JP4740759B2 - Wireless communication system - Google Patents

Wireless communication system Download PDF

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JP4740759B2
JP4740759B2 JP2006032973A JP2006032973A JP4740759B2 JP 4740759 B2 JP4740759 B2 JP 4740759B2 JP 2006032973 A JP2006032973 A JP 2006032973A JP 2006032973 A JP2006032973 A JP 2006032973A JP 4740759 B2 JP4740759 B2 JP 4740759B2
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frame
tma
delivery confirmation
transmission
information
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JP2007214920A (en
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俊之 久世
繁 内田
尚久 山内
明徳 平
幸政 永井
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三菱電機株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system whose wireless communication capacity can be improved. <P>SOLUTION: In the wireless communication system wherein a base station (1) transmits data to wireless terminals (2-1 to 2-n) and each wireless terminal returns an acknowledgement / negative acknowledgement (ACK/NACK) frame corresponding to data addressed to its own terminal, the base station (1) includes a wireless unit (14) that generates TMA information to multiplex the ACK/NACK frame returned from each wireless terminal on a wireless frame and transmits an aggregation frame including the TMA information to each wireless terminal, and each wireless terminal includes a wireless unit (24) for returning the ACK/NACK frame corresponding to the data addressed to its own terminal on the basis of the TMA information, and multiplexes the ACK/NACK frame returned on the basis of the TMA information from each wireless terminal on one wireless frame as a TMA and transmits the resulting frame. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a radio communication system, and more particularly, to a radio communication system for multiplexing and transmitting a control frame such as an ACK / NACK (ACKnowledgement / Negative ACKnowledgement) as a delivery confirmation frame between a plurality of terminals in wireless LAN communication. It is about.

  Hereinafter, a wireless LAN communication system will be described as an example of a conventional wireless communication system. When each wireless terminal constituting the system senses the wireless channel prior to wireless packet transmission and confirms that the channel is in use (channel busy: Busy), it refrains from transmitting the wireless packet and does not use the channel (channel idle: A wireless access method for transmitting a wireless packet when confirming (Idle) is generally called CSMA (Carrier Sense Multiple Access). This CSMA is used, for example, in a wireless packet communication system.

  Currently, products standardized in the US wireless LAN standard IEEE802.11 (see Non-Patent Document 1) are on the market as devices for constructing high-speed wireless network systems for home / office. Specifically, the wireless LAN compliant with the standard described in Non-Patent Document 2 below uses the 2.4 GHz band, uses CCK (Complementary Code Keying) as a modulation method, and has a physical maximum transmission rate of 11 Mbps. It is. In addition, wireless LANs compliant with the standards described in Non-Patent Documents 3 and 4 below use the 5 GHz band and 2.4 GHz band, respectively, and use OFDM (Orghogonal Frequency Division Multiplex) as a modulation method, The maximum transmission rate is 54 Mbps.

  Furthermore, in the standards described in Non-Patent Documents 2 to 4 below, CSMA / CA (Carrier Sense Multiplex Access with Collision Avoidance) is used as an access method.

  On the other hand, in the European wireless LAN standardization standard (see Non-Patent Document 5 below), TDMA (Time Division Multiple Access) that gives a transmission opportunity in response to a transmission request of a wireless terminal is used.

IEEE802.11 Standard IEEE802.11b IEEE802.11a IEEE802.11g HyperLAN2 Standard

  However, the conventional wireless communication system has a problem that the execution speed representing the actual data stream speed is about half of the physical maximum transmission speed.

  Specifically, for example, the transmitted data stream is divided into a plurality of data packets, and transmission control information including a destination / source IP (Internet Protocol) address, a packet length, a packet number, and the like is provided for each data packet. Header information and error correction control information are added and passed to the lower layer as an IP packet. Also in the MAC (Media Access Control) layer, header information including destination / source MAC address and transmission control information, and error correction control information are added, and in some cases, a data frame is encrypted. The decryption information is added to the physical layer (PHY). Furthermore, in the physical layer, header information including transmission control information including a modulation scheme, a frame length, and the like, a training signal for synchronization, and the like are added and transmitted.

  The base station and each wireless terminal use an access method called CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance), for example. Then, an ACK / NACK frame indicating whether or not the radio data frame has been correctly received is returned from the base station or the radio terminal designated by the destination MAC address, and if it has not been received correctly, a frame retransmission operation is also performed.

  Therefore, the execution speed is not the physical transmission speed of the wireless LAN compliant with the IEEE802.11b, IEEE802.11a, or IEEE802.11g, and is actually about half.

  In addition, as the physical transmission rate increases due to the adoption of multiple input multiple output (MIMO) technology and the use of multiple basic channels (Channel Bundling, Multi-Channels), the efficiency depends on the physical transmission rate. Transmission is becoming necessary.

  As one of the methods, attention has been paid to a method aiming at high efficiency by concatenating or continuously transmitting a plurality of frames.

  Specifically, (1) a technique for concatenating and transmitting a plurality of packets addressed to a single address, and (2) using multiple multicast or broadcast addresses, “MAC SDU (Service Data Unit)” of a plurality of different destinations. A technology for concatenating and efficiently transmitting a plurality of “MAC PDUs (Protocol Data Units)” (see FIG. 55). (3) Concatenating a plurality of different destinations “MAC PDUs” to efficiently generate a plurality of “MAC PDUs”. There are techniques for transmitting (see FIGS. 56 and 57), and (4) techniques for transmitting a plurality of different “MAC PDUs” in succession and efficiently transmitting a plurality of “MAC PDUs” (see FIG. 58). .

  In addition, HT (High Throughput) shown in the figure indicates a base station and a wireless terminal using techniques such as MIMO and Multi-Channels, and “HT Training + Signal” is omitted in some cases. Legacy refers to existing base stations and wireless terminals, and IFS (Inter Frame Space) is a predetermined packet transmission / reception interval. There is also a method of using a plurality of “Aggregation Frames” in combination. In addition, an FCS (Frame Check Sequence) for determining whether the frame is correct is added to the end of the frame.

  As described above, when “MAC PDUs” of different destinations are connected, ACK or NACK that is an acknowledgment is transmitted from each wireless terminal. This is shown in FIG. 59 and FIG. In FIGS. 59 and 60, “Aggregation Frame” of a plurality of destinations is simplified and can be applied in all cases of FIGS. 56, 57, and 58.

  In the conventional method, (1) ACK / NACK frames corresponding to “Aggregation Frames” of a plurality of destinations are transmitted at intervals of IFS time. (2) In “Aggregation Frame”, a method is proposed in which the transmission timing of each ACK / NACK frame is notified and the wireless terminals are responded to in turn. Therefore, there is a problem that the communication capacity is reduced by the IFS interval for the destination or the offset between the frames. In addition, there is a method of piggybacking together with other data and transmitting ACK at the polling timing. However, even in this case, it takes time to confirm delivery of ACK / NACK. As described above, it is necessary to receive a frame corresponding to a destination address DA (Destination Address).

  Furthermore, it is also possible to reduce the delivery confirmation frame and the IFS time without performing the delivery confirmation of the ACK / NACK by exchanging the policy that does not require the ACK with respect to the “Aggregation Frame”. In this case, the band can be used efficiently, but depends on retransmission in a higher layer, and there may be a case where a delay or a decrease in retransmission efficiency occurs.

  In addition, the information of the ACK / NACK frame for confirming delivery is a packet only for notifying whether or not the transmitted PDU has arrived correctly. For very small information, PHY such as large training and Signal The addition of the header causes further deterioration in transmission capacity.

  Note that there are “Block ACK” or “Group ACK” that responds to an MPDU addressed to the same address with one ACK / NACK. However, when data of a plurality of destinations is transmitted, FIG. 59 and FIG. The same problem occurs.

  The present invention has been made in view of the above, and is capable of improving wireless communication capacity by avoiding deterioration of communication capacity due to delivery confirmation when a plurality of “MAC PDUs” of different destinations are connected. An object is to obtain a communication system.

  In order to solve the above-described problems and achieve the object, a wireless communication system according to the present invention is provided for a plurality of communication devices (destination communication devices) in which a specific communication device (source communication device) forms a network. A wireless communication system that transmits data and each of the destination communication devices returns a delivery confirmation frame (ACK, NACK) corresponding to the data addressed to the own device, wherein the transmission source communication device returns a response from a plurality of destination communication devices. Information transmission control for generating TMA (Tone Multiple ACK) information for multiplexing a delivery confirmation frame to be transmitted into one radio frame and transmitting a predetermined transmission frame including the TMA information to each destination radio terminal Each destination communication device receives the TMA information, and based on the TMA information, a delivery confirmation frame corresponding to the data addressed to the device itself. A delivery confirmation control means for returning a frame, wherein a delivery confirmation frame returned from a plurality of destination communication devices based on the TMA information is transmitted as TMA in a single radio frame. .

  According to the present invention, it is possible to significantly reduce the radio communication section occupied for ACK / NACK compared to the conventional method, and to greatly improve the radio communication capacity.

  Embodiments of a wireless communication system according to the present invention will be described below in detail with reference to the drawings. In the present invention, a technique for realizing TMA (Tone Multiple ACK) described later will be described in particular. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a wireless communication system (a home / office wireless network) according to the present invention. This wireless communication system is a gateway for interconnection with an access line (for example, Ethernet (registered trademark), xDSL, CATV, FTTH, etc.) connected to an access network constituting a wired or wireless external communication network. A base station (AP) 1 having a plurality of wireless terminals (STA) 2-1 to 2-n.

  The base station 1 terminates a wired or wireless access line connected to the access network, and transmits information received from the access network to a specific wireless terminal via the home / office wireless network. Is provided. The communication unit system 11 includes an access system termination unit 12 that terminates the access line, and a signal interface that controls mutual conversion of a signal format between an access network signal and a home / office wireless terminal signal. A unit (e.g., equivalent to a router or a bridge) 13 and a wireless unit 14 that performs access control and modulation / demodulation of a wireless network in the home / office are provided.

