JP4588083B2 - Base station and radio communication method - Google Patents

Description

  The present invention relates to a base station and a wireless communication method capable of wireless communication using the OFDMA scheme.

  In recent years, terminal devices represented by PHS (Personal Handy phone System) and mobile phones have become widespread, making it possible to make calls and obtain information regardless of location or time. Especially in recent years, the amount of available information has been increasing, and high-speed and high-quality wireless communication systems have been introduced to download large amounts of data.

  In such wireless communication, it is necessary to duplicate signals in order to transmit and receive. Typical duplexing methods include TDD (Time Division Duplex) that switches transmission and reception by time division and FDD (Frequency Division Duplex) that duplexes transmission and reception by changing the frequency. Also, as a method for multiple access to communicate with a plurality of terminal devices at the same time, TDMA (Time Division Multiple Access) for switching a plurality of terminal devices by time division, FDMA (Frequency) for dividing a frequency band Typical examples are Division Multiple Access (frequency division multiple access) and CDMA (Code Division Multiple Access) that multiplies a different code for each terminal device.

  For example, as next-generation PHS communication standards that enable high-speed digital communication, there are ARIB (Association of Radio Industries and Businesses) STD T95 (Non-patent Document 1) and PHS MoU (Memorandum of Understanding). , OFDMA / TDMA TDD Broadband Wireless Access System (next generation PHS system) is being formulated.

  OFDMA (Orthogonal Frequency Division Multiple Access) performs multiple access in OFDM (Orthogonal Frequency Division Multiplexing). OFDM is a method developed from FDM (Frequency Division Multiple), which divides a carrier signal into a large number of subcarriers on the frequency axis and orthogonalizes the phase of a signal wave between adjacent subcarriers. This is a method of effectively using the frequency band by partially overlapping the subcarrier bands. In OFDM, all subcarriers are occupied by one terminal apparatus, but in OFDMA, several subcarriers (for example, 24) are grouped to form a subchannel, and a plurality of terminal apparatuses share all subchannels. Multiple access. For example, the sub-channel divides the frequency band of 18 MHz into 20 pieces.

  Further, in the next generation PHS system, in addition to OFDMA, multiple access by TDMA is performed. TDMA is a system in which a frequency is divided into a plurality of time slots on a time axis and communication is performed with a plurality of opponents. At present, it is assumed that each of uplink (Up Link: terminal device to base station) and downlink (Down Link: base station to terminal device) is divided into four. That is, in the next-generation PHS system, the communication block is subdivided into both the frequency axis and the time axis, and communication is efficiently performed by dynamically allocating the communication block to many terminal devices. A communication block determined by one time slot in one subchannel is called a PRU (Physical Resource Unit), and it is assumed that 80 PRUs are used per base station.

  As described above, the base station can use 20 subchannels, one of which is used as a control channel (CCH), and the remaining subchannels are dynamically allocated to terminal devices (DCA: Dynamic Channel Assign). An anchor channel or an extra channel is allocated to the PRU included in the subchannel used for communication. One anchor channel is assigned to each terminal device, and includes a map of PRUs to which an extra channel for the terminal device is assigned. An extra channel is a channel that actually includes data, and a plurality of extra channels are assigned to one terminal device according to the amount of data and communication status. The notification of the extra channel assignment by the map included in the anchor channel is referred to as FM-mode (Fast access channel based on Map-Mode).

  The anchor channel is assigned to the PRU having the best communication quality obtained by performing carrier sense on all PRUs. The extra channel is basically not subjected to carrier sense. However, when the base station newly uses a PRU that is not performing communication, the extra channel is assigned after performing carrier sense. Thus, since the base station can dynamically change the position and number of extra channels via the anchor channel, it is possible to transmit and receive a large amount of data at high speed.

However, the PRU in the OFDMA scheme has a problem that it is susceptible to interference from adjacent PRUs. Various proposals have been made as proposals for preventing interference in wireless communication. For example, in Patent Document 1, a downlink frame is divided into resource blocks of almost the same size, transmission data is scheduled from the top in the resource block, and data having a capacity exceeding the resource block is allocated to other sectors. Schedule to be sent from the end of. As a result, it is possible to prevent endless communication in the same channel sector and reduce interference of the same channel.
JP-T-2006-515141 ARIB (Association of Radio Industries and Businesses) STD-T95

  As described above, in the OFDMA / TDMA TDD system, communication can be performed with more terminal devices (users) and more communication blocks (PRUs) than in the conventional TDMA-TDD. However, since the communication status and the distance from the base station are different for each terminal device, and the modulation method, power, and delay amount may be different accordingly, interference may occur between adjacent PRUs. As for the delay amount, interference can be effectively prevented by a guard band in TDMA. However, since the frequency bands of subcarriers are overlapped in OFDMA, if the modulation method or power is greatly different, it is affected by the radio waves of adjacent PRUs.

