JP2009290495A - Base station and wireless communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base station avoiding delay in the transmission of control data by adding priority to data included in an extra channel and capable of improving stability in communication, and to provide a wireless communication method. <P>SOLUTION: The base station 120 uses an OFDMA system to perform wireless communications to one or a plurality of terminal units 110, and has a channel assignment section 220 for assigning the extra channel 330 used for communicating data to an PRU 300. The channel assignment section classifies the extra channel into control data 354 of retransmission, those 344 of initial transmission, entity data 352 of retransmission, and those 342 of initial transmission for preferentially assigning to the PRU in this order. <P>COPYRIGHT: (C)2010,JPO&INPIT

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.

  Among such wireless communications, ARIB (Association of Radio Industries and Businesses) STD T95 (Non-Patent Document 1) and PHS MoU (Memorandum of Understanding) are the next-generation PHS communication standards that enable high-speed digital communications. In such communication standards, OFDMA / TDMA TDD Broadband Wireless Access System (next generation PHS system) is being formulated.

  OFDMA (Orthogonal Frequency Division Multiple Access) divides a carrier signal into a number of subcarriers on the frequency axis, and groups several (for example, 24) subcarriers to form subchannels. Multiple access is performed by sharing all subchannels with a plurality of terminal devices. For example, the sub-channel divides the frequency band of 18 MHz into 20 pieces. 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. The extra channel is a channel that actually includes data. The data includes MAC control data that is data for control in the MAC layer, and upper control data that is data for control in a layer higher than the MAC layer. The control data consisting of and the actual data that is the data itself are included. In the extra channel, a plurality of extra channels are assigned to one terminal device in accordance with the amount of data and the 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.

  When the receiving device receives erroneous data, an automatic retransmission request (ARQ: Automatic Repeat reQuest, hereinafter simply referred to as ARQ) is transmitted to the transmitting device that requests retransmission of the data. Since the transmitting apparatus performs data retransmission processing on the ARQ in the MAC layer (low layer), it is possible to efficiently compensate for errors in a short control time (Non-Patent Document 2). In addition, HARQ (Hybrid ARQ) technology is used to further improve the efficiency of packet error correction by combining retransmission data in the physical layer (PHY layer) by combining such ARQ and forward error correction (FEC). Has been.

Since the data retransmitted by the above-described retransmission request is also included in the extra channel, the extra channel includes control data and entity data for initial transmission, and control data and entity data for retransmission.
JP-T-2006-515141 ARIB (Association of Radio Industries and Businesses) STD-T95 A-GN4.00-01-TS Rev.3 `` Next Generation PHS Specifications '', P331-340

  When retransmitting data in response to a retransmission request as described above, retransmission data (retransmission control data and entity data) according to the retransmission request is preferentially allocated to the PRU in the extra channel, and then the initial transmission data (initial transmission data) Transmission control data and entity data) are allocated to the PRU. That is, retransmission data is always transmitted with priority over initial transmission data.

  However, with this conventional method of assigning PRUs, there is a possibility that all the PRUs will be occupied by retransmission data, and there will be no PRUs assigned to initial transmission data. As a result, there may be a problem that a delay in transmission of control data for the initial transmission occurs. The control data includes data for new connection, location registration, and the like, and if a delay occurs, there is a risk that troubles such as difficulty in continuing communication may occur.

  Also, in the OFDMA / TDMA TDD system, the communication status and distance from the base station are different for each terminal device, and the modulation method, power, and delay amount may differ accordingly, so that interference occurs between adjacent PRUs. There is a case. 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. In particular, since the anchor channel includes information (map) of the number and position of extra channels, if the anchor channel becomes unavailable due to interference from other PRUs, communication itself becomes impossible.

  In view of such a problem, the present invention avoids a delay in transmission of control data by adding priority to data included in an extra channel, significantly reduces interference with an anchor channel, and stabilizes communication. It is an object of the present invention to provide a base station and a wireless communication method capable of improving performance.

  In order to solve the above problems, a typical configuration of a base station according to the present invention is a base station that performs radio communication with one or a plurality of terminal apparatuses using the OFDMA scheme, and is used for data communication. A channel allocating unit for allocating channels to the PRUs, and the channel allocating unit classifies the extra channel into retransmission control data, initial transmission control data, retransmission entity data, and initial transmission entity data according to the contents thereof. It is characterized in that it is preferentially assigned to PRUs in order.

  In the conventional extra channel allocation, retransmission control data and entity data are allocated to the PRU first, so the PRU is occupied by such data, and there is no PRU allocated to the initial transmission control data, so that the transmission of the initial transmission control data is performed. There was a risk of delay. On the other hand, according to the above configuration, an extra channel is allocated to the PRU in the order of retransmission control data, initial transmission control data, retransmission actual data, and initial transmission actual data. As a result, it is possible to avoid the occupation of the PRU by the retransmission actual data, and to preferentially assign the PRU to the initial transmission control data. Therefore, it is possible to prevent a delay in transmission of control data for the initial transmission.

