple Access with Collision Avidance) is a connection method for performing multiple access based on carrier detection. Since it is difficult to receive a signal transmitted by itself in wireless communication, it is confirmed that there is no information transmission of other communication devices by CSMA / CA (Collision Aidance) method instead of CSMA / CD (Collision Detection). Then, the collision is avoided by starting the transmission of its own information. The CSMA method is an access method suitable for asynchronous data communication such as file transfer and e-mail.

  Further, in the RTS / CTS system, the data transmission source communication station transmits a transmission request packet RTS (Request To Send) and responds to reception of the confirmation notification packet CTS (Clear To Send) from the data transmission destination communication station. To start data transmission. When the hidden terminal receives at least one of RTS and CTS, it avoids a collision by setting its own transmission stop period only during a period in which data transmission based on the RTS / CTS procedure is expected to be performed. Can do. The hidden terminal for the transmitting station receives the CTS and sets the transmission stop period to avoid collision with the data packet, the hidden terminal for the receiving station receives the RTS and stops the transmission period, and the ACK To avoid collisions.

  Here, the wireless network will be described by taking IEEE 802.11a, which is an extension standard of IEEE 802.11, as an example.

  FIG. 15 shows a frame format in IEEE 802.11a.

  A preamble for indicating the existence of the packet is added to the head of each packet. A known symbol pattern is defined in the preamble according to the standard. The receiver can determine whether or not the received signal deserves a preamble based on this known pattern.

  Following the preamble, a signal field is defined. The signal field stores information necessary for decoding the information part of the packet. Information necessary for decoding a packet is called a PLCP header (Physical Layer Convergence Protocol header), and the PLCP header includes a service field that is a part of the PLCP header. A RATE field indicating a transmission rate of the information section, a LENGTH field indicating the length of the information section, a parity bit, a tail bit of the encoder, and the like. Based on the decoding result of the RATE of the PLCP header and the LENGTH field, the receiver performs subsequent decoding of the information section.

  The SIGNAL part storing the PLCP header is encoded with noise resistance, and is transmitted at 6 Mbps. On the other hand, the information portion is transmitted in a normal packet in a transmission rate mode in which the highest bit rate is provided within a range where errors do not occur as much as possible according to the SNR in the receiver.

  In IEEE802.11a, eight types of transmission rate modes of 6, 9, 12, 18, 24, 36, and 54 Mbps are defined, and any one of these is selected. When the transceiver is located in the vicinity, a high bit rate transmission rate mode is selected and the communication station located far away may not be able to decode this information.

  The information part is transferred to the link layer, which is an upper layer, as PSDU (Physical Layer Service Data Unit). Here, only four types of frames, RTS, CTS, ACK, and DATA, which are necessary for the description of the present invention, will be described. 16A shows the configuration of the frame field of the PSDU of the RTS frame, FIG. 16B shows the configuration of the frame field of the PSDU of the CTS and ACK frame, and FIG. 16C shows the configuration of the frame field of the PSDU of the DATA frame. Each is shown.

  In each frame, a Frame Control field and a Duration field are defined in common. In the Frame Control field, information indicating the type and usage of the frame is stored. Specifically, the information shown in Table 1 is described. In the Duration field, information on the use of NAV (Network Allocation Vector) (described later) is stored, and the time until the transaction of the packet is completed is recorded.

  In addition to the above, the Data frame includes four address fields Addr1 to 4 for specifying the source and destination communication stations, a sequence field (SEQ), and FrameBody which is net information provided to the upper layer. FCS (Frame Check Sequence) that is a checksum is included.

  In addition to the above, the RTS frame includes a Receiver Address (RA) indicating a destination, a Transmitter Address (TA) indicating a transmission source, and an FCS that is a checksum.

  In addition to the above, the CTS frame and the ACK frame include an RA indicating the destination and an FCS that is a checksum.

  Here, an access contention method defined in IEEE 802.11 will be described.

  In IEEE 802.11, four types of frame intervals (IFS) are defined, and SIFS (Short IFS), PIFS (PCF IFS), and DIFS (DCF IFS) are defined in order from the shortest.

  IEEE 802.11 employs CSMA as the basic media access procedure (described above), but before the transmitter sends anything, it monitors the media status and sets a backoff timer for a random time. Only when there is no transmission signal during this period is a transmission right granted and packets can be transmitted on the media.

  When a normal packet is transmitted according to the CSMA procedure, the DCF (called Distributed Coordination Function) must first monitor the media status by the DIFS after transmission of some packet, and there must be no transmission signal during this period. For example, a transmission right is given when random back-off is performed and there is no transmission signal during this period.

  On the other hand, when an exceptionally urgent packet such as ACK is transmitted, it is allowed to transmit the packet after a shorter frame interval called SIFS. As a result, a packet with a high degree of urgency can be transmitted before a packet transmitted in accordance with a normal CSMA procedure.

  In short, the reason why different types of frame interval IFS are defined is that priority is given to packet transmission right contention depending on whether the IFS is SIFS, PIFS, or DIFS, that is, the length of the frame interval.

  Next, the RTS / CTS procedure in IEEE 802.11 will be described with reference to FIGS. In a wireless LAN network in an ad hoc environment, it is generally known that a hidden terminal problem occurs, and CSMA / CA based on an RTS / CTS procedure is known as a methodology for reducing many of the problems (described above). . This methodology is also adopted in IEEE 802.11.

  FIG. 17 schematically shows an operation example of the RTS / CTS procedure. In the figure, an example in which some information (Data) is transmitted from STA0 to STA1 is shown.

  Prior to actual transmission of information, STA0 transmits an RTS (Request To Send) packet to STA1, which is the destination of the information, according to the procedure of CSMA. On the other hand, in response to receiving the RTS packet, the STA1 transmits a CTS (Clear To Send) packet that feedbacks that the RTS has been received to the STA0.

  If the STA0 on the transmitting side successfully receives the CTS packet, it is assumed that the medium is clear, and transmission of the information (Data) packet is started immediately. When STA1 has successfully received the information (Data) packet, it returns an ACK packet, thereby completing the transmission / reception transaction for one packet.

  FIG. 18 illustrates actions that can occur in the peripheral stations when performing the RTS / CTS procedure between the transmitting and receiving stations. In this figure, there is assumed a communication environment in which there are four communication stations, STA2, STA0, STA1, and STA3, and only adjacent communication stations in the figure are located in the radio wave reachable range. Here, it is assumed that STA0 wants to send information to STA1.

  After confirming that the medium is clear for a certain period (from time T0 to time T1) according to the CSMA procedure, the STA0 that is the transmission source transmits an RTS packet to STA1 from time T1. Information indicating that the packet is RTS is described in the Type / SubType information of the FrameControl field of the RTS packet, and the time until the packet transmission / reception transaction ends (that is, the time until time T8) is described in the Duration field. The address of the destination communication station (STA1) is described in the RA field, and the address of the local station (STA0) is described in the TA field.

  Here, in order to describe the time until the transaction based on the RTS / CTS procedure ends in the Duration field, STA0 needs to determine the end time of the transaction at the time of transmitting the RTS. Please note that. Specifically, the transmission source STA0 must determine all transmission rate modes including the CTS packet, the Data packet, and the ACK packet that are subsequently transmitted / received in the transaction at the time of transmitting the RTS. It will not be. The transmission rate mode determined here relates to the entire transaction, and it is not permitted to set a different transmission rate mode for each packet transmission within the transaction.

  FIG. 19 illustrates a procedure for determining a transmission rate mode for the entire transaction when the transmission source STA0 transmits an RTS. Since it is necessary to determine the end time of the transaction (time T8 in FIG. 18) at the time of RTS transmission, the transmission rate mode is caused only by information held by the transmitting station at the time of RTS transmission (for the entire transaction). Based on the amount of communication data and the transmission rate). Thereafter, the transmission rate of each frame of CTS, DATA, and ACK transmitted and received basically follows the rate applied in RTS. That is, it is not allowed to set a different transmission rate mode for each packet transmission within a transaction.

  Here, it returns to FIG. 18 again and demonstrates. The RTS packet is also received by STA2 located in the vicinity of STA0. When the STA2 receives the RTS signal, the STA2 starts reception by finding the preamble, and further decodes the PSDU based on the information obtained by decoding the PLCP header. Then, the Frame Control field in the PSDU recognizes that the packet is an RTS packet and knows that STA0 wants to transmit some information. Further, it recognizes from the RA field that the local station is not the destination communication station. Then, the STA2 recognizes that the medium is occupied without monitoring the medium until the transaction is finished so as not to disturb the transmission request of the STA0, and stops the transmission. This operation is referred to as “NAV (Network Allocation Vector) is established by the peripheral station”, etc. NAV is valid for the period indicated by the Duration field, and STA2 is in a transmission non-permission state until time T8.

  On the other hand, the RTS packet is also received by the destination STA1. When STA1 recognizes that STA0 wants to transmit a packet to its own station by decoding PSDU by the same procedure as described above, STA1 returns a CTS packet at time T3 with a SIFS interval (described above).

  Here, the transmission rate mode of the CTS packet must be the same as that of the RTS. In addition, the Frame Control field of the PSDU describes that the packet is a CTS packet, the Duration field describes the time until the transaction ends (that is, the time until the time T8), and the RA field indicates the destination. The address of the communication station (STA1) is described.

  The CTS packet is also received by STA3 located in the vicinity of STA1, which is the transmission destination. STA1 recognizes that “a nearby communication station is scheduled to receive a packet until time T8” by decoding the PSDU by the same procedure as described above. In addition, the STA3 stops transmission by setting up a NAV until the transaction is completed so as not to disturb the reception request of the STA1. The NAV is valid for the period indicated in the Duration field, and the STA3 is also in a transmission non-permission state until time T8.

  The CTS packet is also received by the destination STA0. When STA0 recognizes that STA1 is ready for reception by decoding PSDU according to the same procedure as described above, STA0 starts transmitting a Data packet at time T5 with a SIFS interval.

  When the data packet transmission ends at time T6 and STA1 can decode it without error, STA1 returns an ACK at time T7 with a SIFS interval, and STA0 receives this and transmits and receives one packet. Ends at time T8.

  At time T8, the neighboring communication stations STA2 and STA3 lower the NAV and return to the normal transmission / reception state.

  In short, in the above RTS / CTS procedure, the “peripheral station of STA0 as a transmitting station” that can receive RTS, that is, the STA2 and the “peripheral station of STA1 that is a receiving station” that can receive CTS, that is, STA3 Is prohibited. As a result, information transmission and return of ACK addressed from STA0 to STA1 are performed without being interrupted by a sudden transmission signal from a peripheral station, so that communication quality is maintained.

  FIG. 20 shows an example of an operation sequence when a packet transmission / reception transaction based on the RTS / CTS procedure in IEEE802.11 as described above is realized by traffic via TCP / IP (Transmission Control Protocol / Internet Protocol). Yes. TCP / IP is a typical communication protocol for performing transmission control and path control.

  Even in the case of unidirectional communication in terms of application, an ACK is typically returned every two segments by the TCP layer, and asymmetric bi-directional communication is formed in the MAC layer. Since the TCP layer ACK has a small data amount, RTS / CTS is not used together, but for data traffic, an example in which RTS / CTS is used together is shown here.

  In the example shown in FIG. 20, in order to transmit five segments from Data0 to Data4, a total of 24 packets are transmitted and received in the MAC layer. That is, the operation in the TCP layer is relatively simple, whereas the MAC layer performs a complicated operation.

  As described above, in IEEE802.11, the transmission / reception procedure based on CMSA combined with the RTS / CTS method can be used to solve the access contention and bandwidth guarantee problems. Some issues remain.

(1) Incomplete transmission rate When data transmission / reception is performed according to the RTS / CTS procedure, it is necessary to determine the transmission rate of the data packet before transmitting the RTS packet.

  This is because in order for the transmitting station to describe the time until the transaction based on the RTS / CTS procedure ends in the Duration field, it is necessary to determine the end time of the transaction at the time of transmitting the RTS. However, this means that all transmission rate modes including CTS packets, Data packets, and ACK packets that are subsequently transmitted / received in the transaction must be determined at the time of transmitting the RTS. In addition, the transmission rate mode determined at the time of RTS transmission relates to the entire transaction, and it is not allowed to set a different transmission rate mode for each packet transmission within the transaction. Is complete.

  In addition, since the transmitting station cannot grasp the reception status at the receiving station in real time, determining the transmission rate of the entire transaction at the time of RTS transmission means that data packets are transmitted at the optimal transmission rate according to the reception status of the receiving station. It is also unlikely that the

  For example, in Patent Document 1, when the receiving side receives an RTS packet, the communication environment state at that time is measured, and the measurement result is added to the CTS packet and sent back to the transmitting side. A packet communication method to be optimized is disclosed. However, in this case as well, the transmission rate of the entire transaction is determined before the RTS packet is transmitted on the transmission side, and therefore the incompleteness of the transmission rate is not eliminated.

  The RTS transmitting station determines the transmission rate of the entire transaction including the CTS packet, Data packet, and ACK packet transmitted / received due to the RTS transmission, and ends the transaction based on the value obtained by dividing the transmission data amount by the transmission rate. It is necessary to obtain a value to be written as time, that is, Duration, and write it in the RTS. On the other hand, in Patent Document 1, the CTS transmitting station determines the transmission rate by receiving the RTS. Prior to this, it is mentioned how the RTS transmitting station should obtain the Duration field described in the RTS. It has not been.

  Here, when a faster transmission rate is set on the CTS transmitting station side, the transaction ends at a time earlier than the duration determined at the time of RTS transmission. Therefore, the peripheral station that heard the RTS sets up a NAV even after the end of the transaction. It will be waiting for transmission and waste of bandwidth. Conversely, if the CTS transmitting station sets a slower transmission rate, the peripheral station that heard the RTS cancels the NAV even though the transaction has not ended even after the duration determined at the time of RTS transmission has elapsed. The transmission operation is started, and a collision is induced.