  If an error is detected in the extra channel due to interference, it can be compensated by making a retransmission request such as ARQ (Automatic Repeat reQuest) or HARQ (Hybrid-Automatic Repeat reQuest). However, since the anchor channel includes information (map) on the number and position of extra channels, if the anchor channel becomes unavailable due to interference from other PRUs, communication itself becomes impossible.

  On the other hand, as described above, the anchor channel is allocated by performing carrier sense, and the position of the PRU of the anchor channel is not changed until communication is disconnected. For this reason, it is possible to determine whether or not there is interference with the predetermined PRU at the time of performing carrier sense, but it is not possible to determine whether or not there is interference with the predetermined PRU at the subsequent frame timing. Therefore, even if the communication status of the PRU to which the anchor channel is allocated during communication deteriorates, this cannot be dealt with.

  As a specific example, since an extra channel is dynamically allocated, after an anchor channel is allocated based on the result of carrier sense, other PRUs adjacent to the anchor channel (especially adjacent to the frequency axis direction) An extra channel of the terminal device may be assigned. In particular, when the extra channel uses a high-output modulation scheme (for example, 256 QAM (Quadrature Amplitude Modulation)), the anchor channel may be interfered by an extra channel of another terminal device and communication may not be performed.

  In view of such a problem, the present invention can minimize the interference received by the anchor channel by devising the position of the PRU to which the anchor channel and the extra channel used by one terminal apparatus are allocated. It is an object of the present invention to provide a base station and a wireless communication method capable of performing communication.

In order to solve the above-described problems, a typical configuration of the present invention performs wireless communication by assigning at least a part of a plurality of PRUs constituting a communication frame to one or a plurality of terminal devices using the OFDMA scheme. a base station, wherein the communication frame includes a frequency region including a first sub-channel having a predetermined number of the PRU extra channelization Le is assigned to be used for communication of data to the communication terminal, the position of the extra channel A frequency region including a second subchannel having a predetermined number of PRUs to which an anchor channel including a map to be assigned is allocated, and for the communication terminal, the anchor channel is assigned to the PRU included in the second subchannel. assignment, the first channel to assign the extra channel to PRU included in the subchannel And hook part, included in the communication frame, the number of the first sub-channel, and the number of the second sub-channel, the number of channels set to set according to the number of connections of the terminal device to the base station and wherein the obtaining Bei and means.

  With the above configuration, since only an anchor channel is assigned to a PRU in a predetermined frequency region, a PRU frequency region to which an anchor channel is assigned and a PRU frequency region to which an extra channel is assigned can be reliably distinguished. Therefore, after the anchor channel is assigned, the extra channel of another terminal apparatus is not assigned to the PRU adjacent to the anchor channel, so that interference to the anchor channel by the extra channel can be prevented. Thereby, it becomes possible to improve the stability of communication.

The frequency region including the second subchannel may be adjacent to the frequency region to which the control channel is assigned.

  Since the control channel is transmitted intermittently, the control channel does not communicate until after the control channel transmission until the next control channel transmission. For this reason, the PRU to which the control channel is allocated has little interference with the adjacent PRU. Therefore, according to the above configuration, interference with the anchor channel can be reduced, and communication stability can be improved.

The frequency region including the second subchannel may be biased to the highest frequency or the lowest frequency among the frequencies used by the base station.

  When the predetermined frequency region is an intermediate region of the frequency used by the base station, the PRU to which the anchor channel is assigned is an extra channel assigned to a PRU having a frequency higher and lower than the predetermined frequency region of the PRU. There is a possibility of receiving interference from. On the other hand, according to the above configuration, the number of PRUs adjacent to the PRU to which the anchor channel is allocated can be halved when the predetermined frequency region is set to the middle of the frequency. It is possible to reduce interference due to the channel.

