JP4334485B2 - Control station apparatus, terminal apparatus, and scheduling method - Google Patents

Description

  The present invention relates to a control station apparatus, a terminal apparatus, and a mobile station apparatus that adaptively allocates the same frequency channel or the same time channel to mobile station apparatuses belonging to the same group in a one-cell repetitive OFDM / (TDMA, FDMA) system communication. And a scheduling method.

  Currently, transmission and access technologies in mobile communication systems are rapidly progressing in Japan, such as IMT-2000 (International Mobile Telecommunications 2000) service started in October 2001. In addition, technologies such as HSDPA (High Speed Down-link Packet Access) have been standardized, and the practical application of data transmission at a maximum of about 10 Mbps is being promoted.

  On the other hand, standardization for realizing broadband wireless Internet access targeting a transmission rate of 10 Mbps to 100 Mbps is being promoted, and various technologies have been proposed. A requirement necessary for realizing wireless communication at a high transmission rate is to improve frequency utilization efficiency. Since the transmission rate and the bandwidth to be used are in a proportional relationship, in order to increase the transmission rate, it is a simple solution to increase the frequency bandwidth to be used. However, the frequency bands that can be used are tight, and it is impossible to allocate a sufficient bandwidth for constructing a new wireless communication system. Therefore, it is necessary to increase the frequency utilization efficiency.

  Another requirement is to seamlessly provide a service in a private area (isolated cell) such as a wireless LAN while realizing a service in a communication area composed of a cell such as a mobile phone.

  One technology that has the potential to solve these is one-cell repeated OFDM / (TDMA, FDMA) (Orthogonal Frequency Division Multiplexing / Time Division Multiple Access, Frequency Division Multiples) technology. This is a technique in which communication is performed using the same frequency in all cells in a communication area composed of cells, the modulation method used for communication is OFDM, and the access method is TDMA or FDMA. It is. Of course, the isolated cell is a communication method that can realize higher-speed data communication while having a wireless interface common to the cell area.

  Hereinafter, OFDM, TDMA, and FDMA, which are elemental technologies of OFDM / (TDMA, FDMA), will be briefly described.

  First, OFDM is a method used in IEEE 802.11a, which is a 5 GHz band wireless system, and terrestrial digital broadcasting. OFDM is a system in which tens to thousands of carriers are arranged at the minimum frequency interval where no theoretical interference occurs and are communicated simultaneously. In normal OFDM, this carrier is called a subcarrier, and each subcarrier is modulated by a modulation scheme such as PSK or QAM for communication. Further, it is said to be a modulation method that is strong against frequency selective fading by combining with an error correction method. In this specification, the number of subcarriers used for OFDM is 768 waves.

  Next, TDMA is a method of dividing and accessing data when transmitting and receiving data. Usually, in a communication system using TDMA as an access method, a frame configuration having a plurality of slots, which are units of communication time, is used, and in Down-link, the frame is received at the head of the frame. It is common to assign the required control slots. In this specification, a frame is composed of nine slots, and the first slot is assigned to the control slot.

  Next, FDMA is a method of dividing and accessing a frequency when transmitting / receiving data. Usually, in a communication system using FDMA as an access method, a frequency is divided into several bands, and a terminal (mobile station apparatus) to be accessed is distinguished by dividing a frequency band for communication. Usually, a guard band called a guard band is prepared between the divided frequency bands. However, in OFDM / (TDMA, FDMA), a guard band is not used or used in order not to impair frequency utilization efficiency. Is a very narrow band of several subcarriers. In the present specification, 768 subcarriers used for OFDM are divided into 12 parts by 64 subcarriers to perform FDMA.

  Next, OFDM / (TDMA, FDMA) will be described based on the above introduction. FIG. 35 is a diagram showing an OFDM / (TDMA, FDMA) two-dimensional frame configuration that is an object of the present invention. In FIG. 35, the vertical axis represents frequency and the horizontal axis represents time. In FIG. 35, one of the squares is a minimum unit used for data transmission, and is composed of a plurality of OFDM symbols. In this specification, this is called a slot. Periodically slots are arranged. A frame in which slots are arranged according to this cycle is defined as a frame.

  FIG. 35 shows a structure for one frame. A control slot is arranged at the head of the downlink frame, and a data slot is arranged behind it. A random slot is arranged at the head of the uplink frame, and a data slot is arranged behind it. In FIG. 35, one control slot, one random slot, and eight data slots are arranged in one frame in one frame, but this number varies depending on the system. The control slot includes information indicating to which terminal the data slot is assigned. The random slot is used when the terminal transmits data to the base station in a state where no data slot is allocated. Since random slots are literally used randomly, there is a possibility of data collision between terminals.

  In this specification, a group of slots in the frequency axis direction at the same time is referred to as a frequency channel, and a group of slots in the time axis direction at the same frequency is referred to as a time channel.

  When communication is performed from a base station (referred to as AP or base station device) to a mobile station (MT, mobile station device or simply referred to as “terminal”), the base station may communicate with a communication partner during a control slot. Information indicating that a downlink slot is allocated to a terminal is indicated, and information addressed to the terminal is transmitted to the slot. When communicating from a mobile station to a base station, a slot allocation request is first made using a random slot. When the base station receives the slot allocation request using the random slot, the base station indicates information indicating that an uplink slot is allocated to the mobile station that has requested the slot allocation in the control slot. The mobile station confirms that uplink slot allocation has been performed for the control slot, and transmits using the data slot.

  The OFDM / (TDMA, FDMA) system is a system in which a plurality of mobile stations transmit and receive data to and from a base station at different frequencies and times based on the above. In FIG. 35, for the sake of convenience, it is expressed that there is a gap between the slots, but the presence or absence of the gap has no significant meaning.

  FIG. 36 is a block diagram showing a schematic configuration of a transmission circuit used for OFDM / (TDMA, FDMA). The transmission circuit shown in FIG. 36 has a data multiplex unit 431. In addition, twelve error correction code units 432-a to 432-l and twelve serial / parallel conversion units (S / P conversion units) 433-a to 433-l are provided. The transmission power control unit 435 exhibits a function for changing the transmission power for each frequency channel.

  The data multiplex unit 431 divides the information data into 12 series for each packet to be transmitted. That is, in the data multiplex unit 431, an OFDM / (TDMA, FDMA) slot designated by a module such as a CPU (not shown) is physically designated. Thereafter, the error correction code units 432-a to 432-l apply error correction codes, the S / P conversion units 433-a to 433-l separate the 64 systems, and the mapping unit 434 modulates each carrier. The The transmission power control unit 435 converts the transmission power for each subchannel specified by a module such as a CPU (not shown), and the IFFT unit 436 performs IFFT processing (Inverse Fast Fourier Transform). When generating a 768-wave OFDM signal, the number of IFFT points normally used is 1024.

  Thereafter, the P / S conversion unit 437 converts the data into serial data, and then the guard interval insertion unit 438 inserts a guard interval. The guard interval is inserted in order to reduce intersymbol interference when receiving an OFDM signal. Thereafter, the data is converted into an analog signal by the D / A conversion unit 439, and then converted into a frequency to be transmitted by the wireless transmission unit 440, and then the data is transmitted from the antenna unit 441.

  FIG. 37 is a block diagram showing a schematic configuration of a receiving circuit used for OFDM / (TDMA, FDMA). The receiving circuit shown in FIG. 37 has a data demultiplexing unit 461 and further has twelve error correction decoding units 460-a to 460-l. Also, twelve parallel / serial converters (P / S converters) 459-a to 459-l are provided.

  In the receiving circuit, an operation reverse to that of the transmitting circuit is basically performed. The radio wave received by the antenna unit 451 is converted in frequency to a frequency band in which the radio receiving unit 452 can perform A / D conversion. The data converted into the digital signal by the A / D conversion unit 453 is subjected to OFDM symbol synchronization in the synchronization unit 454, and the guard interval is removed in the guard interval removal unit 455. Thereafter, the data is parallelized to 1024 data by the S / P converter 456.

  Thereafter, FFT (Fast Fourier Transform) section 457 performs 1024-point FFT, and propagation path estimation demapping section 458 demodulates 768 subcarriers. Usually, propagation path estimation estimates a propagation path in a receiver by sending a known signal from a transmitter to a receiver. Thereafter, necessary data is serialized in P / S conversion units 459-a to 459-1, error correction is performed in error correction decoding units 460-a to 460-1, and input to data demultiplexing unit 461. Is done. In the data demultiplexing unit 461, the information data is processed and output.

  Next, an outline of a communication system composed of cells will be described. FIG. 38A shows an example where the cell is hexagonal and seven frequency bands are used. A base station is placed at the center of the cell, communication is performed using the frequency band Fc0 in the cell B0, Fc1 in B1, and so on. When there is a sufficient frequency band as in this cell configuration, the same frequency is not used in adjacent cells, and good communication can be performed without being affected by the adjacent cells.

  FIG. 38 (b) shows an example in which one-cell repetition OFDM / (TDMA, FDMA) is used. Similarly, cells are formed of hexagons, but all frequencies use Fc0. Therefore, when the one-cell repetition OFDM / (TDMA, FDMA) operates ideally, it is possible to achieve seven times the frequency utilization efficiency as compared with the case of FIG. Therefore, it can be said that realizing one-cell repetition is an indispensable technique for realizing high-speed communication.

  As is clear from FIG. 38 (b), the point that determines whether one-cell repetition operates ideally is to prevent interference from other cells. There are two major techniques for preventing interference from other cells. One is to establish a communication method (interference removal) in which each terminal removes radio waves from other cells, and the other is to avoid interference as much as possible. Of these, two specific techniques relating to the latter will be described next.

  First, a wireless data communication system, a wireless data communication method, and a program thereof disclosed in Japanese Patent Laid-Open No. 2003-18091 (Patent Document 1) will be described. A cell configuration relating to the invention described in Patent Document 1 is shown in FIG. In FIG. 39, a hexagon indicated by a dotted line is written in each cell with respect to FIG. This means that one cell is divided into two areas near and far from the base station. Focusing on the cell of B0, communication with a terminal in an area far from the base station is performed using the frequency Fc0, and communication with terminals in an area close to the base station is performed using Fc1 to Fc6. This indicates that the frequency utilization efficiency is increased. Furthermore, it is explained that the efficiency increases when the sector antenna is used within the dotted line. This is because it is possible to reduce the transmission power when communicating with a terminal close to the base station, so even if the frequency band of Fc1 to Fc6 is used, it does not affect adjacent cells. Technology.

  Next, a mobile communication system, a base station apparatus, and a control method for the mobile communication system disclosed in Japanese Patent Laid-Open No. 2003-46437 (Patent Document 2) will be described. A cell configuration related to the invention described in Patent Document 2 is shown in FIG. In FIG. 40, two hexagons indicated by dotted lines are written in each cell with respect to FIG. Focusing on the B0 cell. The area farthest from the base station is Ts1, the next area is Ts2, and the nearest area is Ts3. This Ts represents time, and one frame is composed of Ts1 to Ts3. In B0, communication is performed with the largest transmission power during Ts1, and communication is performed with power reduced to Ts2 and Ts3. Similarly, each cell performs communication by changing transmission power according to each time.

  In B0, when communication is performed with the transmission power increased during Ts1, other adjacent cells do not perform communication with the largest transmission power, so B0 has less interference from other cells. It is possible to communicate with. Similar advantages are secured for the cells B1 to B6.

These patent documents mainly describe the downlink, but the basic part is the same for the uplink.
JP 2003-18091 A JP 2003-46437 A

  However, when the techniques disclosed in Patent Document 1 and Patent Document 2 are used for one-cell repetitive OFDM / (TDMA, FDMA) uplink, the utilization efficiency of radio resources may be increased depending on the arrangement of mobile stations in the cell. There is a problem of getting worse. This is because when a group of mobile stations that require a certain amount of power gathers at a certain location in the cell, the range of interference generated by the group of mobile stations is also limited. Therefore, it should be possible to reuse the radio resources used by the previous uplink mobile station group outside the range in which this interference is received in the adjacent cell. However, in the techniques disclosed in Patent Document 1 and Patent Document 2, This cannot be realized.

  In addition, the techniques disclosed in Patent Document 1 and Patent Document 2 are such that the area where the transmission power is increased comes outside the concentric circles. There is a problem in that communication efficiency is lowered because mobile stations are arranged and radio resources in this area must be shared between these mobile stations.

  Furthermore, when the number of isolated cells and adjacent cells is different, it is not possible to adaptively cope with the case where a base station is newly built after the base station is established once and the service is started. There are challenges. Furthermore, in the technique disclosed in Patent Document 2, it is an implicit assumption that each base station is time-synchronized, and no solution is shown when it is not synchronized.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a control station apparatus, a terminal apparatus, and a scheduling method that perform scheduling capable of reducing interference to adjacent cells as much as possible. And

  (1) In order to achieve the above object, the present invention has taken the following measures. That is, the control station apparatus according to the present invention controls a communication slot specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band. A control station apparatus that allocates each apparatus and causes each terminal apparatus to perform uplink communication based on the allocation of the communication slot, the receiving section receiving information from each terminal apparatus, and the received Based on the information, a transmission power determining unit that determines transmission power for each terminal device for each terminal device based on the information, and a group of terminal devices based on the transmission power determined for each terminal device And assigning the same time channel or the same frequency channel communication slot to terminal devices belonging to the same group. Te is characterized by comprising: a scheduling section that generates a communication slot allocation information, and a transmission unit that transmits the communication slot assignment information the generated to each terminal device.

  In this way, the transmission power when each terminal device existing within the control range of the control station device performs uplink communication is determined for each terminal device, and a group of terminal devices is formed based on the determined transmission power. Since the communication slots of the same time channel or the same frequency channel are allocated to the terminal devices belonging to the same group, the uplink given to the control range of another adjacent control station device in each time channel or each frequency channel Can be made substantially constant in an autonomous and distributed manner. As a result, in uplink communication in the control range of each control station device, it is possible to realize good communication in an autonomous and distributed manner without greatly affecting the mutual control range.

  (2) Further, the control station apparatus according to the present invention controls a communication slot specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band. A control station apparatus that is assigned to each terminal apparatus and causes each terminal apparatus to perform uplink communication based on the communication slot assignment, and includes information including position information of each terminal apparatus. A group of terminal devices is formed based on the receiving unit that receives from the device and the received positional information of each terminal device, and the same time channel or the same frequency channel is set for the terminal devices belonging to the same group. A scheduling unit that allocates communication slots and generates communication slot allocation information, and the generated communication slot allocation It is characterized in that it comprises a transmitter which transmits the information to each terminal device.