(2) Difficulties in multiplexing data units when using RTS / CTS together In the conventional RTS / CTS procedure, the data sending side determines the data rate before sending the RTS. . It is not considered that the data receiving side determines the data rate and transmits a plurality of data units as one data packet. Considering the efficiency of the MAC layer (see FIG. 20), it is preferable that the receiving side can determine the data rate and further transmit a plurality of data units as one data packet. However, this cannot be realized with the conventional RTS / CTS format.

(3) Combination of Delay Acknowledgment and RTS / CTS Procedure According to the IEEE 802.11 standard, an immediate ACK (Immediate ACK) that immediately returns an acknowledgment (ACK) when data is received is assumed. On the other hand, it is conceivable to use delayed ACK (Delay ACK) for the purpose of reducing ACK and frame overhead.

  However, when the delayed ACK and RTS / CTS procedure are used together, there is a possibility that RTS is transmitted for the purpose of retransmission without ACK being returned to the transmitting side. The combined use has a limit for the purpose of increasing the efficiency.

(4) Methodology of Selective Acknowledgment It is known that the MAC layer efficiency is improved by performing the selective acknowledgment, but the IEEE 802.11 standard does not consider the selective acknowledgment itself. As used herein, the selective acknowledgment is a retransmission control in which retransmission is performed only for a packet that has not been received by the receiving side by feeding back ACK or NACK information for any packet that has been received or could not be received to the transmitting side. It is a method.

  The implementation of selective acknowledgments has not yet been applied in many cases due to the large amount of memory required and the weight of processing, but it will become increasingly necessary in the future. Will. Based on such a situation, a selective confirmation response is not implemented in the initial communication station, but a selective confirmation response is implemented in a communication station to be developed later. In such a case, it is not preferable that both cannot communicate, and a format that maintains backward compatibility is desired.

  Further, since it has not been considered so far to use the selective confirmation response and the method of determining the data rate by the receiving side and the RTS / CTS procedure, it cannot be realized in the existing format.

(5) Influence of Overhead Generated at the MAC Layer According to the IEEE 802.11 standard, an RTS frame, a CTS frame, an ACK frame, and the like are defined independently (see FIG. 16). For this reason, when it is desired to send each piece of information, it is necessary to perform transmission in separate frames. However, every time a frame is transmitted, there is an overhead such as a preamble, and the amount of overhead rises so much that it cannot be ignored, especially when the transmission rate increases.

  Needless to say, an increase in overhead in the MAC layer is undesirable because it contributes to the direction of limiting the bandwidth that can be provided to higher layers such as TCP / IP.

Japanese Patent Application Laid-Open No. 2000-151639

International Standard ISO / IEC 8802-11: 1999 (E) ANSI / IEEEEsted 802.11, 1999 Edition, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layers (PHY) ETSI Standard ETSI TS 101 761-1 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part 1: Basic Control Data ETSI TS 101 761-2 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part2: Radio Link Control (LC) C. K. “Ad Hoc Mobile Wireless Network” by Thor (published by Prentice Hall PTR)

  An object of the present invention is to provide an excellent radio communication system, radio communication apparatus and radio communication method, and computer program capable of suitably performing access control based on CSMA while using the RTS / CTS scheme together. is there.

  A further object of the present invention is to provide a flexible transmission / reception procedure by multiplexing a plurality of types of frames such as RTS, CTS, DATA, ACK, etc., and to reduce overhead. An apparatus, a wireless communication method, and a computer program are provided.

The present invention has been made in consideration of the above-described problems. The first aspect of the present invention is that a data transmission source communication station transmits a transmission request packet RTS, and a data transmission destination communication station transmits a confirmation notification packet CTS. A wireless communication system in which random access is performed in combination with an RTS / CTS method for starting data transmission in response to reception,
The communication station on the RTS receiving side measures the quality of the received signal, determines the data rate based on the measurement result, writes it in the CTS, and transmits it.
The communication station on the CTS receiving side performs data transmission resulting from reception of the CTS information based on the data rate described in the CTS.
This is a wireless communication system.

  However, “system” here refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter whether or not.

  The communication station on the RTS transmission side describes the time until the reception of the packet including the CTS information transmitted due to the reception of the RTS information is completed in the RTS as the media reservation time information Duration. Further, the communication station on the CTS transmission side describes the time until the reception of the data packet transmitted due to the reception of the CTS information is completed in the CTS as the media reservation time information Duration. Then, another communication station that has received the RTS or CTS sets up a NAV (Network Allocation Vector), validates it over the media reservation time information Duration, and enters a transmission non-permission state.

  According to the wireless communication system according to the first aspect of the present invention, it is possible to select the transmission rate based on the quality of the received signal, and thus it is possible to eliminate the incompleteness of the transmission rate.

  Here, the communication station on the RTS transmitting side describes in the RTS factor information that is referred to when determining the data rate in the communication station on the RTS receiving side, and the communication station on the RTS receiving side adds to the quality measurement result of the received signal. The data rate may be determined in consideration of factor information described in the RTS.

  As the factor information here, information regarding whether to actively determine a high data rate or to passively determine a low data rate is described. Then, the communication station on the RTS transmission side may measure the transmission error rate for the communication station on the RTS reception side and determine the factor information (Rate Strategy) based on the measurement result. Alternatively, the factor information can be determined based on the transmission power difference between the RTS packet and the data packet or the causal relationship between the data rate and the transmission power.

  In such a case, the data rate is determined by the quality of the RTS received signal on the receiving side, but the transmission rate is determined in consideration of information such as the error rate monitored by the transmitting side. It is possible to correct the correspondence between the reception quality and the error rate associated with the change in the state and the change in the interference amount in a second-order loop.

  The communication station on the RTS transmitting side described information on one or more data units to be transmitted in the RTS, while the communication station on the RTS receiving side determined that the information was related to the data units described in the RTS. Based on the data rate, the media reservation time information Duration for completing the reception of all data packets may be determined and described in the CTS. In this case, the communication station on the data transmission side that has received the CTS is caused by the reception of the CTS information based on the data rate described in the CTS and completed within the time specified by the media reservation time information. Send data.

  The information on the data unit mentioned here is, for example, the total data length of each data unit to be transmitted, the data length of one or more data units to be transmitted, and one or more data unit transmissions to be transmitted. And the number of data units to be transmitted (provided that the data unit has a fixed length).

  In such a case, it is possible to effectively multiplex the data unit while using the RTS / CTS procedure together, and further, it is possible to accommodate the RTS / CTS procedure and the delayed ACK. As a result, it is possible to reduce the amount of overhead generated in the MAC layer.

  In this case, when determining the media reservation time information after receiving the RTS, the communication station on the RTS receiving side considers the reception to be terminated until the time when the local station can receive it. Alternatively, when determining the media reservation time information after receiving the RTS, consideration is given so as not to exceed the period information described in the RTS.

  For example, the communication station on the RTS transmitting side gives a sequence number to the transmission data unit, describes the first sequence number of the data to be transmitted in the RTS, and notifies information on the data unit to be transmitted, The communication station on the RTS receiving side refers to the start sequence number of the data unit described in the RTS, extracts the already received data unit from the data units to be transmitted, and excludes it from the reception target. Then, media reservation time information may be determined.

  When the selective acknowledgment is applied, the communication station on the RTS transmission side compares the start sequence number of the data unit attempting data transmission and the reception confirmation information of the subsequent data unit relative to the start sequence number. The reception confirmation response information including the bitmap information mapped to the bit corresponding to the position is described in the RTS, and the information about the data unit is created only for the data unit for which the reception confirmation has not been obtained, On the other hand, the communication station on the RTS receiving side refers to the bitmap information described in the RTS, extracts the already received data unit from the data units to be transmitted, and excludes it from the reception target. Above, media reservation time information may be determined.

  The communication station on the RTS receiving side may describe the ACK information in the CTS when the already received data unit is included as the data unit to be transmitted described in the RTS. In this case, based on the ACK information added to the CTS, the communication station on the CTS receiving side excludes the data unit already received by the communication station on the RTS receiving side from the transmission target, and is described in the CTS. Data transmission may be performed based on the data rate.

  Further, the communication station on the RTS receiving side stores one or more pieces of data length information of the data unit to be received among the data to be transmitted due to the RTS, and the sequence number of the stored last data unit May be described in the CTS. In this case, the communication station on the CTS receiving side stores the sequence number of the final data unit described in the CTS, and indicates the sequence number of the final data unit when transmitting the next RTS. Information regarding a data unit to be transmitted in a format that does not include a data unit to be transmitted may be created.

According to a second aspect of the present invention, there is provided a wireless communication system for transmitting / receiving a plurality of data units, wherein a transmission data unit is assigned a sequence number to identify the data unit, and a selective acknowledgment is received. Is applied,
The communication station on the receiving side uses the sequence number up to the data units received in the order of the sequence number and the bitmap information represented by mapping the data reception status after the sequence number to the relative bit position from the sequence number. , Send it in the acknowledgment response information ACK,
The transmitting and receiving communication stations provide information indicating the data flow resulting from the transmission data and the acknowledgment,
This is a wireless communication system.

  According to the wireless communication system of the second aspect of the present invention, it is necessary for the selective confirmation response such as the sequence number of all received data units and the bitmap information describing the reception status of the subsequent data units. By managing information for each data flow, a plurality of service classes can be handled with different sequence numbers. Therefore, communication can be maintained regardless of whether or not the selective confirmation response is implemented.

  Here, the receiving station that does not support the selective confirmation response can ensure communication with the transmission station that supports the selective confirmation response function by transmitting the bitmap information in an all-clear manner. it can.

  Further, the transmitting station that does not support the selective confirmation response ignores the bitmap information transmitted from the reception side, and further transmits the bitmap information to be transmitted in an all-clear manner, thereby transmitting the selective confirmation response. It is possible to secure communication with a receiving station that supports the above function.

  In addition, for at least one data flow, an ARQ scheme without a sequence number is adopted, and when a link session is established, the sequence numbers of the transmitting station and the receiving station are synchronized by transmitting and receiving data via the data flow. To take.

The third aspect of the present invention starts data transmission in response to the fact that the data transmission source communication station has transmitted the transmission request packet RTS and has received the confirmation notification packet CTS from the data transmission destination communication station. A wireless communication system in which RTS / CTS is used in combination for random access,
Permit transmission / reception of packets in which any two or more of the transmission request RTS, confirmation notification CTS, data, and confirmation response ACK are multiplexed.
This is a wireless communication system.

  By including information having different purposes such as RTS, CTS, DATA, and ACK in one packet in this way, it is possible to greatly reduce the amount of overhead generated in the MAC layer.

  In such a case, the communication station that has received the packet containing the RTS information transmits the packet containing the CTS information according to the contents of the RTS. Further, the communication station that has received the packet including the CTS information transmits the packet including the data according to the contents of the CTS.

  Here, the communication station on the RTS transmission side may be able to designate whether or not the communication station on the reception side can add the RTS information to the CTS. In this case, the RTS describes first information indicating whether or not the RTS information may be added to the CTS transmitted due to the RTS. Then, the communication station on the RTS receiving side determines whether or not the RTS information may be added to the CTS based on the first information of the RTS, and data to be transmitted to the communication station on the RTS transmitting side Is present, RTS information for transmitting the data is added and a CTS is transmitted.

  In such a case, the communication station that transmits the RTS determines the first information based on an information element included in a packet received from the destination station of the RTS in the past, for example. The information element mentioned here refers to Morebit indicating that there is subsequent transmission data in the packet. Alternatively, the first information may be determined by determining that the subsequent transmission data exists in the RTS destination station by means other than the information element. For example, when an RTS is received from an RTS destination station, but the local station has set a NAV by receiving a packet from another peripheral station, the CTS cannot be returned and the data transmission sequence is stopped. Etc. Alternatively, it may be possible to determine that the subsequent transmission data exists at the destination station of the RTS based on other past communication history.

  When the RTS receiving communication station recognizes from the RTS information that the RTS transmitting communication station is attempting to transmit data already received by the RTS transmitting station, the RTS receiving communication station transmits ACK information to the CTS. May be added to notify the data reception state.

  Further, in the data transmission / reception procedure, the communication station on the data transmission side may specify whether or not the communication station on the data reception side should return ACK. ACK includes immediate ACK (Delay ACK) and delayed ACK (Immediate ACK). In such a case, if the communication station on the data receiving side has received the data requesting the ACK from the communication station on the data transmitting side, but determines that it has not transmitted the ACK for the data, the data transmitting side ACK information may be added when a packet is transmitted to the communication station on the side. In some cases, ACK information may be added in response to a request from the transmitting station. At this time, if it is determined that the ACK information related to the previously transmitted data has not been received, the transmitting station delivers a request to add the ACK information. However, ACK information may not be added exceptionally to a packet transmitted by RTS information alone.

  Further, data requesting ACK may be transmitted as a packet destined for two or more communication stations.

  In addition, when the RTS transmitting communication station requests the RTS receiving communication station to return an ACK related to the data transmitted so far, the RTS for starting the next data transmission transaction is set to ACK. ACK requests for requesting a reply may be multiplexed and transmitted.

  In addition, although the RTS transmission side communication station requests ACK, ACK may not be returned. In this case, there are cases where the transmission data is not correctly received, or the data is correctly received but the reception of the ACK has failed. The communication station on the RTS transmission side confirms whether the data should be retransmitted. There is a need. In such a case, the communication station on the RTS transmission side may multiplex and transmit an ACK request for returning an ACK to the RTS for starting the data retransmission transaction.

