JP2007215244A - Transmission method and transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system (a transmission method and a transmitter) capable of improving the throughput by efficiently using the radio band. <P>SOLUTION: The transmission method adopted by the transmitter in the radio communication system for transmitting data frames to a receiver is characterized in to include the step of : dividing, e.g. one data frame corresponding to a plurality of communication channels; or dividing the data frame corresponding to a plurality of antennas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a base station and a wireless terminal that transmit and receive wireless signals compliant with the wireless LAN standard IEEE802.11, and more particularly to a base station and a wireless terminal that realize a wide band using a plurality of communication channels.

  A conventional wireless communication system (wireless LAN communication system) will be described below. Currently, it is compliant with the IEEE802.11b, IEEE802.11a standards, etc., standardized by the US wireless LAN standard IEEE802.11 (see Non-Patent Document 1) as equipment for building high-speed wireless network systems for home / office The product is on the market.

  A wireless LAN compliant with the IEEE802.11b standard (see Non-Patent Document 2) uses a 2.4 GHz band, and uses CCK (Complementary Code Keying) as a modulation method and has a physical maximum transmission rate of 11 Mbps. In addition, a wireless LAN (see Non-Patent Document 3) compliant with the IEEE802.11a standard uses a 5 GHz band, uses OFDM (Orthogonal Frequency Division Multiplex) as a modulation method, and has a physical maximum transmission rate of 54 Mbps. In addition, a wireless LAN based on the IEEE802.11g standard, whose specifications are currently being studied, uses the 2.4 GHz band, uses OFDM as a modulation method, and has a physical maximum transmission rate of 54 Mbps.

IEEE802.11 (http://standards.ieee.org/getieee802/802.11.html) IEEE802.11b IEEE802.11a

  However, in the above-described conventional wireless communication system, the effective speed indicating how much the data stream can actually be transmitted is often reduced to about half of the physical maximum transmission speed or less. There was a problem.

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

  In addition, the base station and each wireless terminal, for example, perform carrier sensing on a wireless channel prior to wireless frame transmission, and refrain from transmitting a wireless frame when confirming that the channel is in use (channel busy) and not using the channel (channel After confirming (idle), a random access method called CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) for transmitting a radio frame is used. 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 cannot be received correctly, a frame retransmission operation is also performed.

  Therefore, the effective speed is not the physical transmission speed of a wireless LAN compliant with IEEE802.11b, IEEE802.11a, or IEEE802.11g, but is about half or less depending on the environmental conditions of the transmission system. Is real.

  That is, in a conventional home / office wireless network system (wireless LAN) compliant with the IEEE802.11a, IEEE802.11b, IEEE802.11g standards, etc., for example, a high-definition television HDTV that requires a bandwidth of about 20 Mbps When performing bidirectional communication of a data stream of a video signal of (High Definition Television), the effective speed is insufficient.

  In addition, as an example of a method for solving the shortage of the effective speed, for example, when transmitting / receiving a broadband data stream, IP packets are allocated to a plurality of wireless units operating on different channels, and independent by each wireless unit. A method for transmitting and receiving IP packets under control (Japanese Patent Laid-Open No. 2002-135304) has been proposed. However, since it is distributed to each wireless unit in units of IP packets, for example, when the modulation method between wireless units is different or when the sizes of IP packets are not equal, the processing is performed such as packet rearrangement. There was a problem that a delay occurred. There is also a problem that due to independent control of the wireless unit, the leakage power from the adjacent channel becomes larger than the carrier sense threshold, and transmission may not be performed normally.

  In addition, as a method different from the above, when one wireless unit becomes a master and a wide transmission band is required for video transmission or the like, a sub wireless unit corresponding to a pre-assigned channel is operated as a slave, There has also been proposed a method in which a master transmits and receives control signals for acquiring wireless channel access rights and transmits and receives IP packets by a plurality of wireless units. However, as described above, since transmission is performed to each wireless unit in units of IP packets, transmission is completed in a certain wireless unit when the modulation method between wireless units is different or when the size of IP packets is not equal. In spite of the fact that transmission has not been completed in a certain wireless unit, a situation occurs in which it is not possible to shift to a reception state. On the other hand, in a terminal receiving an IP packet, transmission is performed in a certain wireless unit. In spite of the fact that transmission has not been completed, there is a situation in which a wireless unit has not completed transmission, so it cannot be transferred to the transmission state. As a result, the wireless band cannot be used efficiently. There was a problem.