  The channel allocating unit determines an extra channel used by each terminal device as an earlier time slot among PRUs allocated to each terminal device in the order of retransmission control data or entity data, initial transmission control data or entity data. And it is good to arrange | position from PRU of a higher frequency.

  By assigning the extra channel in accordance with the above-mentioned priority order, the PRU has retransmission data (retransmission control data or retransmission entity data) in the order of retransmission control data, initial transmission control data, and retransmission entity data. In some cases, initial transmission data (initial transmission control data or initial transmission entity data) is mixed and assigned. Further, for example, when there is no retransmission control data, an extra channel may be allocated to the PRU in the order of initial transmission control data and retransmission entity data.

  However, in PHS MoU, there is a rule that retransmission data is arranged in order from the highest PRU of the time slot, that is, the PRU having the highest frequency among the PRUs assigned to each terminal apparatus. Therefore, with the above configuration, the extra channels (retransmission data and initial transmission data) allocated to the PRUs according to the above-described priority order can be arranged according to the regulations. Note that the arrangement order of the control data and the entity data included in the retransmission data and the initial transmission data can be set as appropriate.

  The channel allocation unit classifies the control data into MAC control data that is data for control in the MAC layer and upper control data that is data for control in a layer higher than the MAC layer, and controls initial transmission When assigning data to the PRU, it is preferable to preferentially assign higher-order control data and MAC control data in this order.

  The MAC layer is a data link layer of the OSI (Open System Interconnection) reference model composed of seven layers, manages the data in the transmission buffer, and actually exchanges communication packets (frames) using the physical layer. Is doing. The MAC control data is data for control in the MAC layer. The upper layer corresponds to a layer higher than the MAC layer, that is, a network layer or a transport layer in the OSI reference model, and performs new connection and location registration in wireless communication between the base station and the terminal device. The upper control data is data for control in the upper layer.

  According to the above configuration, by assigning priorities to the first transmission control data in the order of higher control data and MAC control data, PRUs are preferentially assigned to higher control data that plays an important role in wireless communication control. Is possible.

  The channel assignment unit also assigns an anchor channel including a map indicating the position of the PRU to which the extra channel is assigned to the PRU, and assigns the anchor channel to another PRU in the same time slot as the time slot of the PRU to which the anchor channel is assigned. An extra channel used by a terminal device to which a channel is assigned is assigned.

  With this configuration, an extra channel of a terminal device using the anchor channel is allocated to the PRU of the time slot to which the anchor channel is allocated. Therefore, the extra channel of another terminal device is not assigned to the PRU in the time slot to which the anchor channel is assigned. As a result, interference from the extra channel of another terminal device with respect to the anchor channel can be prevented, and stable communication can be performed.

  When the channel allocating unit allocates a plurality of anchor channels to PRUs in the same time slot, an extra channel used by a terminal device in which the one anchor channel is allocated to a PRU adjacent in the frequency direction of one anchor channel. Assign it.

  Since the anchor channel is assigned based on the result of carrier sense, a plurality of anchor channels may be assigned to the same time slot. At this time, if an extra channel of a terminal device using the anchor channel is assigned to a PRU adjacent in the frequency direction of the anchor channel, interference from the extra channel of another terminal device can be suppressed.

  The channel allocation unit allocates an extra channel used by one terminal apparatus to a PRU in one time slot. In addition, the base station may include an adaptive array antenna.

  With the configuration in which an extra channel used by one terminal device is assigned to a PRU in one time slot, communication can be performed in a time-sharing manner for each terminal device, and beam forming by an adaptive array antenna is appropriately directed to that terminal device. Therefore, the effect of the adaptive array antenna can be maximized.

  The channel allocation unit may allocate an extra channel to a PRU in the same time slot as an anchor channel used by a terminal device that allocates the extra channel.

  Since the anchor channel is assigned based on the result of carrier sense, a plurality of anchor channels may be assigned to the same time slot. At this time, if an extra channel of a terminal device using the anchor channel is assigned to a PRU adjacent in the frequency direction of the anchor channel, interference from the extra channel of another terminal device can be suppressed.

  The channel allocation unit may allocate an anchor channel to PRUs having different time slots for each terminal device.

  With the configuration in which the anchor channel is assigned to a different time slot for each terminal device, the extra channel is assigned to a different time slot for each terminal device. Therefore, one time slot is used by one terminal device, and interference with an anchor channel from an extra channel of another terminal device can be suppressed. Further, communication can be performed in a time division manner for each terminal device, and the effect of the adaptive array antenna can be obtained to the maximum.

  The channel assignment unit may assign an anchor channel to a PRU in a predetermined frequency region and assign an extra channel to a PRU other than the predetermined frequency region.