  On the other hand, the communication station that has received the RTS in which the ACK request is multiplexed returns an ACK indicating whether or not the data transmitted from the communication station on the RTS transmission side has been correctly received. Alternatively, when the data transmitted from the communication station on the RTS transmission side cannot be received, an ACK indicating that the data could not be received correctly may be multiplexed and a CTS requesting data retransmission may be returned.

According to a fourth aspect of the present invention, there is provided a wireless communication system in which a data transmission side communication station obtains a transmission right on a medium and performs data communication with a data reception side communication station.
After data transmission from the data transmission side communication station is stopped, the presence or absence of subsequent data in the data transmission side communication station is detected, and if there is subsequent data, the data transmission side communication station Make it easier to acquire the right to send subsequent data,
This is a wireless communication system.

  Here, the state in which data transmission is stopped despite the presence of subsequent data in the communication station on the data transmission side is, for example, that the RTS has arrived from the communication station on the data transmission side to the communication station on the data reception side. This corresponds to the case where the data receiving communication station returns a CTS but the data transmitting communication station does not start transmitting data or the transmission data does not reach the data receiving communication station. To do.

  The communication station on the data receiving side can detect the presence / absence of subsequent data in the communication station on the data transmitting side based on the communication history of transactions based on such RTS / CTS. Alternatively, when a data transmission side communication station performs packet transmission including a specific information element indicating the presence or absence of subsequent data, the data reception side communication station confirms this information element. It is possible to detect the presence or absence of subsequent data in the communication station on the data transmission side.

  In a communication environment in which media access control based on CSMA is performed in which a transmission right is acquired after waiting for an arbitrary back-off time after confirming the clear state of the medium for a predetermined time, the communication station on the data receiving side Tries to acquire the transmission right on the media, and transmits a signal on the medium to exclude the transmission right by other communication stations, so that the communication station on the data transmission side can transmit the subsequent data. The transmission right can be easily acquired.

  In addition, a medium that uses an RTS / CTS method in which a data transmission source communication station transmits a transmission request packet RTS and starts data transmission in response to receiving a confirmation notification packet CTS from the data transmission destination communication station. When access control is performed, the data receiving communication station transmits a pseudo RTS on the medium to exclude the transmission right from other communication stations, so that the data transmitting communication station An RTS for transmitting subsequent data can be easily transmitted. For example, when the communication station on the data transmission side receives a pseudo RTS, it can transmit an RTS for transmitting subsequent data with a shorter frame interval.

According to a fifth aspect of the present invention, data transmission is started in response to a data transmission source communication station transmitting a transmission request packet RTS and receiving a confirmation notification packet CTS from the data transmission destination communication station. A computer program described in a computer-readable format so as to execute processing for controlling a communication operation in a communication environment in which random access is performed by using an RTS / CTS method, on a computer system,
A communication quality measurement step for measuring the quality of a received signal at the time of RTS reception;
A data rate determining step for determining a data rate based on the measured quality of the received signal;
A CTS transmission step of transmitting the data rate in a CTS resulting from the received RTS;
A data transmission step of transmitting data resulting from the CTS information based on the data rate described in the CTS when the CTS information is received;
A computer program characterized by comprising:

According to a sixth aspect of the present invention, there is provided a computer program written in a computer-readable format so as to execute a control of a communication operation for transmitting / receiving a plurality of data units on a computer system. When a data unit is identified by assigning a sequence number to the data unit, and selective acknowledgment is applied,
In response to data reception, the sequence number up to the data units received in order of the sequence number and the bitmap information represented by mapping the data reception status after the sequence number to the relative bit position from the sequence number A step of transmitting the information in the acknowledgment response information ACK,
Sending transmission data and confirmation response with information indicating the resulting data flow; and
A computer program characterized by comprising:

Further, according to a seventh aspect of the present invention, data transmission is started in response to a data transmission source communication station transmitting a transmission request packet RTS and receiving a confirmation notification packet CTS from the data transmission destination communication station. A computer program described in a computer-readable format so as to execute processing for controlling a communication operation on a computer system in a communication environment in which RTS / CTS is used for random access.
An information generation step for generating each information of a transmission request RTS, a confirmation notification CTS, data, and a confirmation response ACK;
A packet communication step of transmitting and receiving a packet in which any two or more pieces of information among a transmission request RTS, a confirmation notification CTS, data, and a confirmation response ACK are multiplexed;
A computer program characterized by comprising:

According to an eighth aspect of the present invention, there is provided a computer in which processing for controlling a communication operation in a communication environment in which data communication is performed after a communication station obtains a transmission right on a medium is executed on a computer system. A computer program written in a readable format,
Detecting the presence or absence of transmission data from other communication stations;
In order to eliminate the transmission right by another communication station so that the communication station can easily acquire the transmission right for transmitting data in response to detecting the presence of transmission data from the other communication station. A medium access control step for transmitting a signal on the medium;
A computer program characterized by comprising:

  The computer program according to each of the fifth to eighth aspects of the present invention defines a computer program described in a computer-readable format so as to realize predetermined processing on a computer system. In other words, by installing the computer program according to each of the fifth to eighth aspects of the present invention in the computer system, a cooperative action is exhibited on the computer system, and it operates as a wireless communication device. By activating a plurality of such wireless communication devices to construct a wireless network, the same operational effects as those of the wireless communication system according to the first to fourth aspects of the present invention can be obtained.

  According to the present invention, it is possible to provide an excellent radio communication system, radio communication apparatus and radio communication method, and computer program capable of suitably performing access control based on CSMA while using the RTS / CTS scheme together. it can.

  Further, according to the present invention, an excellent wireless communication system, wireless communication, which can provide a flexible transmission / reception procedure by multiplexing a plurality of types of frames such as RTS, CTS, DATA, ACK, etc., and reduce overhead. A communication apparatus, a wireless communication method, and a computer program can be provided.

  According to the present invention, since it is possible to select a transmission rate based on the quality of the received signal, it is possible to eliminate imperfections in the transmission rate. In addition, since the transmission rate is determined in consideration of information such as the error rate monitored by the transmission side, the correspondence between the reception quality and the error rate associated with the fluctuation of the channel state and the fluctuation of the interference amount is like a second-order loop. It becomes possible to correct to.

  Further, according to the present invention, it is possible to effectively multiplex data units while using the RTS / CTS procedure together, and further, it is possible to accommodate the RTS / CTS procedure and the delayed ACK. As a result, it is possible to reduce the amount of overhead generated in the MAC layer.

  Further, according to the present invention, it is possible to maintain communication for selective confirmation responses regardless of whether or not they are implemented.

  Further, according to the present invention, it is possible to greatly reduce the amount of overhead generated in the MAC layer by including information having different purposes such as RTS, CTS, DATA, and ACK in one packet.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

FIG. 1 is a diagram illustrating an arrangement example of communication apparatuses constituting a wireless communication system according to an embodiment of the present invention. FIG. 2 is a diagram schematically illustrating a functional configuration of a wireless communication apparatus that operates as a communication station in the wireless network according to the embodiment of the present invention. FIG. 3 is a diagram showing a configuration example of a frame format used in the wireless communication system according to the present invention. FIG. 4A is a diagram illustrating a configuration example of PSDU (RTS frame). FIG. 4B is a diagram illustrating a configuration example of PSDU (CTS frame). FIG. 4C is a diagram illustrating a configuration example of a PSDU (ACK frame). FIG. 4D is a diagram illustrating a configuration example of PSDU (data frame). FIG. 5A is a diagram showing a packet (multiple data frame) in which two MSDUs are multiplexed. FIG. 5B is a diagram showing a packet (data + RTS frame) in which one MSDU and RTS information are multiplexed. FIG. 5C is a diagram illustrating a packet (CTS + ACK frame) in which CTS information and ACK information are multiplexed. FIG. 5D is a diagram illustrating a packet (data + RTS + CTS + ACK frame) in which one MSDU, RTS information, CTS information, and ACK information are multiplexed. FIG. 6 is a diagram for explaining a process for determining a transmission rate in the wireless communication system according to the present invention. FIG. 7 is a diagram showing an example of an operation sequence of the RTS / CTS procedure in the present invention. FIG. 8 is a diagram for explaining an application example of the transmission / reception procedure in the present invention. FIG. 9 is a diagram for explaining an application example of the transmission / reception procedure in the present invention. FIG. 10 is a diagram for explaining an application example of the transmission / reception procedure in the present invention. FIG. 11 is a diagram showing a confirmation response procedure regarding data other than data flow 0 assumed in the present invention. FIG. 12 is a diagram showing a specific example of the interaction of each field when performing a selective confirmation response using both RTS / CTS. FIG. 13 is a diagram illustrating an example of a data transmission / reception procedure when the delayed ACK and the RTS / CTS procedure are applied. FIG. 14 is a diagram showing an example of a sequence when traffic is transmitted / received via TCP / IP according to the MAC procedure according to the present invention. FIG. 15 is a diagram showing a frame format in IEEE 802.11a. FIG. 16A is a diagram showing the structure of the frame field of the PSDU of the RTS frame. FIG. 16B is a diagram showing the structure of the frame field of the PSDU of the CTS and ACK frame. FIG. 16C is a diagram showing the structure of the frame field of the PSDU of the DATA frame. FIG. 17 is a diagram schematically illustrating an operation example of the RTS / CTS procedure. FIG. 18 is a diagram for explaining an action that can occur in a peripheral station when an RTS / CTS procedure is performed between transmitting and receiving stations. FIG. 19 is a diagram for explaining the procedure for determining the transmission rate mode for the entire transaction at the time when STA0 as the transmission source transmits the RTS. FIG. 20 is a diagram showing an example of an operation sequence when a packet transmission / reception transaction based on the RTS / CTS procedure in IEEE802.11 is realized by traffic via TCP / IP. FIG. 21 is a diagram for explaining an application example of the transmission / reception procedure in the present invention. FIG. 22 is a diagram for explaining an application example of the transmission / reception procedure in the present invention. FIG. 23 is a diagram for explaining an application example of the transmission / reception procedure in the present invention. FIG. 24 is a diagram for explaining a mechanism for controlling determination as to whether or not “information that RTS may be multiplexed” is set in CTS. FIG. 25 is a diagram for explaining a mechanism for controlling determination as to whether or not “information that RTS may be multiplexed” is set in CTS. FIG. 26 is a diagram for explaining a mechanism for controlling determination as to whether or not “information that RTS may be multiplexed” is set in CTS.

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

A. System Configuration The communication propagation path assumed in the present invention is wireless, and a network is constructed among a plurality of communication stations. The communication assumed in the present invention is a storage and exchange type traffic, and information is transferred in units of packets. In the following description, each communication station assumes a single channel. However, the communication station can be extended when a transmission medium including a plurality of frequency channels, that is, multi-channels is used.

  In the wireless network according to the present invention, each communication station transmits information directly (randomly) according to an access procedure based on CSMA (Carrier Sense Multiple Access) to construct an autonomous distributed wireless network. Can do.

  In an autonomous decentralized wireless communication system that does not have a relationship between a control station and a controlled station, for example, each communication station broadcasts beacon information, so that other communication stations in the vicinity (that is, within the communication range) are self-existing. And notify the network configuration. In addition, a communication station that newly appears in the communication range of a certain communication station detects that it has entered the communication range by receiving a beacon signal, and recognizes the network by decoding the information described in the beacon. And can enter the network.

  In the wireless network according to the present invention, transmission control that effectively utilizes channel resources by transmission (MAC) frames having a time division multiple access structure that is time-synchronized gradually by exchanging beacon signals between communication stations. Is done. Therefore, each communication station can perform an access method based on time synchronization, such as reserving a band or setting a priority use period.

  The processing in each communication station described below is basically processing executed in all communication stations that enter the network. However, depending on the case, not all communication stations configuring the network execute the processing described below.

  FIG. 1 shows an arrangement example of communication devices constituting a wireless communication system according to an embodiment of the present invention. In this wireless communication system, there is no relationship between a control station and a controlled station, and each communication device operates in an autonomous distributed manner to form an ad hoc network. In the figure, a state where communication devices # 0 to # 6 are distributed in the same space is shown.

  In addition, the communication range of each communication device is indicated by a broken line in the same figure, and is defined as a range in which signals transmitted by itself can interfere with each other as well as communication with other communication devices within the range. That is, the communication device # 0 is in a range in which communication is possible with communication devices # 1, # 4 in the vicinity, and the communication device # 1 is in a range in which communication is possible with communication devices # 0, # 2, # 4 in the vicinity. The communication device # 2 is in a range in which communication with the communication devices # 1, # 3, and # 6 in the vicinity is possible, and the communication device # 3 is in a range in which communication is possible with the communication device # 2 in the vicinity. , Communication device # 4 is in a range where it can communicate with neighboring communication devices # 0, # 1, # 5, and communication device # 5 is within a range where it can communicate with neighboring communication device # 4. Device # 6 is in a range where it can communicate with communication device # 2 in the vicinity.

  When communication is performed between specific communication devices, there is a communication device that can be heard from one communication device that is a communication partner but cannot be heard from the other communication device, that is, a “hidden terminal”.

  Note that the scope of application of the present invention is not limited to the above-described ad hoc environment, and each communication station can directly and asynchronously transmit information according to an access procedure based on CSMA using an RTS / CTS procedure together. The present invention can also be widely applied to the above communication forms.

  FIG. 2 schematically shows a functional configuration of a wireless communication apparatus that operates as a communication station in a wireless network according to an embodiment of the present invention. The illustrated wireless communication apparatus can form a network by performing access control based on CSMA in combination with an RTS / CTS procedure in an autonomous distributed communication environment in which no control station is arranged.