  The present invention has been made in view of the above, and an object of the present invention is to provide a wireless communication system (base station and wireless terminal) capable of improving throughput by efficiently using a wireless band. .

  In order to solve the above-described problems and achieve the object, a transmission method according to the present invention is a transmission method employed by a transmitter in a wireless communication system that transmits a data frame to a receiver, and includes one data frame. A frame allocation step of dividing the frame in correspondence with a plurality of communication channels.

  According to the present invention, for example, wireless signals conforming to the IEEE802.11a, IEEE802.11b, IEEE802.11g standards, etc. are distributed to a plurality of communication channels and transmitted to a home / office wireless network. At this time, in the MAC, the entire frame is a division target, and the divided frame is distributed to each physical layer. As a result, since the radio band can be used efficiently, there is an effect that the throughput can be significantly improved as compared with the conventional case. Further, since IEEE 802.11a, IEEE 802.11b, and IEEE 802.11g, which are existing physical layers, can be used, there is an effect that backward compatibility can be maintained with respect to an existing system.

  Embodiments of a wireless communication system (base station, wireless terminal) according to the present invention will be described below in detail with reference to the drawings. 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. And a plurality of wireless terminals (STAs) 2A, 2B,...

  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 specific wireless terminals 2A, 2B,... Via the home / office wireless network. A communication unit system 11 is provided. The communication unit system 11 includes an access system termination unit 13 that terminates the access line, and a mutual signal format between the signal of the access network and the signal of the wireless terminals 2A, 2B,. A signal interface unit 14 (e.g., equivalent to a router or bridge) that controls conversion, and a wireless signal in conformity with the IEEE802.11a, IEEE802.11b, IEEE802.11g standards, etc., for multiple channels in a home / office wireless network .., And antennas 12-1, 12-2,... In the present embodiment, a plurality of antennas are connected to the broadband wireless unit 15, but the present invention is not limited to this, and one antenna may be used.

  The wireless terminals 2A and 2B respectively include information equipment bodies 21A and 21B such as personal computers, PDAs, and television receivers, and data between the information equipment bodies 21A and 21B and the communication unit system 11 of the base station 1. Terminal unit systems 22A and 22B for controlling transmission and reception. And this terminal unit system 22A, 22B is terminal interface unit 24A, 24B which controls the mutual conversion of the signal format between the signal of the base station 1, the other radio | wireless terminal, and the information apparatus main body 21A, 21B, Broadband wireless units 25A and 25B for transmitting and receiving a plurality of channels of wireless signals compliant with the IEEE802.11a, IEEE802.11b, IEEE802.11g standards, etc. to home / office wireless networks, and antennas 23A-1, 23A-2,. , 23B-1, 23B-2,. In the present embodiment, a plurality of antennas are connected to the broadband wireless units 25A and 25B. However, the present invention is not limited to this, and one antenna may be used. Further, in this 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 establish their own networks and perform communication. Is also applicable.

  FIG. 2 is a diagram showing the configuration of the broadband wireless units 15 and 25 of the present embodiment. The broadband wireless units 15, 25A, 25B (25A, 25B correspond to 25 in FIG. 2) are a host interface unit (HostInterface) 33 for connection with the signal interface unit 14 or the terminal interface units 24A, 24B, A MAC (Media Access Control) 32 that conforms to the IEEE802.11 standard (a, b, e, f, g, h, i, etc.) and is expanded to satisfy the present embodiment, IEEE802.11a, IEEE802 And a plurality of physical layers (PHY) 31 (corresponding to 31-1, 31-2, 31-3,...) That operate on a plurality of different channels conforming to the .11b, IEEE802.11g standards, and the like.

  The MAC 32 is an extension of the IEEE802.11 standard (a, b, e, f, g, h, i, etc.). When the physical layer for a plurality of channels is not used, the IEEE802.11 standard (a , b, e, f, g, h, i, etc.). In the TxControl unit 37 in the MAC 32, frame distribution processing for transmitting transmission frames through a plurality of channels, FCS (Frame Check Sequence) addition, time stamp addition, buffer read control, back-off processing, RTS (Request to Send) Processing such as automatic creation of frames, CTS (Clear to Send) frames and ACK frames is performed. The RxControl unit 36 performs processing for combining frames received by a plurality of channels, FCS check, buffer writing processing, address decoding processing, channel status processing, and the like.