  In this way, a group of terminal devices is formed based on position information of each terminal device, and communication slots of the same time channel or the same frequency channel are assigned to terminal devices belonging to the same group. Alternatively, the uplink interference power given to the control range of another adjacent control station apparatus in each frequency channel can be made substantially constant in an autonomous distributed manner. That is, the transmission power of the terminal device that is controlled by the transmission power greatly depends on the distance attenuation from the control station device, and the amount of interference that the terminal device gives to the control range of another adjacent control station device is from the control station device. Because it depends on the distance and direction of the terminal, grouping terminal devices having the same distance and direction from the control station device, and assigning the same time channel or frequency channel, the control range of other adjacent control station devices The amount of interference given to can be kept constant. As a result, in uplink communication in each adjacent control range, it is possible to realize good communication in an autonomous and distributed manner without greatly affecting the mutual control range.

  (3) Further, in the control station apparatus according to the present invention, the location information received by the receiving unit is a control station identifier, and the scheduling unit forms a group of terminal devices based on the received control station identifier. It is characterized by doing.

  Thus, since the group of terminal devices is formed based on the control station identifier, for example, the terminal devices whose control station identifiers all match can be made into one group. As a result, terminal devices with the same distance and direction from the control station device are grouped and the same time channel or frequency channel is assigned, so that the amount of interference given to the control range of other adjacent control station devices is constant. Can be kept in. As a result, in uplink communication in the control range of each control station apparatus, it is possible to realize good communication in an autonomous and distributed manner without greatly affecting the mutual control range.

  (4) Moreover, the control station apparatus which concerns on this invention is further provided with the transmission power determination part which determines the transmission power at the time of each said terminal device performing uplink communication based on the said received information for every terminal device. The scheduling unit further forms a subgroup based on the transmission power determined for each terminal device within the formed group, and the same time channel or the same time channel for the terminal devices belonging to the same subgroup. Communication slot assignment information is generated by assigning communication slots of the same frequency channel.

  In this way, the transmission power when each terminal apparatus performs uplink communication is determined for each terminal apparatus, and within the group formed as described above, further subgroups are based on the transmission power determined for each terminal apparatus. Therefore, it is possible to collect terminal devices having the same transmission power to some extent. Since the same time channel or the same frequency channel is assigned to each subgroup that is subdivided, even in an environment where terminal devices having different maximum outputs are mixed, the control range of other adjacent control station devices is reached. It is possible to perform highly efficient communication while keeping the applied interference constant.

  (5) The control station apparatus according to the present invention further includes an acquisition unit that acquires information on a communication environment in each time channel or each frequency channel from information received by the reception unit, and the scheduling unit includes the communication According to information on the environment, communication slot allocation information is generated by allocating communication slots of the same time channel or the same frequency channel to terminal devices belonging to the same group or the same subgroup. .

  In this way, information on the communication environment in each time channel or each frequency channel is acquired from the information received by the receiving unit. The terminal device can be assigned to the channel. As a result, in uplink communication in the control range of each control station device, it is possible to realize good communication in an autonomous and distributed manner without giving large interference to each other's control range.

  (6) In the control station apparatus according to the present invention, the receiving unit receives communication slot allocation information generated by another control station device from each terminal device, and the scheduling unit receives the received communication slot. According to the allocation information, communication slot allocation information is generated by allocating communication slots of the same time channel or the same frequency channel to terminal devices belonging to the same group or the same subgroup.

  In this way, communication slots of the same time channel or the same frequency channel for terminal devices belonging to the same group or the same subgroup according to the information on the communication environment and the communication slot assignment information of other adjacent control station devices Therefore, the position of the terminal device existing in the control range of another adjacent control station device is generally grasped, and not only interference from the control range of another adjacent control station device but also other adjacent control stations It is possible to perform adaptive scheduling in consideration of interference given to the control range of the apparatus. As a result, interference in uplink communication can be further reduced, and efficient communication can be performed as a whole system.

  (7) Moreover, in the control station apparatus according to the present invention, the control station device further includes an acquisition unit that acquires information related to a communication environment in each time channel or each frequency channel from the information received by the reception unit, The communication slot assignment information generated by another control station device is received from the terminal device, and the scheduling unit is a terminal belonging to the same group or the same subgroup according to the information on the communication environment and the received communication slot assignment information. Communication slot assignment information is generated by assigning communication slots of the same time channel or the same frequency channel to a device.

  In this way, information on the communication environment in each time channel or each frequency channel is acquired from the information received by the receiving unit. The terminal device can be assigned to the channel. As a result, in uplink communication in the control range of each control station device, it is possible to realize good communication in an autonomous and distributed manner without giving large interference to each other's control range. In addition, according to information on the communication environment and communication slot assignment information of other adjacent control station devices, communication slots of the same time channel or the same frequency channel are assigned to terminal devices belonging to the same group or the same subgroup. Therefore, the position of the terminal device existing in the control range of another adjacent control station device is roughly grasped, and not only the interference from the control range of another adjacent control station device but also the other control station device adjacent to It is possible to perform adaptive scheduling in consideration of interference given to the control range. As a result, interference in uplink communication can be further reduced, and efficient communication can be performed as a whole system.

  (8) Moreover, in the control station apparatus according to the present invention, the scheduling unit determines a plurality of levels by dividing the magnitude of transmission power of the terminal apparatuses belonging to the group into a plurality of numerical ranges, and For each terminal device, the subgroup is formed by specifying a level to which the determined magnitude of transmission power belongs.

  In this way, a plurality of levels are defined, and for each terminal device within the control range of the control station device, a subgroup is formed by specifying the level to which the determined transmission power level belongs. Terminal devices having substantially the same size can be subgrouped. That is, even if the terminal device is located at the same location, radio signals from the same control station device cannot always be received due to the influence of shadowing or the like. In addition, when the maximum output is different for each terminal device, transmission is not always performed with the same transmission power even if the presence position of the terminal device is the same. For this reason, by using the level to which the magnitude of the transmission power belongs as a reference for forming the subgroup, it is possible to subgroup terminal devices having a closer magnitude of the transmission power.

  (9) In the control station apparatus according to the present invention, the scheduling unit extracts information on interference power in each time channel or each frequency channel from information on the communication environment, and determines the magnitude of the determined transmission power A communication slot of a time channel or a frequency channel with relatively low interference power is allocated to each terminal apparatus in a group or subgroup to which a terminal apparatus having a relatively large value belongs, and communication slot allocation information is generated It is characterized by.

  Thus, since a communication slot of a time channel or a frequency channel with relatively small interference power is allocated to each terminal device in a group to which a terminal device with relatively large transmission power belongs, the transmission power is It is possible to avoid the situation where groups to which large terminal devices belong use the same time channel or frequency channel, and the influence of interference on the control range of other adjacent control station devices while maintaining good communication quality. Can be reduced.

  (10) Further, in the control station apparatus according to the present invention, the scheduling unit applies to each terminal apparatus in a group or subgroup to which a terminal apparatus having a relatively large transmission power is included. A terminal device in which a communication channel of a time channel or a frequency channel that is not assigned to a terminal device to be controlled by another control station device is assigned with a first priority, and the magnitude of the determined transmission power is relatively large Time channel or frequency assigned to a terminal device located on a different side from the group, centered on the other control station device, for each terminal device in the group or subgroup to which The communication slot of the channel is assigned with the second priority, and the group to which the terminal device having the relatively large transmission power is assigned. To each terminal device in the inside or subgroups flop, a communication slot of the interference power is relatively small time channel or frequency channel allocation in the third priority, it is characterized by generating a communication slot assignment information.

  By allocating communication slots with such priorities, the influence of interference on the control range of other adjacent control station apparatuses is reduced, and efficient communication slot allocation can be performed.

  (11) Further, in the control station apparatus according to the present invention, the scheduling unit includes two or more subgroups belonging to the same group, and is larger than transmission power required by a terminal apparatus belonging to a certain subgroup. When there is an empty communication slot in the time channel or frequency channel assigned to another subgroup to which the terminal device requiring transmission power belongs, the subgroup with the lower transmission power is included in the empty communication slot. It is characterized by assigning terminal devices belonging to.

  In this situation, there is an empty channel in the time channel or frequency channel allocated to the subgroup requiring high transmission power, and the time channel or frequency channel allocated to the subgroup requiring small transmission power is insufficient. In addition, it is possible to allow a terminal requiring a small transmission power to be allocated to an empty communication slot of a time channel or a frequency channel to which a subgroup requiring a large transmission power is allocated. This is because there is a high possibility that a time group or frequency channel to which a subgroup requiring a large transmission power is allocated has a subgroup requiring a small transmission power in the control range of another adjacent control station device. This is because even when a terminal requiring low transmission power is assigned to an empty communication slot of the corresponding time channel or frequency channel, interference with the control range of another adjacent control station apparatus does not occur. As a result, it is possible to adaptively allocate transmission power without affecting the control range of another adjacent control station apparatus.

  (12) In the control station apparatus according to the present invention, the scheduling unit includes two or more subgroups belonging to the same group, and is smaller than transmission power required by a terminal apparatus belonging to a certain subgroup. When there is an empty communication slot in the time channel or frequency channel assigned to another subgroup to which the terminal device requiring transmission power belongs, the subgroup with the higher transmission power is included in the empty communication slot. It is characterized by assigning terminal devices belonging to.

  In this situation, there is an empty channel in the time channel or frequency channel assigned to the subgroup requiring low transmission power, and the time channel or frequency channel assigned to the subgroup requiring high transmission power is insufficient. In addition, it is possible to allow a terminal requiring a large transmission power to be allocated to an empty communication slot of a time channel or a frequency channel to which a subgroup requiring a small transmission power is allocated.

  (13) In the control station apparatus according to the present invention, the scheduling unit may change at least one of transmission power and a modulation scheme when allocating the terminal apparatus to the vacant communication slot. Yes.

  Thus, when allocating transmission data and transmission power to be transmitted to a terminal device to an empty communication slot, at least one of transmission power or modulation scheme is changed. For example, a terminal device that requires high transmission power When a radio signal is transmitted to the communication channel of each time channel or each frequency channel to which low transmission power is allocated, the transmission power is lowered and the modulation scheme is also low, that is, reception is performed. By changing to a modulation scheme that is easy to be performed, it is possible to avoid the occurrence of errors and avoid the influence on the control range of another adjacent control station apparatus. On the other hand, for example, when a radio signal is transmitted to a terminal device that requires low transmission power, if a communication slot of each time channel or each frequency channel to which high transmission power is allocated is vacant, transmission is performed. By increasing the power and the modulation scheme, it is possible to improve the transmission efficiency and avoid the influence on the control range of other adjacent control station apparatuses.

  (14) In the control station apparatus according to the present invention, the scheduling unit may allocate the communication slot in the same time channel or the same frequency channel to terminal devices belonging to the same group or subgroup. In addition, the communication slot allocation information is generated by identifying a communication slot to be allocated to each terminal device based on the information on the communication environment acquired by the acquisition unit.

  As described above, the communication slot to be allocated to each terminal device is specified based on the information on the communication environment, and the communication slot allocation information is generated. A time channel or frequency channel with a small power ratio) or a time channel or frequency channel with a large error rate is a time channel or frequency channel that is not used because of large interference at the outer periphery of the control range of the control station apparatus. A small amount of power is allocated for use only in the inner periphery of the control range. In addition, a time channel or frequency channel with a small interference power, a time channel or frequency channel with a large SINR, or a time channel or frequency channel with a low error rate has a small interference even in the outer periphery of the control range of the control station device. A large transmission power is assigned to the time channel or frequency channel used in the outer periphery of the control range. As a result, it is possible to adaptively allocate transmission power without affecting the control range of another adjacent control station apparatus.

  (15) In the control station apparatus according to the present invention, the communication slots are allocated to the terminal apparatuses in order from communication slots with relatively small interference power, or the received signal power pair in each communication slot. It is characterized in that it is performed in order from a terminal device having a relatively large interference and noise power ratio.

  By defining the allocation conditions in this way, it becomes possible to adaptively allocate transmission power without affecting the control range of other adjacent control station apparatuses.

  (16) A terminal device according to the present invention is a terminal device including a transmission / reception unit that performs wireless communication with the control station device according to any one of claims 2 to 15, wherein the transmission / reception is performed. The unit wirelessly transmits information indicating a base station identifier received from another control station apparatus that is not a connection destination to the control station apparatus that is a connection destination.

  As described above, since the control station identifier is wirelessly transmitted to the control station apparatus of the connection destination, the control station apparatus can form a group of terminal apparatuses based on the control station identifier. For example, in the connection destination control station device, terminal devices whose control station identifiers received from the terminal devices all match can be made into one group. As a result, terminal devices with the same distance and direction from the control station device are grouped and the same time channel or frequency channel is assigned, so that the amount of interference given to the control range of other adjacent control station devices is constant. Can be kept in. As a result, in uplink communication in the control range of each control station apparatus, it is possible to realize good communication in an autonomous and distributed manner without greatly affecting the mutual control range.

  (17) Further, in the terminal device according to the present invention, the transmission / reception unit, when the received power of a signal received from another control station device that is not a connection destination is equal to or greater than a certain threshold value, The information indicating the identifier is wirelessly transmitted to the control station apparatus of the connection destination.

  In this way, when the received power of a signal received from another adjacent control station apparatus is equal to or greater than a certain threshold, information indicating the control station identifier of the control station apparatus is wirelessly transmitted to the connected control station apparatus. Therefore, only the control station identifier of the control station apparatus in the control range that may cause interference can be transmitted to the connection-destination control station apparatus. As a result, the control station apparatus can exclude the control station apparatus that is unlikely to cause interference and perform communication slot assignment, so that efficient scheduling can be performed.

  (18) Further, in the terminal device according to the present invention, the transmission / reception unit wirelessly transmits communication slot allocation information received from another control station device that is not the connection destination to the control station device that is the connection destination. .

  As described above, since the communication slot allocation information received from another control station apparatus that is not the connection destination is wirelessly transmitted to the control station apparatus that is the connection destination, the communication station allocation information of other adjacent control station apparatuses is transmitted in the control station apparatus. Thus, communication slots of the same time channel or the same frequency channel can be assigned to terminal devices belonging to the same group. Thereby, in the control station apparatus, the existence position of the terminal apparatus existing in the control range of another adjacent control station apparatus is roughly grasped, and not only the interference from the control range of another adjacent control station apparatus but also adjacent It is possible to perform adaptive scheduling in consideration of interference with the control range of other control station apparatuses. As a result, interference in uplink communication can be further reduced, and efficient communication can be performed as a whole system.