  As illustrated, the wireless communication device 100 includes an interface 101, a data buffer 102, a central control unit 103, a beacon generation unit 104, a wireless transmission unit 106, a timing control unit 107, an antenna 109, and wireless reception. Unit 110, beacon analysis unit 112, and information storage unit 113.

  The interface 101 exchanges various types of information with an external device (for example, a personal computer (not shown)) connected to the wireless communication apparatus 100.

  The data buffer 102 is used to temporarily store data sent from a device connected via the interface 101 and data received via the wireless transmission path before sending the data via the interface 101. The

  Central control unit 103 centrally performs a series of information transmission and reception processing management and transmission path access control in radio communication apparatus 100. In the central control unit 103, for example, access control based on CSMA is performed while using an RTS / CTS procedure together. In this embodiment, a transmission / reception procedure for multiplexing a plurality of types of frames such as RTS, CTS, DATA, and ACK is performed. Details of these processing procedures will be described later.

  The beacon generation unit 104 generates a beacon signal that is periodically exchanged with a nearby wireless communication device.

  The wireless transmission unit 106 includes a modulator that modulates a transmission signal by a predetermined modulation method, a D / A converter that converts a digital transmission signal into an analog signal, an upconverter that converts the frequency of the analog transmission signal and upconverts, Includes a power amplifier (PA) that amplifies the power of the converted transmission signal (both not shown), and wirelessly transmits data, beacon signals, etc. temporarily stored in the data buffer 102 at a predetermined transmission rate .

  The radio reception unit 110 includes a low noise amplifier (LNA) that amplifies a signal received from another station via the antenna 109, a down converter that downconverts the voltage amplified reception signal by frequency conversion, and an automatic gain controller ( AGC), an A / D converter that digitally converts an analog received signal, synchronization processing for acquisition of synchronization, channel estimation, a demodulator that performs demodulation processing according to a predetermined demodulation method (all not shown), and the like It receives and processes signals such as information and beacons sent from other wireless communication devices over time.

  As a wireless transmission / reception method in the wireless transmission unit 106 and the wireless reception unit 110, various communication methods suitable for relatively short-distance communication applicable to a wireless LAN, for example, can be applied. Specifically, a UWB (Ultra Wide Band) method, an OFDM (Orthogonal Frequency Division Multiplexing) method, a CDMA (Code Division Multiple Access) method, or the like can be adopted.

  The antenna 109 wirelessly transmits a signal to another wireless communication device on a predetermined frequency channel, or collects a signal transmitted from the other wireless communication device. In this embodiment, it is assumed that a single antenna is provided and that transmission and reception cannot be performed in parallel.

  The timing control unit 107 controls timing for transmitting and receiving radio signals. For example, the transmission timing and reception timing of each packet such as RTS, CTS, DATA, ACK, etc. or a packet obtained by multiplexing these packets, the beacon transmission timing of the own station, the beacon reception timing from other stations, and the like are controlled.

  The beacon analysis unit 112 analyzes a beacon signal that can be received from an adjacent station, and analyzes the presence of a nearby wireless communication device. For example, information such as beacon reception timing of neighboring stations and neighboring beacon reception timing is stored in the information storage unit 113 as neighboring device information.

  The information storage unit 113 stores an execution procedure instruction (a program describing a collision avoidance processing procedure, etc.) such as a series of access control operations executed in the central control unit 103, neighboring device information obtained from the analysis result of the received beacon, and the like. Save it.

B. Frame format (packet format)
FIG. 3 shows a configuration example of a frame format used in the wireless communication system according to the present invention. However, in the same figure, the preamble and PLCP header shown in FIG. 15 are omitted, and only the part indicated as PSDU (PHY Service Data Unit) is extracted and shown.

  As shown in the figure, the PSDU is composed of a MAC header part and an MSDU (MAC Service Data Unit: one data unit passed from an upper layer) part. In the present embodiment, a plurality of MSDUs can be stored for one PSDU. The MAC header part is composed of a common MAC header part, a sub MAC header part, and an HCS (Header Check Sequence) part. A plurality of sub MAC headers can be stored as sub MAC headers.

  FIG. 4 shows a configuration example of the PSDU according to the present embodiment. Each of the frames shown in FIGS. 4A, 4B, 4C, and 4D corresponds to a conventional RTS frame, CTS frame, ACK frame, and data frame (see FIG. 16).

  The header length (HLen), destination address (RA), source address (TA), and Duration defined in common for each frame correspond to a common MAC header portion. Table 2 shows details of each field of the common MAC header part.

The sub MAC header part is defined in a different manner depending on the purpose of each frame. For example, RTSSMH (Sub MAC Header) is stored as a sub MAC header in a packet corresponding to an RTS frame, CTSSMH is stored as a sub MAC header in a packet corresponding to a CTS frame, and as a sub MAC header in a packet corresponding to an ACK frame. ACK
SMH is stored, and DATASMH is stored as a sub MAC header in a packet corresponding to a data frame.

  In each frame of RTS, CTS, and ACK, a PSDU is composed only of the MAC header part, and no MSDU part exists. On the other hand, data specified by DATASMH is added to the data frame as a frame body.

  FIG. 5 shows some examples of PSDUs that can be defined in the present invention. FIG. 5A shows a packet (multiple data frame) in which two MSDUs are multiplexed. FIG. 5B shows a packet (data + RTS frame) in which one MSDU and RTS information are multiplexed. FIG. 5C shows a packet (CTS + ACK frame) in which CTS information and ACK information are multiplexed. FIG. 5D shows a packet (data + RTS + CTS + ACK frame) in which one MSDU, RTS information, CTS information, and ACK information are multiplexed.

If you want to send RTS, add RTS SMH as SMH, if you want to send CTS, add CTS SMH as SMH, if you want to send ACK, add ACKSMH as SMH, and if you want to send a data unit DATA for the number of data units you want to send
Add SMH. This makes it possible to multiplex information of different purposes such as RTS, CTS, DATA, and ACK into one packet.

  Next, details of the constituent elements of each SMH will be described with reference to Tables 3 to 6. The head field of each SMH is a Type field, and an identifier indicating what information the SMH contains is described. Although the length of the SMH differs depending on the type of the SMH, each SMH type has a unique length. Therefore, the receiving side can know the length of the SMH by referring to the Type field.

DATA SMH fields:
Table 3 describes details of DATA SMH fields used when transmitting general-purpose data other than RTS, CTS, and ACK. As shown below, DATA SMH is composed of Attribute, Sequence, and Length fields.

  In the Attribute field, an identifier indicating the attribute of data designated by the DATA SMH is described.

  In the Data Flow section, the data flow of the data is stored. Here, it is assumed that a data flow having a plurality of attributes can be defined for each link. Data flows with different attributes are used for purposes such as defining different ARQ (Automatic Repeat reQuest) schemes for each data flow, or handling different priority traffic for each data flow.

  The ACK Type section stores information indicating what kind of ACK is requested to be returned to the receiver that has received the data. Specifically, the ACK Type section includes an immediate ACK (Im-ACK) request, a delayed ACK ( Del-ACK) request and three types of information not requiring ACK are notified. When an immediate ACK request is specified, the receiving side returns a packet containing ACK information immediately after receiving the data. Also, when a delayed ACK request is specified, ACK return preparation is performed, but ACK information is not transmitted until some packet is transmitted to the data transmission source (other than RTS for the data transmission source). ACKSMH is added when transmitting any of the packets). In addition, when an ACK unnecessary message is notified, ACK is not returned.

  The More Bit section stores information indicating whether or not data to be transmitted is accumulated even though the packet is transmitted. The receiver stores the address of the transmission source station of the packet in which the More Bit part was most recently set, and in some cases, performs polling to the station. The polling procedure is not directly related to the gist of the present invention and will not be further described.

  The Fragment part is used for the purpose of indicating a break in data when the data is fragmented.

  In the Sequence field, a sequence number assigned to the data is stored. It is assumed that sequence numbers are assigned to data units in ascending order as 0, 1, 2, 3,... As performed in general data communication. Further, the sequence numbers are reused by circulating from 0 to 255 in a ring shape.

  In the Length field, the length of the data is stored.

ACK SMH fields:
Table 4 describes the components of the ACK SMH field used when transmitting ACK information. As described below, the ACK SMH is composed of fields of ACK Attribute, ACK Sequence / Type, and Received MAP.

  In the ACK Attribute field, an identifier indicating the ACK attribute is described, and in the Data Flow part, it is indicated in which data flow the ACK information of the transmitted data is. Here, immediate ACK (Im-ACK) is used when 0 is selected as the data flow, and selective ACK (Sel-ACK) is used when any other data flow is selected. Assume the case.

  When the data flow is not 0, the ACK Sequence / Type field is a field indicating up to which sequence number of the data flow reception has been completed sequentially. For example, when the value 6 is stored, it indicates that all data up to sequence number 6 has been received. When 0 is selected as the data flow, immediate ACK is used, and the data type of the data is transcribed to indicate which data is ACK.

  The Received MAP field is a field that indicates whether there is data that has been received after the data indicated by ACK Sequence. Subsequent sequence numbers are associated in the bitmap with reference to the sequence number indicated by ACK Sequence, and the bit corresponding to the received data (sequence number) is marked. This corresponds to the number next to the sequence number indicated by the MSB in the ACK Sequence. For example, if the Received MAP field is composed of 8 bits, the sequence number of the ACK Sequence field is 23, and the Received MAP is 00100000, all the data up to 23 has been received and (Received MAP is The data that can be received from the 24th to the 8th is represented by a bitmap, and after that, the 24th and 25th are NG, the 26th is received, and the data after that is not received "means To do.

A transmission / reception method in which the receiving side holds data units received in such a manner is called selective acknowledgment (Selective ACK). If the receiver supports the selective confirmation response, a Received MAP is created according to the above-described rules. On the other hand, if the receiver does not support the selective acknowledgment, the data that could not be received sequentially is discarded and Received
All zero is described in MAP.

RTS SMH fields:
Table 5 describes the components of the RTS SMH field used when transmitting RTS information. As described below, RTSSMH is composed of fields of RTS Attribute, RTS Sequence, RTS Received MAP, Max Duration, and Length (or Number Of Data Unit).

  In the RTS Attribute field, an identifier indicating the attribute of the RTS information is described.

  The Data Flow section stores a data flow of data to be transmitted.

  The Rate Strategy section stores auxiliary information that is referred to when determining the data transmission rate. This ancillary information is whether the transmission rate should be aggressively high, should be chosen to be slightly aggressive, should be chosen to be slightly more aggressive, should be chosen to be somewhat less aggressive, or should be chosen to be less aggressive, It is used for the purpose of biasing the decision criteria. Details of how to use the Rate Strategie part will be described later.

  The Rate Set section stores instruction information indicating whether or not transmission can be performed at a fixed transmission rate applied in RTS. When transmission is performed at a fixed transmission rate, the above description of the Rate Storage portion is ignored.

  The RTS / CTS Mux section stores information as to whether or not to permit addition of RTS information to a CTS packet transmitted in response to the RTS. If the addition of the RTS is permitted, the station that receives the RTS and returns the CTS adds the RTS information to the CTS and transmits the data when the station addressed to the transmission source station of the RTS is held. It is allowed to perform bidirectional communication in one transaction.

  The ACK Request section stores information on whether or not to request addition of ACK information to the CTS packet transmitted in response to the RTS. If the addition of ACK information is requested, the station that receives the RTS and returns the CTS adds the ACK information of the data received from the RTS transmission source station to the CTS and transmits it.

  The RTS Sequence field is a field in which the sequence number of the first data is described among the data that the transmission source station is trying to transmit. By referring to this field, the destination station of the RTS can know whether or not the transmission source station is attempting to transmit data that overlaps with data that has already been received.

The RTS Received MAP field is effective when a selective acknowledgment is used together. Based on the sequence number indicated in the RTS Sequence field, the data corresponding to the subsequent sequence number is associated with the bit map in the bitmap, and the bit corresponding to the data (sequence number) recognized by the receiving station is marked. To do. The MSB corresponds to the sequence number indicated by the RTS sequence. For example, RTS
When the Received MAP field is composed of 8 bits, the sequence number of the RTS Sequence field is 23, and the Received MAP is 00100000, “23rd, 24th and 25th data are skipped and the 26th and subsequent data are continuous. And try to send ". By referring to this field, the destination station of the RTS can know whether or not the transmission source station is attempting to transmit data that overlaps with data that has already been received.

  The Max Duration field is used for the purpose of the transmission side setting the maximum data transmission period in the current data transmission transaction. For example, if it is desired to end the transmission of data within 200 microseconds in this transaction due to the circumstances of the transmitting station, a value indicating 200 microseconds in this field (or the RTS / CTS procedure from 200 microseconds) Value obtained by subtracting the time required for. The RTS destination station has the right to determine the data reception period. At this time, the RTS destination station determines the data reception period so as not to exceed the period indicated by the Max Duration field.

  In the Length field, the length of data to be transmitted is described. In the first configuration example, when transmission of a plurality of data units in one packet is permitted, one or more pieces of Length information (number of bits and number of bytes) are defined. Here, for example, a case is assumed where N pieces of length information (typically fixed values, but may not be fixed values) are defined. Note that a data unit that the receiving side has already recognized has been excluded from data to be transmitted. For example, if the sequence number in the RTS Sequence field is 23 and the Received MAP is 00100000, the length of the 23th data unit is set in Length0, and the length of the 24th data unit is set in Length1. Store. Also, Length 2 stores the length of the 26th data unit instead of the 25th received data.

  As a second configuration example, the total length of a plurality of data units to be transmitted may be posted as Length information. In this case, the RTS Sequence field describes the sequence number of the head data of the plurality of data units.