  Further, the MAC 32 exchanges data and control signals with the individual physical layers 31 in order to exchange a plurality of Transmission (Tx) units 34 (corresponding to 34-1, 34-2, 34-3,...) And Reception ( Rx) unit 35 (corresponding to 35-1, 35-2, 35-3,...), Which performs primitive issuance, data write processing, data read processing, and the like for the corresponding physical layer.

  Therefore, the Tx unit 34 and the Rx unit 35 perform necessary processes for individual frames, and the TxControl unit 37 and the RxControl unit 36 perform necessary processes for all frames.

  Further, the ProtocolControl unit 38 determines the transmission rate of each channel, the frame distribution ratio for each channel, and the amount of transmission data for each channel in addition to the control based on the CSMA / CA protocol such as acquisition of access right to the channel. Etc. are provided.

  In addition, although not specified, a transmission / reception buffer, an encryption unit, an authentication management unit, and the like are provided. Each physical layer 31 is not specified, but modulates a signal from the MAC 32 into a transmission signal, demodulates a reception signal into a signal to the MAC 32, a signal from the BaseBand unit, the BaseBand It is equipped with an RF unit consisting of an up-converter / down-converter, power amplifier, etc. that convert the signal to the unit into the desired signal.

Next, the operation of the wireless communication system will be described. FIG. 3 is a diagram showing a data frame format compliant with IEEE802.11a, and FIG. 4 is a diagram showing a frame format when using a plurality of channels (3ch). When the frame is distributed to a plurality of channels and transmitted, the burst time of each channel is constant. N _DBPS (Data bits per OFDM symbol) is specified in IEEE 802.11a and indicates the number of data bits that can be transmitted per OFDM. In the present embodiment, for convenience of explanation, the number of octets that can be transmitted per OFDM symbol is defined as N _DOPS (Data octets per OFDM symbol) (N _DOPS = N _DBPS / 8).

  A data frame (MPDU) 40 compliant with IEEE802.11a shown in FIG. 3 includes a MAC header 41, an LLC header / SNAP header 42, a Frame Body 43, and an FCS 44. Further, when the MPDU 40 is transmitted from the MAC 32 to the physical layer 31, the OFDM signal 50 is transmitted in the order of the synchronization preamble 51, the SIGNAL 52 including the transmission rate and the transmission data length, and the DATA 53 including the SERVICE field and the MPDU 40 transmission part. It is shown that. However, a guard interval included between OFDM symbols, a bit arrangement order due to modulation in the physical layer 31, and a change in the number of bits are omitted.

  FIG. 4 shows the frame division state of the MPDU 40 in a plurality of channels and the division of each channel when a plurality of physical layers 31-1, 31-2, and 31-3 are used in the present embodiment. The MPDUs 40-1, 40-2, and 40-3 and the OFDM signals 50-1, 50-2, and 50-3 in the physical layers 31-1, 31-2, and 31-3 are shown.

In this embodiment, the MAC header 41, LLC header / SNAP header 42, Frame Body 43, and FCS 44 defined in IEEE 802.11 are all targeted for division, and as shown in FIG. In accordance with the transmission rates of the layers 31-1, 31-2, 31-3, it is divided in advance by N _DOPS (MAC header 41-1, LLC header / SNAP header 42-2, Frame Body 43-1, 43- 2, 43-3, which corresponds to FCS 44-2), is transferred to each physical layer in a data unit that can be transmitted by 1 OFDM. FIG. 5 is a diagram showing a method for dividing / distributing the MPDU 40. Therefore, in FIG. 4, the OFDM signals 50-1, 50-2, 50-3 in each physical layer have substantially the same burst time.

  Although not shown, since the ACK frame is composed of only the MAC header and the FCS, the same frame is transmitted through a plurality of channels without being divided. At this time, if at least one ACK frame is successfully received, the receiving side recognizes the ACK frame as an ACK frame, and reduces the occurrence of data retransmission due to failure to receive the ACK frame, thereby improving the system throughput. . Also, control frames such as RTS / CTS with a short frame length, data frames with a short frame length, management frames, etc. are transmitted at the same rate without being divided. At this time, if at least one of the frames can be normally received on the receiving side, the receiving side recognizes it as a transmitted frame and reduces the occurrence of data retransmission, thereby improving the system throughput. In addition, for a system compliant with the IEEE802.11a, IEEE802.11b, IEEE802.11g standards, etc., notification of bandwidth reservation time and the like is simultaneously performed.