  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 predetermined frequency region may be adjacent to a frequency region to which a 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 predetermined frequency region 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.

  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, When the station allocates an extra channel to be used for data communication to the PRU, the channel allocating unit allocates the extra channel according to the contents of the extra channel, retransmission control data, initial transmission control data, retransmission actual data, initial transmission actual data. And is preferentially assigned to PRUs in this order.

  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, the data included in the extra channel is classified according to the contents thereof, and the control data of the initial transmission is preferentially assigned to the PRU over the actual data of retransmission, and is used by one terminal device By devising the position of the PRU to which the extra channel to be assigned is devised, it is possible to significantly reduce the interference to the anchor channel while avoiding the delay of transmission of control data, and to improve the stability of communication Become.

  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 a wireless communication system. The wireless communication system 100 includes a PHS terminal 110 (110A, 110B, 110C), a base station 120 (120A, 120B), an ISDN (Integrated Services Digital Network) line, the Internet, a dedicated line, and the like. And the 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 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, 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, beam forming is to form a beam with increased radio field intensity by matching the phases of radio waves output from a plurality of antennas 218. The position of the null steering is shifted from each antenna 218 by shifting the phase of the radio waves. The beam is offset to weaken the radio field intensity.

  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.

  Further, as will be described in detail later, channel allocation section 220 classifies EXCH into retransmission control data, initial transmission control data, retransmission entity data, and initial transmission entity data according to the contents, and prioritizes in this order. Assigned to the PRU.

  FIG. 3 is a diagram for explaining a frame configuration of data transmitted and received in wireless communication using the OFDMA scheme. OFDMA (or OFDM) has a two-dimensional map in the time axis direction and the frequency direction, and a plurality of subchannels 302 are arranged with a uniform baseband distance in the frequency axis direction. The PRU 300 is arranged for each time slot (TDMA slot) 304.

  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 302, 20 subchannels 302 are formed in one carrier. Thus, the occupied band of one subchannel 302 is 900 kHz. For example, if one frame 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 304 is 625 μsec.

  Therefore, the PRU 300 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 320 related to a control signal and an EXCH 330 that stores data.

  The ANCH 320 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 the EXCH 330.

  The ANCH 320 is individually assigned to each PHS terminal 110 and occupies one PRU 300. Based on the carrier sense result of the base station 120, the PRU 300 with high communication quality is assigned to the ANCH 320. Here, the carrier sense is performed based on a signal-to-interference and noise ratio (SINR) or a bit error rate in the PRU 300 of a frame in which transmission / reception with the PHS terminal 110 is performed.

  The EXCH 330 is a PRU 300 assigned to each user as a communication channel in FM-Mode, and a plurality of EXCHs 330 can be assigned to one PHS terminal 110 as indicated by a broken line in FIG. The EXCH 330 is assigned based on the result of carrier sense for determining whether or not the PRU 300 is used by another user. The assigned result is shown in the map of the ANCH 320 as described above.

  Also, in FIG. 3, a control channel 310 (CCH: Control CHannel, hereinafter referred to as CCH) is assigned to the PRU 300 in the highest frequency region among the frequencies used by the base station 120. The CCH 310 is intermittently transmitted from the base station 120, and the PHS terminal 110 receives the CCH 310 to recognize 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 310 is assigned to the PRU 300 in the highest frequency region, but is not limited to this, and can be assigned to the PRU 300 in other regions.

  FIG. 4 is a diagram for explaining the details of EXCH. FIG. 4A shows the classification of data included in EXCH. The data of EXCH 330 can be classified as shown in FIG. 4 (a) by the channel allocation unit according to the contents. The EXCH 330 is roughly classified into initial transmission data 340 and retransmission data 350. The retransmission data 350 is data to be retransmitted in response to a request by HARQ.

  The initial transmission data 340 can be classified into initial transmission entity data 342 and initial transmission control data 344. Further, the initial transmission control data 344 can be subdivided into initial transmission upper control data 346 and initial transmission MAC control data 348.

  The retransmission data 350 can be classified into retransmission actual data 352 and retransmission control data 354. Further, retransmission control data 354 can be subdivided into retransmission upper control data 356 and retransmission MAC control data 358. In this embodiment, retransmission upper control data 356 and retransmission MAC control data 358 are processed together as retransmission control data 354. However, the present invention is not limited to this, and retransmission higher control data 356 is not limited thereto. It is also possible to process the retransmitted MAC control data 358 by subdividing it.

  Next, FIG. 4B shows an example of EXCH data. Here, it is assumed that base station 120 communicates with PHS terminal 110A, PHS terminal 110B, and PHS terminal 110C. The alphabetical character at the end of the code indicates the PHS terminal 110 that uses the data. For example, the “first / entity 342a” is the PHS terminal 110A, the “first / entity 342b” is the PHS terminal 110B, The “entity 342c” is initial transmission entity data 342 used by the PHS terminal 110C.