Another typical configuration of the present invention uses one or a plurality of terminal devices and a base station that allocates at least a part of a plurality of PRUs constituting a communication frame to the terminal devices using the OFDMA scheme. a wireless communication method, the communication frame includes a frequency region including a first sub-channel having a predetermined number of the PRU extra channelization Le is assigned to be used for communication of data to the communication terminal, the position of the extra channel And a frequency region including a second subchannel having a predetermined number of PRUs to which an anchor channel including a map indicating the base station is allocated, and the base station is included in the second subchannel with respect to the communication terminal allocating the anchor channel to PRU, split the extra channel to PRU included in the first sub-channel A step of applying, said included in the communication frame, the number of the first sub-channel, the steps of the number of the second sub-channel, set according to the number of connections of the terminal device to the base station, It is characterized by having .

  The component corresponding to the technical idea in the base station mentioned above and its description are applicable also to the said radio | wireless communication method.

  According to the base station and the wireless communication method according to the present invention, it is possible to minimize interference with the anchor channel by devising the position of the PRU to which the anchor channel and the extra channel used by one terminal device are allocated. And stable communication can be performed.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  A terminal device represented by a PHS terminal, a mobile phone, or the like constructs a wireless communication system that performs wireless communication with a wireless communication device (base station) that is fixedly arranged at a predetermined interval. In this embodiment, in order to facilitate understanding, the entire wireless communication system will be described, and then a specific configuration of a base station as a wireless communication apparatus and a PHS terminal as a terminal apparatus will be described. In this embodiment, a PHS terminal is cited as the terminal device. However, the present invention is not limited to such a case. A mobile phone, a notebook personal computer, a PDA (Personal Digital Assistant), a digital camera, a music player, a car navigation system, a portable TV. Various electronic devices capable of wireless communication such as game devices, DVD players, and remote controllers can also be used as terminal devices.

(Wireless communication system 100)
FIG. 1 is a diagram illustrating a schematic connection relationship of a wireless communication system. The wireless communication system 100 includes a PHS terminal 110 (110A, 110B), a base station 120 (120A, 120B), an ISDN (Integrated Services Digital Network) line, an Internet, a dedicated line, etc. And a relay server 140.

  In the wireless communication system 100, when a user connects a communication line from his / her PHS terminal 110A to another PHS terminal 110B, the PHS terminal 110A makes a wireless connection request to the base station 120A within the communicable range. . The base station 120A that has received the wireless connection request requests the relay server 140 to establish a communication connection with the communication partner via the communication network 130, and the relay server 140 refers to the location registration information of the other PHS terminal 110B to For example, the base station 120B within the wireless communication range of the terminal 110B is selected to secure a communication path between the base station 120A and the base station 120B, and communication between the PHS terminal 110A and the PHS terminal 110B is established.

  In such a wireless communication system 100, various techniques are employed to improve the communication speed and communication quality between the PHS terminal 110 and the base station 120. In this embodiment, for example, next-generation PHS communication technologies such as ARIB STD T95 and PHS MoU are adopted, and wireless communication based on the OFDMA / TDMA-TDD scheme is executed between the PHS terminal 110 and the base station 120. . In this embodiment, an anchor channel for transmitting control information such as MCS (Modulation and Coding Scheme), communication channel map, and error information in such wireless communication is assigned to a PRU in a predetermined frequency region, thereby improving communication stability. Plan. Hereinafter, a specific configuration of the base station 120 in the wireless communication system 100 will be described.

(Base station 120)
FIG. 2 is a block diagram showing a schematic configuration of the base station. The base station 120 includes a base station control unit 210, a base station memory 212, a base station wireless communication unit 214, and a base station wired communication unit 216.

  The base station control unit 210 manages and controls the entire base station 120 by a semiconductor integrated circuit including a central processing unit (CPU). In addition, the base station control unit 210 controls communication connection of the PHS terminal 110 to the communication network 130 and other PHS terminals 110 using the program in the base station memory 212.

  The base station memory 212 includes ROM, RAM, EEPROM, nonvolatile RAM, flash memory, HDD, and the like, and stores programs processed by the base station control unit 210, time information, and the like.

  The base station wireless communication unit 214 establishes communication with the PHS terminal 110 and transmits / receives data. It is also possible to determine an optimal MCS for performing efficient communication according to the communication quality with the PHS terminal 110 and request the MCS from the PHS terminal 110 through the anchor channel 180.