  (19) A radio communication system according to the present invention includes the control station apparatus according to any one of claims 2 to 15 and the terminal apparatus according to claim 16 or claim 17. It is characterized by.

  With this configuration, each terminal device that is within the control range of the control station device determines transmission power for each terminal device and forms a group of terminal devices based on the determined transmission power. Since the communication slots of the same time channel or the same frequency channel are allocated to the terminal devices belonging to the same group, the uplink given to the control range of another adjacent control station device in each time channel or each frequency channel Can be made substantially constant in an autonomous and distributed manner. As a result, in uplink communication in the control range of each control station device, it is possible to realize good communication in an autonomous and distributed manner without greatly affecting the mutual control range.

  (20) In addition, the scheduling method according to the present invention controls a communication slot specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band. A scheduling method to be assigned to each terminal device, the step of receiving information from each terminal device, and the transmission power when each terminal device performs uplink communication based on the received information for each terminal device A step of forming a group of terminal devices based on transmission power determined for each terminal device, and the same time channel or the same frequency for terminal devices belonging to the same group Assigning a communication slot of the channel.

  In this way, the transmission power when each terminal device existing within the control range of the control station device performs uplink communication is determined for each terminal device, and a group of terminal devices is formed based on the determined transmission power. Since the communication slots of the same time channel or the same frequency channel are allocated to the terminal devices belonging to the same group, the uplink given to the control range of another adjacent control station device in each time channel or each frequency channel Can be made substantially constant in an autonomous and distributed manner. As a result, in uplink communication in the control range of each control station device, it is possible to realize good communication in an autonomous and distributed manner without greatly affecting the mutual control range.

  (21) Further, the scheduling method according to the present invention controls communication slots specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band as control targets. A scheduling method assigned to each terminal device, the step of receiving information including location information of each terminal device from each terminal device, and each terminal device performing uplink communication based on the received information Determining the transmission power for each terminal device, forming a group of terminal devices based on the received location information of each terminal device, and the same for the terminal devices belonging to the same group Assigning a communication slot of a time channel or the same frequency channel. It is a symptom.

  In this way, a group of terminal devices is formed based on position information of each terminal device, and communication slots of the same time channel or the same frequency channel are assigned to terminal devices belonging to the same group. Alternatively, the uplink interference power given to the control range of another adjacent control station apparatus in each frequency channel can be made substantially constant in an autonomous distributed manner. That is, the transmission power of the terminal device that is controlled by the transmission power greatly depends on the distance attenuation from the control station device, and the amount of interference that the terminal device gives to the control range of another adjacent control station device is from the control station device. Because it depends on the distance and direction of the terminal, grouping terminal devices having the same distance and direction from the control station device, and assigning the same time channel or frequency channel, the control range of other adjacent control station devices The amount of interference given to can be kept constant. As a result, in uplink communication in each adjacent control range, it is possible to realize good communication in an autonomous and distributed manner without greatly affecting the mutual control range.

  According to the present invention, the transmission power when each terminal apparatus existing within the control range of the control station apparatus performs uplink communication is determined for each terminal apparatus, and a group of terminal apparatuses is determined based on the determined transmission power. And the communication slots of the same time channel or the same frequency channel are allocated to the terminal devices belonging to the same group, so that they are given to the control range of other adjacent control station devices in each time channel or each frequency channel. It is possible to make the uplink interference power almost constant in an autonomous distributed manner. Then, by performing allocation in consideration of information such as interference power, in the uplink communication in the control range of each control station apparatus, each of the control ranges is excellent in autonomous decentralization without greatly affecting the mutual control range. Communication can be realized.

  Hereinafter, the radio transmission apparatus according to the present embodiment will be described. In the scheduling (slot allocation) method according to the present embodiment, in uplink communication of a one-cell repetitive OFDM / (TDMA, FDMA) system, a terminal that requires similar transmission power or a control received at the time of cell search In this method, terminals whose signal base station IDs all match are grouped, and the same frequency channel or the same time channel is adaptively allocated to terminals belonging to the same group while considering the influence of interference coming from adjacent cells. In the present embodiment, the base station is referred to as an AP (access point) or a base station apparatus, and is collectively referred to as a “control station apparatus”. The mobile station is also referred to as MT, terminal device, terminal device, or simply “terminal”. The control range of the control station apparatus corresponds to, for example, a “cell” in a cellular system or a range in which an access point can be controlled in a wireless LAN system.

  In this slot allocation method, when terminals that require the same level of transmission power are grouped, the terminals located at points (ranges) that have the same distance from the base station are grouped. In addition, when grouping terminals whose base station IDs of the control signals received at the time of cell search are all the same, not only the distance from the base station but also the direction (range) of the direction is the terminal. Will be grouped. Here, FIG. 1 shows a state in which terminals having the same base station ID are grouped. The cell 1 in FIG. 1 includes 12 terminals A to L, and there are 6 cells 2 to 7 around the cell 1.

  When there is a terminal at the position shown in FIG. 1, the terminals A and B in the cell 1 communicate with the base station 1 after the initial connection. 2 or 3 control signals are received (usually, the terminal that originated the call is connected to the base station that transmitted the signal received at the highest power among the signals received during cell search. Here, it is assumed that the signal of the base station 1 is received with the highest power among the base stations 1 to 3 and the terminals A and B are accommodated in the base station 1). That is, terminals A and B receive signals having base station IDs of base stations 1 to 3 at the time of cell search. Therefore, when the present invention is used, terminals A and B are in the same group and are the same. A frequency channel or the same time channel will be assigned.

  Similarly, since the terminals C to E receive signals coming from the base stations 1, 3, and 4, respectively, the terminals C to E belong to the same group. Further, one group is formed by the terminals F and G, one group is formed by the terminal H, and one group is formed by the terminal I. Furthermore, since terminals J, K, and L are located at points away from the base stations of all adjacent cells, only the control signal transmitted from base station 1 is received, and another group of terminals J, K, and L is received. Will be formed.

  An example of slot allocation to terminals grouped in this way is shown in FIG. However, FIG. 2A shows an example of assigning the same frequency channel to terminals belonging to the same group, and FIG. 2B shows an example of assigning the same time channel to terminals belonging to the same group. When the same frequency channel is assigned to terminals belonging to the same group, as shown in FIG. 2A, terminals located in a range surrounded by a dotted line in FIG. 1 are assigned to the same frequency channel. Similarly, when the same time channel is assigned to terminals belonging to the same group, as shown in FIG. 2B, terminals located in the range surrounded by the dotted line in FIG. 1 are assigned to the same time channel. It will be.

  In the present embodiment, terminals located at points having similar distances and directions from the base station are grouped, and the same frequency channel or the same time channel is assigned to the same group in consideration of inter-cell interference. Thus, it is an object to reduce the influence of inter-cell interference in uplink communication in an autonomous and distributed manner. It is another object of the present invention to keep the amount of interference given to adjacent cells constant by not changing the allocation of frequency channels or time channels to terminal groups as much as possible in successive frames.

  Hereinafter, in the present embodiment, an embodiment in which the same time channel is allocated to terminals belonging to the same group will be described in detail with reference to the drawings. In addition, the device configuration and control flow in the following embodiments are examples, and various configurations other than the following embodiments are conceivable.

(First embodiment)
In the first embodiment, first, an example in which terminals having similar transmission power are grouped will be described. FIG. 3 is a block diagram illustrating a schematic configuration of the base station apparatus according to the first embodiment. However, here, as shown in FIG. 35, an apparatus configuration in the case where the number of frequency channels is 12 is shown. In FIG. 3, 300 is an antenna unit, 301 is a radio reception unit, 302 is an A / D conversion unit, 303 is a synchronization unit, 304 is a GI removal unit, 305 is an S / P conversion unit, 306 is an FFT unit, and 307 is a propagation unit. The path estimation demapping unit, 308-a to l are P / S conversion units, 309-a to l are error correction decoding units, 310 is a demultiplexing unit, 311 is a desired signal power / interference signal power measuring unit, and 312 is A scheduling unit, 313 is a downlink modulation unit, and 314 is a wireless transmission unit.

  As shown in FIG. 3, the base station apparatus in the case of performing scheduling according to the first embodiment includes a desired signal power / interference signal power measuring unit 311 and transmission power control information calculated from the measured desired signal power. Is transmitted to the terminal, used as a reference for performing uplink transmission power control, and also used for grouping terminals when performing scheduling according to the first embodiment. The interference signal power measured by the desired signal power / interference signal power measurement unit 311 is used when assigning a time channel to a terminal group (during scheduling). The scheduling unit 312 groups terminals based on the transmission power of each terminal required for uplink communication, and sets a time channel to the terminal group based on the interference power of the empty slot measured by the desired signal power / interference signal power measurement unit 311. Make assignments. The antenna unit 300, the wireless reception unit 301, the A / D conversion unit 302, the synchronization unit 303, the GI removal unit 304, the S / P conversion unit 305, the FFT unit 306, the propagation path estimation demapping unit 307, and the P / S conversion. Units 308-a to l, error correction decoding units 309-a to l, and demultiplex unit 310 constitute a receiving unit in the base station apparatus (control station apparatus). In addition, scheduling section 312 constitutes a transmission power determination section in the base station apparatus (control station apparatus), and downlink modulation section 313, radio transmission section 314, and antenna section 300 are in the base station apparatus (control station apparatus). Configure the transmitter. The desired signal power / interference signal power measurement unit 311 constitutes an acquisition unit in the base station apparatus (control station apparatus).

  FIG. 4 is a block diagram of the device configuration of the terminal. 4, 400 is an antenna unit, 401 is a wireless transmission unit, 402 is a D / A conversion unit, 403 is a GI insertion unit, 404 is a P / S conversion unit, 405 is an IFFT unit, 406 is a transmission power control unit, and 407 is A mapping unit, 408 is an S / P conversion unit, 409 is an error correction code unit, 410 is a multiplex unit, 411 is a downlink demodulation unit, and 412 is a radio reception unit. Each component described above constitutes a transmission / reception unit in a terminal (device).

  As shown in FIG. 4, the terminal device in the case of performing scheduling according to the first embodiment performs transmission power control in the transmission power control unit 406 based on the transmission power control information notified by the downlink, It is configured to perform data communication in the uplink.

  Next, FIGS. 5 and 6 are flowcharts of uplink scheduling according to the first embodiment. As shown in FIG. 6, when a communication request occurs in the terminal, the terminal first receives a control signal and detects a base station to be connected (cell search: step S321). However, the control slot periodically transmitted from the base station of each cell is transmitted with power that can be sufficiently received even by the terminal located at the cell edge, and the contents of the control information include slot allocation information and the like Shall. During this time, the base station measures the interference power in the uplink empty slot of the own cell (step S304). Then, the interference power measured for each slot is averaged for each time channel, and the average interference power in each time channel is calculated. The average interference power in each time channel is used later as a reference when assigning the same time channel to terminals belonging to the same group.

  After performing a cell search for a certain time, a connection request is transmitted to the base station to be connected. At this time, the necessary slot number information in each terminal is transmitted to the base station together with the connection request. In the present embodiment, these uplink control information is transmitted in the random access slot of FIG. 2, but may be transmitted using other uplink resources.

  As described above, the connection request and necessary slot number information transmitted from the terminal are received by the connection destination base station as shown in step S305. The base station measures the received signal power when receiving such information, and generates transmission power control information in the uplink (step S306). Next, as shown in step S307, the base station groups terminals based on uplink transmission power control information. Here, the grouping of terminals is a process of handling, as a group, terminals having the same transmission power required when each terminal performs uplink communication.

  After grouping the terminals shown in step S307, as shown in step S308, the base station selects a terminal group that requires the highest transmission power and assigns time channels in order from that group. First, in the selected terminal group, the presence / absence of a slot-assigned terminal (terminal that has started communication) is checked, and if there is a slot-assigned terminal, the channel assigned to that terminal Slots that are vacant in the same time channel are assigned to other terminals (terminals that are newly starting communication) belonging to the same group (from step S309 to step S311).

  On the other hand, when there is no slot-assigned terminal (when all terminals belong to the group are terminals that are about to start communication), step S304 is performed in the time channel to which no terminal group is assigned. A time channel having the lowest interference power measured in step S3 is assigned to a terminal group (step S310).

  Then, each terminal belonging to the group is assigned an empty slot in the time channel assigned to the group according to the required number of slots (step S311). In such slot assignment, highly efficient slot assignment can be realized by assigning each terminal in order from the slot with the lowest interference power. Also, considering not only the interference power but also the fading situation that varies from terminal to terminal, the reception characteristics in the control station apparatus can be further improved by assigning each terminal with a slot having the maximum received SINR in the base station. it can. At this time, if there are not enough empty slots in the time channel assigned to the terminal group, the process moves from step S312 to step S313 in FIG. 5 to determine whether or not all channels have been assigned to the corresponding terminal group. . As a result, if all channels have been attempted to be assigned to the corresponding terminal group, the process proceeds to step S314, and channels that have not been attempted to be assigned to the corresponding terminal group (hereinafter referred to as candidate channels) remain. In step S310, a time channel is newly allocated from the remaining channels (candidate channels). When such a procedure is repeated and slots are allocated to all terminals desiring to connect to the base station, scheduling according to the present invention ends (step S315), and data transmission starts in the slots to which the respective terminals are allocated. Will be.

  With such a procedure, it is possible to perform adaptive scheduling considering the influence of interference coming from neighboring cells, but the amount of interference given to neighboring cells in uplink communication is not limited to the distance between the base station and the terminal. , Also depends on the direction in which the terminal is located. In the following, as a method for performing scheduling more efficiently, a method for grouping terminals located at points (ranges) having the same distance and direction from the base station and allocating the same time channel for each group will be described.

(Second Embodiment)
FIG. 7 is a block diagram illustrating a schematic configuration of a base station apparatus when the scheduling method according to the second embodiment is used. However, here, as shown in FIG. 35, an apparatus configuration in the case where the number of frequency channels is 12 is shown. In FIG. 7, 700 is an antenna unit, 701 is a radio reception unit, 702 is an A / D conversion unit, 703 is a synchronization unit, 704 is a GI removal unit, 705 is an S / P conversion unit, 706 is an FFT unit, and 707 is propagation. The path estimation demapping unit, 708-a to l are P / S conversion units, 709-a to l are error correction decoding units, 710 is a demultiplexing unit, 711 is a desired signal power / interference signal power measuring unit, and 712 is A scheduling unit, 713 is a downlink modulation unit, and 714 is a wireless transmission unit.

