JP4654267B2 - 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 between 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 a large number of 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 36 to 40 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 likely to receive interference from a PRU adjacent in the frequency direction. 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 interference with an anchor channel by devising a position of a PRU to which an extra channel used by one terminal device is allocated, and can stably communicate. It is an object of the present invention to provide a base station and a wireless communication method capable of performing the above.

In order to solve the above problems, a representative configuration of the present invention, by using the OFDMA scheme, a 1 or a plurality of terminal devices and a base station that performs wireless communication, for each of the terminal device, data A channel for allocating an extra channel used for the communication of one and an anchor channel corresponding to a terminal device including a map indicating a position of the PRU to which the extra channel used by the terminal device is allocated to a PRU included in the same time slot It includes an assignment unit, the channel assignment section, to assign the anchor channel for each of a plurality of terminal devices P RU of the same time slot, an extra channel and frequency direction anchor channel for one terminal device to other terminal devices It is characterized in that it is assigned to a PRU so as not to be adjacent to the PRU .

With this configuration, an anchor channel for one terminal apparatus is allocated to a PRU so that it is not adjacent to an extra channel for another terminal apparatus in the frequency direction. This ensures that it is possible to prevent interference from an extra channel of other terminal devices for anchor channel, it is possible to perform stable communication.

The channel assignment unit may assign an anchor channel to a PRU adjacent to or close to a control channel assigned in advance to a PRU in a predetermined frequency band.

Since the control channel is used intermittently, the PRU to which the control channel is assigned may not communicate. Therefore, since the PRU adjacent to the control channel or the adjacent PRU has little interference, it is possible to avoid disconnection of communication due to interference with the anchor channel by allocating the anchor channel to the PRU.

The base station may include an adaptive array antenna. By forming beam forming using an adaptive array antenna, radio waves can be narrowed in a predetermined direction, and by forming null steering, it is possible to minimize interference with other base stations.

In order to solve the above problems, a representative configuration of a radio communication method according to the present invention is a radio communication method using one or more terminal devices and a base station using the OFDMA method, The station, for each of the terminal devices, one anchor corresponding to the terminal device including an extra channel used for data communication and a map indicating a position of the PRU to which the extra channel used by the terminal device is allocated. when assigning the PRU included a channel, the same time slot, to assign an anchor channel for each of a plurality of terminal devices P RU of the same time slot, the other terminal apparatus anchor channel for one terminal device The PRU is assigned so as not to be adjacent to the extra channel in the frequency direction .

  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.

  As described above, in the base station of the present invention, it is possible to minimize interference with the anchor channel by devising the position of the PRU to which the extra channel used by one terminal apparatus is allocated, and stably communicate. 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 base station that is fixedly arranged at a predetermined interval. Here, the entire wireless communication system will be described first, and then the specific configuration of the base station 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 an explanatory diagram showing a schematic connection relationship of the wireless communication system 100. 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 PHS terminal 110B to obtain another PHS terminal. For example, the base station 120B within the wireless communication range of 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. . Hereinafter, a specific configuration and operation of the base station 120 that performs wireless communication with the PHS terminal 110 will be described.

(Base station 120)
FIG. 2 is a block diagram illustrating a schematic configuration of the base station 120. The base station 120 includes a base station control unit 210, a base station memory 212, a base station wireless communication unit 214, a base station wired communication unit 216, and a plurality of antennas 218.

  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 performs array processing on the signal received from the antenna 218 to establish communication with the PHS terminal 110, and transmits and receives data.

  In this embodiment, the antenna 218 has an adaptive array function, and the directivity of radio waves to be transmitted and received can be dynamically changed by forming beam forming and null steering. Here, in the beam forming, the radio wave intensity is strengthened by matching the phases of the radio waves output from the plurality of antennas 218, and the position of the null steering is offset by shifting the phase of the radio wave, and the radio wave intensity is weakened. .

  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.

  The channel allocator 220 assigns an anchor channel (ANchor CHannel or less) related to a control signal to a PRU (Physical Resource Unit or PRU) defined with a 900 kHz occupation band corresponding to the baseband distance and a time length of 625 μsec by time division. And an extra channel for storing data (hereinafter referred to as EXCH).

  FIG. 3 is an explanatory diagram for explaining a frame configuration according to the present embodiment. OFDMA / TDMA has a two-dimensional map in the time axis direction and the frequency direction. A plurality of subchannels are arranged with a uniform baseband distance in the frequency axis direction, and a PRU is arranged for each time slot (TDMA slot) in each subchannel.