  Each wireless terminal is a terminal that controls data transmission / reception between an information device main body 21 such as a personal computer, PDA, mobile phone, and television receiver, and each information device main body and a communication unit system of a base station. A unit system 22. This terminal unit system includes a base station, a terminal interface unit 23 that controls mutual conversion of signal formats between signals of other wireless terminals and signals of the information equipment main body 21, and a wireless network in a home / office. And a wireless unit 24 that performs access control and modulation / demodulation.

  Further, in the present embodiment, a wireless communication system in which a wireless terminal is connected to a base station is shown. However, the present invention is not limited to this, for example, an ad hoc network in which wireless terminals construct an original network and perform communication, It can also be applied to multi-hop networks. Furthermore, the present invention is also applicable to a network in which communication is performed between specific wireless terminals registered in the base station at the time allocated from the base station.

  FIG. 2 is a diagram illustrating the configuration of the wireless units 14 and 24 of the present embodiment. This wireless unit is a MAC (Media Access Control) 31 that performs transmission data generation / reception data generation and access control based on data from the host interface for connection to the signal interface unit 13 or the terminal interface unit 23. And a physical layer (PHY) 32 that performs modulation / demodulation and the like. The MAC 31 includes a transmission control unit (MAC Tx) 33 that manages transmission data creation and transmission timing, and a reception control unit (MAC Rx) 34 that performs reception timing detection and reception data success / failure confirmation. And having. The PHY 32 includes a transmission modulation unit (Tx PHY) 35 that modulates transmission data from the MAC 31 and a reception demodulation unit (Rx PHY) 36 that demodulates reception data. Although not shown, the MAC 31 also includes a call admission control unit, an authentication unit, an encryption unit, and the like.

  FIG. 3 is a diagram showing a frame transmission / reception sequence using TMA (Tone Multiple ACK) of the present embodiment. In the present embodiment, a method of multiplexing acknowledgment (ACK / NACK) frames transmitted from a plurality of users into one radio frame is shown. This method is called “Tone Multiplex ACK”. In the present embodiment, information related to transmission of a delivery confirmation frame (TMA frame configuration) is a field composed of a plurality of parameters (timing, transmission method, transmission position, power, etc.) called a TMA information field. In addition, an aggregation frame (Aggregation Frame) in which the TMA information field is arranged at a predetermined position is notified to each wireless terminal. In this embodiment, as an example, a case where the base station notifies the TMA information field will be described. However, the present invention is not limited to this. For example, a specific wireless terminal transmits a frame in which the TMA information field is allocated to another frame. Notification may be made to each wireless terminal, and TMA may be received from each of the other wireless terminals.

  First, the base station 1 creates an aggregation frame addressed to each wireless terminal including the TMA information field by the transmission control unit 33 in FIG. 2, modulates by the transmission modulation unit 35 in accordance with the access procedure, and transmits.

  Next, each wireless terminal receives the aggregation frame at the reception demodulator 36 and extracts the TMA information field and data for the terminal itself at the reception controller 34. Here, frame error check is performed. When the reception is successful, the reception data is handed over to the upper layer via the host interface and a delivery confirmation frame (ACK) indicating the delivery success is transmitted.

  At that time, the transmission control unit 33 creates a transmission frame with the frame configuration (timing, subcarrier, etc.) specified in the TMA information field, and the transmission modulation unit 35 follows the assigned transmission timing and access procedure. , Transmission is performed by the transmission method specified in the TMA information field.

  Next, in the base station 1, a reception confirmation frame transmitted from each radio terminal is received by the reception demodulator 36 based on the previous TMA information field, and the reception control unit 34 analyzes the contents, and each radio It recognizes that the acknowledgment frame (TMA) multiplexed from the terminal is ACK or NACK.

  In FIG. 3, a right-pointing arrow extending from the base station 1 indicates transmission of an aggregation frame to each wireless terminal, and a left-pointing arrow extending from each wireless terminal indicates TMA from each wireless terminal.

  FIG. 4 is a diagram showing a frame transmission / reception sequence and a frame format when the TMA according to the present embodiment is used.

  The left rectangle is an aggregation frame including a plurality of destinations transmitted from the base station 1 (or a specific wireless terminal). This aggregation frame includes a training part for performing timing synchronization, frequency synchronization, AGC, and the like, and a Signal part (“HT Training + Signal” and “Legacy Training + Signal”) indicating a modulation scheme, data length, etc. for subsequent symbols, The TMA information field for notifying the destination STA of the configuration and control parameters of the TMA is followed by the MPDU (MAC Protocol Data Unit).

  In addition, about the position which arrange | positions a TMA information field, not only the above but another position may be sufficient. In some cases, a delimiter indicating the configuration and delimiter of the MPDU is included at the head of each MPDU. In addition, in the aggregation frame, it is also possible to reserve a band until the TMA reception completion time using NAV (Network Allocation Vector) or spoofing technology.

  Further, the aggregation frame is not limited to this method, and any configuration such as FIGS. 55 to 58 may be used. Further, the TMA information field necessary for the receiving side terminal to transmit the TMA may be notified by a frame such as an RTS / CTS frame, a setup frame, or a Beacon in advance. Since the TMA information field is not included in the aggregation frame and the TMA information field is not included in the aggregation frame every time, the overhead due to the insertion of the TMA information field can be reduced.

  Next, the right rectangle in FIG. 4 is a diagram illustrating the TMA in the present embodiment, which is a delivery confirmation frame for the aggregation frame transmitted from the base station 1 (or a specific wireless terminal), and transmits the aggregation frame. And then transmitted after IFS (InterFrame Space). The TMA transmits 1 ACK / NACK information with 1 Tone (Minimum granularity) and notifies ACK from a plurality of wireless terminals within 1 OFDM (Minimum granularity) symbol. In an environment where only HT (High Throughput) terminals exist, “Legacy Training + Signal” may be omitted. In an environment where no HT terminals exist, “HT Training + Signal” is omitted. It doesn't matter.

  However, in this embodiment, since a wireless LAN is assumed, the type of terminal is defined as HT and Legacy, but the present invention relates to an efficient ACK transmission method for an aggregation frame. It does not depend on the type such as Legacy.

  FIG. 5 is a diagram showing an example of TMA in the present embodiment, and shows the relationship between the base station 1 (or a specific wireless terminal) and the destination wireless terminals 2-1, 2-2, 2-3. Yes. Here, as in FIG. 4, the wireless terminals 2-1, 2-2, 2-3 are connected to the base station 1 that is the transmission source of the aggregation frame based on the notified information on the delivery confirmation frame (TMA). On the other hand, a state in which a TMA is transmitted is shown. The rectangle next to each terminal (AP, STA) is a position where each wireless terminal is assigned in advance when the horizontal axis is time (or symbol) and the vertical axis is frequency (or Tone, subcarrier). (Time and frequency) are used to transmit a delivery confirmation frame to the transmission source base station 1, and the base station 1 receives the multiplexed delivery confirmation frame. Here, as shown in FIG. 4, two TMAs are transmitted from the wireless terminal 2-1 using two tones, and one TMA is transmitted from the wireless terminal 2-2. One TMA is transmitted from 3. Note that the base station 1 receiving the TMA receives all the TMAs in a frequency-divided state at the same time. In FIG. 5, since the wireless terminal 2-1 receives two MPDUs in the aggregation frame, the TMA is set using two tones. However, the present invention is not limited to this, and the TMA is set as one tone. It is also possible to transmit.

  FIG. 6 is a diagram showing a delivery confirmation frame when the carrier sense method is adopted. This method is a method of notifying transmission confirmation information on Tone (subcarrier) and, for example, a method of determining that ACK is power ON and NACK is power OFF is called a carrier sense method. For example, the wireless terminal 2-1 performs delivery confirmation (ACK / NACK) for three MPDUs, the wireless terminal 2-2 performs delivery confirmation for two MPDUs, and the wireless terminal 2-3 performs delivery confirmation for two MPDUs. An example is shown in which the terminal 2-4 responds to the delivery confirmation for six MPDUs, and the wireless terminal 2-5 responds to the delivery confirmation for three MPDUs.

  In FIG. 6, a delivery confirmation frame for 16 MPDU is returned using 2 OFDM symbols. In the second MPDU of the wireless terminal 2-1, the first MPDU of the wireless terminal 2-3, and the first MPDU of the wireless terminal 2-5, NACK is returned, otherwise ACK is returned. Has been sent. Here, since ACK / NACK is determined based on the power for each Tone, there is an advantage that phase / amplitude correction is not required in the radio.

  Next, a description will be given of what is coded with respect to power ON / OFF in the carrier sense system. In FIG. 6, delivery confirmation is performed for one MPDU with 1 Tone and 1 symbol. However, in order to prevent an acknowledgment frame from being erroneously determined due to interference from other terminals and interference from other systems, In order to increase the reliability of the delivery confirmation frame, delivery confirmation is performed using a plurality of symbols or a plurality of Tones.

  FIG. 7 is a diagram illustrating an example of encoding in the symbol direction. In this method, the symbol direction is doubled and the efficiency is halved, but the reliability of the delivery confirmation frame is improved. Similarly, encoding in the Tone direction is also possible.

  As described above, in this embodiment, the TMA is used, and the carrier sense method is adopted as a method for realizing the TMA. Thereby, compared with the conventional system, the radio communication section occupied for ACK / NACK can be greatly reduced, and the radio communication capacity can be greatly improved. In addition, when using a plurality of Tones, symbols, multi-level modulation, differential modulation, etc. in addition to the carrier sense method, it is possible to notify a plurality of ACK / NACK information. (As a TMA system, a synchronous detection system, a differential system, a CDM system, etc. can be considered).