  As shown in FIG. 7, the base station apparatus in the case of performing scheduling according to the second embodiment has a desired signal power / interference signal power measuring unit 711 unlike the conventional example, and is calculated from the measured desired signal power. The transmitted transmission power control information is notified to the terminal and used as a reference for performing uplink transmission power control. The interference signal power measured by the desired signal power / interference signal power measurement unit 711 is used when a time channel is allocated to a terminal group (during scheduling). The scheduling unit 712 groups terminals based on base station ID information (base station IDs of all signals received at the terminal during cell search) sent from the terminal together with the connection request and necessary slot number information, The time channel is allocated to the terminal group based on the interference power of the empty slot measured by the desired signal power / interference signal power measurement unit 711. The antenna unit 700, the wireless reception unit 701, the A / D conversion unit 702, the synchronization unit 703, the GI removal unit 704, the S / P conversion unit 705, the FFT unit 706, the propagation path estimation demapping unit 707, and the P / S conversion Units 708-a to l, error correction decoding units 709-a to l, and demultiplex unit 710 constitute a receiving unit in the base station apparatus (control station apparatus). Moreover, the downlink modulation part 713, the radio | wireless transmission part 714, and the antenna part 700 comprise the transmission part in a base station apparatus (control station apparatus). Further, the desired signal power / interference signal power measurement unit 711 constitutes an acquisition unit in the base station apparatus (control station apparatus).

  FIG. 8 is a block diagram of the device configuration of the terminal. In FIG. 8, 200 is an antenna unit, 201 is a radio transmission unit, 202 is a D / A conversion unit, 203 is a GI insertion unit, 204 is a P / S conversion unit, 205 is an IFFT unit, 206 is a transmission power control unit, 207 Is a mapping unit, 208 is an S / P conversion unit, 209 is an error correction code unit, 210 is a multiplex unit, 211 is a downlink demodulation unit, 212 is a radio reception unit, 213 is an A / D conversion unit, and 214 is RSS ( Received Signal Strength) measurement unit. Each component described above constitutes a transmission / reception unit in a terminal (device).

  As shown in FIG. 8, unlike the conventional example, the terminal device in the case of performing scheduling according to the second embodiment connects all base station ID information included in the signal received at the time of cell search. It is configured to notify the base station. Also, based on the transmission power control information notified by the downlink, the transmission power control unit 206 controls the transmission power and performs uplink communication.

  Next, FIGS. 9 and 10 are flowcharts of uplink scheduling according to the second embodiment. As shown in FIG. 10, when a communication request occurs in the terminal, first, a cell search is performed, and the terminal receives control information of all frequency channels periodically transmitted from the base station of each cell in the control slot. (Step S121). Next, as shown in step S122, the RSSI (Received Signal Strength Indicator) of the received signal is measured at each terminal that has received the control signal. However, the control slot periodically transmitted from the base station of each cell is transmitted with power that can be sufficiently received by the terminal located at the cell edge, and the contents of the control information include the base station ID (which base information the control information is in It is assumed that information indicating whether the information is transmitted from a station) and slot allocation information are included. After the RSSI measurement shown in step S122, the terminal demodulates the reception control signal and obtains ID information of the base station that transmitted the control signal. A terminal that has made a communication request performs such an operation for a certain period of time, and receives a control signal (cell search) arriving from each neighboring base station.

  During this time, the base station measures the interference power in the uplink empty slot of the own cell (step S104). Then, the interference power measured for each slot is averaged for each time channel, and the average interference power in each time channel is calculated. The average interference power in each time channel is used later as a reference when assigning the same time channel to terminals belonging to the same group.

  After performing a cell search for a certain period of time, as shown in step S124, the terminal transmits a connection request to the base station that transmitted the control signal received with the highest power. In this embodiment, uplink control information such as a connection request is transmitted in the random access slot of FIG. 2, but may be transmitted using other uplink resources. At this time, all base station IDs included in the control signal received at the terminal at the time of cell search (for example, when control signals transmitted from two base stations are received, the two base station IDs) And the number of slots required for uplink communication is notified to the connected base station. However, the base station ID notified from the terminal to the base station may be one obtained by removing the base station ID of the connection destination from all the base station IDs included in the received control signal. It is good also as ID of the transmitted base station.

  As described above, the connection request, base station ID, and necessary slot number information transmitted from the terminal are transmitted to the connection destination base station (the control signal received at the highest power at the terminal, as shown in step S105. Base station). First, the base station measures received signal power when receiving such information, and generates transmission power control information in the uplink (step S106).

  Next, as shown in step S107, the base station groups terminals based on base station IDs included in all control signals received at the terminal during cell search among these pieces of information. Here, as described above, the grouping of terminals is a process of handling, as a group, terminals whose base station IDs reported from each terminal to the base station all match. However, not all terminals located at the same point can receive signals from the same base station due to the influence of shadowing or the like. Therefore, as a criterion for grouping the terminals, the base station IDs having a number equal to or greater than a certain threshold value are not grouped instead of grouping terminals having the same base station ID included in the control signal received at the time of cell search. It is good also as a form which groups the terminals with which agrees.

  After grouping terminals in step S107, as shown in step S108, the base station selects a terminal group that receives signals from the most base stations (reports the most base station IDs). Then, time channels are assigned in order from the group. Here, the allocation is performed in order from the terminal group in which the most base station IDs are reported because the terminal devices belonging to the terminal group in which the base station IDs are frequently reported are relatively close to other control station devices (control). This is because it is considered to require high transmission power because it is located near the boundary of the range, and when the number of reported base station IDs is the same, the terminal that requires the highest transmission power Allocation is performed in order from the group to which the group belongs. In the terminal group selected in this order, it is checked whether there is a terminal that has been assigned a slot (a terminal that has started communication earlier), and if there is a terminal that has already been assigned a slot, it is assigned to that terminal. An empty slot in the same time channel as the current channel is assigned to another terminal belonging to the same group (a terminal that is newly starting communication) (from step S109 to step S111).

  On the other hand, when there is no slot-assigned terminal (when all terminals belong to the group are terminals that are about to start communication), step S104 is performed in the time channel to which no terminal group is assigned. The time channel with the lowest interference power measured in step 1 is assigned to the terminal group (step S110). As described above, in this embodiment, time channels with low interference power are allocated in order from a terminal group that requires high transmission power (a large number of base station IDs are reported). Among them, a channel having relatively low interference power is assigned to a terminal group to which a terminal device having a relatively large transmission power belongs. By performing such assignment, it is possible to avoid a situation in which terminal groups that require high transmission power between adjacent cells are assigned to the same channel and interfere with each other, enabling highly efficient channel assignment. It becomes.

  After the time channel is assigned to the terminal group according to the above procedure, the slot is assigned to the terminal belonging to the corresponding group, and each terminal belonging to the corresponding group has an empty slot in the time channel assigned to the group. Are allocated according to the required number of slots (step S111). In such slot allocation, highly efficient slot allocation can be realized by allocating to each terminal in order from the slot with the lowest interference power. Also, considering not only the interference power but also the fading situation that varies from terminal to terminal, the reception characteristics in the control station apparatus can be further improved by assigning each terminal with a slot having the maximum received SINR in the base station. it can. However, at this time, if there are not enough empty slots in the time channel allocated to the terminal group, the process proceeds from step S112 to step S113 in FIG. 9 to determine whether all channels have been allocated to the corresponding terminal group. judge. As a result, if all channels have been attempted to be assigned to the corresponding terminal group, the process proceeds to step S114, and channels that have not been attempted to be assigned to the corresponding terminal group (hereinafter referred to as candidate channels) remain. In step S110, a time channel is newly assigned from the remaining channels (candidate channels). When such a procedure is repeated and slots are allocated to all terminals that wish to connect to the base station, scheduling according to the present invention ends (step S115), and data transmission starts in the slots to which the respective terminals are allocated. Will be.

  Here, FIG. 11 shows a state of data transmission / reception between the base station and the terminal when the scheduling according to the second embodiment is used. Although FIG. 11 is directed to an FDD (Frequency Division Duplex) scheme as a duplex scheme, the scheduling method according to the second embodiment is not limited to the FDD scheme and can be applied to a TDD scheme. Further, in FIG. 11, processing (other than signal transmission / reception) in the base station or the terminal is displayed surrounded by an ellipse.

  As illustrated in FIG. 11, a terminal that is newly starting communication receives a control signal 1100, measures a received RSSI of the control signal 1100, and acquires a base station ID included in the control signal 1100. Such processing is also performed on the control signals of other cells, and it is determined which base station to connect to. Thereafter, a connection request 1111 including the base station ID and the required number of slots is transmitted to the base station that desires connection. The base station that has received this connection request 1111 performs the scheduling shown in the control flow of FIGS. Here, the control flow shown in FIG. 9 and FIG. 10 includes from transmission / reception of the control signal 1100 of FIG. 11 to transmission of the downlink data 1101, reception of the uplink data 1110, transmission / reception of the connection request 1111 and scheduling at the base station. This process is shown. After scheduling shown in FIG. 9 and FIG. 10, after the slot allocation information to the terminal newly starting communication is notified in the control information 1104 shown in FIG. 11, the downlink data 1105 to the new communication starting terminal, up Transmission / reception of link data 1113 is started.

  In the scheduling method according to the second embodiment, terminals are grouped by the above procedure, and the same time channel is assigned to terminals belonging to the same group. As described above, when such a scheduling method is used, terminals whose base station IDs of the control signals received at the time of cell search all match are adaptively grouped and assigned the same time channel. . Here, since the terminals whose base station IDs of the control signals received at the time of the cell search all match, that is, the terminals located at the same distance and direction from the base station are adaptively grouped, The transmission power required for uplink communication by terminals belonging to the same group is substantially equal. Therefore, by using the scheduling method according to the present invention, it is possible to make the uplink interference power given to adjacent cells in each time channel substantially constant in an autonomous distributed manner. And the rapid fluctuation | variation of interference electric power can be suppressed by restraining the frequency which changes the time channel allocated to the terminal group low in this way. In the scheduling method according to the present invention, the time channel assigned to the terminal group is changed only when the interference observed at the base station changes greatly. In this case, all previous assignments are reset. After that, it is necessary to newly group terminals and perform scheduling. In addition, when a change occurs in transmission power required for uplink communication and when the position of the terminal moves greatly, it is desirable to change the terminal group only for the corresponding terminal, in which case the terminal group It is assumed that the channel assigned to is not changed.

  Here, in order to grasp the position of the terminal, the terminal periodically performs the operations of steps S121 to S124 shown in FIG. 10 and reports to which base station the control signal can be received from the connected base station. It is also possible to detect a situation where the position of the terminal moves greatly (the base station ID reported from the terminal changes).

  Next, FIG. 12 shows an example when slot allocation is performed using the scheduling method according to the second embodiment. FIG. 12A shows the arrangement of terminals in two adjacent cells, and FIG. 12B shows the slot allocation status in each cell. However, here, an example is shown in which a communication request is generated in the cell 2 after the slot allocation is performed in the cell 1 first. FIG. 12 shows an example in which the same time channel is assigned to terminals belonging to the same group, and only three time channels are described in one frame. FIG. 12 shows an example of slot assignment when base stations are synchronized, but the second embodiment is a scheduling method in which base stations and terminals in one cell operate autonomously and distributedly. Yes, it is also applicable when the base stations are asynchronous.

  In the terminal arrangement state shown in FIG. 12A, when the scheduling method according to the second embodiment is performed and ideally operates, as shown in FIG. The terminals G and H that are located (giving a large interference to the base station 2) are assigned the same time channel as the terminals M to O located at a point close to the base station 2 in the cell 2. Here, since the terminals M to O are located close to the base station 2, control is performed so that the uplink transmission power is kept low, and even if the uplink transmission is performed with a margin added, It does not reach the maximum power that can be transmitted. Therefore, in the uplink communication between the terminals M to O and the base station 2, a good communication can be achieved even if an interference signal arrives from the terminals G and H of the cell 1 to the base station 2 by adding a margin to the transmission power. Can do. Furthermore, since the transmission power in the uplink of the terminals M to O in the cell 2 is originally controlled to be low, even if a margin is added, the interference to the base station 1 in the cell 1 does not occur. For this reason, uplink communication between the terminals G and H and the terminals M to O allocated to the same time channel in the adjacent cell is simultaneously established with good characteristics.

  Similarly, terminals A to C located at a point close to the base station 1 in the cell 1 and terminals R and S located at a cell edge close to the cell 1 in the cell 2 are assigned to the same time channel. Uplink communication is also established at the same time. Further, terminals K and L located at a cell edge far from the base station 2 in the cell 1 and terminals P and Q located at a cell edge far from the base station 1 in the cell 2 are assigned to the same time channel. Here, since the terminals K and L of the cell 1 are located far from the base station 2 and similarly, the terminals P and Q of the cell 2 are located far from the base station 1, the respective base stations in uplink communication. Thus, good communication is possible in an autonomous and distributed manner.

  However, in the scheduling method according to the second embodiment, the connection destination bases such as the terminals A, B, and C in the cell 1 and the terminals M, N, and O in the cell 2 shown in FIGS. It is necessary to secure at least one time channel to be allocated to a terminal group located near the station, that is, a terminal group whose transmission power in the uplink is controlled to be low. This is because, as shown in FIG. 12, a channel to which a terminal group with low transmission power is assigned has a high probability that a terminal group requiring high transmission power is assigned in an adjacent cell, and thus there is no terminal with low transmission power. Even in this case, if a channel for the corresponding terminal group is not secured, a situation is considered in which terminal groups that require high transmission power are allocated to the same channel between adjacent cells, causing mutual interference.

  Further, here, terminals having the same base station ID of the control signal received at the time of cell search are grouped, and thus terminals having the same distance and direction from the base station are treated as a group. . This is because the transmission power of the terminal whose transmission power is controlled largely depends on the distance attenuation from the base station, and the amount of interference that the terminal gives to the adjacent cell depends on the distance and direction from the base station. This is because the amount of interference given to the adjacent cell can be kept constant by grouping terminals having the same distance and direction from and assigning the same time channel. However, considering the situation where terminals with greatly different maximum outputs are mixed and support for systems in which the transmission power varies depending on the modulation method used, terminals with different transmission power even if the distance from the base station is the same. Because it exists, it is necessary to deal with such terminals.