  Then, as shown in FIG. 4B, the channel assignment unit 220 classifies the data of the EXCH 330 according to the contents. Specifically, the data of the EXCH 330 is divided into initial transmission data 340 and retransmission data 350. Furthermore, the initial transmission data 340 includes initial transmission entity data 342, initial transmission upper control data 346, and initial transmission data. The retransmission control data 350 is classified into retransmission retransmission data 352, retransmission higher control data 356, and retransmission MAC control data 358, and stored in the transmission buffer of the base station memory 212.

  FIG. 5 is a diagram showing the EXCH data shown in FIG. 4B for each PHS terminal. As shown in FIG. 5, the EXCH 330 used by the PHS terminal 110A and the PHS terminal 110B includes retransmission control data 354, initial transmission upper control data 346, initial transmission MAC control data 348, retransmission entity data 352, initial transmission. Are classified into entity data 342. In the EXCH 330 used by the PHS terminal 110C, since the retransmission control data 354 does not exist, it is classified into the upper transmission control data 346, the initial transmission MAC control data 348, the retransmission actual data 352, and the initial transmission entity data 342. Has been.

  FIG. 6 is a diagram for explaining the priority order of data classified according to the contents. As shown in FIG. 6, the channel allocation unit 220 converts the data of the EXCH 330 stored in the transmission buffer of the base station memory 212 into retransmission control data 354, initial transmission control data 344, retransmission actual data 352, The PRU 300 is preferentially assigned in the order of the transmission entity data 342. Here, the feature of this embodiment is that the control data 344 of the initial transmission is preferentially assigned to the PRU 300 over the actual data 352 of retransmission.

(First embodiment)
7 and 8 are diagrams for explaining a frame configuration by PRU allocation to EXCH according to the first embodiment. As shown in FIG. 7A, the CCH 310 is assigned to the PRU 300 of one subchannel 302. In this example, the CCH 310 is assigned to the subchannel 302 having the highest frequency. In channel allocation, carrier sense is first performed by the base station 120, and based on the result, the channel allocation unit 220 allocates the ANCH 320 to the PRU 300 with high communication quality. Here, ANCH 320a, ANCH 320b, and ANCH 320c, which are ANCHs 320 used by PHS terminal 110A, PHS terminal 110B, and PHS terminal 110C, are allocated to PRU 300.

  Next, channel assignment section 220 assigns EXCH 330 to PRU 300. As shown in FIG. 7B, among the data of EXCH 330, first, retransmission control data 354, that is, retransmission upper control data 356 and retransmission MAC control data 358 are preferentially assigned to PRU 300.

  After allocating retransmission control data 354 (retransmission upper control data 356 and retransmission MAC control data 358) to PRU 300, channel allocating section 220 first transmission upper control data 346 and initial transmission control data 344 are transmitted. The MAC control data 348 for transmission is assigned to the PRU 300. Thereafter, the EXCH 330 is allocated to the PRU 300 in the order of the retransmission entity data 352 and the initial transmission entity data 342, and all data is allocated to the PRU 300 as shown in FIG. If there is more data to be allocated here than the number of PRUs 300, the surplus data remains in the transmission buffer of the base station memory 212 and is allocated in the next frame.

  In this way, the EXCH 330 is classified into retransmission control data 354, initial transmission control data 344, retransmission entity data 352, and initial transmission entity data 342 in accordance with the contents, and are assigned to the PRU 300 with priority in this order. It can be avoided that all PRUs 300 are occupied by retransmission data 350 (retransmission control data 354 and entity data 352). Therefore, the PRU 300 can be assigned to the initial transmission control data 344, and the transmission delay of the initial transmission control data 344 can be prevented.

  Further, as in this embodiment, the initial transmission control data 344 is classified into upper control data 346 and MAC control data 348, and assigned to PRUs in this order in order, thereby enabling wireless communication such as new connection or location registration. The PRU 300 can be preferentially assigned to the higher-level control data 346 that plays an important role in the control. Therefore, it is possible to improve the reliability of communication.

  Further, the channel assignment unit 220 assigns all the EXCH 330 data to the PRU 300 as shown in FIG. 8A, and then rearranges the EXCH 330 data used by each PHS terminal 110. The rearrangement is higher among the PRUs 300 assigned to each PHS terminal 110 in the order of retransmission data 350 and initial transmission data 340 for each EXCH 330 used by each PHS terminal 110. It arranges from frequency PRU300.