Embodiment 2. FIG.
Next, the radio communication system according to the second embodiment will be described. In the first embodiment described above, the TMA implementation method using the carrier sense method has been described. In the second embodiment, a TMA implementation method using the synchronous detection method will be described.

  The configuration of the wireless communication system, the TMA transmission / reception sequence, and the outline of the frame format such as the aggregation frame are substantially the same as those in FIGS. The description is omitted. In this embodiment, as an example, wireless terminals 2-1 to 2-5 are assumed and described.

  FIG. 8 is a diagram showing a delivery confirmation frame when the synchronous detection method is adopted. Here, each wireless terminal notifies control information (for example, power information) in addition to 1 bit of acknowledgment information (ACK / NACK), and the base station 1 uses a synchronous detection method using multilevel modulation. To determine the delivery confirmation frame. In addition, R of illustration shows Reference (reference). Hereinafter, operations different from those of the first embodiment will be described.

  First, the base station 1 transmits an aggregation frame including a TMA information field. In the TMA information field in this embodiment, as the configuration information of the delivery confirmation frame, the Tone (subcarrier) position and number used by each wireless terminal, the reference (R) pattern and the number of symbols, “ACK + control information” The degree of modulation and the corresponding ACK position are included. In this method, each symbol is corrected using the amplitude and phase of the reference. The reference symbol amount depends on the transmission path quality and is defined for each user by cell system information such as Beacon.

  Each of the wireless terminals 2-1 to 2-5 that has received the aggregation frame including the TMA information field that is the configuration information of the delivery confirmation frame uses the designated Tone position, number, reference, and modulation degree after the IFS. “Delivery confirmation information (ACK / NACK) + control information” is transmitted.

  For example, FIG. 8 shows that “delivery confirmation + control information” for the MPDU (s) addressed to the wireless terminal 2-1 is “2 Tone (1R, 2 symbols)” and “delivery confirmation + for the MPDU (s) addressed to the wireless terminal 2-2. The control information is returned as 1 Tone (2R, 1 symbol), the “delivery confirmation + control information” for the MPDU (s) addressed to the wireless terminal 2-3 is returned as 1 Tone (1R, 2 symbols)... .

  As described above, in this embodiment, TMA is used, and further, a synchronous detection method is adopted as a method for realizing TMA. Thereby, compared with the conventional system, the radio communication section occupied for ACK / NACK can be greatly reduced, and the radio communication capacity can be greatly improved.

Embodiment 3 FIG.
Next, the radio communication system according to the third embodiment will be described. In the first and second embodiments described above, the TMA implementation method using the carrier sense method and the synchronous detection method has been described. In the third embodiment, the TMA implementation method using the differential modulation method is described. To do.

  The configuration of the wireless communication system, the TMA transmission / reception sequence, and the outline of the frame format such as the aggregation frame are substantially the same as those in FIGS. The description is omitted. In this embodiment, as an example, wireless terminals 2-1 to 2-5 are assumed and described.

  FIG. 9 is a diagram showing a delivery confirmation frame (TMA) when the differential modulation method is employed. Here, each wireless terminal notifies control information (for example, power information) in addition to 1 bit of transmission confirmation information (ACK / NACK), and base station 1 transmits a delivery confirmation frame using a differential modulation scheme. judge. In addition, R of illustration shows Reference (reference). Hereinafter, operations different from those of the first and second embodiments will be described.

  First, the base station 1 transmits an aggregation frame including a TMA information field. In the TMA information field in this embodiment, as the configuration information of the delivery confirmation frame, the Tone position and number used by each wireless terminal, the reference pattern and the number of symbols, the modulation degree of “ACK + control information”, the corresponding ACK Position, included. In this method, each symbol is corrected using the amplitude and phase of the reference. The reference symbol amount depends on the transmission path quality and is defined for each user by cell system information such as Beacon.

  Each of the wireless terminals 2-1 to 2-5 that has received the aggregation frame including the TMA information field that is the configuration information of the delivery confirmation frame uses the designated Tone position, number, reference, and modulation degree after the IFS. “Delivery confirmation information + control information” is transmitted.

  In this method, the reference symbol of the wireless terminal that uses the Tone is arranged in the first symbol, and the second and subsequent symbols are modulated and demodulated using the differential with the previous symbol. And For example, FIG. 9 shows that “delivery confirmation + control information” for the MPDU (s) addressed to the wireless terminal 2-1 is “2Done (1R, 2 symbols)” and “delivery confirmation +” for the MPDU (s) addressed to the wireless terminal 2-2. The control information ”is shown as a response when 1Tone (1R, 2 symbols) is returned, and the“ delivery confirmation + control information ”for the MPDU (s) addressed to the wireless terminal 2-3 is returned as 1Tone (1R, 2 symbols). .

  As described above, in this embodiment, TMA is used, and further, a differential modulation method is adopted as a method for realizing TMA. Thereby, compared with the conventional system, the radio communication section occupied for ACK / NACK can be greatly reduced, and the radio communication capacity can be greatly improved.

Embodiment 4 FIG.
Next, the radio communication system according to the fourth embodiment will be described. In the first, second, and third embodiments described above, the TMA implementation method using the carrier sense method, the synchronous detection method, and the differential modulation method has been described. In the fourth embodiment, a CDM (Code Division Multiplex) is used. A method of realizing TMA using the method will be described. In the present embodiment, a method of combining with the CDM for securing robustness using the TMA described in the first, second, or third embodiment will be described.

  The configuration of the wireless communication system, the TMA transmission / reception sequence, and the outline of the frame format such as the aggregation frame are substantially the same as those in FIGS. The description is omitted.

  In the CDM system, there are a method of CDM multiplexing ACK information for a plurality of MPDUs addressed to the same wireless terminal, and a method of CDM multiplexing ACK information from different wireless terminals. When multiplexing ACK from one wireless terminal, spreading is performed in the frequency axis direction, and when multiplexing ACK from multiple wireless terminals, it is performed in the time axis direction. Hereinafter, processes different from those of the first, second, and third embodiments will be described.

  FIG. 10 is a diagram illustrating an example in which an ACK frame of one wireless terminal is spread in the frequency direction (Tone direction). Here, ACK frames and control information (Ctrl) for three MPDUs are spread using a code (Code) assigned to the terminal itself.

  FIG. 11 is a diagram illustrating another example of spreading the ACK frame of one wireless terminal in the frequency direction (Tone direction). Here, ACK frames for three MPDUs are spread using three codes (Code) assigned to the terminal itself.

  FIG. 12 is a diagram illustrating an example of multiplexing ACK frames of a plurality of (three as an example) wireless terminals in the time axis direction. Here, each wireless terminal spreads ACK frames and control information (Ctrl) for three MPDUs using a code (Code) assigned to the terminal itself.

  FIG. 13 is a diagram illustrating another example of multiplexing ACK frames of a plurality (three as an example) of wireless terminals in the time axis direction. Here, each wireless terminal spreads an ACK frame for the MPDU using a code (Code) assigned to the terminal itself.

  Then, in the base station 1 (or a specific wireless terminal) that receives the frame spread by the CDM method shown in FIGS. 10 to 13, the reception demodulator 36 appropriately separates the multiplexed and transmitted TMA. And receive.

  As described above, in the present embodiment, TMA is used, and further, the CDM method is adopted as a TMA realizing method. Thereby, compared with the conventional system, the radio communication section occupied for ACK / NACK can be greatly reduced, and the radio communication capacity can be greatly improved. Further, in the carrier sense method, the synchronous detection method, and the differential modulation method coded as in the present embodiment, for example, robustness is improved as compared with a simple carrier sense method that does not employ coding. ing.

Embodiment 5 FIG.
Next, the radio communication system according to the fifth embodiment will be described. In the first to fourth embodiments described above, the TMA implementation method using the carrier sense method, the synchronous detection method, the differential modulation method, and the CDM method has been described. However, in the fifth embodiment, the above-described embodiment is described. A description will be given of a method for realizing timing synchronization of TMAs transmitted from a plurality of different wireless terminals when the methods 1 to 4 are employed.

  The timing synchronization method is, for example, a method in which all OFDMA symbols perform time synchronization control with a base station (centralized control) using ranging as proposed in IEEE 802.16, and a guard interval is used. There is a method for absorbing timing deviation.

  If the base station can correct the path difference error and frequency error of each wireless terminal by centralized control, the control information and the TMA information field including the TMA transmission timing, position, etc. The wireless terminals are notified, and each wireless terminal transmits a TMA to the base station based on the correction information.

  Hereinafter, in the present embodiment, a method for absorbing timing deviation using a guard interval (GI) will be described. The configuration of the wireless communication system, the TMA transmission / reception sequence, and the outline of the frame format such as the aggregation frame are substantially the same as those in FIGS. The description is omitted.

  As shown in FIG. 5 described above, the TMA receives ACKs from different wireless terminals in a state where the ACK is mapped to one or more OFDMA symbols and subcarriers. The arrival times of radio frames differ accordingly. Therefore, when TMA is used, the TMA timing transmitted from each wireless terminal is different, and the length of the guard interval becomes a problem.

  FIG. 14 shows symbol # 2-1 transmitted from the wireless terminal 2-1 to symbol # 2-1 transmitted from the wireless terminal 2-1 and symbol # 2-2 transmitted from the wireless terminal 2-2. 3 is a diagram showing a state in which 3 arrives at the base station 1 with a large delay. Here, since the symbol # 2-3 transmitted from the wireless terminal 2-3 is out of the FFT window with respect to the FFT window (FFT Window) created by the reception demodulator 36 of the base station 1. This indicates interference with other symbols # 2-1 and # 2-2. Note that, in a wireless LAN, a guard interval is originally a section intended to deal with the effects of multipath, and is not defined for solving the perspective problem due to the terminal position.