  Therefore, in the scheduling method according to the present invention, as described above, firstly, terminals having the same base station ID are grouped. Assume further grouping (subgrouping). By assigning to the same time channel for each subdivided group, high-efficiency communication is possible while maintaining constant interference to adjacent cells even in an environment where terminals with different maximum outputs are mixed. Become.

  When such subgrouping is performed, even terminals located at the same point are divided into different groups due to the difference in transmission power, and a subgroup requiring high transmission power and a subgroup requiring low transmission power are formed. Is done. Here, in the situation where there is an empty slot in the time channel assigned to the subgroup requiring high transmission power, and the slot is insufficient in the time channel assigned to the subgroup requiring low transmission power. Alternatively, a terminal in a subgroup requiring low transmission power may be allowed to be assigned to an empty slot of a time channel to which a subgroup requiring high transmission power is assigned. This is because a time channel to which a subgroup requiring high transmission power is assigned has a high possibility that a terminal group requiring low transmission power is assigned to an adjacent cell, and low transmission power is assigned to an empty frequency channel of the corresponding time channel. This is because interference between adjacent cells does not occur even when a terminal requiring the same is assigned. Also, when assigning a terminal requiring low transmission power to a time channel assigned to a subgroup requiring high transmission power, the transmission power of the corresponding terminal is set high, and a modulation scheme is set according to the set transmission power. May be changed to one that can achieve a high transmission rate.

  Conversely, in a situation where there are empty slots in the sub-group allocation time channel that requires low transmission power and slots are insufficient in the time channel allocated to the sub-group that requires high transmission power, the transmission power is high. When a terminal that requires the transmission is assigned to an empty slot of a time channel to which a subgroup that requires low transmission power is assigned, a large amount of interference occurs between adjacent cells. Therefore, instead of allocating a terminal requiring high transmission power to an empty slot in a time channel to which a terminal group requiring low transmission power is assigned as it is, the modulation scheme of the terminal requiring high transmission power is changed to a low level and transmitted. After the power is set low, the allocation of the time channel to which the subgroup requiring low transmission power is allocated to the free frequency channel may be permitted. By adopting such a form, even when assignment to a time channel to which different subgroups are assigned, while avoiding errors due to setting the transmission power to the corresponding terminal low, By setting the transmission power low, it is possible to suppress interference to adjacent cells.

  As described above, in the second embodiment, the embodiment in which the same time channel is assigned to terminals belonging to the same group has been described. However, the present invention is not limited to this, and the same frequency channel is assigned to terminals belonging to the same group. It is also applicable to cases.

(Third embodiment)
Next, the base station apparatus and terminal apparatus configuration when the scheduling method according to the third embodiment is used. The base station apparatus and terminal apparatus according to the third embodiment are the same as those in the second embodiment. 7 and FIG. 8 can be realized. In the third embodiment, in the cell search by each terminal, not only the base station ID of the received signal but also the slot allocation status of the adjacent cell and the transmission power control information for the terminal are acquired and notified to the connected base station And Therefore, the terminal device according to the third embodiment differs from the configuration according to the second embodiment (FIG. 8) only in the base station ID information of the received signal in the information passed from the downlink demodulation unit 211 to the multiplex unit 210. Instead, the slot allocation information of the adjacent cell and the transmission power control information for each terminal of the adjacent cell (both included in the control downlink broadcast signal) are added.

  Also, the base station apparatus according to the third embodiment differs from the configuration according to the second embodiment (FIG. 7) in that the base station ID information notified from the terminal, the slot allocation information of the adjacent cell, the terminal of the adjacent cell The transmission power control information is demodulated and sent from the demultiplex unit 110 to the scheduling unit 712. In the third embodiment, by changing the device configuration according to the second embodiment as described above, the base station transmits not only the base station ID information but also slot allocation information of adjacent cells and transmission to terminals of adjacent cells. The power control information can be used for scheduling of the own cell.

  Next, FIG. 13 and FIG. 14 show flowcharts of uplink scheduling according to the third embodiment. As shown in FIG. 14, in the same way as in the second embodiment, when a communication request occurs, first, a cell search is performed at the terminal, and all frequencies periodically transmitted from the base station of each cell in the control slot. Channel control information is received (step S221). Next, as shown in step S222, the RSSI of the received signal is measured at each terminal that has received the control signal. However, as described above, the contents of the control information include a base station ID, slot allocation information, transmission power control information of each terminal, and the like. After the measurement of RSSI shown in step S222, the terminal demodulates the reception control signal, the ID information of the base station that transmitted the control signal, the slot allocation information of the terminal accommodated by the base station, and the base station accommodates it. The transmission power control information for the terminal that is being acquired is obtained. A terminal that has made a communication request performs such an operation for a certain period of time, and receives a control signal (cell search) arriving from each neighboring base station.

  Also in the third embodiment, as in the second embodiment, as shown in step S204, the base station measures the interference power in the uplink empty slot of the own cell. Then, the interference power measured for each slot is averaged for each time channel, and the average interference power in each time channel is calculated.

  After performing a cell search for a certain period of time, as shown in step S224, the terminal transmits a connection request to the base station that has transmitted the control signal received with the highest power. The uplink control information such as the connection request is transmitted in the random access slot shown in FIG. 2 as in the second embodiment. At this time, all base station IDs included in the control signal received at the terminal at the time of cell search, slot allocation information of cells (adjacent cells) other than the connection destination, and cells (adjacent cells) other than the connection destination The uplink transmission power control information for the terminal and the number of slots required for uplink communication are notified to the connected base station.

  As described above, the connection request, base station ID, neighboring cell slot assignment information, neighboring cell uplink transmission power control information, and necessary slot number information transmitted from the terminal are as follows. Received at the base station. First, the base station measures received signal power when receiving such information, and generates transmission power control information in the uplink (step S206).

  Next, as shown in step S207, the base station groups terminals based on base station IDs included in all control signals received at the terminal during cell search among these pieces of information. The grouping of terminals here is a process of handling, as a group, terminals whose base station IDs reported from each terminal to the base station all match, as in the second embodiment.

  After grouping the terminals shown in step S207, the base station performs scheduling shown in step S208. Here, the detailed control flow of the scheduling part of step S208 is shown in FIGS.

  15 to 17, as shown in step S250, in the scheduling in the third embodiment, first, signals from the largest number of base stations are received from among the terminal groups previously grouped ( Select the terminal group (in the figure, indicated as terminal group A) that requires the highest transmission power, and assign the time channel in order from that group. Go.

  Next, in step S251, it is determined whether there is a slot assigned terminal in the terminal group A selected in step S250. At this time, if there is a terminal already assigned with a slot in terminal group A (not a terminal that starts communication newly, but a terminal that is already in data communication), the process proceeds to step S252. An empty slot of the time channel used by the slot-assigned terminals is assigned to the terminal unassigned terminal of the terminal group A. At this time, if there are not enough slots to be assigned to the terminal unassigned terminals of terminal group A (determined in step S253), the process proceeds to step S254 to search for another channel that can be assigned to terminal group A. If it is determined in step S253 that there are enough slots, the process moves to step S273, and channel assignment to another terminal group is started.

  If it is determined in step S251 that there is no slot assigned terminal in the terminal group A, the process proceeds to step S254. In step S254, it is determined whether the number of base station IDs reported from the terminal group A is one. Here, when the base station ID reported from the terminal group A is one, only the base station ID of the base station that accommodates the terminal group A (the base station that is currently performing scheduling) is reported, The case where no cell base station ID is reported, that is, the case where the terminal group A is located in the vicinity of the base station is shown.

  If it is determined in step S254 that the number of base station IDs reported from the terminal group A is one, the terminal group A is located in the vicinity of the base station and the transmission power is kept low. Even if transmission is performed by adding, the maximum transmission power is not reached. Therefore, even if the channel is assigned to a channel with high interference power, good characteristics can be obtained by transmitting with a certain amount of power margin, and the interference to adjacent cells is not so great. Therefore, in this case, as shown in step S255, a channel with the highest interference power (referred to as channel Y) is selected and terminal group A is assigned to this channel Y.

  Next, as shown in step S256, it is determined whether a terminal group (terminal group C. A ≠ C) has already been assigned to channel Y. If another terminal group has already been assigned, step S256 is performed. The process moves to S257 to determine whether there is a candidate channel. If it is determined in step S257 that there are no candidate channels, the allocation for the insufficient slots fails, and the process proceeds to step S276. Conversely, if it is determined that there is a candidate channel, the process returns to step S255, and a channel other than the previous channel Y is selected from the remaining channels.

  If a terminal group has not yet been assigned to channel Y, the process moves to step S258, and terminals of terminal group A are assigned to slots of channel Y according to the required number of slots. Here, if the number of slots is insufficient (determined in step S259), the presence / absence of candidate channels is determined as shown in step S260, and if there are no candidate channels, the allocation of insufficient slots fails. Control goes to step S276. If it is determined in step S260 that there is a candidate channel, the process returns to step S255, and another channel is selected from the remaining channels. If the number of slots is sufficient, the process moves to step S276 to consider channel assignment to another terminal group.

  In step S254, if the number of base station IDs reported from the terminal group A is not one, it is considered that the terminal group A is located not near the base station but near the cell edge. It is desirable to assign to a channel with low interference from the cell. Therefore, the channel with the lowest interference power (referred to as channel X) is selected as shown in step S261, and another terminal group (terminal group B. A ≠ B) is already assigned to channel X as shown in step S262. If another terminal group is not assigned, the process proceeds to step S264, and it is considered to assign the terminal group A to the channel X. Conversely, if another terminal group has already been assigned to channel X, the process proceeds to step S263 to check whether there is another candidate channel. If there is no other candidate, the process proceeds to step S276. If there is, return to step S261 to select another channel.

  In step S264, it is determined whether the terminal group of the adjacent cell (referred to as adjacent cell Z) has been assigned to the channel X. The determination in step S264 is made based on the slot allocation information of neighboring cells reported from all terminals in the own cell in step S205. If it is determined in step S264 that the terminal group using channel X is not in an adjacent cell, the process proceeds to step S271, and the allocation of terminals in terminal group A to the slot in channel X is set to the required number of slots. Do it accordingly.

  If it is determined in step S264 that there is a terminal group using channel X in the adjacent cell, the process proceeds to step S265, and the interference power of channel X is set to a certain threshold value (threshold 1). judge. Here, the threshold 1 is, for example, a value of interference power that satisfies a required error rate of uplink communication (if the observed interference power exceeds the threshold 1, the required error rate cannot be satisfied, If the threshold value is 1 or less, the required error rate is set to a value).

  As a result of the determination in step S265, when it is determined that the interference power measured in the channel X is larger than the threshold 1, uplink communication is performed with high power in the channel X of the adjacent cell Z as shown in step S266. It is determined that the performing terminal is located in the vicinity of the cell edge close to the own cell among the cell edges of the adjacent cell Z. In this case, even if the terminal group A is assigned to the channel X, good characteristics cannot be secured. Therefore, as shown in step S267, it is checked whether there is another free channel. If there is, the process returns to step S261. If not, channel assignment to terminal group A is stopped and assignment to other terminal groups is performed.

  On the other hand, as a result of the determination in step S265, when it is determined that the interference power measured in the channel X is smaller than the threshold 1, the process proceeds to step S268, and the transmission power of the terminal group allocated to the channel X in the adjacent cell. Is determined as to a certain threshold value (threshold value 2). The determination in step S268 is performed based on the transmission power control information of the terminal of the adjacent cell reported in step S204. Here, the threshold value 2 is set, for example, in the vicinity of a power value necessary for a terminal having a distance from the base station to be about a half of the cell radius to perform uplink communication.

  As a result of the determination in step S268, if it is determined that the transmission power of the terminal group assigned to channel X in the adjacent cell is larger than the threshold value 2, as shown in step S269, high in channel X of adjacent cell Z. It is determined that the terminal performing uplink communication with power is located in the vicinity of the cell edge far from the own cell among the cell edges of the adjacent cell Z. In this case, next, the process proceeds to step S270, and it is determined whether or not the base station ID of the adjacent cell Z is included in the base station ID reported from the terminal group A.

  In step S270, when the base station ID of the adjacent cell Z is not included in the base station ID reported from the terminal group A, the terminal group A and the terminal group using the channel X in the adjacent cell Z It is considered that the distance is very far among adjacent cells, and that each uplink communication hardly causes interference with each other's base station. Therefore, when the terminal group A is assigned to the channel X, good characteristics can be ensured, and the interference given to the adjacent cell is also small. Therefore, the process moves to step S271, and the slot of channel X is assigned to terminal group A.

  On the other hand, when the base station ID of the adjacent cell Z is included in the base station ID reported from the terminal group A in step S270, the terminal group A is located around the cell edge between the own cell and the adjacent cell Z. It is thought to do. Here, when the terminal group A is assigned to the channel X, the uplink communication by the terminal group A can secure good characteristics, but the uplink communication by the terminal group A may cause a large interference to the adjacent cell Z. Becomes higher. Therefore, in this case, the process moves from step S270 to step S272 to search for another free channel. If there is another free channel, the process returns to step S261. If there is no other free channel, the process moves to step S271, and the terminal group A is assigned to the channel X.

  Further, as a result of the determination in step S268, if it is determined that the transmission power of the terminal group assigned to channel X in the adjacent cell is smaller than the threshold value 2, as shown in step S273, the channel X of adjacent cell Z Is determined to be assigned a terminal group that requires low transmission power (located near the base station of the adjacent cell Z). In this case, next, the process proceeds to step S274, and it is determined whether or not the base station ID of the adjacent cell Z is included in the base station ID reported from the terminal group A.

  In step S274, if the base station ID of the neighboring cell Z is not included in the base station ID reported from the terminal group A, the terminal group A is far from the neighboring cell Z, and the terminal group A is located in the neighboring cell Z. It is considered that it hardly interferes with the In this case, it is less desirable to allocate the terminal group A to the same channel as the terminal group requiring the low transmission power of the adjacent cell Z. This is because, as described above, a terminal group that requires low transmission power has sufficient transmission power and can transmit with a certain margin, so communication is possible even in a channel where a certain amount of interference is observed. This is because it is considered that the overall efficiency is better if a corresponding channel is secured for a terminal group that gives large interference to the adjacent cell Z (located near the cell edge close to the adjacent cell Z). Therefore, the process moves from step S274 to step S272 to search for another empty channel. If there is another free channel, the process returns to step S261. If there is no other free channel, the process moves to step S271, and the terminal group A is assigned to the channel X.