  In FIG. 8A, retransmission data 350 and initial transmission data 340 are mixedly assigned to the PRU 300. However, in the PHS MoU, there is a rule that the retransmission data 350 is arranged in order from the PRU 300 having the highest frequency among the PRUs 300 allocated to each PHS terminal 110. Therefore, when the initial transmission data 340 of the PHS terminal 110 is allocated to the PRU 300 at a higher frequency than the PRU 300 to which the retransmission data 350 of each PHS terminal 110 is allocated, the arrow in FIG. As shown, the retransmission data 350 and the initial transmission data 340 are rearranged.

  As a result, as shown in FIG. 8B, the EXCH 330 allocated to the PRU 300 can be arranged in the order of the retransmission data 350 and the initial transmission data 340, and can comply with the definition of PHS MoU. In the present embodiment, only the order of retransmission data 350 and initial transmission data 340 is determined. Regarding the arrangement order of control data and entity data included in retransmission data 350 and initial transmission data 340, It is possible to set appropriately.

  Hereinafter, another embodiment of the base station according to the present invention will be described in detail. In FIG. 9, FIG. 10, and FIG. 11, EXCH 330 includes initial transmission entity data 342, initial transmission upper control data 346, initial transmission MAC control data 348, and retransmission. In the following description, all the above EXCH data are combined, unless otherwise specified, for ease of understanding, as entity data 352, upper control data 356 for retransmission, and MAC control data 358 for retransmission. Collectively named EXCH.

(Second Embodiment)
FIG. 9 is a diagram for explaining a frame configuration by PRU allocation to EXCH according to the second embodiment. As shown in FIG. 9A, in the second embodiment, the channel assignment unit 220 includes the PHS in which the ANCH 320 is assigned to another PRU 300 that is the same as the time slot 304 of the PRU 300 to which the ANCH 320 is assigned. An EXCH used by the terminal 110 is allocated.

  For example, another PRU 300 having the same time slot 304 as that of the PRU 300 to which the ANCH 320a is allocated includes the EXCH 330a used by the PHS terminal 110A to which the ANCH 320a is allocated, that is, the retransmission control data 354a (the upper control data 356a and the MAC Control data 358a), initial transmission upper control data 346a, initial transmission MAC control data 348a, retransmission entity data 352a, and initial transmission entity data 342a are sequentially assigned.

  As a result, the PRU 300 in the time slot 304 to which the ANCH 320a is assigned is not assigned the EXCH of the PHS terminals 110B and 110C to which the ANCHs 320b and 320c are assigned to the other time slot 304.

  Further, as shown in FIG. 9 (a), the PCH 300 adjacent to or close to the ANCH 320 is assigned the EXCH of the PHS terminal 110 that uses the ANCH 320 in order from the PRU on the high frequency side, so that a modulation scheme is established between the adjacent PRUs 300. And the intensity of radio waves are the same, and interference from EXCH of other PHS terminals 110 can be suppressed.

  Further, the channel allocation unit 220 allocates the ANCH 320 to the PRU 300 in the different time slot 304 for each PHS terminal 110 (ANCHs 320a, b, and c in FIG. 9A). As a result, one PHS terminal 110 is used for one time slot 304, and interference with the ANCH 320 from the EXCH of another PHS terminal 110 can be suppressed.

  In addition, since communication can be performed in a time-sharing manner (for each time slot 304) for each PHS terminal 110, radio waves can be narrowed down in a predetermined direction by forming beam forming using the antenna 218 having an adaptive array function. In addition, by forming null steering, it is possible to significantly reduce 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.

  In addition, when the amount of data is large and the initial transmission actual data 342c used by the PHS terminal 110C cannot be allocated to the same time slot 304 as the time slot 304 to which the ANCH 320c is allocated, communication is not performed. An EXCH can also be assigned to the PRU 300 in the time slot 304 (see the third slot in FIG. 9A).

  Also in this case, since the EXCH used by the same PHS terminal 110 is arranged in the same time slot 304, communication can be performed in a time division manner (for each time slot 304) for each PHS terminal 110. A radio wave can be narrowed in a predetermined direction using the antenna 218 having a function, and interference with other base stations 120 can be extremely reduced.

  As shown in FIG. 9A, after assigning all the data of the EXCH 330 to the PRU 300, the channel allocating unit 220 assigns the assigned EXCH 330 to each EXCH 330 used by each PHS terminal 110 as indicated by the arrow in FIG. As shown in FIG. 4, the data is reordered in the order of retransmission data 350 and initial transmission data 340. Then, as shown in FIG. 9B, the PRU 300 assigned to each PHS terminal 110 is arranged from the PRU 300 having an earlier time slot and a higher frequency.

  Specifically, focusing on the EXCH 330 of the PHS terminal 110A in FIG. 9A, the upper control data 356a for retransmission of the PHS terminal 110A is the highest frequency among the PRUs 300 to which the EXCH 330 of the PHS terminal 110A is assigned. Since the PRU 300 is assigned to the PRU 300, no rearrangement is performed. However, since the initial transmission control data 344 (the initial transmission upper control data 346a and the initial transmission MAC control data 348a) is allocated to the PRU 300 having a higher frequency than the PRU 300 to which the retransmission actual data 352a is allocated, Retransmission entity data 352a is rearranged and arranged.