(Basic guard interval)
In order to solve the problem related to the interference, in this embodiment, ACK information having a two-symbol structure is constructed in TMA. For example, FIG. 15 shows the existing IEEE802.11a symbol configuration and the symbol configuration of the present embodiment. In the case where the symbols of the present embodiment coexist with the IEEE802.11a system, as shown in the figure, one symbol is used as a guard interval, and a two-symbol configuration is used in which ACK information is transmitted by the next one symbol.

  FIG. 16 is a diagram showing an example when the symbol configuration of the present embodiment is applied. For example, in the case of a 20 MHz frequency band, the guard interval is 4.0 μs when the above configuration is adopted. Therefore, since it can respond to a propagation path difference of 1200 m, the guard interval length is sufficient. On the other hand, with a guard interval of 0.8 μs defined in the existing IEEE802.11a, only a path difference of 240 m can be handled.

  Also, in this embodiment, even if a larger guard interval than usual is taken, the control symbol information to be combined with the ACK symbol is several bits, and wasteful IFS is reduced in the environment of a plurality of wireless terminals. Since the effect becomes dominant, the transmission efficiency deterioration by this method does not become a problem.

  In the present invention, the guard interval is one symbol, but the guard interval length is not determined only from the path difference, and includes a processing delay until each wireless terminal responds with an ACK.

(Variable guard interval)
In addition to the above, there is a method for making the guard interval variable as a method for solving the problem related to the interference. Below, this method is demonstrated concretely.

  For example, the base station 1 broadcasts a guard interval for TMA using a Beacon frame or the like according to the cell size. Here, in communication between the base station 1 and each communication terminal, the base station 1 detects how much the frame received by the reception demodulator 36 deviates from the reception timing assumed by the base station 1. Based on the time difference, the reception control unit 34 detects that there is a propagation path difference and a device difference in each wireless terminal, and determines the length of the guard interval for absorbing the propagation path difference and the device difference.

  Next, the base station 1 notifies the new guard interval length to each wireless terminal. Here, it may be notified using the TMA information field, or may be notified as another frame.

  Next, each wireless terminal that has received the new guard interval length changes the setting of its own terminal so that the transmission modulation unit 35 and the reception demodulation unit 36 can also perform modulation / demodulation at the new guard interval.

  Further, in each wireless terminal, the transmission control unit 33 and the reception control unit 34 change the time management method according to the change of the guard interval. Thereafter, each wireless terminal returns a TMA using a new guard interval. Further, FIG. 17 shows a state where the guard interval length is changed in the TMA information field, and the FFT window is appropriately set for the symbols transmitted from each wireless terminal.

Embodiment 6 FIG.
Next, the radio communication system according to the sixth embodiment will be described. In this embodiment, timing synchronization of ACK frames transmitted from a plurality of wireless terminals in the wireless communication systems of Embodiments 1 to 5 described above will be described. In the present embodiment, processing different from that in the first to fifth embodiments will be described.

  In the conventional IEEE802.11, carrier timing is used as a trigger to establish synchronization timing using a pilot. In TMA, since there is usually no pilot, this method cannot be used. When the base station 1 can correct the path difference error and frequency error of each wireless terminal by centralized control, the TMA information field including the control information, TMA transmission timing, position, etc. It is also possible to notify the wireless terminal, and each wireless terminal can transmit a TMA to the base station 1 based on the received TMA information field.

  However, in the conventional IEEE802.11, TMAs from a plurality of wireless terminals are received at almost the same timing (see FIG. 18). The base station 1 cannot determine which wireless terminal is synchronized with an ACK symbol. . In addition, there is a problem that synchronization establishment by carrier sense becomes difficult because multipath exists for each ACK symbol from each wireless terminal and a plurality of delay spreads are included.

(PHY layer timing management method)
In order to solve the above problem, the present embodiment adopts a PHY layer timing management method. For example, in the case of ACK, IFS from the data transmission timing from the base station 1 is defined as described above. By counting this time with PHY 32, the base station 1 determines the ACK arrival time. FIG. 19 is a diagram illustrating a PHY layer timing management method according to the present embodiment.

  When the base station 1 manages the arrival time of the TMA by the PHY 32 and sets the FFT window timing for reception as described above, the accuracy of the IFS from the completion of data transmission at the PHY 32 to the arrival time of the ACK is It becomes important (see FIG. 20).

  In addition, the aggregation frame may be a very long PHY frame even if a technique such as MIMO or Multi-Channels is used. Therefore, on the wireless terminal side, there is a possibility that the synchronization timing created by reception of the leading preamble may fluctuate during PHY frame reception. In addition, the wireless terminal side needs to receive the aggregation frame and respond with an ACK within a fixed time, and it is desirable that the final frame position can be specified.

  Therefore, in the present embodiment, a pilot is inserted into the final symbol of the aggregation frame. FIG. 21 is a diagram showing a configuration of “Re-Synchronization preamble” which is a pilot of the present embodiment. The wireless terminal side uses this pilot to re-synchronize and transmit ACK within a specified time.

  FIG. 22 is a diagram illustrating a configuration of the wireless unit 24 of the present embodiment. Specifically, each wireless terminal uses the “Re-Synchronization Preamble” to reset timing synchronization and start a timer for determining its own ACK timing (starts clock counting). Then, the ACK transmission unit (Tx ACK) 41 executes ACK determination processing within a specified time, and writes ACK information to the transmission queue (Tx Queue) 42. Thereafter, a TMA timing management unit (TMA Timing Management) 43 reads ACK information from the transmission queue 42 at a specified time, and transmits ACK as a TMA frame.

(Timing adjustment between wireless terminals)
Further, when the TMA transmission timing management mechanism of PHY 32 is used, it is possible to perform adjustment so that the TMA transmission timings between the wireless terminals coincide with each other in the base station 1. FIG. 23 is a diagram illustrating a configuration of the wireless unit 14 according to the present embodiment.

  When the base station 1 performs one-to-one communication with each wireless terminal, the base station 1 measures the delay of the ACK arrival time from those wireless terminals. This measurement can be performed periodically under the control of the base station 1.

  In FIG. 23, when receiving the transmission data from the transmission control unit 33, the transmission modulation unit 35 of the base station 1 notifies the timing management unit (Timing Management) 37 of the transmission time. Next, when receiving the radio frame, the base station 1 records the reception time. Since the reception demodulator 36 cannot determine whether or not the frame is an ACK, the reception demodulator 36 transfers the frame to the MAC 31 and receives the received frame type (data, ACK) from the reception controller 34.

  Thereby, the timing management part 37 can acquire the time from the data transmission to the ACK reception. In the present embodiment, the combination of data and ACK has been described, but the same measurement is possible in a frame such as RTS / CTS.

  Next, the base station 1 notifies ACK transmission timing information (Tx Timing Info) of each wireless terminal in the TMA information field in the aggregation frame. Each wireless terminal uses this information to adjust the ACK transmission timing so that the reception timing of the TMA ACK symbol in base station 1 matches. FIG. 24 is a diagram showing ACK transmission timing information included in the TMA information field. Here, the base station 1 notifies the ACK transmission timing individually for each destination wireless terminal.

  Then, the TMA timing management unit 43 of each wireless terminal adjusts the transmission timing of data output from the transmission queue 42 according to the ACK transmission timing.

  With the above control, the base station 1 can match the ACK symbol timings by TMA from the wireless terminals (see FIG. 25). If the TMA symbol timing adjustment function of this embodiment is provided, a guard interval having a normal size may be used.

Embodiment 7 FIG.
Next, the radio communication system according to the seventh embodiment will be described. In this embodiment, power control of ACK transmitted from a plurality of wireless terminals in the wireless communication systems of Embodiments 1 to 6 described above will be described. In the present embodiment, processing different from those in the first to sixth embodiments will be described.

  In TMA, since ACKs from a plurality of wireless terminals are multiplexed within the same symbol (Tone, subcarrier multiplexing), a perspective problem occurs depending on the position of the wireless terminal. FIG. 26 is a diagram illustrating a perspective problem depending on the position of the wireless terminal. For example, when the STAs 2-1 2-2, 2-3 transmit TMA with the same power, the base station 1 receives from each wireless terminal The received power of the frame is shown.

Therefore, in the present embodiment, a method for solving the above-described perspective problem, that is, autonomous power control, centralized control, and power control unique to carrier sense type TMA according to the present embodiment will be described. Note that power control unique to carrier sense type TMA, which will be described later, can be applied to both autonomous power control and centralized control.

(7.1 Autonomous power control)
FIG. 27 is a diagram illustrating a state of power control. The wireless terminal can calculate the power loss in the propagation path by knowing the power of the frame transmitted by the base station 1. In order to set the ACK power of TMA transmitted by each wireless terminal to the same value, each wireless terminal determines a transmission power value based on the power loss. In the present embodiment, power loss is acquired by two methods.

(7.1.1 Acquisition of power loss by Beacon)
The base station 1 sets the transmission power value information of the frame transmitted by the base station, the power information received from each wireless terminal, and the received power of the local station requested by the base station 1 in the Beacon frame. The power path loss can be calculated on the side. That is, each wireless terminal uses these values to control the transmission power when transmitting the TMA ACK frame.

Each wireless terminal calculates a power loss in the propagation path based on the difference between the transmission power value embedded in the Beacon frame and the power value when the terminal receives it. Also, each wireless terminal determines how much transmission power is necessary to receive the same power on the base station 1 side based on the reception power requested by the base station 1, and adaptively and autonomously Control transmission power.

(7.1.2 Aggregation frame power)
In addition, as a method of acquiring a power loss different from the above, for example, the base station 1 includes the transmission power value information (AP Tx Power Info) in the control information of the aggregation frame, that is, the TMA information field. The terminal calculates a path loss from the received power of the received frame. FIG. 28 is a diagram showing transmission power value information included in the TMA information field, and the base station 1 notifies the transmission power individually to each wireless terminal. Each wireless terminal controls transmission power at the time of ACK frame transmission by TMA based on the transmission power value information.