  As a third configuration example, the Length field may describe the length of data to be transmitted in terms of time. In this case, in the Length field, a plurality of times for occupying a channel when transmitting data to be transmitted or a plurality of data groups are described for each case when transmitting at several data rates. Here, for example, it is assumed that N pieces of Length information are defined (the time length required for data transmission in each case assuming that transmission is performed at N types of data rates is described).

  As a fourth configuration example, when the length of the data unit to be transmitted is a fixed value, the Number Of Data Unit field may be defined instead of the Length field. In this case, this field describes the number of data units to be transmitted.

  In addition to the above, the Directed Address field may be defined in the RTS SMH. This is used when the destination of the common MAC header is broadcast or multicast and it is desired to send RTS information to a specific station. In the Directed Address field, the RTS destination address is described.

CTS SMH fields:
Table 6 describes the components of the CTS SMH field used when transmitting CTS information. As described below, the CTS SMH is composed of CTS Attribute, RATE, and Stored Sequence fields.

  In the CTS Attribute field, an identifier indicating the attribute of the CTS information is described.

  The Data Flow section stores a data flow of data that is about to be received.

  The RATE field stores a value indicating the transmission rate of data transmitted in response to CTS transmission.

  In the Stored Sequence field, a sequence number indicating how many data length information of the sequence number the data reception side (CTS transmission side) holds is stored. When the communication station does not have a function for holding data length information, the number immediately preceding the Sequence number indicated in the RTS Sequence field is stored, or the communication station holds data length information. Is stored as a value indicating NULL.

  In the above, for convenience of explanation, CMH and SMH exist independently in PSDU, and an example in which a plurality of each type of SMH is added independently is shown, but a format including similar information components Then, since one aspect of the object of the present invention is achieved, the present invention is not limited to the above format.

  For example, it is desirable that the information elements corresponding to the MAC header are arranged together at the beginning of the packet as described above, but may be arranged after or between data units constituting the packet. In particular, DATA SMH may be used in a case where it is arranged immediately before the data unit corresponding to the SMH.

  For example, the RA, TA, and Duration fields are illustrated as being arranged in the CMH, but there are also examples in which these fields are arranged in the PLCP section. In the Duration field, media reservation time information is stored. However, the Duration field is not necessarily composed of a field in which length information is described in units of microseconds, and it is possible to instruct a transmission non-permission state over a desired time zone to a communication station other than the destination. There is also a usage example that is composed of information or information groups. Hereinafter, for convenience of explanation, the case where the Duration field exists will be described as an example.

C. Transmission Rate Determination Process A process for determining a transmission rate in the wireless communication system according to the present invention will be described with reference to FIG.

  In the present invention, access control based on CSMA is performed using the RTS / CTS procedure together. In such a case, the CTS information is transmitted in response to the reception of the RTS information, and the data is transmitted in response to the reception of the CTS. The CTS transmitting station determines the receivable transmission rate by measuring the quality of the RTS received signal, and notifies the CTS destination station. The destination station of CTS transmits data in response to the CTS information, and the transmission rate indicated in the RATE field of CTS is applied as the transmission rate of this data. The process for determining the transmission rate is as follows.

Step 1) Measure quality such as received SINR based on RTS received signal.
Step 2) Determine the transmission rate by biasing the measured quality or transmission rate class according to the value indicated in the Rate Strategy field of the RTS. For example, in the case of IEEE802.11a, it is determined from eight types of transmission rate modes of 6, 9, 12, 18, 24, 36, and 54 Mbps defined.

  Here, when biasing the measured quality, the received SINR value measured in accordance with the value indicated by Rate Strategie is biased by ± several dB level, and a lookup table or the like is used based on the biased received SINR value. Determine the transmission rate class that can be received.

  In addition, when the transmission rate class is biased, a transmission rate class that can be received is extracted using a lookup table or the like based on the measured received SINR value, and the extracted transmission rate class is indicated by Rate Strategy. Shift according to the value.

  Depending on the characteristics of the physical layer, this shift processing may be applied only when a high rate class is selected, or may be applied only when a low rate class is selected. To do.

  The data transmission station (RTS transmission station) that received the CTS holds the transmission rate class specified in the RATE field as the default transmission rate class addressed to the CTS transmission source station, and at the next RTS or data transmission time Make it available for reference. When transmitting an RTS, this default transmission rate class is referred to, and this transmission rate class or a transmission rate class one lower (tolerant to one-stage noise) is applied. Further, when data is transmitted without using RTS / CTS, the default transmission rate class is applied instead of the transmission rate class notified by CTS.

  When transmitting the data unit, the RTS transmitting station counts the number of times of transmitting the data unit for the first time and the number of times of transmitting the data unit as retransmissions for each destination. By referring to these values, it is possible to extract the transmission error rate for each destination. Based on the transmission error rate for each destination, the Rate Strategy of the RTS information can be determined. Specifically, a lower limit threshold and an upper limit threshold of the transmission error rate are defined, and when the transmission error rate exceeds the upper limit threshold, the value for Rate Strategie is decremented in a negative direction and retained. Conversely, if the transmission error rate exceeds the lower threshold, the value for Rate Strategy is incremented in the positive direction and held. When transmitting the RTS, the held Rate Strategy is transferred to the Rate Strategy field of the RTS. It is important to reset the count value for obtaining the transmission error rate when the held value for Rate Strategy is changed.

  Through the above procedure, the transmission rate is determined by the received signal quality of the RTS, but is adapted according to the error rate (bit error rate (BER) or packet error rate (PER)) monitored by the transmission side. It is possible to control by a double loop that the transmission rate is biased.

  In other words, as a method different from the above, an implementation in which the transmission error rate is measured on the reception side instead of the data (RTS) transmission side may be considered. In this case, the error rate is monitored on the receiving side, and similarly, control by a double loop in which the transmission rate applied according to the error rate is biased is performed. However, this method involves certain risks if it is not accompanied by an RTS / CTS procedure. This is because in an environment where errors occur frequently, the receiving side cannot even recognize that a packet is being transmitted. When RTS / CTS is used together, the error rate is calculated using the packet received after transmitting the CTS as a parameter.

  The essence of Rate Strategy is to provide a methodology for conveying auxiliary information for rate selection decisions at the convenience of the sender. As described above, when the reception side measures the transmission error rate, the transmission side may set the value of Rate Strategy due to factors other than the error rate. For example, the value of Rate Strategy can be set due to the transmission power difference between the RTS packet and the data packet, or the value of Rate Strategy can be set due to the causal relationship between the transmission rate and the transmission power (for example, (See Japanese Patent Application No. 2003-6973, which has already been assigned to the present applicant).

D. Basic CSMA Procedure In the wireless communication system according to the present invention, access control based on CSMA is performed using the RTS / CTS procedure together. FIG. 7 shows an example of an operation sequence of the RTS / CTS procedure in the present invention. In this figure, there is assumed a communication environment in which there are four communication stations, STA2, STA0, STA1, and STA3, and only adjacent communication stations in the figure are located in the radio wave reachable range. Here, it is assumed that STA0 wants to send information to STA1.

  STA0 confirms that the medium is clear for a certain period (from time T0 to time T1), for example, according to a general CSMA procedure, and then transmits a packet including RTS information to STA1 from time T1.

  Here, in the Duration field of the packet including RTS information, the time until the reception of the packet including the CTS information transmitted due to the reception of the RTS information is completed (that is, the time from T2 to T4) is described. The At this time, the time length described in the Duration field may include the time up to around time T5 with a slight margin added to the time up to time T4. Alternatively, the time until slightly before time T4 may be described.

  In addition, STA0 maintains a list of length information of data units to be transmitted to STA1, and this is called a “transmission data unit candidate list”.

  When the RTS SMH adopts the first configuration example described above, the length field in the RTS SMH indicates the length (number of bits and number of bytes) of data units in the transmission data unit candidate list. Describe as data length information. When the number N of Length fields is less than the number of data units to be transmitted, the result of adding the lengths of several data units is written in the Length field, as in the second configuration example described later. There is also a case.

  In addition, when the RTS SMH adopts the second configuration example, the length field in the RTS SMH includes the total length of one or more data units in the transmission data unit candidate list as data length information. Describe.

  Further, when the RTS SMH adopts the third configuration example, the length field in the RTS SMH includes the time length required for transmitting the data unit in the transmission data unit candidate list as the data length information. Describe. Since the time length varies depending on the data rate to be transmitted, a plurality of time lengths in the case of transmission at several data rates may be listed.

  In addition, when the RTS SMH adopts the fourth configuration example, the Number Of Data Unit field (defined in place of the Length field) in the RTS SMH includes a data unit in the transmission data unit candidate list. The number is described as data length information.

  The packet including this RTS information is also received by STA2 located in the vicinity of STA0. STA2 confirms the destination of the common MAC header based on the transmission rate information of the PSDU part obtained from the RATE field in the PLCP header, and if it cannot confirm that it is destined for its own station, the STA2 uses the RATE field and LENGTH field in the PLCP header. The time T2 is recognized, and further, the time T4 is recognized by referring to the Duration field of the common MAC header, and the NAV is set for the time until T4 and transmission is not permitted.

  The packet including this RTS information is also received by the destination STA1. The STA1 confirms the destination of the common MAC header based on the transmission rate information of the PSDU part obtained from the RATE field in the PLCP header, and recognizes that it is addressed to its own station. Further, when the STA1 succeeds in decoding the sub MAC header, the STA1 recognizes that there is a data packet transmission request addressed to the local station from the STA0, and determines the transmission rate based on the information obtained from the packet including the received RTS information.

  Further, the STA1 obtains the data length information to be received by referring to the Length field (or Number Of Data Unit field) of the RTS SMH.

  When the RTS SMH adopts the above-described first configuration example, the STA1 obtains a list of length information of received data units. This list is referred to as a “received data unit candidate list”. By sequentially referencing this list, the number of data units that can be received and the reception period (data.multidot.data) when receiving at the determined transmission rate, as long as the period specified in the Max Duration of RTS SMH is not exceeded. The time until T6, which is the time when packet transmission ends, is counted.

  Further, when the RTS SMH adopts the second configuration example, the STA1 obtains the total length of one or more data units to be received. STA1 considers whether or not the data unit group of the specified length can be received when receiving at the determined transmission rate, as long as it does not exceed the period specified by the Max Duration of RTS SMH. The reception period is counted.

  Further, when the RTS SMH adopts the third configuration example, the STA1 obtains a time length candidate of the received data packet. The STA1 extracts one reception period (time length) corresponding to the determined transmission rate from the Length field.

  Further, when the RTS SMH adopts the fourth configuration example, the STA1 obtains information on the number of data units to be received from the Number Of Data Unit field. If the length of the data unit is uniquely fixed, this information is equivalent to the “Received Data Unit Candidate List”, and by referring to the length and number of data units, the RTS SMH As long as the period specified by Max Duration is not exceeded, the number of data units that can be received and the reception period are counted when reception is performed at the determined transmission rate.

  At this time, if the STA1 wants to limit the reception period for the convenience of its own station, the STA1 may set this reception period as a threshold for the reception period together with the period instructed by Max Duration. Further, STA1 transmits a packet including CTS information, transcribes the value obtained in the reception period calculated here in the Duration field of the packet, and the determined transmission rate class in the RATE field. Post.

  The packet itself including CTS information is transmitted at a transmission rate that is most excellent in noise characteristics in many cases, and the possibility that a packet including CTS information cannot be decoded is minimized.

  On the other hand, if STA1 fails to decode the packet including RTS information, the packet including CTS information is not returned by the expected time T4, so STA0 includes RTS information again according to the random backoff procedure. Try to retransmit the packet. At this time, STA2 also lowers the NAV at time T4, changes to a normal transmittable state, and the damage in which a packet containing CTS information is not returned is minimized.

  When STA1 succeeds in decoding a packet including RTS information, a packet including CTS information is returned to STA0 as scheduled at time T4 by the above procedure.

  The packet including this CTS information is also received by STA3 located in the vicinity of STA1. STA3 decodes the Duration field of the packet including the CTS information, and if it cannot confirm that it is addressed to itself by referring to the RA address, STA3 stops transmission by setting NAV for the time indicated by the Duration field . As a result, the STA3 is not allowed to transmit until time T6, which is the time indicated by the Duration field.

  The packet including this CTS information is also received by the destination STA0. STA0 recognizes that STA1 is ready to receive STA1 by decoding PSDU and desires reception within the period indicated by Duration at the transmission rate indicated in the RATE field. The STA0 calls data units that can be transmitted in the specified period at the specified transmission rate in order from the top of the transmission data unit candidate list, and creates and transmits a transmission data packet.

  Data packet transmission ends at time T6, and STA3, which is a neighbor station of STA1, refrains from transmitting until T6, so that reception of STA1 is not hindered.

E. Applications of CSMA Procedure FIGS. 8 to 10 and FIGS. 21 to 23 show some applications of the transmission / reception procedure of the present invention. Here, an application example of the communication method of the present invention will be described in detail based on the CSMA procedure described with reference to FIG.

E-1. First Application Example FIG. 8 shows a first application example of a transmission / reception procedure in the wireless communication system of the present invention. In the figure, a case where two data units are transmitted from STA0 to STA1 is taken as an example. In this example, the number of data units that can be transmitted per packet is limited to one, indicating a delayed ACK (Del-ACK) or an immediate ACK (Im-ACK) as the case may be.

  STA0 activates the data unit transmission procedure at time T0 and starts a backoff count to acquire the transmission right according to the CSMA procedure. Since the backoff count is completed at T1 and it is confirmed that the medium is clear during this time, a packet including RTS information is transmitted.

  When STA1 receives RTS addressed to itself, STA1 returns a packet including CTS information based on information posted in RTS SMH at time T2.