  The base station wired communication unit 216 can be connected to various servers including the relay server 140 via the communication network 130.

  In the present embodiment, the base station control unit 210 also functions as the channel allocation unit 220. As described above, in the OFDMA / TDMA-TDD scheme, communication blocks are subdivided on both the frequency axis and the time axis, and communication is efficiently performed by dynamically allocating communication blocks to a large number of terminal devices. A communication block determined by one time slot in one subchannel is called a PRU (Physical Resource Unit).

  The channel allocation unit 220 allocates an extra channel (hereinafter referred to as EXCH) and an anchor channel (hereinafter referred to as ANCHor) to the PRU. One ANCH is assigned to each terminal device, and includes a map of PRUs to which the EXCH for the terminal device is assigned. EXCH is a channel that actually includes data, and a plurality of EXCHs are assigned to one terminal apparatus according to the amount of data and communication status.

  In the above PRU allocation, the channel allocation unit 220 allocates an ANCH to a PRU in a predetermined frequency region, and allocates an EXCH to a PRU other than the predetermined frequency region to which the ANCH is allocated. As a result, the PRU frequency region to which the ANCH is allocated can be reliably distinguished from the PRU frequency region to which the EXCH is allocated. Therefore, since the EXCH of another PHS terminal 110 is not assigned to the PRU adjacent to the ANCH after the ANCH is assigned to the PRU, it is possible to prevent the EXCH from interfering with the ANCH.

  FIG. 3 is a diagram for explaining a frame configuration of data transmitted and received in wireless communication using the OFDMA scheme. FIG. 3A shows a frame configuration based on conventional PRU allocation, and FIG. ) Shows a frame configuration by PRU allocation according to the present embodiment. OFDMA (or OFDM) has a two-dimensional map in the time axis direction and the frequency direction, and a plurality of subchannels 160 are arranged with a uniform baseband distance in the frequency axis direction. The PRU 170 is arranged for each time slot (TDMA slot) 162.

  For example, when the effective frequency band of an OFDM carrier is 18 MHz, this is divided into 480 subcarriers, and when 24 subcarriers are bundled to form one subchannel 160, 20 subchannels 160 are formed in one carrier. The occupied band of one subchannel 160 is 900 kHz. For example, if one time slot is 5 msec, it is 2.5 msec when divided into uplink and downlink by TDD. Since 2.5 msec is divided into four by TDMA, one time slot 162 is 625 μsec.

  Therefore, the PRU 170 is defined by an occupation band of 900 kHz corresponding to the baseband distance and a time length of 625 μsec by time division. A frame used for communication with a specific PHS terminal 110 includes an ANCH 180 related to a control signal and an EXCH 182 storing data.

  The ANCH 180 is an FM-Mode control signal, and includes, for example, an MI (Mcs Indicator), an MR (Mcs Requirement), an ACK field, and a map. Here, MI indicates the MCS identifier of MCS when data is modulated. MR is an MCS request for data transmitted to itself. In terms of time, MI indicates MCS used for modulation of data transmitted simultaneously with the MCS identifier, and MR indicates desired MCS after the next time. The ACK field indicates the error detection result of the demodulated data. Further, the map exists only in the transmission frame from the base station 120 to the PHS terminal 110, and indicates the allocation of EXCH 182.

  The ANCH 180 is individually assigned to each PHS terminal 110 and occupies one PRU 170. Based on the carrier sense result of the base station 120, the PRU 170 having high communication quality is assigned to the ANCH 180. Here, the carrier sense is performed based on a signal-to-interference and noise ratio (SINR) or a bit error rate in the PRU 170 of a frame in which transmission / reception with the PHS terminal 110 is performed.

  The EXCH 182 is a PRU 170 that is assigned to each user as a communication path in FM-Mode, and a plurality of EXCHs 182 can be assigned to one PHS terminal 110 as indicated by a broken line in FIG. The EXCH 182 is assigned based on the result of carrier sense for determining whether or not the PRU 170 is being used by another user. The assigned result is shown in the ANCH 180 map as described above.

  In FIG. 3, the control channel 184 (CCH: Control CHannel, hereinafter referred to as CCH) is assigned to the PRU 170 in the highest frequency region among the frequencies used by the base station 120. The CCH 184 is intermittently transmitted from the base station 120, and the PHS terminal 110 receives the CCH 184, thereby recognizing the identifier (CSID) and the received electric field strength (RSSI) of the base station 120 that is a candidate for communication. can do. In the present embodiment, the CCH 184 is assigned to the PRU 170 in the highest frequency region, but the present invention is not limited to this, and the CCH 184 can also be assigned to a PRU 170 outside this region.