  Here, the division / distribution processing in the present embodiment will be described. The ProtocolControl unit 38 determines the transmission rate of each channel with which each physical layer 31-1, 31-2, 31-3 communicates, and sets the transmission frame length, the transmission rate of each channel, the number of channels used, and the like to the TxControl unit 37. Notify

  In the TxControl unit 37, it is necessary to specify a transmission rate, a data length, and the like with TXVECTOR for each channel prior to transmission. Therefore, the TxControl unit 37 receives the above notification from the ProtocolControl unit 38 and performs the following division / distribution processing on each channel.

  Hereinafter, a method for calculating the number of octets of the DATA portion necessary for the division / distribution processing and the data length of each channel will be described. Here, for convenience of explanation, the case of 3 channels (physical layer 31-1: Channel-A, physical layer 31-2: Channel-B, physical layer 31-3: Channel-C) will be described.

For example, the size of an MPDU composed of a MAC header, LLC header, SNAP header, FrameBody, and FCS is set to L [octet], and the transmission rate of each channel is set to RATE (a), RATE (b), and RATE (c) [Mbps]. If the number of transmission octets per OFDM of each channel is defined as N _DOPS (a), N _DOPS (b), N _DOPS (c) [octet], and the number of channels is defined as k, the number of OFDM symbols necessary for MPDU transmission N is obtained by the following equation (1).

  However, floor [•] represents rounding up of a decimal value, and “frame length + k” takes into account tailbit. Also, RATE (a) ≧ RATE (b) ≧ RATE (c) is satisfied, and the number of OFDM symbols does not include the number of symbols in the SIGNAL field transmitted by BPSK (Binary Phase Shift Keying: R = 1/2). . Also, the first OFDM symbol is 2 octets less than the other symbols due to 2 octets in the SERVICE field.

  Further, the general expression of the number N of OFDM symbols can be expressed as the following expression (2).

  Therefore, the number N of OFDM symbols in the case of 3ch can be expressed as the following equation (3).

  Also, the calculation formula for the frame length of each channel is as follows. When the frame length of each channel is defined as LENGTH (A), LENGTH (B), LENGTH (C), the following (4) Equations (6) to (6) can be derived. However, frames are allocated in descending order of transmission rate (in order from Channel-A). Equation (4) represents the case where the final data of the MPDU ends in Channel-A, Equation (5) represents the case where the final data of the MPDU ends in Channel-B, and Equation (6) This represents the case where the final data of the MPDU ends in Channel-C.

  That is, as described above, the ProtocolControl unit 38 calculates the frame length to be transmitted in each channel, and the TxControl unit 37 performs FCS addition, time stamp addition, and buffering according to the frame division / distribution processing. Integrated read control, backoff processing, etc.

  The Tx units 34-1, 34-2, and 34-3 perform primitive issuance, data write processing, and the like for each physical layer in order to exchange data and control signals with each physical layer. In the physical layers 31-1, 31-2, and 31-3, a transmission data frame is created from the data from each Tx unit and transmitted.

  On the other hand, in the reception processing, the Rx units 35-1, 35-2, and 35-3 perform primitive reception and reading processing from the physical layers 31-1, 31-2, and 31-3, and the results are displayed as RxControl. Pass to unit 36. In the RxControl unit 36, processing for combining frames received by a plurality of channels, FCS checking, buffer writing processing, address decoding processing, channel status processing, and the like are performed in an integrated manner. If transmission of an ACK frame is necessary, a return procedure is performed through the ProtocolControl unit 38 as necessary.

  In this embodiment, when the final data of the MPDU ends with Channel-A, the number of OFDM symbols of Channel-B and Channel-C is one less than Channel-A, and when the data ends with Channel-B, The number of OFDM symbols of -C is one less than that of Channel-A and Channel-B. In such a case, when the MAC 32 is handed over from the MAC 32 to the physical layer 31, the channel ends with one OFDM symbol earlier than the other channels. Can be made equal, and the OFDM symbol length of all channels can be made equal. In this embodiment, three channels are used, but the number of channels is arbitrary. Further, when using with one channel, the dividing and combining procedures are not necessary, and the operation is the same as the existing IEEE802.11a, IEEE802.11b, and IEEE802.11g. Furthermore, the channel to be used can be realized even if it is not an adjacent channel. Further, the division / distribution processing in the present embodiment is an example, and any expression may be used as long as the transmission timing and burst time of each channel are the same.