  When STA0 receives the CTS addressed to its own station, STA0 transmits a data packet at time T3. At this time, information indicating that an ACK should be returned with a delayed ACK (Del-ACK) is described in the ACK Type portion of the data packet, and the transmission data unit is still stored in the More Bit portion. The information indicating is described. This data packet is received by STA1 without error.

  STA0 transmits a packet containing RTS information at time T5 after a random time delay to further transmit the stored data unit addressed to STA1. At this time, since STA0 has not yet received the ACK of the previously transmitted data unit, the transmission data unit candidate list is created including the previously transmitted data unit, and RTS SMH is created based on this list. Constitute.

  Upon receiving this, STA1 returns a packet containing CTS information based on the information posted on RTS SMH at time T6. At this time, by referring to the RTS sequence of RTS SMH and RTS Received MAP, it is recognized that STA0 has not recognized the reception confirmation of the data unit received earlier, and ACK information is included in the packet including CTS information. Decide that Alternatively, STA1 decides to include ACK information due to the fact that it holds an untransmitted ACK addressed to STA0. The STA1 deletes the already received packet from the received data unit candidate list, updates the received data unit candidate list, and creates CTS information.

  As a result, STA1 returns a packet including CTS information and ACK information (ie, CTS in which ACK is multiplexed) at time T6. In the ACK information, ACK information corresponding to the data flow specified by the received RTS information is posted.

  When STA0 receives a packet including CTS information and ACK information, STA0 deletes the data unit that STA1 has already received from the held transmission data unit candidate list based on the ACK information, and creates new transmission data. A unit candidate list is created, and a transmission data unit is determined based on the new list. The data packet created in this way is transmitted at time T7. At this time, in the ACK Type portion of the data packet, information indicating that an ACK should be returned immediately by ACK is described, and in the More Bit portion, there is no more data unit to be transmitted. Enter the information to show.

  When the STA1 receives the data packet, the STA1 recognizes that it wants to immediately send an ACK from the ACK Type portion of the DATA SMH, and returns an immediate ACK (Im-ACK) packet corresponding to the data flow at time T8. .

  In this application example, the Duration field of each packet is set so as to indicate the time indicated by the arched arrow in FIG.

E-2. Second Application Example FIG. 21 shows a second application example of the transmission / reception procedure in the wireless communication system of the present invention. In the figure, a case where two data units are transmitted from STA0 to STA1 is taken as an example. In this example, it is assumed that the number of data units that can be transmitted per packet is limited to one and immediate ACK (Im-ACK) is always applied.

  STA0 activates the data unit transmission procedure at time T0 and starts a backoff count to acquire the transmission right according to the CSMA procedure. Since the backoff count is completed at T1 and it is confirmed that the medium is clear during this time, a packet including RTS information is transmitted.

  When STA1 receives RTS addressed to itself, STA1 returns a packet including CTS information based on information posted in RTS SMH at time T2.

  When STA0 receives the CTS addressed to itself at time T2, STA0 transmits a data packet at time T3. At this time, information indicating that ACK is desired to be returned by immediate ACK (Im-ACK) is written in the ACK Type portion of the data packet.

  However, STA1 finds an error when receiving a data packet and cannot accurately extract this data. Therefore, although ACK should be returned originally, ACK is not transmitted at time T4 (ACK in the figure is not transmitted).

  Since STA0 does not receive an ACK at the expected time, it determines that an error has occurred in the previous data, and after a delay of a random time, in order to retransmit the data unit destined for STA1 A packet including RTS information is transmitted at time T5. At this time, since STA0 has not received the ACK of the previously transmitted data, it posts a request to add ACK information in the ACK Request part of RTS SMH (that is, the ACK request is multiplexed) Send RTS).

  Upon receiving this, STA1 returns a packet containing CTS information based on the information posted on RTS SMH at time T6. At this time, by referring to the ACK Request portion of the RTS SMH, it is recognized that the STA0 requests transmission of ACK information, and it is determined that the ACK information is included in the packet including the CTS information. The STA1 deletes the already received packet from the received data unit candidate list, updates the received data unit candidate list, and creates CTS information.

  As a result, STA1 returns a packet including CTS information and ACK information (that is, CTS in which ACK is multiplexed) at time T6. In the ACK information, ACK information corresponding to the data flow specified by the received RTS information is posted.

  When STA0 receives a packet including CTS information and ACK information, STA0 deletes the data unit that STA1 has already received from the held transmission data unit candidate list based on the ACK information, and creates new transmission data. Create a unit candidate list and determine a transmission data unit based on this new list (in this example, the data unit transmitted at time T3 is retransmitted). The data packet created in this way is transmitted at time T7. At this time, information indicating that an ACK should be returned by an immediate ACK is written in the ACK Type portion of the data packet.

  When the STA1 receives the data packet, the STA1 recognizes that it wants to immediately send an ACK from the ACK Type portion of the DATA SMH, and returns an immediate ACK (Im-ACK) packet corresponding to the data flow at time T8. .

  In this application example, the Duration field of each packet is set so as to indicate the time indicated by the arched arrow in FIG.

E-3. Third Application Example FIG. 22 shows a third application example of the transmission / reception procedure in the wireless communication system of the present invention. In the figure, a case where one data unit is transmitted from STA0 to STA1 is taken as an example. In this example, it is assumed that the number of data units that can be transmitted per packet is limited to one and immediate ACK (Im-ACK) is always applied.

  STA0 activates the data unit transmission procedure at time T0 and starts a backoff count to acquire the transmission right according to the CSMA procedure. Since the backoff count is completed at T1 and it is confirmed that the medium is clear during this time, a packet including RTS information is transmitted.

  When STA1 receives RTS addressed to itself, STA1 returns a packet including CTS information based on information posted in RTS SMH at time T2.

  When STA0 receives CTS addressed to itself at time T2, STA0 transmits a data packet at time T3. At this time, information indicating that an ACK is requested to be returned by immediate ACK (Im-ACK) is described in the ACK Type portion of the data packet, and no more transmission data units are accumulated in the More Bit portion. The information indicating that This data packet is received by STA1 without error.

  STA1 returns an ACK for the received data. However, STA0 finds an error when receiving ACK, and cannot accurately extract this data. Since STA0 does not receive an ACK at the expected time, it determines that an error has occurred in the previous data, and after a delay of a random time, in order to retransmit the data unit destined for STA1 Then, a packet including RTS information for data retransmission is transmitted at time T5. At this time, since STA0 has not received the ACK of the previously transmitted data, the ACK request part of the RTS SMH requests that ACK information be added. That is, the RTS in which the ACK request is multiplexed is transmitted.

  Upon receiving this, STA1 returns a packet containing CTS information based on the information posted on RTS SMH at time T6. At this time, by referring to the ACK Request portion of the RTS SMH, it is recognized that the STA0 requests transmission of ACK information, and it is determined that the ACK information is included in the packet including the CTS information. Also, as a result of deleting the already received packet from the received data unit candidate list, STA1 recognizes that all the data that STA0 already wants to transmit has been received, and returns only ACK, and CTS No information is returned.

  As a result, STA1 returns a packet containing only ACK information at time T6. In the ACK information, ACK information corresponding to the data flow specified by the received RTS information is posted.

  When receiving a packet including ACK information, STA0 determines that all transmission data units held for STA1 have been transmitted, and ends the transaction.

  In this application example, the Duration field of each packet is set so as to indicate the time indicated by the arched arrow in FIG.

E-4. Fourth Application Example FIG. 23 shows a fourth application example of the transmission / reception procedure in the wireless communication system of the present invention. In the figure, a case where two data units are transmitted from STA0 to STA1 is taken as an example. In this example, it is assumed that the number of data units that can be transmitted per packet is limited to one and a plurality of data packets are allowed to be transmitted continuously.

  STA0 activates the data unit transmission procedure at time T0 and starts a backoff count to acquire the transmission right according to the CSMA procedure. Since the backoff count is completed at T1 and it is confirmed that the medium is clear during this time, a packet including RTS information is transmitted.

  When STA1 receives RTS addressed to itself, STA1 returns a packet including CTS information based on information posted in RTS SMH at time T2.

  When STA0 receives the CTS addressed to its own station, STA0 transmits a data packet at time T3. At this time, information indicating that an ACK should be returned with a delayed ACK (Del-ACK) is described in the ACK Type portion of the data packet, and the transmission data unit is still stored in the More Bit portion. The information indicating is described. This data packet is received by STA1 without error.

  Furthermore, when STA0 continuously transmits data packets from time T4, STA0 determines whether transmission can be completed within the period indicated by the Duration field of the CTS transmitted by STA1 at time T2. . In the illustrated example, STA0 determines that data transmission can be completed in the period indicated by the Duration field of CTS even if the next data packet is transmitted, and the data unit addressed to STA1 that has been stored is stored. Is further transmitted at time T4. At this time, information indicating that an ACK is requested to be returned by immediate ACK (Im-ACK) is described in the ACK Type portion of the data packet, and no more transmission data units are accumulated in the More Bit portion. The information indicating that This data packet is received by STA1 without error.

  When STA1 receives the data packet, STA1 recognizes that it wants to immediately send ACK from the ACK Type part of DATA SMH, and returns an immediate ACK (Im-ACK) packet corresponding to the data flow at time T5. .

  In this application example, the Duration field of each packet is set to point to the time indicated by the arched arrow in FIG.

E-5. Fifth Application Example FIG. 9 shows a fifth application example of the transmission / reception procedure in the wireless communication system of the present invention. In the figure, the case where two data units are transmitted from STA0 to STA1 is taken as an example. In this example, the number of data units that can be transmitted per packet is limited to one, both data units are instructing immediate ACK, and the transmitting station is allowed to transmit consecutive packets.

  STA0 activates the data unit transmission procedure at time T0 and starts a backoff count to acquire the transmission right according to the CSMA procedure. At T1, since the back-off count is completed and it is confirmed that the medium is clear during this time, a packet including RTS information is transmitted.

  When STA1 receives RTS addressed to itself, STA1 returns a packet including CTS information based on information posted in RTS SMH at time T2.

  When STA0 receives the CTS addressed to its own station, STA0 transmits a data packet at time T3. At this time, information indicating that an ACK is to be returned by immediate ACK is described in the ACK Type part of the data packet, and information indicating that the transmission data unit is still accumulated is described in the More Bit part. To do. Further, RTS information for transmitting another data unit is added. That is, a data packet in which RTS is multiplexed is transmitted. This data packet is received by STA1 without error.

  When STA1 recognizes that the RTS information is included in the data packet, STA1 attempts to transmit the packet including the CTS information. At this time, by referring to the RTS Sequence and the RTS Received MAP, if the STA0 recognizes that it has not recognized the reception confirmation of the previously received data unit, the ACK information is included in the packet including the CTS information. decide. In addition, the reception data unit candidate list is created based on the information posted in the RTS SMH, but after the already received packet is deleted from the reception data unit candidate list and the reception data unit candidate list is updated, Create CTS information. In the ACK information, ACK information corresponding to the data flow specified by the received RTS information is posted. In this way, STA1 returns a packet including ACK information and CTS information (that is, a CTS packet in which ACK is multiplexed) at time T4.

  When STA0 receives a packet including ACK information and CTS information, STA0 attempts to transmit a data unit based on the CTS information. Based on the ACK information, STA0 deletes the data unit that STA1 has already received from the held transmission data unit candidate list, creates a new transmission data unit candidate list, and creates this new list. Based on the transmission data unit. At this time, in the ACK Type portion of the data packet, information indicating that an ACK should be returned immediately by ACK is described, and in the More Bit portion, there is no more data unit to be transmitted. Enter the information to show. STA0 transmits the data packet created in this way at time T5.

  When the STA1 receives the data packet in which the ACK information is multiplexed, the STA1 recognizes that it wants to send the ACK immediately, and returns the corresponding ACK information packet at time T6.

  In this application example, the Duration field of each packet is set to point to the time indicated by the arched arrow in FIG. The Duration value of the packet transmitted at time T6 stores zero indicating NULL.

E-6. Sixth Application Example FIG. 10 shows a sixth application example of the transmission / reception procedure in the wireless communication system of the present invention. In the figure, two-way communication in which two data units are transmitted from STA0 to STA1 and at the same time two data units are transmitted from STA1 to STA0 is taken as an example. In this example, the number of data units that can be transmitted per packet is limited to one, but it is allowed to multiplex RTS to CTS.

  STA0 activates the data unit transmission procedure at time T0 and starts a backoff count to acquire the transmission right according to the CSMA procedure. At T1, since the back-off count is completed and it is confirmed that the medium is clear during this time, a packet including RTS information is transmitted. In the RTS / CTS Mux section of the RTS SMH, information indicating that the RTS may be multiplexed in the CTS is set.

  When STA1 receives the RTS information, STA1 returns a packet including the CTS information based on the information posted in the RTS SMH at time T2. At this time, the RTS / CTS Mux part of the RTS SMH recognizes that the RTS may be multiplexed into the CTS, and further holds the data unit addressed to the STA0. As a result, a packet including CTS information and RTS information (that is, a CTS packet in which RTS is multiplexed) is transmitted.

  When STA0 receives a packet including CTS information and RTS information, STA0 attempts to transmit a data unit at time T3 based on the CTS information. At this time, information indicating that an ACK is to be returned by immediate ACK is described in the ACK Type part of the data packet, and information indicating that the transmission data unit is still accumulated is described in the More Bit part. To do. Further, RTS information for transmitting another data unit is added. Also, since RTS information is included in the received packet, CTS information is created in response to this, and CTS information is also added.

  As a result, a packet in which data, RTS information, and CTS information are multiplexed is transmitted from STA0 (that is, a data packet in which CTS for RTS from STA1 and RTS for transmitting subsequent data units are multiplexed. ) Is transmitted at time T3. This data packet is received by STA1 without error.