  In step S274, when the base station ID of the adjacent cell Z is included in the base station ID reported from the terminal group A, it is determined that the terminal group A is located near the adjacent cell Z, and the process proceeds to step S271. As shown, terminal group A is assigned to channel X.

  Through the above processing, channel assignment to one terminal group can be performed, and then slot assignment to terminals belonging to the group is performed. In the slot allocation to each terminal, an empty slot in the time channel allocated to the group is allocated according to the required number of slots of each terminal (step S271). In such slot allocation, highly efficient slot allocation can be realized by allocating to each terminal in order from the slot with the lowest interference power. Further, considering not only the interference power but also the fading situation at each terminal, the slot having the maximum received SINR at the base station is assigned to each terminal, so that the reception characteristics at the control station apparatus can be further improved. . However, depending on the number of slots required by the terminal, one channel may not have enough slots. If there are not enough slots, the process moves from step S275 to step S277 to search for other candidate channels. As a result, if there are other candidate channels, the process returns to step S261 to consider the assignment of a new channel. If there are enough slots, the process proceeds to step S276, and the above processing is repeated until there is no terminal group to which no channel is assigned. When there are no terminal groups to which no channel is assigned, the scheduling according to the present invention is terminated.

  Here, when a plurality of neighboring cells are targeted in the process of step S268, there may be a cell that is determined to perform the process of step S269 and a cell that is determined to perform the process of step S273. In such a case, the subsequent control is not necessarily one way. Therefore, in the third embodiment, when there are a plurality of cells having different correspondences in step S268, priority is given to the case where the transmission power of the terminal group assigned to channel X exceeds the threshold value 2, and the process of step S269 is performed. Shall.

  Thus, the scheduling according to the third embodiment is completed, and the base station broadcasts the slot allocation information and the transmission power control information as a scheduling result in the downlink as in the second embodiment (FIG. 11). Based on this broadcast information, the terminal performs transmission power control and performs uplink communication in the assigned slot. A terminal located near the base station can perform better communication by performing transmission with transmission power obtained by adding a margin to the transmission power notified by the transmission power control information.

  Also in the third embodiment, as in the second embodiment, the time channel assigned to the terminal group is changed only when the interference observed at the base station changes significantly. Needs to reset all previous assignments and then group new terminals and perform scheduling. In addition, when the transmission power required for uplink communication changes or when the position of the terminal moves greatly, the terminal group is replaced only for the corresponding terminal. In that case, the terminal group is assigned to the terminal group. The channel is not changed.

  Similarly to the second embodiment, when the transmission power of the terminals is greatly different in the group in which the terminals having the same base station ID are grouped, the terminals having the same transmission power are gathered together and further subdivided into groups (sub Group), and assign to the same time channel for each subgroup. Furthermore, in a situation where there are empty slots in the time channel assigned to the subgroup requiring high transmission power, and slots are insufficient in the time channel assigned to the subgroup requiring low transmission power, It is also possible to allow a terminal in a subgroup that requires low transmission power to be assigned to an empty slot of a time channel to which a subgroup that requires high transmission power is assigned. On the other hand, in the situation where there are empty slots in the allocation time channel of the subgroup requiring low transmission power, and there are not enough slots in the time channel allocated to the subgroup requiring high transmission power, A mode in which a modulation scheme of a terminal that requires high transmission power is changed to low and transmission power is set to low may be allowed to be assigned to an empty slot of a time channel to which a subgroup requiring low transmission power is assigned.

  By performing the scheduling as described above, it becomes possible to grasp the approximate position of the terminal of the neighboring cell that could not be grasped in the second embodiment, thereby not only considering the interference from the neighboring cell. Thus, it is possible to perform adaptive scheduling in consideration of interference given to adjacent cells. Therefore, compared with the second embodiment, inter-cell interference in uplink communication can be further reduced, and efficient communication can be performed as a whole system.

(Fourth embodiment)
Next, a slot allocation method according to the fourth embodiment of the present invention will be described. The slot allocation method according to the fourth embodiment is a slot allocation method in downlink communication from a base station to a mobile station, and considers the influence of interference coming from an adjacent cell, with the same level of transmission power at the base station. A plurality of terminals requiring level are adaptively allocated to different frequency channels of the same time channel. FIG. 18 shows an example of an assignment result when such adaptive slot assignment is performed.

  FIG. 18A shows the arrangement of a cell and terminals in the cell, and FIG. 18B shows the transmission power required for downlink communication for each terminal in the cell. In such a situation, when the slot allocation method according to the fourth embodiment of the present invention is applied, terminals having the same level of transmission power required for the downlink are grouped. Here, terminal A, terminal B, and terminal C are grouped as group 1, terminal D, terminal E, terminal F, and terminal G are grouped as 2, and terminal H and terminal I are grouped as group 3. Then, terminals belonging to the same group are assigned to different frequency channels of the same time channel. Here, group 1 is time channel 3, group 2 is time channel 2, and group 3 is time channel 5. As a result, channel allocation as shown in FIG. 18 (c) is performed, and transmission power required for downlink communication to the terminal is maintained at the same level for each time channel, and average interference power given to adjacent cells Can be kept substantially constant for each time channel. Hereinafter, a channel allocation procedure based on such adaptive slot allocation will be described.

  First, FIG. 19 shows a slot configuration according to the fourth embodiment of the present invention. As shown in FIG. 19, in the slot configuration according to the fourth embodiment of the present invention, the number of frequency channels is 12, and control slots (hereinafter, a single time channel for transmitting control information in a single frequency channel is called a control slot). The number of time channels including control information transmission time channels over a plurality of frequency channels is referred to as a control slot group), and the same frequency band is used in all cells. In the following, a system in which base stations are synchronized will be described as an example. However, the present invention is not limited to the inter-base station synchronization system. Applicable.

  Further, in the case of the inter-base station synchronization system, it is assumed that the cell arrangement is in a state as shown in FIG. 20, and the transmission timing of the control slot group is a common timing in all cells as shown in FIG. Alternatively, the timing may be different for each cell as shown in FIG. Furthermore, the transmission timing of the control slot may be different for each frequency channel. Hereinafter, a case where the control slot group is transmitted at a common timing predetermined in all cells will be described.

  First, FIG. 22 shows an apparatus configuration of a terminal when performing slot allocation according to the fourth embodiment of the present invention. FIG. 22 is a block diagram of a terminal device configuration. 22, 100 is an antenna unit, 101 is a radio reception unit, 102 and 111 are A / D conversion units, 103 is a symbol synchronization unit, 104 is a guard interval removal unit, 105 is an S / P unit, 106 is an FFT unit, 107 Is a propagation path estimation and demapping unit, 108 is a P / S unit, 109 is an error correction decoding unit, 110 is a demultiplexing unit, 112 is an RSS measurement unit, 113 is an interference power measurement unit, 114 is a control unit, and 115 is It is an uplink transmission unit.

  As shown in FIG. 22, the terminal in the case of performing slot allocation according to the fourth embodiment of the present invention has an RSS measurement unit 112 unlike the conventional example, and measures the received power level in the downlink. In addition, the interference power measurement unit 113 measures the interference power. However, in FIG. 22, the interference power measurement unit 113 is located after the FFT unit 106 and is configured to measure the power of the interference signal after the FFT. However, the configuration is not limited thereto, and the interference signal power before the FFT is measured. It is good also as a structure to measure.

  The RSSI and the interference power information in each time channel measured in this way are sent to the control unit 114 in the same manner as the information data, and an uplink packet is formed. Then, information is transmitted to the base station by the uplink transmission unit 115.

  Processes other than these (such as demodulation of information data) are performed in the same manner as in the conventional technique. First, the received signal is symbol-synchronized by the synchronization unit 103 via the A / D conversion unit 102. Thereafter, the guard interval is removed by the guard interval (GI) removal unit 104, serial / parallel converted by the S / P conversion unit 105, and then sent to the FFT unit 106, from the time domain signal to the frequency domain signal. Converted to The received signal converted into the frequency domain in this way is subjected to propagation path estimation and demapping in the propagation path estimation demapping unit 107, and after parallel / serial conversion in the P / S conversion unit 108, an error occurs. The transmission data is decoded by the correction decoding unit 109 and sent to the demultiplexing unit.

  FIG. 23 is a block diagram of the device configuration of the base station. 23, 120 is a scheduling unit, 121 is a multiplex unit, 122 is an error correction code unit, 123 is an S / P unit, 124 is a mapping unit, 125 is a transmission power control unit, 126 is an IFFT unit, and 127 is a P / P unit. S section, 128 is a guard interval insertion section, 129 is a D / A conversion section, 130 is a radio transmission section, 131 is an antenna section, and 132 is an uplink reception section.

  As shown in FIG. 23, the base station in the case of performing slot allocation according to the fourth embodiment of the present invention differs from the conventional example in that the RSSI information and the interference information obtained from the uplink receiving unit are sent to the scheduling unit 120. And slot assignment according to the fourth embodiment of the present invention. Then, in the slot allocated by the scheduling unit 120, transmission of information data of each terminal is performed. At this time, transmission power control information for each terminal is obtained from the scheduling unit 120, and the transmission power control unit 125. Similar to the scheduling unit 312 shown in FIG. 3, the scheduling unit 120 constitutes a transmission power determination unit in the base station apparatus (control station apparatus). Moreover, the uplink receiving part 132 comprises the receiving part in a base station apparatus (control station apparatus). More specifically, the uplink reception unit 132 includes the antenna unit 300, the radio reception unit 301, the A / D conversion unit 302, the synchronization unit 303, the GI removal unit 304, the S / P conversion unit 305, which are illustrated in FIG. An FFT unit 306, a channel estimation demapping unit 307, P / S conversion units 308-a to l, error correction decoding units 309-a to l, and a demultiplex unit 310 are configured.

  Next, FIGS. 24 and 25 show flowcharts of slot allocation in the base station according to the fourth embodiment of the present invention. Hereinafter, the control flows shown in FIGS. 24 and 25 will be described while actually grouping the terminals in the cell 1 of FIG. 26A and performing channel assignment. Here, channel 2 and slot allocation have already been performed in cell 2 (adjacent cell of cell 1) in FIG. 26A, and the channel allocation status as shown in FIG. To do. At this time, the terminals I to T of the cell 2 are at the positions shown in FIG. 26A, and the transmission power (transmission power required for the downlink) in the base station for each terminal is as shown in FIG. Suppose that

  In the above situation, when a communication request occurs in terminal A, terminal B, and terminal C located in cell 1, as shown in FIGS. 24 and 25, first, the control slot group is transmitted from the base station of each cell. (Step S2), the terminals A to C receive the control information of all frequency channels (step S21), and measure the RSSI of the received signal at each terminal as shown in step S22. However, the control slot group periodically transmitted from the base station of each cell is transmitted with power that can be received also by the terminal located at the cell edge, and the content of the control information is as follows. Transmission power information (information indicating how much transmission power is being transmitted), slot allocation information, and the like.

  After the RSSI measurement at each terminal, terminals A to C demodulate the received signal and obtain transmission power information at the base station when transmitting control information, as shown in step S23. Next, based on the transmission power information in the base station obtained in step S24 and the RSSI obtained in step S22, the amount of radio wave attenuation in the propagation path (propagation loss: here propagation loss = transmission power−RSSI). ) Is calculated (step S25).

  Further, as shown in step S26, each terminal (terminals A to C) measures the interference power coming from the adjacent cell. Each of the terminals A to C notifies the base station via the uplink of the interference power obtained in this way and the downlink propagation loss information between the base station and the terminal obtained in step S26 (step S27). ).

  Through the procedure described above, the base station-terminal downlink propagation loss information and the interference power information arriving from adjacent cells necessary for performing adaptive slot allocation according to the fourth embodiment of the present invention in the base station Can be obtained for each terminal.

  Next, in the base station, as shown in step S5 to step S7 in FIG. 24, the terminals are grouped based on the propagation loss information of each terminal obtained via the uplink. The terminal grouping here means that, as shown in FIG. 27 (a), the transmission power required for performing downlink transmission to each terminal is calculated from the propagation loss of each terminal (step S6). As a result, this is a process of handling terminals that require the same transmission power as a group (step S7).

  In addition, as shown in FIG. 26 (b) and FIGS. 27 (a) and (b), it is assumed here that the downlink transmission power for each terminal takes a discrete value. The present invention is also applicable when the downlink transmission power for each terminal takes a continuous value.

  As shown in FIG. 27 (a), here, the downlink transmission power for terminal A and the downlink transmission power for terminal C are at the same level, and are in the same group (here, group 2). Will belong to. Terminal B requires high transmission power and belongs to a different group (here, referred to as group 1) from terminals A and C.

  After the terminals having communication requests (terminals A to C in this case) are grouped in this way, the base station performs time channel allocation to each group and frequency channel allocation to each terminal belonging to the group. . In the slot allocation method according to the fourth embodiment of the present invention, time channels are allocated in order from the group with the highest transmission power in the downlink (step S8). Therefore, here, the time channel is assigned from group 1 (only terminal B belongs), and as shown in step S9, the terminal that has already been assigned a slot to the selected group (group 1). Determine if exists. Here, since only terminal B that newly starts communication belongs to group 1, the process proceeds to step S10 and is observed at terminal B of group 1 in an empty time channel (here, all time channels). The time channel with the lowest interference power is assigned to group 1.

  As shown in FIG. 28, the interference power in the time channel 4 is the smallest among the interference powers of each time channel observed in the cell 1, and the time channel 4 is assigned to the group 1. As shown in FIG. 28, the interference power given to the cell 1 is the minimum in the time channel 4, which is located near the base station of the cell 2 and the downlink transmission power is set low. This is because the terminals I to K are assigned to the time channel 4.

  By such a procedure, time channel assignment to group 1 is performed, and then frequency channel assignment to each terminal belonging to the group is performed (steps S11 to S13). First, as shown in step S11, a downlink data amount for a terminal not assigned to a slot (terminal B) in the corresponding group (here, group 1) is calculated, and as shown in step S12, the data amount required per frame is calculated. Calculate the number of frequency channels. Then, as shown in step S13, an empty frequency channel is assigned to the corresponding terminal in accordance with the required number of frequency channels. Here, if the number of necessary frequency channels of terminal B is 3, three frequency channels of time channel 4 are allocated to terminal B as shown in FIG.