  Further, as in the PHS terminal 110C in FIG. 9A, when the EXCH 330 of one PHS terminal 110 is assigned to a plurality of time slots, the retransmission entity data 352c is assigned the EXCH 330 of the PHS terminal 110C. Among the PRUs 300, the PRUs 300 are rearranged and arranged in an earlier time slot and a higher frequency PRU 300.

  In the allocation of the EXCH 330 to the PRU 300, when there are only a few PRUs 300 that can be allocated, the allocation is performed only up to the retransmission control data 354, the initial transmission upper control data 346, and the initial transmission MAC control data 348. Since the arrangement order of EXCH 330 is the order of retransmission data 350 and initial transmission data 340, it is not necessary to rearrange them.

  However, when there are many PRUs 300 that can be used and it is possible to allocate up to the retransmission actual data 352, the retransmission data 350 and the initial transmission data 340 are mixed, so the arrangement by the rearrangement described above is performed. . As a result, the EXCH 330 allocated to the PRU 300 can be arranged from the PRU 300 having a higher time slot and higher frequency in the order of the retransmission data 350 and the initial transmission data 340, and can comply with the PHS MoU regulations.

  In this embodiment, the EXCH 330 is allocated to the PRU 300 at the same time as the allocation, and then rearranged (rearranged). However, the present invention is not limited to this, and the channel allocating unit 220 first counts the number of PRUs 300 that can be allocated to each PHS terminal 110 and first determines which EXCH 330 is allocated. (Retransmission control data and entity data) may be arranged, and then initial transmission data 340 (initial transmission control data and entity data) may be arranged. In this case, the rearrangement operation (work) does not occur. In the case of a train, allocation is equivalent to a ticket, and arrangement is equivalent to a reserved seat ticket. That is, as a result, the control data or entity data for retransmission, the control data or entity data for initial transmission, and the PRU 300 assigned to each PHS terminal 110 are arranged from the PRU 300 having an earlier time slot and higher frequency. That's fine.

(Third embodiment)
FIG. 10 is a diagram for explaining a frame configuration by PRU allocation to EXCH according to the third embodiment. As shown in FIG. 10, the third embodiment describes a case where the channel assignment unit 220 assigns each ANCH 320 used by a plurality of PHS terminals 110 to the same time slot 304. In the example of FIG. 10, the CCH 310 is arranged in the subchannel 302 substantially in the middle of the OFDMA occupied band, and the ANCH 320 is assigned to the subchannel 302 adjacent thereto.

  The channel assignment unit 220 may assign the ANCHs 320a and 320b used by the plurality of PHS terminals 110 to the PRU 300 in the same time slot 304 based on the result of carrier sense. At this time, the channel assignment unit 220 assigns the EXCH used by the PHS terminal 110A to which the ANCH 320a is assigned to the PRU 300 adjacent to the ANCH 320a. Similarly, an EXCH used by the PHS terminal 110B to which the ANCH 320b is assigned is assigned to the PRU 300 adjacent to the ANCH 320b.

  When a plurality of ANCHs 320 are assigned to the same time slot 304 in this way, if the EXCH of the PHS terminal 110 that uses the ANCH 320 is assigned to the PRU 300 adjacent to the ANCH 320, the modulation method and the radio wave intensity are the same between the adjacent PRUs 300. Therefore, interference from EXCH of other PHS terminals 110 can be suppressed.

(Fourth embodiment)
FIG. 11 is a diagram for explaining a frame configuration by PRU allocation to EXCH according to the fourth embodiment. As shown in FIG. 11, in the fourth embodiment, the channel assignment unit 220 assigns ANCH 320 to the PRU 300 in the predetermined frequency region 370 and assigns EXCH to the PRU 300 in the region 380 other than the predetermined frequency region to which the ANCH 320 is assigned. Explains.

  By dividing the frequency region of the PRU 300 to which the ANCH 320 is assigned from the frequency region of the PRU 300 to which the EXCH is assigned, only the ANCH 320 is assigned to the PRU 300 in the predetermined frequency region 370 and is adjacent to the ANCH 320 after the ANCH 320 is assigned. The assignment of EXCH to the PRU 300 to be performed can be avoided. Therefore, interference with ANCH 320 due to EXCH can be reduced, and communication stability can be improved.

  Further, the channel allocation unit 220 may allocate the ANCHs 320a and 320b used by the plurality of PHS terminals 110 to the PRU 300 in the same time slot 304 in the predetermined frequency domain 370. Even in this case, since the ANCH 320 is concentrated in the area close to the CCH 310, interference from the EXCH of the other PHS terminals 110 can be suppressed.