When the STA1 receives the packet in which the data, the RTS information, and the CTS information are multiplexed and recognizes that the RTS information is included in the packet, the STA1 tries to transmit the packet including the CTS information. At this time, by referring to the RTS Sequence and the RTS Received MAP, it is recognized that the STA0 has not recognized the reception confirmation of the previously received data unit, and the ACK information is included in the packet including the CTS information. Make a decision. In addition, the reception data unit candidate list is created based on the information posted in the RTS SMH, but after the already received packet is deleted from the reception data unit candidate list and the reception data unit candidate list is updated, Create CTS information. In the ACK information, ACK information corresponding to the data flow specified by the received RTS information is posted. Furthermore, when STA1 recognizes that this packet includes CTS information, it also transmits a data unit based on the CTS information. In the ACK Type part of this DATA SMH, information indicating that an ACK should be returned immediately with an ACK is described, and More
In the Bit part, information indicating that transmission data units are still stored is written. Furthermore, STA1 also adds RTS information for transmitting another data unit.

  Thus, STA1 returns a packet including ACK information, CTS information, data unit, and RTS information at time T4. That is, a data packet for CTS reception from STA0, a CTS for RTS from STA0, an RTS for transmitting subsequent data units, and an ACK for data unit reception from STA0 are multiplexed and transmitted. .

  When STA0 receives a packet including ACK information, CTS information, a data unit, and RTS information, STA0 attempts to transmit the data unit based on the CTS information. STA0 deletes the data unit that STA1 has already received from the held transmission data unit candidate list based on the ACK information of the received packet, creates a new transmission data unit candidate list, The transmission data unit is determined based on this new list. At this time, in the ACK Type portion of the data packet, information indicating that an ACK should be returned immediately by ACK is described, and in the More Bit portion, there is no more data unit to be transmitted. Enter the information to show. Furthermore, since STA0 has extracted a new data unit from the received packet without error, it determines to return ACK information. Since the received packet also includes RTS information, it is determined to create CTS information corresponding to this and transmit the CTS information. Since the CTS information creation procedure is performed in the same manner as described above, the description thereof is omitted here.

  In this way, STA0 returns a packet including the data unit, ACK information, and CTS information at time T5. That is, the data unit for CTS from STA1, the CTS for RTS from STA1, and the ACK for the data unit received from STA1 are multiplexed and transmitted.

  When STA1 receives a packet including a data unit, ACK information, and CTS information, STA1 extracts the data unit and determines transmission of ACK information corresponding to the data unit. When recognizing that the packet includes CTS information and ACK information, the transmission data unit candidate list is updated based on the ACK information, and the data unit is also transmitted based on the CTS information. decide. In this way, STA1 returns a packet including ACK information and a data unit (that is, a data packet multiplexed with the data unit ACK received from STA0) at time T6.

  When STA1 receives a packet including ACK information and a data unit, STA1 recognizes that it wants to send ACK immediately by referring to the ACK Type portion of DATA SMH, and returns a corresponding ACK information packet at time T7. .

  In the above example, the Duration field of each packet is set to point to the time indicated by the arched arrow in FIG. Since the data length is determined when the CTS information is created, each Duration value can be set.

  Since it may be unknown whether RTS information or ACK information is multiplexed in a returned packet, there is a case where Duration cannot be specified exactly. In preparation for such a case, the Duration value may be set longer including a margin.

  In addition, the Duration value is set on the assumption that RTS information and ACK information are not multiplexed, and actual packets may be transmitted for a slightly longer period. However, since these information lengths are not so large, a large loss occurs. Not connected. The Duration value of the packet transmitted at time T8 stores zero indicating NULL.

  In each of the above-described embodiments E-1 to E-6, it is determined whether or not “information indicating that RTS may be multiplexed in CTS” is set in the RTS / CTS Mux portion of the RTS SMH. This determination can also be made based on the communication history between the RTS transmitting station and the destination station so far, and the packets received in the past from the RTS destination station. Several examples of cases where control is performed depending on whether or not the destination station of the RTS holds data to be transmitted to the own station will be described below with reference to the drawings.

  In the example shown in FIG. 24, STA1 transmits RTS (P0), STA0 returns CTS (P1), STA1 transmits DATA (P2), and STA0 returns ACK (P3).

  Here, it is assumed that STA1 still holds data addressed to STA0 in the More Bit part of DATA SMH of packet P2 including DATA.

  STA0 can recognize that STA1 holds data that it wants to transmit to its own station by holding the information of the MoreBit part of the data received from STA1 most recently.

When STA0 recognizes that STA1 holds data addressed to itself when transmitting RTS addressed to STA1, RTS / CTS of RTS SMH
“Information indicating that RTS may be multiplexed in CTS” is set in the Mux section.

FIG. 24 shows a case where this RTS is transmitted as P4. In response to this, the STA1 returns a packet including the CTS and the RTS SMH related to the data transmission of the local station, that is, the packet (P5) in which the CTS is multiplexed with the RTS. Then, STA0 receives data and RTS corresponding to the received CTS SMH.
A packet including CTS SMH corresponding to SMH, that is, a packet (P6) in which data and CTS are multiplexed is transmitted. Subsequently, the STA1 transmits a packet including data corresponding to the ACK SMH and CTS SMH corresponding to the received data, that is, a packet (P7) obtained by multiplexing the data and the ACK. STA0 transmits a packet (P8) including ACK SMH corresponding to the received data.

  25, as in the example shown in FIG. 24, STA1 transmits RTS (P0), STA0 returns CTS (P1), STA1 transmits DATA (P2), and STA0 transmits ACK ( P3) is returned.

  Here, it is assumed that STA1 still holds data addressed to STA0 in the More Bit part of DATA SMH of packet P2 including DATA.

  The STA0 can recognize that the STA1 holds the data to be transmitted to the own station by holding the information of the More Bit part of the data received from the STA1 most recently.

  In such a case, even if there is no data addressed to the STA1 from the local station, the STA0 holds the data that the STA1 wants to transmit to the local station, so that the RTS / CTS of the RTS SMH An RTS in which “information indicating that RTS may be multiplexed in CTS” is set in the Mux section may be transmitted. At this time, information indicating that there is no data to be transmitted is written in the other field of the RTS SMH.

  Such an RTS is a pseudo RTS that is different from an original RTS that requests data transmission to a data transmission destination. By receiving this pseudo RTS, peripheral stations other than STA1 set NAV for the duration of Duration described in RTS and wait for transmission. On the other hand, since other peripheral stations are waiting for transmission, STA1 can easily transmit an RTS for transmitting subsequent data units. That is, STA0 can make it easier for STA1 to obtain the RTS transmission right by transmitting a pseudo RTS, and as a result, STA0 can efficiently receive subsequent data units from STA1. become.

  FIG. 25 shows a case where such a pseudo RTS is transmitted as P4. In response to this, the STA1 performs the transmission operation of the structured data unit based on the normal RTS / CTS procedure. That is, STA1 returns a packet (P5) including the RTS SMH related to the data transmission of the local station, STA0 transmits a packet (P6) including the CTS SMH corresponding to the received RTS SMH, and the STA1 receives the packet. A packet (P7) including data corresponding to CTS SMH is transmitted, and STA0 transmits a packet (P8) including ACK SMH corresponding to the received data.

  In the example shown in FIG. 26, STA1 transmits RTS (P0) to STA0, and STA0 can receive it without error. However, in this time zone, STA0 is in a state in which NAV is established by interpreting the Duration field of a packet transmitted from another station (not shown, hidden terminal of STA1) and CTS cannot be returned. By receiving the RTS packet (P0), the STA0 recognizes that the STA1 holds data that it wants to transmit to its own station.

  In the example shown in FIG. 25, STA1 recognizes that STA1 has a subsequent data unit when STA1 sets the Morebit, but in the example shown in FIG. 26, STA0 receives the RTS from STA1. This is different in that it recognizes that STA1 has a subsequent data unit. In the latter case, since STA0 cannot set NAV and return CTS, STA1 temporarily stops the data transmission operation with the subsequent data unit.

In such a case, even if there is no data addressed to STA1 from the local station, STA0 holds the data that STA1 wants to transmit to the local station, and therefore RTS / CTS Mux of RTSSMH In some cases, an RTS in which “information that RTS may be multiplexed in CTS” is set in the part is transmitted. At this time, RTS
Information indicating that there is no data to be transmitted is written in the other field of the SMH. (Although not shown in the figure, even if there is data addressed to STA1 from the own station, similarly, “information that RTS may be multiplexed in CTS” is set in the RTS / CTS Mux part of RTS SMH. Send RTS that has been done.)

  Such an RTS is a pseudo RTS that is different from the original RTS. When a peripheral station other than the STA1 receives the pseudo RTS, it sets a NAV and waits for transmission. On the other hand, since other peripheral stations are waiting for transmission, STA1 can easily transmit an RTS for transmitting subsequent data units. That is, STA0 can make it easier for STA1 to obtain the RTS transmission right by transmitting a pseudo RTS, and as a result, STA0 can efficiently receive subsequent data units from STA1. (Same as above).

  FIG. 26 shows a case where this RTS is transmitted as P4. In response to this, the STA1 performs the transmission operation of the structured data unit based on the normal RTS / CTS procedure. That is, STA1 returns a packet (P5) including the RTS SMH related to the data transmission of the local station, STA0 transmits a packet (P6) including the CTS SMH corresponding to the received RTS SMH, and the STA1 receives the packet. A packet (P7) including data corresponding to CTS SMH is transmitted, and STA0 transmits a packet (P8) including ACK SMH corresponding to the received data.

  Note that, as a usage example different from the above, there is a case where “information indicating that the RTS may be multiplexed is set in the CTS” is always set in the RTS / CTS Mux part of the RTS SMH.

F. Sequence Number Acknowledgment Procedure FIG. 11 shows an acknowledgment procedure related to data other than data flow 0 assumed in the present invention. The interaction of each field when performing selective acknowledgment is shown. An example is shown. For the sake of simplicity, it is assumed that the Received MAP field is composed of 4 bits, but the present invention is not limited to this.

  The data transmission side first transmits data units of sequence numbers “0”, “1”, “2”, and “3” from the transmission data unit candidate list. It is assumed that the data unit “2” is received in an error state.

  In the ACK Sequence field of the acknowledgment ACK returned by the data receiving side, “1” indicating that all the data units of “1” have been received is stored. In addition, “2” is NG (0) and “3” is OK (1) in the Received MAP field based on the data unit “2” that is the data unit next to “1” (as MSB). , “4” stores “NG (0)”, and “5” stores “0100” indicating NG (0).

  Upon receiving this, the data transmitting side recognizes that “1” has been received and “3” has also been received, and in the next data transmission, these are deleted from the transmission data unit candidate list, Data units with sequence numbers “2”, “4”, “5”, “6” are transmitted. Of these, it is assumed that the data units “4” and “5” are received in an error state.

  In the ACK Sequence field of the acknowledgment ACK returned by the data receiving side, “3” indicating that all the data units “3” have been received is stored. In addition, “4” is NG (0) and “5” is NG (0) in the Received MAP field based on the data unit “4” that is the data unit next to “3” (as MSB). , “6” is stored as “0010” indicating OK (1) and “7” as NG (0).

  In this manner, ARQ (automatic retransmission request) is executed by using the ACK Sequence field and Received MAP together. If the data transmission side does not support the selective acknowledgment, the Received MAP is ignored when the transmission data unit candidate list is updated when an ACK is received. If the data receiving side does not support the selective acknowledgment, the decoding of the data after the data unit in which the error has occurred is ignored, and the data is linked with the ACK Sequence field, and all zeros are inserted into the Received MAP. . In this way, even when communication is performed between a communication station that supports the selective confirmation response and a communication station that does not support the selective confirmation response, the communication can be maintained without causing a failure.

G. FIG. 12 shows a sequence number confirmation response procedure when the RTS / CTS procedure is used together . FIG. 12 shows a case where RTS / CTS is used together as another specific example of the interaction of each field when performing the selective confirmation response. Show. Here, for the purpose of focusing on only the part related to the sequence number and Received MAP, the other fields will not be mentioned, but the procedure using other fields is also operated at the same time according to the procedure described elsewhere. To do. For the sake of simplicity, it is assumed that the Received MAP field is composed of 4 bits, but the present invention is not limited to this. Here, it is assumed that the first configuration example or the fourth configuration example is adopted as the RTS SMH.

  The data transmission side transmits an RTS indicating that data units of sequence numbers “3”, “4”, “5”, “6”,... Are registered in the transmission data unit candidate list. At this time, RTS sequence of RTS SMH indicates “3” indicating the head data unit, and RTS Received MAP indicates that all data units from “4” to “7” are transmission candidates. “0000” is stored in each.

  Since the data receiving side has not yet received all the data units indicated by the RTS, it returns CTS without waiting for the reception of the data unit without returning the ACK.

  It is assumed that the data units “4” and “5” are received in an error state. In addition, it is assumed that this data requests a delayed ACK. Due to the delayed ACK, the receiving side does not immediately return an ACK.

  On the data transmission side, data units “3”, “4”, “5”, “6”,... Are registered in the transmission data unit candidate list again for the purpose of further data transmission. RTS indicating this is transmitted. As before, RTS sequence of RTS SMH indicates “3” indicating the head data unit, and RTS Received MAP indicates that all data units from “4” to “7” are transmission candidates. Therefore, “0000” is stored respectively.

  On the data receiving side, since some of the data units indicated by RTS have already been received, ACK information is also added when returning the CTS. Here, “3” indicating that all the data units “3” have been received is stored in the ACK SEQUENCE field of ACK SMH. In addition, “4” is NG (0) and “5” is NG (0) in the Received MAP field based on the data unit “4” that is the data unit next to “3” (as MSB). , “6” is stored as “0010” indicating OK (1) and “7” as NG (0).