  In the conventional assignment of the PRU 170 to the ANCH 180 and the EXCH 182, the ANCH 180 is assigned to the PRU 170 having high communication quality and the EXCH 182 is assigned to the PRU 170 that is not used by other users, based on the carrier sense result of the base station 120. As a result, as shown in FIG. 3A, the PRU 170 to which the EXCH 182 is assigned is adjacent to the PRU 170 to which the ANCH 180 is assigned. When such EXCH 182 uses a high-output modulation method (for example, 256QAM), interference by EXCH 182 to ANCH 180 occurs, and communication quality deteriorates.

  In order to solve the above problem, in this embodiment, as shown in FIG. 3B, the channel allocation unit 220 allocates the ANCH 180 to the PRU 170 in the predetermined frequency region 190, and other than the predetermined frequency region to which the ANCH 180 is allocated. An EXCH 182 is assigned to the PRU 170 in the area 192.

  As described above, by dividing the frequency region of the PRU 170 to which the ANCH 180 is assigned from the frequency region of the PRU 170 to which the EXCH 182 is assigned, only the ANCH 180 is assigned to the PRU 170 in the predetermined frequency region 190, and after the ANCH 180 is assigned. Assignment of EXCH 182 to PRU 170 adjacent to the ANCH 180 can be avoided. Therefore, interference with ANCH 180 by EXCH 182 can be reduced, and communication stability can be improved.

  The predetermined frequency region 190 of the PRU 170 to which the ANCH 180 is allocated is preferably adjacent to the frequency region to which the CCH 184 is allocated, and more preferably, the highest frequency or the lowest frequency among the frequencies used by the base station 120. It should be biased.

  Since CCH 184 is transmitted intermittently, communication may not be performed. Therefore, since the PRU 170 to which the CCH 184 is assigned has little interference with the adjacent PRU 170, the interference with the PRU 170 to which the ANCH 180 is assigned can be reduced by assigning the ANCH 180 to the PRU 170.

  Further, by biasing the predetermined frequency region 190 to the highest frequency or the lowest frequency among the frequencies used by the base station 120, the number of PRUs 170 adjacent to the predetermined frequency region 190 can be reduced. Therefore, it is possible to reduce interference to the PRU 170 to which the ANCH 180 is assigned by the adjacent PRU 170.

  Further, a blank area 194 to which neither the ANCH 180 nor the EXCH 182 is assigned may be provided adjacent to the predetermined frequency area 190 for assigning the ANCH 180. When the communication quality of the ANCH 180 decreases due to the ANCH 180 and the EXCH 182 being adjacent in the frequency axis direction, even if the allocation of the ANCH 180 is limited to the predetermined frequency region 190, the ANCH 180 and the EXCH 182 are adjacent at the boundary. End up. However, by providing the blank area 194 as described above, the ANCH 180 and the EXCH 182 can be more reliably separated, and the interference can be extremely reduced.

In this embodiment, two subchannels 160 (second subchannels) are arranged in the predetermined frequency region 190 for assigning the ANCH 180, but the present invention is not limited to this. The number can be set arbitrarily. For example, when the base station 120 is installed in an area where the population density is low, the number of subchannels 160 to be arranged is 1. As a result, the number of subchannels 160 (first subchannels) arranged in the region 192 other than the predetermined frequency region is increased, and the number of PRUs 170 to which the EXCH 182 is allocated can be increased. Therefore, the communication speed between the PHS terminal 110 and the base station 120 can be improved. Further, for example, in a base station 120 in a place with a large number of connections such as in a downtown area, by increasing the number of subchannels 160 allocated to the predetermined frequency region 190, stable communication that prevents the ANCH 180 from being disconnected while increasing the number of simultaneous connections is achieved. It can be carried out.

  The band (number of subchannels 160) allocated to the predetermined frequency region 190 can be set semi-fixed as a parameter for each base station 120. Further, the number of subchannels can be switched by remote operation, or can be changed dynamically according to the number of terminals connected.