  This completes the slot assignment for group 1. However, since there are still groups that need to be assigned in addition to group 1, the process returns to step S8, and the time channel assignment to the corresponding group (here, group 2). To do. When a time channel is assigned to group 2 by the same procedure as described above, time channel 7 having the smallest interference power other than the time channel already assigned to group 1 is assigned to group 2.

  After this time channel assignment in units of groups, frequency channels are assigned to the terminals A to C belonging to the group 2 to which the time channel is assigned in the same manner as before, and the slot assignment procedure is terminated. The result of such slot assignment is notified to the terminals in the cell by the control slot group (steps S16 and S17), and thereafter, each terminal occupies the assigned slot for a certain period of time and performs communication.

  Here, when the slot allocation according to the fourth embodiment of the present invention is updated and the allocation to a certain time channel is changed to a terminal group different from that of the previous frame, in order to minimize the fluctuation of interference to neighboring cells It is desirable to operate the algorithm so that a terminal group that requires transmission power close to that of the terminal group assigned to the corresponding time channel in the previous frame is assigned as much as possible.

  The slot allocation results so far are shown in FIG. As shown in FIG. 29, terminal B that requires high transmission power in the downlink of cell 1 is assigned to the same time channel as terminals I to K in which downlink transmission is performed with the lowest transmission power in cell 2. In addition, terminals A and C having slightly higher transmission power in cell 1 are assigned to the same time channel as terminal L in which downlink transmission is performed with lower transmission power in cell 2.

  Thus, by performing slot allocation according to the fourth embodiment of the present invention, the situation where terminals that require high transmission power in both adjacent cells are allocated to the same time channel is reduced, and inter-cell interference can be suppressed. it can.

  Furthermore, the slot allocation process according to the same procedure will be described in the case where a new communication request is issued from the terminals D to H in the cell 1. First, as in the previous step (steps S21 to S29), each terminal that has received control information from the base station reports downlink propagation loss information and interference power information to the base station via the uplink. Here, assuming that the downlink transmission power for terminals D to H is as shown in FIG. 27A, terminals D and F are added to group 2 to which terminals A and C already belong. Further, the terminal E is added to the group 1 to which the terminal B already belongs, and the terminal G belongs to the group 3 and the terminal H belongs to the group 4 (steps S5 to S7).

  Next, as shown in step S8, if time channels are assigned in order from the group with the highest transmission power in the downlink, the time channel is assigned to group 1 to which terminal E belongs. At this time, the terminal B belongs to the group 1, and the time channel 4 has already been assigned. Since the number of free frequency channels of the time channel 4 is larger than the number of required frequency channels of the terminal E, the terminal E is assigned the required frequency channels from the free frequency channels of the time channel 4 (steps S11 to S11). Step S16).

  Similarly, the terminals D and F are assigned to the free frequency channel of the time channel 7 to which the group 2 is assigned first, but the free frequency channel in the time channel 7 has three frequencies as shown in FIG. There are only channels. If the required frequency channel number of the terminal D is 3, it is possible to assign the terminal D to the time channel 7, but if the required frequency channel number of the terminal F is 5, the terminal F is assigned to the time channel 7. It cannot be assigned. In such a case, terminal D is assigned to the remaining frequency channel of time channel 7, and terminal F is assigned to a time channel to which no other group is assigned. Thus, control is performed to increase the number of time channels allocated to the same group (steps S14 and S15).

  Therefore, in the time channel to which no group is assigned (time channels 1 to 3, 5, 6, 8), the time channel 3 with the lowest interference power reported from the terminal F is assigned to the terminal F (group 2), Frequency channels are allocated by the number of necessary frequency channels of terminal F (five frequency channels).

  Also, among the remaining time channels, the time channel 8 with the lowest interference power reported from the terminal G is assigned to the group 3 to which the terminal G belongs, and the frequency channels are assigned by the number of necessary frequency channels of the terminal G. It becomes. Similarly, the time channel 6 is assigned to the group 4 to which the terminal H belongs, and frequency channels corresponding to the number of necessary frequency channels of the terminal H are assigned.

  The above slot allocation results are shown in FIG. As shown in FIG. 30, terminals B and E that require high transmission power in the downlink of cell 1 are assigned to the same time channel as terminals I to K in which downlink transmission is performed with low transmission power in cell 2. . Also, terminals A, C, D, and F that require slightly higher transmission power in the cell 1 downlink are assigned to the same time channel as terminals L to O in which downlink transmission is performed in cell 2 with lower transmission power.

  Further, terminals G and H that do not require high transmission power in cell 1 are assigned the same time channel as terminals T and S that require high transmission power in cell 2, respectively. In this way, it is possible to reduce the situation in which terminals having high transmission power are allocated to the same time channel in adjacent cells, and this can be achieved by repeating the above procedure even in the situation where there are multiple adjacent cells. Will be assigned.

  As described above, by repeating the slot allocation procedure according to the fourth embodiment of the present invention, terminals that require the same level of transmission power in the downlink are grouped, and interference coming from neighboring cells is considered. Thus, a different time channel can be assigned to each group. In this way, by adaptively allocating slots according to the required transmission power and interference coming from neighboring cells, the situation where terminals having high transmission power in both neighboring cells are assigned to the same time channel is reduced, In addition, by performing similar control for a terminal that newly starts communication, it is possible to suppress a large fluctuation in the average interference power given to adjacent cells, so that inter-cell interference can be reduced. it can.

  In addition to the slot allocation procedure according to the present invention, a time channel that can be used for each cell is set in advance, or the transmission power of each time channel is set in advance to a different value for each cell, so that adjacent cells However, in the method of previously limiting the usable time channels in this way, in a situation where there are many terminals that require the same transmission power level in a cell, etc. Although there is a channel, time channel allocation is not performed, resulting in a situation where efficiency decreases.

  On the other hand, in the slot allocation according to the present invention, usable time channels are not limited in advance, and time channel allocation is dynamically performed according to necessary transmission power and interference power arriving from adjacent cells. As the base station of each cell performs autonomous control in an autonomous and distributed manner, it is possible to respond flexibly to the increase or decrease of terminals and the addition of cells, realizing highly efficient communication while reducing inter-cell interference it can.

  Next, a modification of the fourth embodiment of the present invention will be described. First, a form in the case of applying adaptive modulation will be described. In the slot allocation procedure according to the fourth embodiment of the present invention, the modulation method of a signal when transmitting user data has not been mentioned, but in the case of using multicarrier transmission such as OFDM, The same modulation method may be used, or a different modulation method may be used for each subcarrier. Instead of always using the same modulation method, a time-dependent modulation method is used according to the propagation path condition. It is good also as a form.

  Similarly, even when OFDM is not used in each frequency channel (when single carrier transmission is used for each frequency channel), a mode in which a temporally different modulation scheme is used according to the propagation path condition may be used. As described above, the procedure for changing the modulation scheme according to the propagation path condition is to measure the received signal power and interference power in the slot assigned to each terminal, calculate the received SINR after taking the ratio, and then change the received SINR to the received SINR. The corresponding modulation method is selected. Thus, by combining adaptive modulation with slot allocation according to the fourth embodiment of the present invention, more efficient communication can be realized.

  Next, another modified example regarding the time channel allocation procedure will be described. In the slot allocation procedure according to the fourth embodiment of the present invention, time channel allocation is performed in order from the terminal group that requires the highest transmission power among the terminal groups having a communication request. The procedure may be such that time channel allocation is performed in order from a terminal group capable of transmitting with the lowest transmission power among terminals having a communication request. In this case, a time channel with high interference power is allocated from the remaining time channels that are not allocated in the order of terminal groups with the lowest transmission power in the downlink.

  Further, in the fourth embodiment of the present invention, in the remaining time channels that are not assigned in order from the terminal group that requires the highest transmission power among the terminal groups having a communication request, the corresponding group Assigned a time channel that minimizes the interference power measured at the terminal. However, when the required transmission power is not so high in a group having a communication request, a time channel that minimizes the interference power is assigned to the group, and then a communication request is made at a terminal located near the cell edge. Even if a group that requires very high transmission power is formed, a new channel that requires high transmission power cannot be assigned a time channel that minimizes interference power.

  In order to avoid such a situation, separately from the fourth embodiment of the present invention, as shown in FIG. 31, the transmission power levels of several stages set in advance are associated with the interference levels of each time channel, Assuming a situation in which a group requiring a transmission power level higher (lower) than that of its own group is formed, the time channel may be assigned based on the association between the transmission power level and the interference power level. Also in this case, not only the time channel of the interference level corresponding to the transmission power level shown in FIG. 31 is targeted for allocation, but in a situation where the number of terminals having the same transmission power level is large and cannot be allocated to the target time channel. By setting a time channel that does not correspond to the transmission power level as an assignment target, it is possible to dynamically cope with the surrounding situation.

  Further, apart from the fourth embodiment of the present invention, the remaining time channels that are not assigned in order from the terminal group that requires the highest (low) transmission power among the terminal groups that have communication requests. Of these, a procedure for allocating an arbitrary time channel from a time channel that is equal to or less than a threshold value of interference power that satisfies predetermined required reception quality may be used.

  Next, contents of control information in the downlink, contents of information to be reported from each terminal to the base station via the uplink, and another form regarding a frequency channel allocation method will be described. In the fourth embodiment of the present invention, transmission power information in a base station when transmitting control information is transmitted in a control slot group in the downlink, and a terminal estimates propagation loss and interference power obtained from RSSI, The report was sent to the base station via the uplink.

  Separately, transmission power information in the base station is transmitted in the downlink control slot group as in the fourth embodiment of the present invention, but each terminal reports the measured RSSI and interference power to the base station. It is good also as a form. In this case, after the propagation loss in the propagation path is calculated in the base station from the difference between the transmission power in the base station and the RSSI in the reported terminal, each propagation loss is calculated from the propagation loss in the same manner as in the fourth embodiment of the present invention. The transmission power required for downlink transmission to the terminals is calculated, and grouping based on the transmission power of each terminal is performed. By using this form, it is possible to reduce the procedure for obtaining the propagation loss at the terminal and its calculation unit.

  Separately, the downlink control slot group transmits the same information as in the fourth embodiment of the present invention, but each terminal measures the RSSI, calculates the propagation loss, and then transmits the transmission power control information. It is also possible to obtain and report the interference power to the base station. However, the transmission power control information is obtained by subtracting the transmission power when transmitting the control slot group from the transmission power necessary for performing downlink transmission obtained from the propagation loss of each terminal. It shows how much power should be raised or lowered from the power.

  The downlink control slot group transmits the same information as in the fourth embodiment of the present invention, but each terminal uses the received signal power of each frequency channel instead of RSSI indicating the received power of the entire frequency channel. It is good also as a form which measures and averages and reports this and interference power to a base station. In this case, after the propagation loss in the propagation path is calculated in the base station from the average difference between the transmission power in the base station and the reception power in each frequency channel in the terminal, as in the fourth embodiment of the present invention, The transmission power required for downlink transmission to each terminal is calculated from the propagation loss, and grouping based on the transmission power of each terminal is performed.

  Further, the downlink control slot group transmits transmission power information in the base station as in the fourth embodiment of the present invention, but each terminal measures the received signal power of each frequency channel instead of RSSI, This and the interference power may be reported to the base station. In this case, the received signal power of each frequency channel is averaged in the base station, and the propagation loss in the propagation path is calculated in the base station from the difference between the average of the transmission power in the base station and the previously obtained received power. Similarly to the fourth embodiment of the present invention, the transmission power required for downlink transmission to each terminal is calculated from the propagation loss, and grouping based on the transmission power of each terminal is performed.

  Thus, in the form in which the received signal power of each frequency channel measured by the terminal is reported to the base station via the uplink, the amount of information in the uplink increases, and the uplink efficiency slightly decreases. However, when the base station grasps the received signal power for each frequency channel at each terminal, when the frequency channel is allocated to the terminals of each group after the time channel allocation to the group, there is a difference in the received power due to the influence of fading. Of the generated frequency channels, it is possible to assign a frequency channel that provides the best received power to each terminal, and the efficiency in the downlink is improved.

  Also, unlike the fourth embodiment of the present invention, the transmission power in the base station is not transmitted in the downlink control slot group, and the received signal power of the RSSI or each frequency channel is measured at the terminal, and the interference power is measured. It is good also as a form reported to a base station by an uplink. At this time, the received signal power of each frequency channel may be averaged, or may not be averaged, and information for frequency channels may be reported. By adopting such a form, it is possible to reduce control information in the downlink.

  In any of the above forms, the period for reporting the measurement results of the received signal power and interference power at the terminal to the base station via the uplink may be set for each frame or may be set at an arbitrary fixed interval.

  Further, as described above, the transmission timing of the control slot group in the downlink may be a timing common to all cells or may be a timing different for each cell (FIG. 21). Here, as shown in the fourth embodiment of the present invention, if the transmission timing of the control slot group in the downlink is the same timing in all cells, the downlink control slot group can be received also by a terminal located at the cell edge. Since the transmission is performed with electric power, control information between adjacent cells may interfere with each other in terminals located near the cell edge. In response to such a problem, the control information transmitted in the power reaching the cell edge (maximum power that can be transmitted) interferes with each other by setting the transmission timing of the control slot group in the downlink to be different for each cell. Can be avoided.

  Furthermore, when slot allocation according to the present invention is performed, high interference power is measured in a time channel to which control information is allocated in the downlink of an adjacent cell. Thus, a terminal group with low transmission power is dynamically allocated. Thereby, it is also possible to avoid a situation in which control information and user data interfere between cells.

  In this way, by making the transmission timing of the control slot group in the downlink different for each cell, a situation in which control information transmitted with power reaching the cell edge interferes with each other is avoided, and control information is transmitted in adjacent cells. It is possible to avoid interference between control information and user data by assigning a terminal with low transmission power to the time channel being transmitted, but there is a problem in the base station of the adjacent cell due to some cause, and control in the downlink Signals with very high power may be transmitted in neighboring cells in the information transmission time channel. In such a case, the control information receives interference having high power, and many terminals in the cell cannot communicate. As a countermeasure against such a problem, as shown in FIG. 32, the control slot group in the downlink is not always transmitted at a predetermined timing (FIG. 32A), but is adapted according to the interference of adjacent cells. Alternatively, it is possible to adopt a form (FIG. 32 (b)) that gives flexibility to change the transmission timing.

  This is because interference power is measured simultaneously with reception of control information in the downlink (SINR measurement or control information error may be detected), and interference having power exceeding a certain threshold is observed. In the case where the control information is continuously incorrect, the control slot group is transferred to the time channel with the lowest interference power among the idle time channels. If there is no idle time channel, the communication with the terminal assigned to the time channel with the lowest interference power is disconnected (interrupted), and the control slot group is moved to the available time channel.