  Upon receiving this, the data transmission side recognizes that “3” has been received and “6” has also been received, and in data transmission, these are deleted from the transmission data unit candidate list, and further, CTS Based on the information, data units of sequence numbers “4”, “5”, “7”, “8” are transmitted.

  In such a situation, by using the RTS Sequence field and the RTS Received MAP field, and also using the CTS SMH and ACK SMH multiplexes together. Data can be sent and received without any failure.

  If the data transmission side does not support the selective acknowledgment, all zeros are always inserted into the RTS Received MAP, and the Received MAP is set when the transmission data unit candidate list is updated when an ACK is received. Ignore it. If the data receiving side does not support the selective confirmation response, the RTS Received MAP may be ignored. In this way, even when communication is performed between a communication station that supports the selective confirmation response and a communication station that does not support the selective confirmation response, the communication can be maintained without causing a failure.

H. Use of CTS Stored Sequence and Usage of Each Field when RTS / CTS Procedure is Used Together FIG. 13 shows an example of a data transmission / reception procedure when a delayed ACK and an RTS / CTS procedure are applied. In this section, the description will be given focusing on the handling of each sequence number and the usage of the stored sequence field of the CTS SMH.

  Here, for simplicity of explanation, it is assumed that both the RTS Received MAP and the Received MAP field are 4 bits, but the gist of the present invention is not limited to this. Further, although it is assumed that there are four Length fields in the RTS SMH, the gist of the present invention is not limited to this. Further, although an appropriate value is indicated in the Duration field, the validity of the value indicated by Duration is not a problem here. It is assumed here that the first configuration example or the fourth configuration example is adopted as the RTS SMH.

The data transmission side transmits RTS (1) prior to data transmission. At this time, it is indicated that data units having sequence numbers “3”, “4”, “5”, and “6” are registered in the transmission data unit candidate list (that is, “3” is set in the RTSS sequence). , “0000” is stored in the RTS Received MAP, respectively)
. In addition, for the convenience of the data transmission side, the fact that the current data transmission is desired to be completed in 255 unit time is notified (that is, “255” is stored in Max Duration). Further, the length of the data unit scheduled to be transmitted is 200, 20, 100, and 80 unit bytes, respectively (that is, “200” for Length 0, “20” for Length 1, and “2” for Length 2. 100 ”and“ 80 ”are stored in Length3). Furthermore, the period until the transmission of the CTS received in response to this RTS is completed is written in Duration as 40 unit times.

  When receiving this, the data receiving side returns CTS (1). At this time, the transmission rate of data reception is determined to be rate class 1 according to the above-described procedure, and this is notified (that is, 1 is stored in RATE). In addition, according to the above-described procedure, it is determined that the data units “3”, “4”, “5”, “6” are received, and the period required to complete the reception is 240 unit hours. (That is, “240” is stored in Duration). Furthermore, the length up to “6” of the data unit decided to be received in the current transaction is held. Then, the fact that the length information of the data units up to “6” is held is notified (that is, “6” is stored in the stored sequence).

  When receiving this, the data transmission side transmits Data (1). At this time, it is recognized that the data units “3”, “4”, “5”, “6” can be transmitted in the designated transmission rate class 1 according to the above-described procedure, Send with class 1. Since delay ACK is designated, 0 is stored in the Duration field. In addition, the sequence number 6 reported in the CTS stored sequence is held so that it can be referred to at the next RTS transmission.

  On the data receiving side, it is assumed that only the data units having the sequence numbers “3” and “6” can be extracted. However, at this time, the data transmitting side has not confirmed the success or failure of the data reception.

  The data transmission side transmits RTS (2) to further transmit the data unit. At this time, data units of sequence numbers “3”, “4”, “5”, “6”,... Are registered in the transmission data unit candidate list. On the other hand, when the CTS (1) is received first, it is reported in the stored sequence that “the length is maintained until the sequence number 6”. Information related to data units prior to sequence number 6 is described. Specifically, the data units of sequence numbers “7” and “8” are registered and their lengths are communicated (that is, “7” is transmitted to RTS Sequence and “0000” is transmitted to RTS Received MAP. , “160” is stored in Length 0, “120” is stored in Length 1, “0” is stored in Length 2, and “0” is stored in Length 3.) Since Length2 and Length3 are 0, the transmission data candidate indicates that there are only two data units of length 160 and length 120. In addition, for the convenience of the data transmission side, the fact that the current data transmission is desired to be completed in 255 unit time is notified (that is, “255” is stored in Max Duration). Furthermore, the period until the transmission of the CTS received in response to this RTS is completed is written in Duration as 40 unit times.

  When receiving this, the data receiving side returns CTS (2). At this time, it is notified that the transmission rate of data reception is determined to be rate class 2 according to the above-described procedure (that is, “2” is stored in RATE of CTS SMH). Further, according to the above-described procedure, it is determined to receive the data units having the sequence numbers “4”, “5”, and “7”, and it is notified that the period required to complete the reception is 200 unit hours. (That is, “200” is stored in Duration). Furthermore, the length of data units up to “7” determined to be received in the current transaction is held. Then, it is informed that the length information of data units up to “7” is held (that is, “7” is stored in the stored sequence of CTSSMH). Also, according to the above-described procedure, it is determined that the ACK information is also returned, and it is notified that all the data units of “3” have been received and that the data unit of “6” has been received (ie, “3” is stored in ACK Sequence of ACKSMH, and “0010” is stored in Received MAP).

  When receiving this, the data transmission side transmits Data (2). At this time, since ACK information is included, after updating the transmission data unit candidate list according to the above-described procedure, each of “4”, “5”, “7” in the designated transmission rate class 2 Recognize that data units can be sent and send them. In addition, since a delayed ACK is designated, “0” is stored in the Duration field. In addition, the sequence number “7” reported in the CTS stored sequence is held, and the sequence number “7” can be referred to at the next RTS transmission.

The data transmission side transmits RTS (3) to further transmit the data unit. At this time, in the transmission data unit candidate list, information related to the data unit ahead of the sequence number “7” which is the stored sequence held at the time of reception of the previous CTS (2) is described. Specifically, the fact that the data unit of sequence number “8” is registered and its length is notified (that is, “8” is sent to RTS Sequence, RTS Received
“0000” is stored in MAP, “120” is stored in Length 0, “0” is stored in Length 1, “0” is stored in Length 2, and “0” is stored in Length 3.) In addition, for the convenience of the data transmission side, the fact that the current data transmission is desired to be completed in 255 unit time is notified (that is, “255” is stored in Max Duration). Furthermore, the period until the transmission of the CTS received in response to this RTS is completed is written in Duration as 40 unit times.

  In such a manner, the transceiver sets the field of each packet header and refers to each other to determine the processing content caused by the received packet. As a result, even when the delayed ACK is used together, the length information is not designated unnecessarily in the RTS, and the efficiency is improved.

I. The transceiver Procedure Figure 14 traffic through the TCP, shows an example of a sequence when the following MAC procedure according to the present invention has been transmitted and received traffic via the TCP / IP. Even in the case of unidirectional communication in terms of application, an ACK is typically returned every two segments by the TCP layer, and asymmetric bi-directional communication is formed in the MAC layer. In the figure, delayed ACK is applied, multiplexing of each packet such as RTS, CTS, DATA, ACK, etc. is permitted, and the case where these are used together is shown.

  In the conventional transmission / reception procedure via TCP, as shown in FIG. 20, in order to transmit five segments from Data0 to Data4, a total of 24 packets are transmitted and received in the MAC layer, which is complicated. Redundant.

  On the other hand, according to the transmission / reception procedure according to the present invention, as shown in FIG. 14, in order to transmit seven segments from Data0 to Data6, a total of 15 packets are transmitted / received in the MAC layer.

  As will be apparent from the foregoing, it will be understood that according to the transmission / reception procedure of the present invention, the procedure in the MAC layer is simplified and the overhead can be greatly reduced.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  In this specification, an embodiment in which the present invention is applied to a system that uses an RTS / CTS procedure and an access method based on CSMA in a wireless network that conforms to the IEEE 802.11 standard has been described. It is not limited to. For example, the present invention can be similarly applied to a system in which the RTS / CTS procedure is used in combination with a random access method other than CSMA, and a random access system in accordance with regulations other than IEEE 802.11.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

DESCRIPTION OF SYMBOLS 100 ... Wireless communication apparatus 101 ... Interface 102 ... Data buffer 103 ... Central control part 104 ... Beacon generation part 106 ... Wireless transmission part 107 ... Timing control part 109 ... Antenna 110 ... Wireless reception part 112 ... Beacon analysis part 113 ... Information storage Part

Claims (17)

Random access using the RTS / CTS method in which the data transmission source communication station transmits a transmission request packet RTS and starts data transmission in response to receiving the confirmation notification packet CTS from the data transmission destination communication station A wireless communication system in which
Permit transmission / reception of packets in which any two or more of the transmission request RTS, confirmation notification CTS, data, and confirmation response ACK are multiplexed.
A wireless communication system. Random access using the RTS / CTS method in which the data transmission source communication station transmits a transmission request packet RTS and starts data transmission in response to receiving the confirmation notification packet CTS from the data transmission destination communication station A wireless communication device for performing
Information generating means for generating each information of a transmission request RTS, a confirmation notification CTS, data, and a confirmation response ACK;
A packet communication means for transmitting and receiving a packet in which any two or more of a transmission request RTS, a confirmation notification CTS, data, and a confirmation response ACK are multiplexed;
A wireless communication apparatus comprising: A means for setting a time until transmission of a packet of another station caused by transmission of the packet is completed, and describes the set time information as media reservation time information of the transmission packet.
The wireless communication apparatus according to claim 2, further comprising: Means for transmitting a packet containing CTS information according to the contents of the RTS in response to receiving a packet containing RTS information;
Means for transmitting a packet containing data according to the contents of the CTS in response to receiving a packet containing CTS information;
The wireless communication apparatus according to claim 2, further comprising: The information generation means describes first information indicating whether or not the RTS information may be added to the CTS transmitted due to the RTS when generating the RTS information.
The wireless communication apparatus according to claim 2. The packet transmission means determines whether or not RTS information may be added to the CTS based on the first information of the resulting RTS when transmitting the return packet, and sends the RTS transmission side communication station to the communication station. On the other hand, when there is data to be transmitted, a CTS to which RTS information for transmitting the data is added or a packet including RTS information for transmitting the data is transmitted.
The wireless communication apparatus according to claim 5. When transmitting a return packet for a packet including RTS information, the packet transmission means adds RTS information for transmitting the data if there is data to be transmitted to the communication station on the RTS transmission side. Send a packet containing CTS or RTS information for the purpose of sending the data,
The wireless communication apparatus according to claim 2. The information generation means determines first information based on information elements included in a packet received from a destination station of the RTS in the past.
The wireless communication apparatus according to claim 5. When the packet communication means recognizes from the information of the RTS that when transmitting the CTS, the originating RTS transmission side communication station recognizes that it is attempting to transmit data already received by the local station, ACK information is added to
The wireless communication apparatus according to claim 2. In response to receiving the data packet, the packet communication means has received data requesting ACK from the communication station on the data transmission side, but determines that it has not transmitted ACK of the data, ACK information is added when transmitting any packet to the communication station on the data transmission side,
The wireless communication apparatus according to claim 2. The packet communication means does not add ACK information to a packet transmitted by RTS information alone.
The wireless communication apparatus according to claim 10. The packet communication means transmits data requesting ACK as a packet destined for two or more communication stations.
The wireless communication apparatus according to claim 10. The packet communication means, when transmitting the RTS, multiplexes the ACK request for requesting the return of the ACK regarding the data transmitted so far.
The wireless communication apparatus according to claim 2. The packet communication means multiplexes an ACK request for requesting a reply of an ACK related to data transmitted so far when transmitting an RTS when an ACK related to data transmitted so far cannot be received.
The wireless communication apparatus according to claim 2. In response to receiving the RTS in which the ACK request is multiplexed, the information generation means generates an ACK indicating whether or not the data transmitted from the communication station on the RTS transmission side has been received,
The packet communication means returns an ACK indicating whether or not reception of data transmitted from the RTS transmission side communication station has been completed, or data transmitted from the RTS transmission side communication station has not been received. Sometimes CTS requesting retransmission of the data and ACK for the ACK request are multiplexed and returned,
The wireless communication apparatus according to claim 13, wherein the wireless communication apparatus is a wireless communication apparatus. Random access using the RTS / CTS method in which the data transmission source communication station transmits a transmission request packet RTS and starts data transmission in response to receiving the confirmation notification packet CTS from the data transmission destination communication station A wireless communication method for performing
An information generation step for generating each information of a transmission request RTS, a confirmation notification CTS, data, and a confirmation response ACK;
A packet communication step of transmitting and receiving a packet in which any two or more pieces of information among a transmission request RTS, a confirmation notification CTS, data, and a confirmation response ACK are multiplexed;
A wireless communication method comprising: Random access using the RTS / CTS method in which the data transmission source communication station transmits a transmission request packet RTS and starts data transmission in response to receiving the confirmation notification packet CTS from the data transmission destination communication station A computer program written in a computer-readable format so as to execute processing for controlling a communication operation on a computer in a communication environment in which the computer is
Information generating means for generating each information of a transmission request RTS, a confirmation notification CTS, data, and a confirmation response ACK;
A packet communication means for transmitting / receiving a packet in which any two or more pieces of information among a transmission request RTS, a confirmation notification CTS, data, and a confirmation response ACK are multiplexed;
Computer program to function as

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