  FIG. 29 is a diagram showing a configuration of the wireless unit 24 of the present embodiment. The reception demodulation unit 36 of each wireless terminal receives and demodulates the aggregation frame, and transfers TMA information and MPDUs to the reception control unit 34. Next, a power loss calculation unit (Rx Level Measurement) 44 calculates a path loss of transmission power. The power loss calculation unit 44 operates in conjunction with the TMA timing management unit 43 and controls the power at the time of TMA ACK transmission based on the path loss.

(7.2 Centralized control)
In order to solve the above-mentioned perspective problem, in the present embodiment, when the base station 1 transmits an aggregation frame, the transmission power of TMA from each wireless terminal may be designated in advance. FIG. 30 is a diagram illustrating TMA transmission power information (STA Requested Tx Power Info) included in the TMA information field. Here, TMA transmission power for each wireless terminal is included in the TMA transmission power information. Note that a relative value (increase / decrease amount, increase / decrease amount) may be used as a method of specifying the power value by the base station 1.

FIG. 31 is a diagram illustrating a centralized control procedure performed by the base station 1. As a specific centralized control procedure, first, each wireless terminal calculates a power path loss value from the aggregation frame according to the above processing, and determines transmission power of TMA (ACK) by autonomous control based on the path loss value. Then, ACK is transmitted (steps S1, S2: Self detection Tx Power Control). Next, the base station 1 receives TMA (ACK), acquires ACK reception power for each wireless terminal, and calculates desired TMA transmission power from these ACK reception powers. The base station 1 then designates a desired TMA transmission power for each wireless terminal and transmits this TMA transmission power information at the time of the next aggregation frame transmission (step S3: Central Control Tx Power Control). Each wireless terminal transmits ACK according to the received TMA transmission power information (step S4: Central Control Tx Power Control). In the TMA transmission power information, not only the relative power (increase amount and decrease amount) of each wireless terminal but also autonomous power control can be specified.

(7.2.1 TMA power control)
In TMA, the number of Tones (subcarriers) used depends on the number of frames that are connected. Therefore, it is possible to use the Tone power that is not used in the Tone that transmits the TMA. There are the following two methods of use.

(7.2.1.1 Frequency diversity)
FIG. 32 is a diagram illustrating “TMA Tone MAP info” in the aggregation frame transmitted by the base station 1. Details of “TMA Tone MAP info” will be described later. Here, each wireless terminal copies and transmits TMCF information, which will be described later, to a free Tone according to the QoS of the connected MAC frame. For example, extra ACK / NACK information is copied and transmitted. FIG. 33 is a diagram illustrating a specific example of frequency diversity. G represents a guard interval. Further, Tone mapping using “TMA Tone MAP info” for each MPDU will be described later.

(7.2.1.2 Power control)
FIG. 34 is a diagram illustrating power control using an empty Tone. In the base station 1, when notifying the power of ACK using TMA, the number of empty Tones is taken into consideration. For example, when the number of empty Tones is 1 and only one MPDU with high QoS is included in the aggregation frame (for example, retransmission PDU), the base station 1 sets the transmission power of TMA (ACK) for this retransmission PDU. , Twice as much as other ACKs (utilizing power of empty Tone). Thereby, the power control shown in FIG. 34 is performed in the wireless terminal, and the delivery probability of TMA having a high QoS can be improved.

(7.3 Carrier sense type TMA inherent power control)
In the carrier sense type TMA, for example, ACK / NACK information is notified by power ON / OFF. In this scheme, the power of the TMA frame is 0 when the acknowledgment of all the connected MPDUs is NACK.

  For this reason, the carrier sense type TMA maps ACK and NACK to different Tones, and gives power to the ACK tone at the time of ACK and gives power to the NACK tone at the time of NACK. FIG. 35 is a diagram illustrating carrier sense type TMA inherent power control according to the present embodiment.

  When this method is used, since only either ACK or NACK is used, the symbol power is doubled (+3 dB). For example, since NACK is not transmitted at the time of ACK, its power is used in ACK and is set to +3 dB.

Embodiment 8 FIG.
Next, the radio communication system according to the eighth embodiment will be described. In the present embodiment, frequency synchronization of each wireless terminal in the wireless communication systems of Embodiments 1 to 7 described above will be described. In the present embodiment, processing different from those in the first to seventh embodiments will be described.

  In TMA, since radio terminals are multiplexed in the Tone direction, the frequency deviation of each radio terminal becomes a problem. If the frequency of each wireless terminal is different, it acts as interference of other Tones.

  In order to solve this problem, each wireless terminal performs frequency synchronization with the base station 1 using Beacon. Each wireless terminal executes AFC at the time of Beacon reception or data reception from the base station 1 and holds the amount of phase rotation. Using this information, each wireless terminal reversely rotates the phase when transmitting TMA (ACK), and controls the base station 1 to synchronize the frequency from each wireless terminal.

  FIG. 36A is a diagram for explaining processing for achieving frequency synchronization between the base station 1 and each wireless terminal. The right arrow means a packet transmitted from the base station 1 to the wireless terminal, and the left arrow means a packet transmitted from the wireless terminal side to the base station 1 (or another wireless terminal). Each wireless terminal executes AFC when receiving Beacon and data transmitted from the base station 1, holds the phase rotation amount, and corrects the phase rotation amount between the base station 1 and the own wireless terminal during TMA transmission. The base station 1 performs control so that the frequencies from the wireless terminals are synchronized.

  FIG. 36-2 is a diagram for explaining a frequency synchronization method in each wireless terminal. The radio terminal receives Beacon or data, down-converts to the operating frequency of its own device by the frequency conversion unit 101 in the reception demodulation unit 36, adjusts the timing by a TR (Timing Recovery) unit 102, and performs AFC ( Automatic frequency control) unit 103 calculates a frequency correction value. Then, the frequency correction unit 104 corrects the received data based on the correction value and passes it to the demodulator at the subsequent stage. On the other hand, on the transmission side, after the MAP unit 201 in the transmission modulation unit 35 modulates transmission data based on modulation information and TMA information, the frequency correction unit 202 performs correction from the AFC unit 103. The frequency deviation of the own terminal is corrected based on the value. Then, the frequency conversion unit 203 performs frequency conversion and transmits in a desired frequency band.

Embodiment 9 FIG.
Next, the radio communication system according to the ninth embodiment will be described. In Embodiments 1 to 4 described above, the basic method for realizing TMA has been described. In the fifth to eighth embodiments, the extended function that can be applied to the first to fourth embodiments has been described. In the present embodiment, an extended function for further improving the performance of the above-described first to eighth embodiments will be described from a more system viewpoint. The following three extended functions will be described below.
(1) Adaptive control
(2) Outstanding TMA
(3) TMCF (Tone Multiplex Control Frame)

(9.1 Adaptive control)
(9.1.1 Adaptive frequency diversity control)
In the differential modulation method / synchronous detection method TMA, the modulation factor and the coding rate are changed according to the propagation environment. Further, the carrier sense type TMA does not control the modulation degree, but controls it by changing the frequency diversity rate. Here, in the carrier sense type TMA, not frequency diversity for power control but frequency diversity for adaptive control is defined.

(9.1.1.1 PTONE / FTONE control)
The MAC 31 controls whether the ACK mapping in the carrier sense type TMA is the PTONE (Partial Tone) type or the FTONE (Full Tones) type according to the transmission path quality. This information is reflected in the “TMA Tone MAP Info” information (see FIG. 32) in the TMA information field and transmitted.

(9.1.1.2 PTONE MAP)
When using “PTONE MAP”, a plurality of Tones are used to transmit 1 ACK. The actual relationship between the physical tone and the logical tone is not arranged in a continuous physical tone because interleaving in the frequency direction acts, but for the sake of easy explanation, the description will be made using the logical tone. FIG. 37A is a diagram illustrating a logical tone mapping of PTONE.

  In the PTONE method (Partial Tone Method), Tone is partially shared by a plurality of ACKs. The number of Tones in the Partial area is reduced as the transmission path quality is improved, and the number of Tones in the Partial area is increased as the transmission path quality is deteriorated.

(9.1.1.3 FTONE MAP)
“FTONE MAP” uses all Tones with 1 ACK. FIG. 37-2 is a diagram illustrating a FTONE Tone map.

  The carrier sense type TMA does not need to perform phase amplitude correction and determines ON / OFF only with Tone power. In addition, in a WLAN such as IEEE802.11a, if there is no other system that is not controlled uniformly, it can be regarded as a system with less interference between other cells / other system interference.

  Therefore, in carrier sense type TMA, interference with other wireless terminals that simultaneously use air becomes a problem, but by taking the FTONE method (Full Tone Method), inter-frequency interference can be avoided, If there is a sufficient guard interval, interference in the time direction can be avoided at the same time (robust communication mode).

  On the other hand, air can be reserved until the TMA reception completion time by notifying the wireless terminal of virtual carrier sense information such as NAV (Net Allocation Vector) in the aggregation frame. Note that the NAV bandwidth reservation method is not a solution for interference from other systems, so the FTONE method is effective.

(9.2 Outstanding TMA)
In the TMA method, it is necessary for all wireless terminals to transmit ACK (Tone multiplexed) within a specified time for an aggregation frame addressed to a multi-user transmitted from the base station 1. However, the PHYs 32 and MACs 31 of all wireless terminals do not hold performance sufficient to guarantee this mechanism. Therefore, the outstanding TMA is shown.

(9.2.1 Issues)
FIG. 38 is a diagram illustrating a problem of the TMA method. In the present embodiment, a wireless terminal (see FIG. 38: corresponding to terminal 2-4 in FIG. 38) whose ACK processing for an aggregation frame addressed to a multi-user is not in time within a specified time is relieved.