  At this time, if the EXCH is assigned to the same time slot 304 as that of the ANCH 320, the EXCH for a plurality of PHS terminals 110 is assigned to the same time slot 304. In this case, by providing the PRU 300 that does not allocate the EXCH between the EXCHs used for each PHS terminal 110, it is possible to avoid duplication of radio waves in frequency and prevent mutual interference.

  The predetermined frequency region 370 of the PRU 300 to which the ANCH 320 is allocated is preferably adjacent to the frequency region to which the CCH 310 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 the CCH 310 is transmitted intermittently, communication may not be performed. Accordingly, since the PRU 300 to which the CCH 310 is assigned has little interference with the adjacent PRU 300, the interference with the ANCH 320 can be reduced by assigning the ANCH 320 to the PRU 300.

  Further, by biasing the predetermined frequency region 370 to the highest frequency or the lowest frequency among the frequencies used by the base station 120, the number of PRUs 300 adjacent to the predetermined frequency region 370 can be reduced. Therefore, it is possible to reduce interference to the PRU 300 to which the ANCH 320 is assigned by the adjacent PRU 300.

  Furthermore, a blank area 390 to which neither ANCH 320 nor EXCH is assigned may be provided adjacent to a predetermined frequency area 370 for assigning ANCH 320. When the communication quality of the ANCH 320 deteriorates due to the ANCH 320 and the EXCH being adjacent in the frequency axis direction, even if the allocation of the ANCH 320 is limited to the predetermined frequency region 370, the ANCH 320 and the EXCH are adjacent at the boundary. End up. However, by providing the blank area 390 as described above, the ANCH 320 and the EXCH can be more reliably separated, and the interference can be extremely reduced.

  In the fourth embodiment, the two subchannels 302 are arranged in the predetermined frequency region 370 for assigning the ANCH 320, but the present invention is not limited to this, and the number of subchannels 302 to be arranged is arbitrary. It is possible to set. For example, when the base station 120 is installed in an area where the population density is low, the number of subchannels 302 to be arranged is 1. As a result, the number of subchannels 302 arranged in the region 380 other than the predetermined frequency region is increased, and the PRU 300 to which EXCH 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 a downtown area, by increasing the number of subchannels 302 allocated to the predetermined frequency region 370, stable communication that prevents the ANCH 320 from being disconnected while increasing the number of simultaneous connections is achieved. It can be carried out.

  The band (number of subchannels 302) allocated to the predetermined frequency region 370 can be set semi-fixed as a parameter for each base station 120. In addition, the number of subchannels 302 can be switched by remote operation, or can be dynamically changed according to the number of connections of the PHS terminal 110.

  In the wireless communication system 100 described above, the channel assignment unit 220 can add a priority to the data included in the EXCH 330, thereby avoiding a delay in transmission of control data. The channel assignment unit 220 assigns the ANCH 320 to the PRU 300 in the predetermined frequency region 370, assigns the EXCH 330 to the PRU 300 in the region 380 other than the predetermined frequency region to which the ANCH 320 is assigned, and further assigns the PRU 300 in the time slot 304 to which the ANCH 320 is assigned. By assigning the EXCH 330 of the PHS terminal 110 that uses the ANCH 320, it is possible to prevent interference from the EXCH 330 of another PHS terminal 110 with respect to the ANCH 320, and to improve the stability of communication.

(Wireless communication method)
Next, a wireless communication method for performing wireless communication using the base station 120 described above will be described. FIG. 12 is a flowchart showing a process flow of the wireless communication method according to the above-described embodiment.

  The base station 120 performs carrier sense for the PRU 300 adjacent to the CCH 310, that is, the PRU 300 in the predetermined frequency region 370, and allocates the ANCH 320 to the PRU 300 with low interference and high communication quality (S400: ANCH allocation step).

  Next, the channel allocation unit 220 retransmits the data of the EXCH 330 stored in the base station memory 212 according to the contents thereof, retransmission control data 354 (retransmission upper control data 356 and retransmission MAC control data 358), and initial transmission The upper control data 346, the initial transmission MAC control data 348, the retransmission entity data 352, and the initial transmission entity data 342 are classified (S402: EXCH classification step).

  Then, the base station 120 performs carrier sense for the PRU 300 in the region 380 other than the predetermined frequency region, determines whether the PRU 300 is being used by another user (another PHS terminal 110), and the PHS terminal 110 The PCH 300 that is not in communication in the same time slot 304 as the time slot 304 to which the ANCH 320 to be used is allocated is transferred to the EXCH 330 by the retransmission control data 354 (retransmission upper control data 356 and retransmission MAC control data 358). ), Priority control data 346 for initial transmission, MAC control data 348 for initial transmission, entity data 352 for retransmission, and entity data 342 for initial transmission are preferentially assigned. (S404: EXCH allocation step).