  In the wireless communication system 100 described above, the frequency region of the PRU 170 to which the ANCH 180 is assigned and the frequency region of the PRU 170 to which the EXCH 182 are assigned are divided, and the base station 120 assigns the ANCH 180 to the PRU 170 in the predetermined frequency region 190, The EXCH 182 is assigned to the PRU 170 in the area 192 other than the assigned predetermined frequency area. Thereby, interference to ANCH 180 by EXCH 182 can be reduced, and it becomes possible to improve the stability of communication. Next, a wireless communication method for performing wireless communication using the base station 120 described above will be described.

(Wireless communication method)
FIG. 4 is a flowchart showing a processing flow of the wireless communication method according to the present embodiment. The base station 120 performs carrier sense on the PRU 170 adjacent to the CCH 184, that is, the PRU 170 in the predetermined frequency region 190, and allocates the ANCH 180 to the PRU 170 with low interference and high communication quality (S300: ANCH allocation step). Next, the base station 120 performs carrier sense on the PRU 170 in the region 192 other than the predetermined frequency region, determines whether the PRU 170 is used by another user, and determines whether the PRU 170 is not used by another user. The EXCH 182 is allocated (S302: EXCH allocation step).

  Then, the position and number of PRU 170 of EXCH 182 are written as allocation information in the map of ANCH 180 and notified to each terminal device (PHS terminal 110) (S304: map writing step). The PHS terminal 110 performs communication by reading the ANCH 180 and acquiring the EXCH 182 according to the map included therein. At this time, since interference with the ANCH 180 is extremely reduced, stable communication can be performed.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  Note that each step in the wireless communication method of the present specification does not necessarily have to be processed in time series in the order described in the flowchart, and may include processing in parallel or a subroutine.

  The present invention is applicable to a base station and a wireless communication method capable of wireless communication using the OFDMA scheme.

It is the figure which showed the rough connection relation of the radio | wireless communications system. It is the block diagram which showed the schematic structure of the base station. It is a figure for demonstrating the frame structure of the data transmitted / received in the radio | wireless communication using an OFDMA system. It is the flowchart which showed the flow of the process of the radio | wireless communication method concerning this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Wireless communication system 110 ... PHS terminal 120 ... Base station 130 ... Communication network 140 ... Relay server 160 ... Subchannel 162 ... Time slot 170 ... PRU
180… ANCH
182 ... EXCH
184 ... CCH
190 ... predetermined frequency region 192 ... non-predetermined frequency region 194 ... blank region 210 ... base station control unit 212 ... base station memory 214 ... base station wireless communication unit 216 ... base station wired communication unit 220 ... channel allocation unit

Claims (4)

A base station that performs radio communication by assigning at least a part of a plurality of PRUs constituting a communication frame to one or a plurality of terminal devices using an OFDMA scheme,
It said communication frame is an anchor channel including a map shown and frequency domain, the position of the extra channel including a first sub-channel having a predetermined number of the PRU extra channelization Le is assigned to be used for communication of data to the communication terminal A frequency domain including a second subchannel having a predetermined number of PRUs to which
To the communication terminal, and the allocation of the anchor channel to PRU contained in the second sub-channel, against Ri said split the extra channel to PRU contained in the first sub-channel channel allocation unit,
Channel number setting means for setting the number of the first subchannel and the number of the second subchannel included in the communication frame according to the number of connections of the terminal device to the base station;
Base station, wherein the obtaining Bei a. The base station according to claim 1, wherein the frequency region including the second subchannel is adjacent to a frequency region to which a control channel is allocated. 3. The base station according to claim 1, wherein the frequency region including the second subchannel is biased to a highest frequency or a lowest frequency among frequencies used by the base station. A wireless communication method using one or a plurality of terminal devices and a base station that allocates at least a part of a plurality of PRUs constituting a communication frame to the terminal devices using the OFDMA scheme,
It said communication frame is an anchor channel including a map shown and frequency domain, the position of the extra channel including a first sub-channel having a predetermined number of the PRU extra channelization Le is assigned to be used for communication of data to the communication terminal A frequency domain including a second subchannel having a predetermined number of PRUs to which
The base station
Allocating the anchor channel to the PRU included in the second subchannel and allocating the extra channel to the PRU included in the first subchannel for the communication terminal ;
Setting the number of the first subchannel and the number of the second subchannel included in the communication frame according to the number of connections of the terminal device to the base station;
Wireless communication method characterized by having a.

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