(9.2.2 Outstanding ACK)
The base station 1 determines the number of outstandings based on the response time of the wireless terminal with the lowest specification. Then, the aggregation frame is transmitted including information on the number of outstandings (outstanding information). FIG. 39 is a diagram illustrating the standing information in the aggregation frame. Each wireless terminal transmits TMA (ACK) according to the designated number of outstandings.

  FIG. 40 is a diagram showing the outstanding TMA method according to the present embodiment, and more specifically shows an example in which the number of standings is 2 (when the number of standings is 1, normal Stop & Wait) Become).

(9.3 TMCF (Tone Multiplex Control Frame))
In the above-described first to eighth embodiments, the TMA is defined and the ACK transmission method for the aggregation frame has been described. In the present embodiment, in order to adapt to control frames (Control Frame) other than ACK, TMCF is defined and an aggregation frame including a TMCF information frame (TMCF info) is transmitted.

  In this embodiment, the same procedure can be applied to the RTS / CTS procedure, which is a control frame used to solve the OBSS (Overlapping Basic Service Set) problem and the hidden terminal problem. is there.

(9.3.1 TMCF (CTS))
41 and 42 are diagrams showing the TMCF (CTS) procedure of the present embodiment. The base station 1 transmits an aggregation frame (RTS) including a TMCF information frame to a plurality of wireless terminals (2-1 to 2-4), and after IFS, a part or all of those wireless terminals simultaneously transmit TMCF ( CTS). Further, the aggregation frame to be transmitted thereafter includes data only for the wireless terminals (in this case, the wireless terminals 2-1 and 2-4) that transmitted TMCF (CTS). And after IFS again, each wireless terminal (2-1, 2-4) transmits ACK which is a response frame by TMCF (ACK). Thereafter, the base station 1 analyzes the received TMCF (ACK), recognizes that the returned delivery confirmation frame is ACK or NACK, and performs processing. As a result, efficient use of bandwidth becomes possible.

  In this way, by using TMCF, in the next aggregation frame, excess data is not transmitted to the wireless terminals 2-2 and 2-3 that have not transmitted CTS. Can be used. In addition, since the CTS frame can be multiplexed and received from each wireless terminal, subsequent aggregation frames (data) can be efficiently transmitted.

  In this embodiment, the base station 1 transmits the RTS to start the sequence. However, the present invention is not limited to this, and the case where the wireless terminal performs communication by transmitting the RTS to other wireless terminals. It is also applicable to.

(9.3.2 TMCF types Mapping)
In TMCF, by combining with an aggregation frame, individual information can be notified to a plurality of wireless terminals.

(9.3.2.1 TMCF (ACK, CTS) from STAs)
In the present embodiment, the same procedure can be applied to the RTS / CTS procedure, which is a control frame used to solve the OBSS problem and the hidden terminal problem.

  43 and 44 are diagrams showing a TMCF (ACK, CTS) procedure according to the present embodiment. The base station 1 transmits an aggregation frame (RTS, data) including a TMCF information frame to a plurality of wireless terminals (2-1 to 2-4), and after the IFS, the wireless terminals (2-1 to 2-4) Simultaneously receive TMCF (ACK, CTS). Specifically, first, RTS is transmitted to the wireless terminals 2-1, 2-2 and 2-4, and a data frame is transmitted to the wireless terminal 2-3. After IFS, the TMCF is used from each wireless terminal. Then, CTS or ACK is transmitted, respectively.

  Further, the base station 1 transmits the aggregation frame to be transmitted thereafter including data only to the wireless terminals (in this case, the wireless terminals 2-1 and 2-4) that transmitted the TMCF (CTS). Here, since there is no CTS from the wireless terminal 2-2, the next aggregation frame does not include the data addressed to the wireless terminal 2-2, and only the aggregation frame for the wireless terminals 2-1 and 2-4. (Data) is transmitted.

  And after IFS again, each wireless terminal (2-1, 2-4) transmits ACK which is a response frame by TMCF (ACK). As a result, efficient use of bandwidth becomes possible.

  In this way, by using the TMCF, a plurality of control frames can be multiplexed (here, CTS and ACK), and at the same time, in the next aggregation frame, an extra amount is added to the radio terminal 2-2 that has not transmitted CTS. Since data is not transmitted, it is possible to use a more efficient band. In general, the RTS and the data frame are transmitted separately, but can be included in the aggregation frame at the same time by combining with the TMCF.

  According to the present embodiment, it is possible to apply the RTS / CTS procedure only to wireless terminals that cause interference areas and hidden terminal problems, and to directly transmit data frames to other wireless terminals.

(9.3.3 Piggy Back Control)
In TMCF, it is possible to carry control information in addition to ACK. In this case, in the differential modulation method / synchronous detection method, multilevel modulation may be used, and a plurality of symbols may be used. In the carrier sense type, a plurality of types of information can be transmitted by using a plurality of Tones and a plurality of symbols. Here, carpool control and its sequence are defined.

(9.3.3.1 TMCF (ACK + RTS))
FIG. 45 is a diagram illustrating a TMCF (ACK + RTS) procedure according to the present embodiment. For example, when uplink (UL: wireless terminals 2-1 to 2-3 → base station 1) is transmitted following the downlink (DL: base station 1 → wireless terminals 2-1 to 2-3) aggregation frame. In this case, the sequence can be shortened by sharing the RTS frame with the TMCF (ACK) (in this case, the wireless terminals 2-2 and 2-3 are combined). The proposed method is shown below.

  The base station 1 aggregates TMCF (RTS) from a plurality of users (corresponding to the wireless terminals 2-2 and 2-3), selects wireless terminals that allow UL, and information such as time allocated in the UL (UL It responds by CTS with respect to the selected radio | wireless terminal (equivalent to radio | wireless terminal 2-2 and 2-3) including allocation information: UL Allocation Info). The selected wireless terminal performs UL communication in the allocated time period.

  At this time, the ACK frame corresponding to the UL data transmission is received during the period of “UL Data Transmission”. With regard to the ACK transmission from the base station 1, the BlockACK is changed according to the exchange of the ACK policy in advance. , No_ACK, etc. can be used.

  This embodiment can also be realized as an improved version of the TXOPs allocation procedure defined in IEEE802.11e. In addition, “ACK for STA2-2” and “ACK for STA2-3” may take a form such as BlockACK, or an access method such as TDMA that performs transmission based entirely on a pre-allocated time. Can also be supported. That is, FIG. 45 is an example, and there are a plurality of other versions.

Embodiment 10 FIG.
Next, the radio communication system according to the tenth embodiment will be described. In the above-described first to ninth embodiments, TMA (or TMCF) is used to reduce physical layer overhead and protocol overhead due to the ACK frame procedure, thereby realizing an increase in communication capacity. In this embodiment, in the wireless communication systems of Embodiments 1 to 9 described above, overhead due to TMA for the aggregation frame addressed to multi-users is further reduced. Specifically, by applying TMCF (or TMA) to a full-duplex communication system, IFS time and unnecessary protocol time required for TMCF transmission are reduced.

(10.1 TMCF for Dual Band Wireless System)
In this embodiment, a physical channel capable of broadband transmission and mainly performing data transmission is defined as a data channel (Data-CH). On the other hand, a physical channel for performing control communication such as a control frame (Control Frame: ACK / NACK, RTS / CTS etc.) is defined as a control channel (Ctrl-CH).

  Each channel can select and use multiple channels from the same frequency band, but the data channel uses a high frequency band to perform large-capacity communication, and the control channel uses the amount of transmitted data. Therefore, the low frequency band is used as compared with the data channel. The TMA information field includes “Tx Timing Info”, “AP Tx Power Info”, “STA Requested Tx Power Info”, etc., as in the previous embodiment, but is omitted in the following description. To do. The configuration of the wireless communication system (home / office wireless network) according to the present embodiment is the same as that shown in FIG.

  FIG. 46 is a diagram showing a configuration of the radio units 14 and 24 of the dual band radio system according to the present embodiment. The wireless unit includes a MAC 31 that performs transmission data generation, reception data generation, and access control based on data from a host interface for connection to a signal interface unit or a terminal interface unit, and a PHY 32 that performs modulation and demodulation. And comprising. The MAC 31 includes a transmission control unit (MAC Tx) 33 that performs transmission data creation and transmission timing management, and a reception control unit (MAC Rx) that performs reception timing detection and reception data success / failure confirmation. 34, and selector sections (SEL) 51 and 52 for selecting which of the data channel and the control channel is used for transmission / reception. In addition, the PHY 32 demodulates the reception data and a transmission modulation unit (Data_CH Tx PHY) 53, a transmission modulation unit (Ctrl_CH Tx PHY) 54 that modulates transmission data from the MAC 31, for each of the data channel and the control channel. A receiving demodulation unit (Data_CH Rx PHY) 55 and a receiving demodulation unit (Ctrl_CH Rx PHY) 56.

  FIG. 47 is a diagram in which the TMA (TMCF) of the present embodiment is made compatible with a dual band system, and shows, for example, a frame transmission / reception sequence and a frame format when TMA is used. Since the basic flow is the same as in FIG. 4, different parts will be described.

  In the data channel, an aggregation frame addressed to multi-users including control information such as TMCF timing and mapping position in the control channel is transmitted. The wireless terminal that has received the aggregation frame transmits TMCF (ACK) using the control channel using the allocated time. As a result, the downlink (DL) and the uplink (UL) can be communicated simultaneously, the extra protocol overhead due to the TMCF can be reduced, and the communication capacity can be increased. As shown in FIG. 57, when a synchronization preamble is periodically inserted for each MPDU, the wireless terminal can maintain synchronization with the base station 1 with high accuracy.

(10.2 Bi-BCN Transmission)
In this embodiment, as apparent from the use of the dual band, interference between other cells / interference between other systems becomes a problem.