  After assigning all the data of EXCH 330 to PRU 300, channel assignment section 220 rearranges EXCH 330 assigned to PRU 300 in the order of retransmission data 350 and initial transmission data 340, and PRU 300 assigned to each PHS terminal 110. Among them, the PRU 300 having the earlier time slot and higher frequency is allocated (S406: EXCH allocation step).

  Then, the position and number of the PRU 300 of the EXCH 330 are written as allocation information in the map of the ANCH 320 and notified to each terminal device (PHS terminal 110) (S408: map writing step). The PHS terminal 110 performs communication by reading the ANCH 320 and acquiring the EXCH 330 according to a map included therein. At this time, since interference with the ANCH 320 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 a figure for demonstrating the frame structure of the data transmitted / received in the radio | wireless communication using an OFDMA system. It is a figure explaining the detail of EXCH. It is the figure which showed the data of EXCH shown in FIG.4 (b) for every PHS terminal. It is a figure explaining the priority of the data classified according to the content. It is a figure explaining the frame structure by PRU allocation to EXCH concerning 1st Embodiment. It is a figure explaining the frame structure by PRU allocation to EXCH concerning 1st Embodiment. It is a figure explaining the frame structure by PRU allocation to EXCH concerning 2nd Embodiment. It is a figure explaining the frame structure by PRU allocation to EXCH concerning 3rd Embodiment. It is a figure explaining the frame structure by PRU allocation to EXCH concerning 4th Embodiment. It is the flowchart which showed the flow of the process of the radio | wireless communication method concerning embodiment mentioned above.

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 ... PRU
302 ... subchannel 304 ... time slot 310 ... CCH
320 ... ANCH
330 ... EXCH
340 ... Initial transmission data 342 ... Initial transmission entity data 344 ... Initial transmission control data 346 ... Initial transmission upper control data 348 ... Initial transmission MAC control data 350 ... Retransmission data 352 ... Retransmission entity data 354 ... Retransmission Control data 356... Retransmission upper control data 358... Retransmission MAC control data 370... Predetermined frequency region 380... Region other than the predetermined frequency region 390.

Claims (13)

A base station that performs radio communication with one or a plurality of terminal apparatuses using the OFDMA scheme,
A channel allocation unit that allocates an extra channel used for data communication to the PRU;
The channel allocation unit
The extra channel is classified into retransmission control data, initial transmission control data, retransmission entity data, and initial transmission entity data according to the contents, and is preferentially assigned to the PRUs in this order. .   The channel allocating unit determines an extra channel used by each terminal device in an earlier time slot among PRUs allocated to each terminal device in the order of retransmission control data or entity data, initial transmission control data or entity data. 2. The base station according to claim 1, wherein the base station is arranged from a PRU having a higher frequency. The channel allocation unit classifies the control data into MAC control data that is data for control in the MAC layer and upper control data that is data for control in a layer higher than the MAC layer,
2. The base station according to claim 1, wherein when the initial transmission control data is allocated to the PRU, priority control data and MAC control data are preferentially allocated in this order. The channel allocation unit also performs allocation of the anchor channel including the map indicating the position of the PRU to which the extra channel is allocated to the PRU,
The base station according to claim 1, wherein an extra channel used by a terminal apparatus to which the anchor channel is allocated is allocated to another PRU in the same time slot as the PRU time slot to which the anchor channel is allocated.   When the channel allocating unit allocates a plurality of anchor channels to PRUs in the same time slot, an extra channel used by a terminal device in which the one anchor channel is allocated to a PRU adjacent in the frequency direction of one anchor channel. The base station according to claim 4, wherein the base station is assigned.   The base station according to claim 1, wherein the channel allocation unit allocates an extra channel used by one terminal apparatus to a PRU in one time slot.   The base station according to claim 6, wherein the channel allocation unit allocates the extra channel to a PRU in the same time slot as the anchor channel used by a terminal device that allocates the extra channel.   The base station according to claim 4 or 6, wherein the channel allocation unit allocates an anchor channel to PRUs of different time slots for each of the terminal devices.   The base station according to claim 4, wherein the base station includes an adaptive array antenna.   The base station according to claim 4 or 6, wherein the channel allocation unit allocates the anchor channel to a PRU in a predetermined frequency domain and allocates the extra channel to a PRU other than the predetermined frequency domain.   The base station according to claim 4 or 6, wherein the predetermined frequency region is adjacent to a frequency region to which a control channel is assigned.   The base station according to claim 4 or 6, wherein the predetermined frequency region 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 using the OFDMA method,
When the base station allocates an extra channel used for data communication to the PRU,
The channel allocation unit
Radio communication characterized in that the extra channel is classified into retransmission control data, initial transmission control data, retransmission actual data, and initial transmission entity data according to the contents, and preferentially assigned to the PRUs in this order. Method.

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