  As described above, in the present embodiment, for example, wireless signals compliant with the IEEE802.11a, IEEE802.11b, IEEE802.11g standards, etc. are distributed and transmitted to a plurality of communication channels in a home / office wireless network. It was decided. At this time, in the MAC, the entire frame is a division target, and the divided frame is distributed to each physical layer. As a result, since the radio band can be used efficiently, the throughput can be significantly improved as compared with the conventional case. In addition, since the existing physical layers IEEE802.11a, IEEE802.11b, and IEEE802.11g can be used, backward compatibility with existing systems can be maintained. Note that the processing of this embodiment can also be applied to MIMO having a plurality of spatial channels.

Embodiment 2. FIG.
In the first embodiment described above, the method for dividing the entire frame has been described. In the second embodiment, a method for dividing a part of the frame will be described. The configurations of the radio communication system, the base station, and the radio terminal are the same as those in FIGS. 1 and 2 of the first embodiment described above, and thus the same reference numerals are given and description thereof is omitted. .

  Here, the operation of the wireless communication system according to the second embodiment will be described. In the present embodiment, only processing different from that of the first embodiment described above will be described.

  FIG. 6 is a diagram showing a data frame format compliant with IEEE802.11a, and FIG. 7 is a diagram showing a frame format when using a plurality of channels (3ch). When the frame is distributed to a plurality of channels and transmitted, the burst time of each channel is constant.

In the present embodiment, among the MAC header 41, LLC header / SNAP header 42, Frame Body 43, and FCS 44 defined by IEEE 802.11, the LLC header / SNAP header 42, Frame Body 43, and FCS 44 are set as the division targets, and the division target of the MPDU 40 The portion is divided from the front in units of N _DOPS according to the transmission rates of the physical layers 31-1, 31-2, 31-3 (LLC header / SNAP header 42-1, Frame Body 43-1, 43-2 shown in the figure). , 43-3, equivalent to FCS 44-2), the data is transferred to each physical layer in units of data that can be transmitted by 1 OFDM. Therefore, in FIG. 7, the OFDM signals 50-1, 50-2, 50-3 in each physical layer have substantially the same burst time.

  Next, the division / distribution process in the present embodiment will be described. Here, a method for calculating the number of octets in the DATA portion and the data length of each channel, which is different from the processing in the first embodiment, will be described. As described above, the case of three channels (physical layer 31-1: Channel-A, physical layer 31-2: Channel-B, physical layer 31-3: Channel-C) will be described.

For example, the size of the MPDU composed of the LLC header, SNAP header, FrameBody, and FCS is set to L [octet], the transmission rate of each channel is set to RATE (a), RATE (b), RATE (c) [Mbps], and each channel. If N _DOPS (a), N _DOPS (b), N _DOPS (c) [octet] and the number of channels are defined as k, the number of OFDM symbols N required for MPDU transmission is The procedure is as shown in FIG.

  However, RATE (a) ≧ RATE (b) ≧ RATE (c) is satisfied, and the number of OFDM symbols does not include the number of symbols in the SIGNAL field transmitted by BPSK (R = 1/2). Also, the first OFDM symbol is 2 octets less than the other symbols due to 2 octets in the SERVICE field.

  First, the number of OFDM symbols required until the RATE (c) with the slowest transmission rate finishes transmitting the MAC header is obtained as in the following equation (7).

  Next, the amount of data transmitted on other channels in that period is calculated.

Therefore, the remaining data amount is L-L _HEADER . Therefore, the number of OFDM symbols necessary for transmitting the remaining data is represented by the following equation (9), and the general equation for the number N of OFDM symbols necessary for transmitting data is represented by the following equation (10). .

  Therefore, the number N of OFDM symbols in the case of 3ch can be expressed as the following equation (11).