  In the present embodiment, the ANCH 300 is an FM-Mode control signal. For example, a map indicating the allocation information of the EXCH 302, a timing control bit, a transmission output control bit, and HARQ (Hybrid Automatic Repeat reQuest) which is one of automatic retransmission requests. ) Including an ACK bit for notifying whether or not data can be reached.

  The ANCH 300 is assigned to the PRU with the least interference based on the carrier sense result, and one ANCH 300 is fixedly assigned to one PHS terminal 110.

  The EXCH 302 is a PRU assigned to each terminal device as a speech path in FM-Mode, and a plurality of EXCHs 302 can be assigned to one PHS terminal 110.

  The assignment of EXCH 302 is performed through carrier sense for determining whether or not the PRU is used by another user. Which PRU is assigned to the predetermined PHS terminal 110 as the EXCH 302 is notified for each terminal device (PHS terminal 110) by the map of the ANCH 300, and is dynamically assigned for each frame.

  As shown in FIG. 3, the channel assignment unit 220 can assign the EXCH 302a used by the PHS terminal 110 to which the ANCH 300a is assigned to another PRU in the same time slot as the PRU to which the ANCH 300a is assigned. .

  As a result, the EXCH 302a of the PHS terminal 110 using the ANCH 300a is assigned to the PRU of the time slot to which the ANCH 300a is assigned. Therefore, the PRU of the time slot to which the ANCH 300 is assigned is not assigned the EXCH 302 of the PHS terminal 110 to which the ANCHs 300b and 300c are assigned to other time slots.

  Further, the channel allocation unit 220 allocates the ANCH 300 to the PRUs of different time slots for each PHS terminal 110 (ANCHs 300a, b, and c in FIG. 3).

  With the configuration in which the ANCH 300 is assigned to different time slots for each PHS terminal 110, the EXCH 302 is assigned to different time slots for each PHS terminal 110. Therefore, one PHS terminal 110 is used for one time slot, and interference with the ANCH 300 from the EXCH 302 of the other PHS terminal 110 can be suppressed.

  In addition, since communication can be performed in a time-sharing manner (each time slot) for each PHS terminal 110, radio waves can be narrowed in a predetermined direction by forming beam forming using an antenna 218 having an adaptive array function. By forming null steering, it is possible to minimize interference with other base stations 120.

  That is, since the PHS terminal 110 as a communication partner can be identified at a certain moment, beam forming is formed in the direction of the identified PHS terminal 110, and null steering is formed in a direction other than the direction of the identified PHS terminal 110. It becomes possible. Thereby, the effect of the adaptive array function can be utilized to the maximum extent.

  Furthermore, in this embodiment, the channel assignment unit 220 assigns the ANCH 300 to the PRU 310a adjacent to the control channel 304 or the adjacent PRU 310b.

  Since the control channel 304 is used intermittently, the PRU allocated to one subchannel to which the control channel 304 is assigned often does not communicate. Accordingly, since the PRU 310a adjacent to the control channel 304 and the adjacent PRU 310b have less interference, it is possible to avoid disconnection of communication due to interference with the ANCH 300 by assigning the ANCH 300 to the PRU.

  FIG. 4 is a diagram for explaining another operation of the channel allocating unit, in which the channel allocating unit allocates each ANCH used by a plurality of PHS terminals to the same time slot.

  As shown in FIG. 4A, the channel assignment unit 220 may assign the ANCHs 300a and 300b used by the plurality of PHS terminals 110 to PRUs in the same time slot based on the result of carrier sense. At this time, the channel assignment unit 220 assigns the EXCH 302a used by the PHS terminal 110 to which the ANCH 300a is assigned to the PRU adjacent to the ANCH 300a. Similarly, the EXCH 302b used by the PHS terminal 110 to which the ANCH 300b is allocated is allocated to the PRU adjacent to the ANCH 300b.

  When a plurality of ANCHs 300 are assigned to the same time slot in this way, if the EXCH 302a of the PHS terminal 110 that uses the ANCH 300 is assigned to the PRU adjacent to the ANCH 300, the modulation method and the radio wave intensity are the same between the adjacent PRUs. Therefore, interference from the EXCH 302b of another PHS terminal 110 can be suppressed.

  Further, as shown in FIG. 4B, the ANCHs 300a and 300b used by the plurality of PHS terminals 110 may be assigned to the PRUs 310b adjacent to the PRUs 310a adjacent to the control channel 304 that are PRUs of the same time slot. is there. Even in this case, since the ANCH 300 is concentrated in a region close to the control channel 304, interference from the EXCH 302 of another PHS terminal 110 can be suppressed.