  Inter-cell interference is solved by transmitting a Beacon (BCN) frame in the data channel and the control channel. The bandwidth reservation method using the Beacon frame is shown below.

  In the present embodiment, broadcast information (Beacon frame) indicating that the base station 1 is operating in a specific band is periodically transmitted on both the data channel and the control channel. The Beacon frame of each channel includes the operating frequency or channel number of both the data channel and the control channel. Even if the base station 1 changes the operation channel by control such as DFS (Dynamic Frequency Selection) by transmitting the Beacon frame of each channel including the information of each channel, each wireless terminal However, it becomes possible to grasp the operating frequency and channel number of the data channel and control channel.

  FIG. 48 is a diagram showing a method of transmitting a Beacon frame in the present embodiment. A state in which Beacon frames are periodically transmitted on the data channel and the control channel is shown. Note that the frame exchange sequence between Beacon frames is not limited to FIG.

Hereinafter, in this embodiment, specific examples of the Beacon transmission method will be described individually.
(1) Centralized management system using base stations (2) Distributed management system using multiple wireless terminals (proxy base stations)

(10.2.1 Centralized management system by base station)
(10.2.1.1 NAV setting)
FIG. 49 is a diagram illustrating an example of a Beacon transmission method when a centralized management method by a base station is applied. It is also possible to reserve a period until the next Beacon by using virtual carrier sense (NAV) information of the Beacon frame. In that case, only the radio terminal assigned by the base station 1 can communicate, and it is possible to avoid the interference between other cells and the hidden terminal problem.

  In addition, UL communication can be scheduled by individually assigning uplink transmission time to each wireless terminal in the uplink MAP (UP link MAP) of the Beacon frame or the aggregation frame. In the present embodiment, the above-described Re-Synchronization field may be added.

(10.1.2.1.2 Delayed Beacon Transmission)
In the present embodiment, as described above, the Beacon frame is transmitted on the data channel and the control channel. However, if there is interference from another cell operating on the same frequency, there is a possibility that Beacon cannot be transmitted at a desired time. In that case, Beacon transmission on the operation channel becomes possible by delaying (delaying) Beacon transmission.

  FIG. 50 is a diagram illustrating a case where Beacon transmission of the control channel is delayed due to interference from another cell or another system. When the control channel Beacon is transmitted, the Beacon period up to the next Beacon is reset and notified within the Beacon frame. That is, “the original Beacon period-delayed time” is notified). The next Beacon timing notifies the normal transmission timing.

  When the power save terminal cannot receive the frame at the scheduled Beacon timing on the control channel, the power save terminal waits for reception of the Beacon frame until the Beacon frame is received on the control channel.

  In addition, the reason why the wireless terminal cannot receive Beacon on the control channel is, for example, when there is much interference in the control channel and “Dynamic Channel Selection (DCS)” is performed in which the operating frequency of the control channel is changed. In other words, when the wireless terminal knows that the operation channel of the control channel has been changed, it stops waiting for the reception of the Beacon frame on the current control channel, and at the next Beacon timing, the Beacon (Data-CH ) The operation channel of the control channel is changed so that Beacon is received on the channel of the control channel notified in (1).

(10.2.2 Distributed management method using multiple wireless terminals (proxy base stations))
(10.2.2.2.1 Beacon Period)
A system in which a specific variable-size slot in a superframe composed of slots of unit time is defined as a Beacon period, and a plurality of wireless terminals transmit Beacon frames within the Beacon period will be described.

(1.2.2.2.2 Beacon transmission method)
FIG. 51 is a diagram showing a Beacon transmission method according to the present embodiment. Each wireless terminal transmits a Beacon only once in a Beacon period (BCN Period), and performs slot reservation for the subsequent superframe. When transmitting Beacon for the first time, transmission is performed in an empty Beacon slot.

  If Beacon is normally transmitted once, transmission is performed using the same Beacon slot unless there is special control. Special control means that if the number of terminals is small but the Beacon period is large and there are slots, the number of Beacon periods is reduced and the wireless terminal currently transmitting in the Beacon slot In this case, we will show the case of increasing the slot when the number of terminals increases and the current Beacon period is not enough.

  Further, as shown in FIG. 52, each wireless terminal adopting the above distributed management method performs a sequence such as transmission of an aggregation frame and reception of a TMA frame within the allocated slot time. Specifically, in FIG. 52, first, after the wireless terminal 2-1 transmits an aggregation frame using a slot reserved by Beacon transmission, the response includes ACKs from the wireless terminals 2-2 and 2-3. TMCF (ACK) is received, and then the wireless terminal 2-2 transmits an aggregation frame using a slot reserved by Beacon transmission, and then responds from the wireless terminals 2-1, 2-3, 2-4. After receiving the TMCF (ACK) including the ACK of the wireless terminal 2-4, the wireless terminal 2-4 transmits an aggregation frame using the slot reserved by the Beacon transmission, and the wireless terminals 2-1, 2-3 receive the response as a response. TMCF (ACK) including ACK is received.

(10.2.2.2.3 Beacon information)
Each wireless terminal puts its own terminal ID in its Beacon frame, receives Beacon from other wireless terminals transmitted in each Beacon period, and puts its terminal ID. Thereby, each wireless terminal can determine whether or not itself is registered in another wireless terminal.

  In addition, when sending a Beacon for the first time, there is a possibility that a frame may collide with another terminal that is about to transmit Beacon from now on. However, by seeing a Beacon from another terminal in the next Beacon period, It can be judged whether the Beacon of the terminal can transmit without colliding with other wireless terminals. If your terminal ID is not registered in Beacon of another wireless terminal, you know that you are using the same Beacon slot as the other wireless terminal, and that wireless terminal changes the Beacon slot, Send Beacon.

(10.2.3 Distributed management method using multiple wireless terminals (proxy base stations))
(10.2.3.3.1 Beacon Period)
A system in which a specific variable-size slot in a superframe composed of slots of unit time is defined as a Beacon period, and a plurality of wireless terminals transmit Beacon frames within the Beacon period will be described. FIGS. 53 and 54 are diagrams showing a Beacon transmission method according to the present embodiment, which is different from FIGS. 51 and 52. In the figure, the superframe includes a beacon transmission period (BCN period) which is a broadcast signal, a non-collision access period (CFP: Contention Free Period) in which communication is performed using a slot notified by Beacon, and a new request. It is comprised from the random access period (CP: Contention Period) used in order to notify.

(10.3.2.3.2 Beacon transmission method)
Each wireless terminal transmits a Beacon only once in the Beacon period, and performs slot reservation for the subsequent superframe. When transmitting Beacon for the first time, transmission is performed in an empty Beacon slot. Further, as shown in FIG. 54, each wireless terminal adopting the above distributed management scheme performs a sequence such as transmission of an aggregation frame and reception of an ACK frame within the allocated slot time. Here, unlike FIG. 52, the non-collision access period and the random access period are divided at the illustrated CPF and CP switching timing.

  As described above, the radio communication system according to the present invention is useful for a radio communication system that multiplexes and transmits a delivery confirmation frame between a plurality of terminals.

It is a figure which shows the structure of the radio | wireless communications system concerning this invention. It is a figure which shows the structure of a radio | wireless unit. It is a figure which shows the frame transmission / reception sequence using TMA. It is a figure which shows the frame transmission / reception sequence and frame format at the time of using TMA. It is a figure which shows the Example of TMA. It is a figure which shows an example of the delivery confirmation frame at the time of employ | adopting a carrier sense system. It is a figure which shows an example of the delivery confirmation frame at the time of employ | adopting a carrier sense system. It is a figure which shows the delivery confirmation frame at the time of employ | adopting a synchronous detection system. It is a figure which shows the delivery confirmation frame at the time of employ | adopting a differential modulation system. It is a figure which shows an example in the case of spread | diffusing the ACK frame of one radio | wireless terminal to a frequency direction. It is a figure which shows an example in the case of spread | diffusing the ACK frame of one radio | wireless terminal to a frequency direction. It is a figure which shows an example in the case of multiplexing the ACK frame of a some radio | wireless terminal to a time-axis direction. It is a figure which shows an example in the case of multiplexing the ACK frame of a some radio | wireless terminal to a time-axis direction. The symbol # 2-3 transmitted from the wireless terminal 2-3 is significantly different from the symbol # 2-1 transmitted from the wireless terminal 2-1, and the symbol # 2-2 transmitted from the wireless terminal 2-2. It is a figure which shows a mode that it arrives at the base station late. FIG. 10 is a diagram illustrating an existing IEEE 802.11a symbol configuration and a symbol configuration according to the fifth embodiment. FIG. 10 is a diagram illustrating an example when the symbol configuration of the fifth embodiment is applied. It is a figure which shows a mode that the guard window length was changed in the TMA information field, and the FFT window was appropriately applied with respect to the symbol transmitted from each radio | wireless terminal. It is a figure which shows the problem of a prior art. FIG. 20 is a diagram illustrating a PHY layer timing management method according to a sixth embodiment. FIG. 20 is a diagram illustrating a PHY layer timing management method according to a sixth embodiment. FIG. 23 is a diagram illustrating a configuration of “Pre-Synchronization preamble” that is a pilot according to the sixth embodiment. FIG. 11 illustrates a configuration of a wireless unit according to a sixth embodiment. FIG. 11 illustrates a configuration of a wireless unit according to a sixth embodiment. It is a figure which shows the ACK transmission timing information contained in a TMA information field. It is a figure which shows the effect of Embodiment 6. FIG. It is a figure which shows the perspective problem by a radio | wireless terminal position. It is a figure which shows the mode of electric power control as a method for solving a perspective problem. It is a figure which shows the transmission power value information included in a TMA information field. It is a figure which shows the structure of a radio | wireless unit. It is a figure which shows the TMA transmission power information included in a TMA information field. It is a figure which shows the centralized control procedure by a base station. It is a figure which shows "TMA Tone MAP info" in the aggregation frame which a base station transmits. It is a figure which shows the specific example of a frequency diversity. It is a figure which shows the electric power control using empty Tone. FIG. 10 is a diagram illustrating carrier sense type TMA inherent power control according to a seventh embodiment. It is a figure for demonstrating the process for frequency synchronization. It is a figure for demonstrating the frequency synchronization method in a radio | wireless terminal. It is a figure which shows the logical tone mapping of PTONE. It is a figure which shows the Tone map of a FTONE system. It is a figure which shows the subject of a TMA system. It is a figure which shows the outstanding information in an aggregation frame. FIG. 38 is a diagram illustrating an outstanding TMA method according to the ninth embodiment. FIG. 25 is a diagram illustrating a TMCF (CTS) procedure according to the ninth embodiment. FIG. 25 is a diagram illustrating a TMCF (CTS) procedure according to the ninth embodiment. FIG. 20 is a diagram illustrating a TMCF (ACK, CTS) procedure according to the ninth embodiment. FIG. 20 is a diagram illustrating a TMCF (ACK, CTS) procedure according to the ninth embodiment. FIG. 25 is a diagram illustrating a TMCF (ACK + RTS) procedure according to the ninth embodiment. FIG. 38 shows a configuration of a radio unit of a dual band radio system according to the tenth embodiment. It is the figure which made TMA (TMCF) of Embodiment 10 respond | correspond to a dual band system. 218 is a diagram illustrating a transmission method of a Beacon frame in Embodiment 10. [FIG. It is a figure which shows an example of the Beacon transmission method at the time of applying the centralized management system by a base station. It is a figure which shows the case where Beacon transmission of a control channel is delayed by interference from another cell or another system. 218 is a diagram illustrating the Beacon transmission method of Embodiment 10. [FIG. 218 is a diagram illustrating the Beacon transmission method of Embodiment 10. [FIG. 218 is a diagram illustrating the Beacon transmission method of Embodiment 10. [FIG. 218 is a diagram illustrating the Beacon transmission method of Embodiment 10. [FIG. It is a figure which shows an example of a prior art. It is a figure which shows an example of a prior art. It is a figure which shows an example of a prior art. It is a figure which shows an example of a prior art. It is a figure for demonstrating the subject of a prior art. It is a figure for demonstrating the subject of a prior art.