  Also, the calculation formula for the frame length of each channel is as follows. When the frame length of each channel is defined as LENGTH (A), LENGTH (B), LENGTH (C), the following (12) Equations (14) to (14) can be derived. However, frames are allocated in descending order of transmission rate (in order from Channel-A). Expression (12) represents a case where the final data of the MPDU ends in Channel-A, Expression (13) represents a case where the final data of the MPDU ends in Channel-B, and Expression (14) represents This represents the case where the final data of the MPDU ends in Channel-C.

  On the other hand, in the reception processing, the Rx units 35-1, 35-2, and 35-3 perform primitive reception and reading processing from the physical layers 31-1, 31-2, and 31-3, and the results are obtained. Pass to RxControl unit 36. In the RxControl unit 36, processing for combining frames received by a plurality of channels, FCS checking, buffer writing processing, address decoding processing, channel status processing, and the like are performed in an integrated manner. In this embodiment, since the MAC address is included at the head of the frame received on each channel, processing is not performed on a frame from an unexpected terminal. If transmission of an ACK frame is necessary, a return procedure is performed through the ProtocolControl unit 38 as described above.

  FIG. 9 is a diagram showing a data frame format compliant with IEEE802.11a, and FIG. 10 is a diagram showing a method of dividing a part of a frame, which is different from FIG. In FIG. 10, MAC headers 41-1, 41-2, 41-3, LLC header / SNAP headers 42-1, 42-2, 42-3, FCS 44-1, 44- defined by IEEE802.11. 2, 44-3 are added to the divided Frame Body 43-1, 43-2, 43-3, respectively.

  As described above, in the present embodiment, for example, wireless signals compliant with the IEEE802.11a, IEEE802.11b, IEEE802.11g standards, etc. are distributed and transmitted to a plurality of communication channels in a home / office wireless network. It was decided. At this time, in MAC, a part of the frame is set as a division target, a frame other than the division target is added to the divided frame, and the subsequent frame is distributed to each physical layer. As a result, since the radio band can be used efficiently, the throughput can be significantly improved as compared with the conventional case. In addition, since the existing physical layers IEEE802.11a, IEEE802.11b, and IEEE802.11g can be used, backward compatibility with existing systems can be maintained. Note that the processing of this embodiment can also be applied to MIMO having a plurality of spatial channels.

Embodiment 3 FIG.
Next, the operation of the wireless communication system according to the third embodiment will be specifically described with reference to the drawings. In the present embodiment, only processing different from the first and second embodiments described above will be described.

  FIG. 11 is a diagram showing an example when a frame is divided into a plurality of channels. Each rectangle represents an OFDM symbol, and a Pad bit and a Tail bit added by PHY are drawn at the end of the frame. However, in the example of FIG. 11, since the number of OFDM symbols in CH1 is different from the number of OFDM symbols in CH2 and CH3, a Pad bit is added as described in the first and second embodiments. It is necessary to match the number of OFDM symbols.

  Therefore, in the present embodiment, the number of OFDM symbols is made to coincide as shown in FIG. FIG. 12 is a diagram showing an example of this embodiment when a frame is divided into a plurality of channels. Each rectangle indicates an OFDM symbol, and a Pad bit and a Tail bit added by PHY are drawn at the end of the frame. Further, FIG. 12 shows a state where the MACPad indicating that the Pad bit is added from the MAC to the PHY is added, and the number of OFDM symbols is coincident as shown in the first and second embodiments. Yes. Each frame is assigned to each OFDM symbol in order from CH1 to CH3, for example.

  FIG. 13 is a diagram showing a Service field of an IEEE802.11 frame. In this embodiment, for the Service [7:15] currently reserved as Reserved, the same frame is copied in the MAC_PAD_USAGE field, the division number field, the division total number field, and the plurality of CHs indicating ON / OFF of the MACPad. A COPY field indicating whether or not there is assigned. The fields may be in any order.

  FIG. 14 is a diagram illustrating a communication state between wireless stations that perform communication using a plurality of channels. First, when the radio station 60 divides a frame, when it is found that OFDM symbols are not available in some channels as shown in FIG. 11, for example, as shown in FIG. 12, MACPad To ensure that the data spans the next OFDM symbol. At this time, it is described that MACPad is added to the MAC_PAD_USAGE field in the Service field in the transmission frame. The radio station 60 writes necessary information in a division number field indicating the order in which frames are allocated to channels and a division total number field indicating how many channels are used for communication. Further, when the same frame is transmitted to a plurality of channels, the ON / OFF information is written in the COPY field, and then the generated frame is transmitted to the radio station 61.