  At this time, if the EXCH 302 is assigned to the same time slot as the ANCH 300, the EXCHs 302a and 302b for a plurality of PHS terminals 110 are assigned to the same time slot. In this case, by providing a PRU that is not allocated between the EXCHs 302a and 302b used by each PHS terminal 110, it is possible to avoid duplication of radio waves in frequency and to prevent mutual interference.

  In addition, when the amount of data is large and the EXCH 302a cannot be allocated to the same time slot as the time slot to which the ANCH 300a is allocated, the EXCH 302a can be allocated to the PRUs of other time slots in which communication is not performed (FIG. 4B). ) See the third slot). Also in this case, since the EXCH 302 used by the same PHS terminal 110 is arranged in the same time slot, communication can be performed in a time division manner (for each time slot) for each PHS terminal 110, so that the adaptive array function is provided. A radio wave can be narrowed in a predetermined direction using the antenna 218 that is provided, and interference with other base stations 120 can be minimized.

  In the wireless communication system 100 described above, the base station 120 assigns the EXCH 302a of the PHS terminal 110 that uses the ANCH 300a to the PRU in the time slot to which the ANCH 300a is assigned. As a result, the EXCH 302 of another PHS terminal 110 is not assigned to the PRU in the time slot to which the ANCH 300 is assigned. Accordingly, interference from the EXCH 302 of another PHS terminal 110 with respect to the ANCH 300 can be prevented, and stable communication can be performed. Next, a wireless communication method for performing wireless communication using the base station 120 described above will be described.

(Wireless communication method)
FIG. 5 is a flowchart illustrating a processing flow of the wireless communication method according to the present embodiment.

  The base station 120 performs carrier sense and allocates the ANCH 300 to the PRU adjacent to or close to the control channel 304 with little interference (S350: ANCH allocation step). Further, carrier sense is performed to determine whether or not the PRU is being used by another user, and a PRU that is not performing communication in the same time slot as the ANCH 300 is allocated to the EXCH 302 (S352: EXCH allocation) Step).

  Then, the position and number of PRUs of EXCH 302 are written as allocation information in the map of ANCH 300 and notified to each terminal device (PHS terminal 110) (S354: map writing step). The PHS terminal 110 performs communication by reading the ANCH 300 and acquiring the EXCH 302 according to a map included therein. At this time, since interference with the ANCH 300 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 explanatory drawing 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 explanatory drawing for demonstrating the flame | frame structure concerning this embodiment. It is a figure explaining other operation | movement of a channel allocation part. 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 210 ... Base station control part 212 ... Base station memory 214 ... Base station wireless communication part 216 ... Base station wired communication part 218 ... Antenna 220 ... Channel allocation unit 300 ... ANCH
302 ... EXCH
304 ... Control channel 310a ... PRU adjacent to control channel
310b ... PRU adjacent to control channel

Claims (4)

A base station that performs radio communication with one or a plurality of terminal apparatuses using the OFDMA scheme,
For each of the terminal devices, an extra channel used for data communication, and one anchor channel corresponding to the terminal device including a map indicating the position of the PRU to which the extra channel used by the terminal device is allocated, A channel allocating unit for allocating to PRUs included in the same time slot ,
The channel allocation unit, when assigning the anchor channel for each of a plurality of the terminal device P RU of the same time slot, the extra channel and frequency direction the anchor channel for one terminal device to other terminal devices A base station that is assigned to a PRU so as not to be adjacent to the base station. The base station according to claim 1, wherein the channel allocation unit allocates the anchor channel to a PRU adjacent to or close to a control channel previously allocated to a PRU in a predetermined frequency band. The base station according to claim 1, wherein the base station includes an adaptive array antenna. A wireless communication method using one or a plurality of terminal devices and a base station using the OFDMA method,
  The base station
  For each of the terminal devices, an extra channel used for data communication, and one anchor channel corresponding to the terminal device including a map indicating the position of the PRU to which the extra channel used by the terminal device is allocated, Are assigned to PRUs included in the same time slot,
  When allocating the anchor channel for each of the plurality of terminal apparatuses to the PRU in the same time slot, the anchor channel for one terminal apparatus is allocated to the PRU so as not to be adjacent to the extra channel for other terminal apparatuses in the frequency direction. A wireless communication method characterized by the above.

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