Explanation of symbols

1 Base station (AP)
2-1 to 2-n wireless terminal (STA)
DESCRIPTION OF SYMBOLS 11 Communication unit system 12 Access system termination | terminus unit 13 Signal interface unit 14 Wireless unit 21 Information equipment main body 22 Terminal unit system 23 Terminal interface unit 24 Wireless unit 31 MAC (Media Access Control)
32 Physical layer (PHY)
33 Transmission Control Unit (MAC Tx)
34 Reception Control Unit (MAC Rx)
35 Transmission Modulator (Tx PHY)
36 Reception Demodulator (Rx PHY)
37 Timing Management Department
41 ACK transmitter (Tx ACK)
42 Transmission queue (Tx Queue)
43 TMA Timing Management Department
44 Power Loss Calculation Unit (Rx Level Measurement)
51,52 Selector part (SEL)
53 Transmission Modulator (Data_CH Tx PHY)
54 Transmission Modulator (Ctrl_CH Tx PHY)
55 Reception Demodulator (Data_CH Rx PHY)
56 Reception Demodulator (Ctrl_CH Rx PHY)

Claims (22)

  1. A specific communication device (source communication device) transmits data to a plurality of communication devices (destination communication devices) constituting the network, and each destination communication device receives an acknowledgment frame (ACK) corresponding to the data addressed to itself. , NACK) in response,
    The source communication device is
    TMA (Tone Multiple ACK) information for multiplexing delivery confirmation frames returned from a plurality of destination communication devices into one radio frame is created, and a predetermined transmission frame including the TMA information is sent to each destination communication device. TMA information transmission control means for transmitting
    TMA reception control means for receiving and analyzing a TMA that is a radio frame in which the delivery confirmation frame is multiplexed, recognizing that the delivery confirmation frame returned from each destination communication device is ACK or NACK, and processing.
    With
    Each of the destination communication devices is respectively
    A delivery confirmation control means for receiving the TMA information and returning a delivery confirmation frame corresponding to the data addressed to the own apparatus based on the TMA information;
    With
    A delivery confirmation frame returned from a plurality of destination communication devices based on the TMA information is transmitted as a TMA, multiplexed into one radio frame,
    The TMA information includes transmission timing information indicating individual timing for causing each destination communication device to transmit a delivery confirmation frame, information for giving power of empty Tone to delivery confirmation Tone for retransmission data ,
    In order to determine the individual timing for sending an acknowledgment frame,
    The source communication device is
    Insert a pilot for re-synchronizing the timing in the final symbol of a predetermined transmission frame, and transmit.
    Receiving a delivery confirmation frame from each destination communication device resynchronized using the pilot;
    Determining an individual timing for causing each destination communication device to transmit a delivery confirmation frame based on the respective required time from inserting the pilot and transmitting the frame to receiving each delivery confirmation frame for the frame;
    A wireless communication system.
  2.   The wireless communication system according to claim 1, wherein the predetermined transmission frame is an aggregation frame obtained by concatenating data of a plurality of destinations.
  3.   In the TMA transmission processing, one delivery confirmation frame is transmitted in one frequency band (Tone, subcarrier), and delivery confirmation frames are transmitted from a plurality of destination communication devices within one symbol. The wireless communication system according to claim 1 or 2.
  4.   The wireless communication system according to claim 3, wherein the delivery confirmation control means transmits a delivery confirmation frame using a position (time and frequency band) allocated in advance by the TMA information.
  5.   The wireless communication system according to claim 3 or 4, wherein a carrier sense method for determining a delivery confirmation frame based on power of each frequency band is adopted as a method for realizing the TMA.
  6.   The TMA information transmission control means may set the mapping of the delivery confirmation frame to a PTONE (Partial Tone) type that uses a plurality of frequency bands to transmit one delivery confirmation frame, depending on the transmission path quality. 6. The method of claim 5, further comprising: determining whether to use a frequency band of FTONE (Full Tones) type used in one delivery confirmation frame, and transmitting the determined information included in the TMA information. Wireless communication system.
  7.   The wireless communication system according to claim 3 or 4, wherein a synchronous detection method for determining a delivery confirmation frame using multi-level modulation is adopted as a method for realizing the TMA.
  8.   5. The wireless communication system according to claim 3, wherein a differential modulation method for determining a delivery confirmation frame using differential modulation is adopted as a method for realizing the TMA.
  9.   The wireless communication system according to any one of claims 5 to 8, wherein a plurality of acknowledgment frames are multiplexed by CDM (Code Division Multiplex).
  10. When adopting OFDM as a communication method,
    10. The delivery confirmation frame has a two-symbol configuration in which one symbol is a guard interval and the next one symbol is delivery confirmation information (ACK, NACK). Wireless communication system.
  11. When adopting OFDM as a communication method,
    The transmission source communication device detects how much the delivery confirmation frame deviates from the reception timing assumed by the own device, adjusts the guard interval length based on the time lag obtained as a detection result, The wireless communication system according to claim 1, wherein the guard interval length is notified to the destination communication device.
  12. The transmission source communication device sets, in the Beacon frame, transmission power of a frame transmitted by the own device, power of a signal received from each destination communication device, and reception power requested by the own device,
    The said delivery confirmation control means calculates the power loss in the transmission path based on the set power information, and adjusts the transmission power of the delivery confirmation frame by autonomous control based on the power loss. The wireless communication system according to any one of 1 to 11.
  13.   The TMA information transmission control means transmits the TMA information including its own transmission power, and the delivery confirmation control means calculates a power loss in the transmission path based on the transmission power, and based on the power loss. The radio communication system according to claim 1, wherein the transmission power of the delivery confirmation frame is adjusted by autonomous control.
  14. The TMA information transmission control means further receives a delivery confirmation frame adjusted by the autonomous control, measures received power for each destination communication device, and transmits a delivery confirmation frame for each destination communication device from these received powers. Determine the power, transmit the transmission power of the acknowledgment frame in the next transmission frame,
    The wireless communication system according to claim 12 or 13, wherein the delivery confirmation control means transmits a delivery confirmation frame according to the received transmission power.
  15.   15. The wireless communication system according to claim 12, 13 or 14, wherein ACK and NACK are mapped to different frequency bands in a delivery confirmation frame returned by each destination communication device.
  16.   The wireless communication system according to claim 1, wherein the destination communication device uses Beacon to achieve frequency synchronization with a transmission source communication device.
  17. The TMA information transmission control means determines the number of outstandings based on the response time of the destination communication device with the lowest specification, and transmits information relating to the determined number of outstandings in the TMA information,
    The delivery confirmation control means includes
    The wireless communication system according to claim 1, wherein a delivery confirmation frame is transmitted based on the outstanding number information.
  18.   2. A physical channel that performs data transmission is a data channel, a physical channel that performs control communication of a control frame (delivery response frame, RTS / CTS) is a control channel, and operates as a full-duplex communication system. The wireless communication system according to any one of ˜17.
  19.   The wireless communication system according to claim 18, wherein the specific communication apparatus periodically transmits a Beacon frame on both a data channel and a control channel.
  20.   The wireless communication system according to claim 19, wherein a period until the next Beacon is reserved using virtual carrier sense (NAV) information of the Beacon frame.
  21.   The wireless communication system according to claim 19 or 20, wherein if the Beacon frame cannot be transmitted at a desired time, the transmission of the Beacon frame is postponed.
  22.   The wireless communication system according to claim 21, wherein a plurality of communication devices constituting the network transmit a Beacon frame only once in a Beacon period and perform slot reservation for data transmission.
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