  In this embodiment, the MAC_PAD_USAGE field, the division number field, the division total number field, and the COPY field are allocated to the Reserved field in the Service field. However, the present invention is not limited to this, and a frame in MAC or PHY is assigned for each channel. It may be expanded.

  On the other hand, when receiving a frame from the transmitting-side radio station 60, the receiving-side radio station 61 checks the MAC_PAD_USAGE field, the division number field, the division total number field, and the COPY field.

  If a frame is copied in the COPY field, the following operation is performed using a frame that has been successfully received from the received frames of each channel. When the COPY field indicates that the frame has been divided and transmitted, processing for combining the divided frames is performed based on the division number field and the total division number field. At this time, the information of the Pad bit added by MAC or PHY is detected by the MAC_PAD_USAGE field notified in each channel, and processing for deleting unnecessary Pad bits is performed. Note that if the number of received channels is smaller than the value written in the total number of divisions field, it indicates that the frame has not been received successfully, and error processing is performed.

  As described above, in this embodiment, the transmission side adds the MAC_PAD_USAGE field, the division number field, the division total number field, and the COPY field. As a result, it is possible to accurately detect how the Pad is inserted in each channel. In addition, since information indicating in what order the frames are allocated to the respective channels is inserted, the receiving side can know the frame combining procedure. Note that the processing of this embodiment can also be applied to the base station and the wireless terminal shown in Embodiments 1 and 2.

  As described above, the base station and the wireless terminal according to the present invention are useful for a communication system that transmits and receives wireless signals compliant with the wireless LAN standard IEEE802.11, and in particular, a wide band using a plurality of communication channels. It is suitable for a communication system that realizes the above.

FIG. 1 is a diagram showing a configuration of a wireless communication system according to the present invention. FIG. 2 is a diagram showing the configuration of the broadband wireless unit. FIG. 3 is a diagram showing a data frame format compliant with IEEE802.11a. FIG. 4 is a diagram showing a frame format when a plurality of channels are used. FIG. 5 is a diagram showing an MPDU division / distribution method. FIG. 6 is a diagram showing a data frame format compliant with IEEE802.11a. FIG. 7 is a diagram showing a frame format when a plurality of channels are used. FIG. 8 is a diagram showing a method of dividing a part of a frame. FIG. 9 is a diagram showing a data frame format compliant with IEEE802.11a. FIG. 10 is a diagram showing a method of dividing a part of a frame. FIG. 11 is a diagram showing an example when a frame is divided into a plurality of channels. FIG. 12 is a diagram showing an example of the third embodiment when a frame is divided into a plurality of channels. FIG. 13 is a diagram showing a Service field of an IEEE802.11 frame. FIG. 14 is a diagram illustrating a communication state between wireless stations that perform communication using a plurality of channels.

Explanation of symbols

1 Base station (AP)
2A, 2B wireless terminal (STA)
12-1, 12-2 Antenna 13 Access system termination unit 14 Signal interface unit 15 Broadband wireless unit 21A, 21B Information equipment main body 22A, 22B Terminal unit system 23A-1, 23A-2, 23B-1, 23B-2 Antenna 24A , 24B Terminal interface unit 25A, 25B Broadband wireless unit 31, 31-1, 31-2, 31-3 Physical layer (PHY)
32 MAC (Media Access Control)
33 Host Interface Unit
34, 34-1, 34-2, 34-3 Transmission (Tx) unit 35, 35-1, 35-2, 35-3 Reception (Rx) unit 36 RxControl unit 37 TxControl unit 38 ProtocolControl unit

Claims (4)

A transmission method employed by a transmitter in a wireless communication system for transmitting a data frame to a receiver,
A frame allocation step of dividing one data frame corresponding to a plurality of communication channels;
The transmission method characterized by including. A transmission method employed by a transmitter in a wireless communication system for transmitting a data frame to a receiver,
A frame allocation step of dividing one data frame corresponding to a plurality of antennas;
The transmission method characterized by including. A transmitter in a wireless communication system for transmitting data frames to a receiver,
Frame allocating means for dividing one data frame corresponding to a plurality of communication channels;
A transmitter comprising: A transmitter in a wireless communication system for transmitting data frames to a receiver,
Frame allocation means for dividing one data frame corresponding to a plurality of antennas;
A transmitter comprising:

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