  By adopting such a form, the communication of some terminals is forcibly disconnected, but in the situation where control information cannot be received correctly due to the influence of interference, the communication of many terminals in the cell is disconnected. Therefore, the communication performed by many terminals in the cell can be maintained by adopting the form described above. At this time, in a frame immediately before moving the control slot group, the terminal may be notified that the control slot group is moved, or such control is not performed, and the terminal cannot receive the control slot group. In this case, the terminal side may have a mechanism for detecting the control slot group over the entire next frame.

  Next, another form relating to the timing for updating the slot allocation in accordance with changes in the surrounding environment will be described. In the fourth embodiment of the present invention, after slot allocation, each terminal occupies the allocated slot for an arbitrary fixed time for communication, and the allocation to a certain time channel is changed to a terminal group different from the previous frame. In this case, a terminal group requiring transmission power close to that of the terminal group assigned to the corresponding time channel in the previous frame is operated so as to be assigned as much as possible.

  That is, once a terminal group is assigned to a certain time channel, the assignment is not changed as much as possible, or is assigned to a terminal group that requires close transmission power even if it is changed. This is because when the terminal group assigned to the time channel is frequently changed, the interference observed in the adjacent cells changes frequently, causing interference between adjacent cells and degrading characteristics.

  Also, when changing the assignment to a terminal group that requires transmission power (particularly extremely high transmission power compared to the previous frame) that is significantly different from the transmission power required for the terminal group assigned in the previous frame, This is because the observed interference changes abruptly, resulting in degradation of characteristics. However, in the following cases, it is considered that better characteristics can be obtained by updating the slot assignment.

  In general, since the terminal moves during communication, the distance from the base station changes due to movement, and transmission power different from the group to which the terminal belongs may be required. As described above, the slot assignment may be updated when the transmission power required for the downlink changes as the terminal moves, that is, when the group configuration is different from the previous group configuration. In addition, when communication is performed in the allocated slot, interference with high power is observed in the terminal (received SINR is deteriorated, data is continuously erroneous), and the slot allocation is updated. It is good also as a form.

  In these cases, it is possible to review the slot allocation for all terminals in all groups, or review the slot allocation only to terminals that correspond to the situation where the transmission power required for the downlink changes. It is good also as a form which performs. However, even when such slot allocation is reviewed, a terminal group or terminal that requires transmission power as close as possible to the terminal group allocated in the previous frame is used in order to suppress a sudden change in interference to adjacent cells. It is desirable to assign to a corresponding time channel (slot).

  Also, in situations where the number of surrounding cells is small, such as isolated cells, the slot assignment may be updated frequently, and the terminal group assigned in the previous frame corresponds to a terminal group whose transmission power is significantly different. It may be assigned to a time channel.

  Next, another mode regarding a case where a plurality of time channels are allocated to one group to which a plurality of terminals requiring the same transmission power belongs in the downlink will be described. In the fourth embodiment of the present invention, the number of frequency channels required per frame is calculated in downlink transmission to each terminal in a group to which a time channel is allocated, and the number of frequency channels required for each terminal is free. A frequency channel was assigned to the terminal. When the number of free frequency channels of the corresponding time channel is less than the required frequency channel number, allocation to another time channel is performed, so that a plurality of terminals that require the same transmission power can be accommodated in one hour channel as much as possible. Had been assigned to.

  Aside from this form, the maximum number of time channels that can be allocated to a terminal group that requires a certain level of transmission power in the downlink is determined in advance, and the base station is free to make a range that does not exceed the maximum number of time channels. It is good also as a form which can perform allocation. At this time, rather than predetermining the maximum number of time channels that can be assigned to a terminal group that requires a certain level of transmission power, the base station measures the interference coming from adjacent cells and estimates the number of adjacent cells. Thus, a mechanism for adjusting the maximum number of time channels according to the number of adjacent cells may be provided.

  In addition, when a plurality of time channels are allocated to a certain group, terminals belonging to the corresponding group may use any time channel of the allocated plurality of time channels and use different time channels during communication. It is also possible to allow a change in assignment to an empty frequency channel. An example of such a case is shown in FIG. As shown in FIG. 33, although terminals A, C, and D are assigned to time channel 7 and terminal F is assigned to time channel 3, since these terminals belong to the same group, terminal D is assigned to terminal F. Reassignment to the assigned time channel 3 may be permitted. This is because the transmission power required for the downlink to terminal D and terminal F is at the same level, and therefore the influence on the adjacent cell does not change even if the allocation time channel of terminal D is changed.

  Similarly, one terminal is assigned to another time channel to which terminals belonging to the same group are assigned in addition to the time channel assigned so far (that is, a plurality of time channels are assigned to one terminal). It is good also as a form which permits this.

  Furthermore, although all the time channels have been allocated, there is an empty frequency channel in the allocation time channel of the terminal group that requires high transmission power, and there is a shortage of frequency channels allocated to terminals that require low transmission power. In FIG. 34, it is possible to allow a terminal requiring low transmission power to be allocated to an empty frequency channel of a time channel to which a terminal group requiring high transmission power is assigned (FIG. 34).

  This is because a time channel to which a terminal group requiring high transmission power is allocated is likely to have a terminal group requiring low transmission power in an adjacent cell, and a low transmission power is assigned to an empty frequency channel of the corresponding time channel. This is because interference between adjacent cells does not occur even when a terminal requiring the same is assigned.

  However, conversely, in a situation where there is an empty frequency channel in the allocation time channel of a terminal group that requires low transmission power and there is a shortage of frequency channels allocated to terminals that require high transmission power, terminals that require high transmission power Is assigned to a free frequency channel of a time channel to which a terminal group requiring low transmission power is assigned, a large interference occurs between adjacent cells. Therefore, instead of directly allocating a terminal requiring high transmission power to an empty frequency channel in a time channel to which a terminal group requiring low transmission power is allocated, the modulation scheme of the terminal requiring high transmission power is changed to be low. After setting the transmission power to be low, it is also possible to allow the allocation of the time channel to which the terminal group requiring low transmission power is allocated to the free frequency channel. By adopting such a form, even when assignment to a time channel to which different terminal groups are assigned, while avoiding the occurrence of errors due to setting the transmission power to the corresponding terminal low, By setting the transmission power low, it is possible to suppress interference to adjacent cells.

  Next, another mode in which an idle time channel is reserved for a terminal that requires high transmission power will be described. As described above, in the fourth embodiment of the present invention, the remaining time channels that are not allocated are sequentially assigned from the terminal group that requires the highest transmission power among the terminal groups that have communication requests. Among them, the time channel that minimizes the interference power measured in the terminals of the corresponding group is allocated. However, when the required transmission power is not so high in a group having a communication request, a time channel that minimizes the interference power is assigned to the group, and then a communication request is made at a terminal located near the cell edge. Even if a group that requires very high transmission power is formed, a new channel that requires high transmission power cannot be assigned a time channel that minimizes interference power.

  As a countermeasure against this problem, at least one time channel may be left for a terminal group requiring high power. Conversely, at least one time channel may be reserved for a terminal group that requires low power. Furthermore, the number of time channels (interference time channels) in which interference over a certain value is observed is counted, and the number of time channels obtained by subtracting the interference time channels from the total number of time channels is used for terminal groups that require high power. It is good also as a form secured as.

  Thus, even in a situation where a terminal requiring high (low) power is not communicating, by providing a free time channel for a terminal group requiring high (low) power, communication is performed later on such a terminal. It is also possible to deal with requests. However, if a free time channel is only reserved, a terminal group requiring high power of an adjacent cell may be assigned to the corresponding time channel (this is not a problem in the case of a terminal group requiring low power). ) This is not an effective measure.

  Therefore, even when there is no terminal group that requires high power, by transmitting dummy data with the same transmission power as at the time of transmission of control information in a time channel in which interference power is determined to be minimum by other terminals, A time channel for a terminal group requiring high power may be reserved. Further, the reserved time channel for transmitting dummy data in this way may be determined in advance so as to be a different time channel for each cell.

  In addition, when there are terminals that require high transmission power and time channels are allocated, but the number of allocated frequency channels is small and most of the frequency channels are free, the corresponding time channel Dummy data may be transmitted in an empty frequency channel. By adopting such a configuration, there is an advantage that it is easy to detect a time channel with high interference power in each terminal of the adjacent cell.

  Furthermore, as an option for transmitting dummy data to reserve a time channel for a terminal group that requires high transmission power, in a situation where no terminal exists in the cell, in order to reduce interference given to adjacent cells, dummy data is transmitted. A function for stopping data transmission may be incorporated.

  In general, in a mobile communication system, control information (base station ID and terminal ID) is transmitted and received between a base station and a terminal (limited to a terminal that is turned on) even for a terminal that does not have a communication request. The base station knows which terminal exists in its own cell, and the terminal knows which cell it belongs to. In a base station of a system in which transmission / reception of such control information is performed between a base station and a terminal, when data communication with the terminal is started, it is estimated how much transmission power is required in the downlink Can do. Therefore, as an option for transmitting dummy data for the purpose of time channel reservation, dummy data is transmitted when there is a terminal in the cell that is assumed to require high transmission power when data communication is started. However, when there is no terminal in the cell that is estimated to require high transmission power when data communication is started, a function of stopping transmission of dummy data may be introduced.

  In this way, the transmission power required in the downlink is estimated at the base station, and by transmitting dummy data based on the estimation result, high power in the own cell is taken into consideration so as not to cause interference to neighboring cells. It is possible to reserve a time channel for a terminal that requires.

  In the above description, the case where the same time channel is assigned to the terminal devices belonging to the same group has been described. However, the present invention is not limited to this, and the case where the same frequency channel is assigned to the terminal devices belonging to the same group. Is also applicable.

It is a figure which shows the example in which the base station apparatus which concerns on embodiment of this invention formed the group of the terminal device. It is a figure which shows a mode that the base station apparatus which concerns on embodiment of this invention allocated the communication slot. It is a block diagram which shows schematic structure of the base station apparatus which concerns on 1st Embodiment. It is a block diagram which shows schematic structure of the terminal device which concerns on 1st Embodiment. It is a flowchart which shows operation | movement of the base station apparatus which concerns on 1st Embodiment. It is a flowchart which shows operation | movement of the terminal device which concerns on 1st Embodiment. It is a flowchart which shows operation | movement of the base station apparatus which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the terminal device which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the base station apparatus which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the terminal device which concerns on 2nd Embodiment. It is a figure which shows the mode of the data transmission / reception between a base station and a terminal in the case of using the scheduling which concerns on 2nd Embodiment. It is a figure which shows an example at the time of performing slot allocation using the scheduling method which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the base station apparatus which concerns on 3rd Embodiment. It is a flowchart which shows operation | movement of the terminal device which concerns on 3rd Embodiment. It is a flowchart which shows the operation | movement of the scheduling in the base station apparatus which concerns on 3rd Embodiment. It is a flowchart which shows the operation | movement of the scheduling in the base station apparatus which concerns on 3rd Embodiment. It is a flowchart which shows the operation | movement of the scheduling in the base station apparatus which concerns on 3rd Embodiment. (A) is a figure which shows the arrangement | positioning condition of a cell and a terminal device regarding 4th Embodiment. (B) is a figure which shows the transmission power which a downlink requires in a cell regarding 4th Embodiment. (C) is a figure which shows the example of slot allocation regarding 4th Embodiment. It is a figure which shows the structural example of the slot which concerns on 4th Embodiment. It is a figure which shows the example of the cell arrangement | positioning which concerns on 4th Embodiment. It is a figure which shows the transmission timing of the control slot group which concerns on 4th Embodiment. It is a block diagram which shows schematic structure of the terminal device which concerns on 4th Embodiment. It is a block diagram which shows schematic structure of the base station apparatus which concerns on 4th Embodiment. It is a flowchart which shows the operation | movement of slot allocation in the base station apparatus which concerns on 4th Embodiment. It is a flowchart which shows the operation | movement of slot allocation in the terminal device which concerns on 4th Embodiment. (A) is a figure which shows the arrangement | positioning condition of the terminal device in the cell 1 and the cell 2 regarding 4th Embodiment. (B) is a figure which shows the transmission power which a cell 2 requires for a downlink regarding 4th Embodiment. (C) is a figure which shows the slot allocation condition in the cell 2 regarding 4th Embodiment. (A) is a figure which shows the transmission power which a cell 1 requires for a downlink regarding 4th Embodiment. (B) is a figure which shows the transmission power which a cell 2 requires for a downlink regarding 4th Embodiment. It is a figure which shows the interference power given to the allocation condition of the terminal device in the cell 2, and the cell 1 regarding 4th Embodiment. It is a figure which shows the state which allocated the slot with respect to terminal device AC in the cell 1 regarding 4th Embodiment. It is a figure which shows the state which allocated the slot with respect to the transmission power required for the downlink in the cell 1 and the cell 2, and the terminal devices DH in the cell 1 regarding 4th Embodiment. It is a figure which shows a mode that the transmission power level and the interference level were matched regarding 4th Embodiment. (A) is a figure which shows a mode that the transmission timing of a control slot group is fixed regarding 4th Embodiment. (B) is a figure which shows a mode that the transmission timing of a control slot group is variable. It is a figure which shows the example which changes the transmission power required for a downlink, and slot allocation in the same group regarding 4th Embodiment. It is a figure which shows the example which permits the allocation to the time channel to which the transmission power required for a downlink, and another group are allocated regarding 4th Embodiment. It is a figure which shows an OFDM / (TDMA, FDMA) two-dimensional frame structure. It is a block diagram which shows schematic structure of the transmission circuit used for OFDM / (TDMA, FDMA). It is a block diagram which shows schematic structure of the receiving circuit used for OFDM / (TDMA, FDMA). (A) is an example when a cell is a hexagon and seven frequency bands are used. (B) is an example when one-cell repetition OFDM / (TDMA, FDMA) is used. It is a figure which shows the cell structure regarding the invention described in patent document 1. FIG. It is a figure which shows the cell structure regarding the invention described in patent document 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Antenna part 101 Radio | wireless receiving part 102 A / D conversion part 103 Synchronization part 104 GI removal part 105 S / P conversion part 106 FFT part 107 Channel estimation demapping part 108-a-108-l P / S conversion part 109- a to 109-l error correction decoding unit 110 demultiplexing unit 112 RSS measurement unit 113 interference power measurement unit 114 control unit 115 uplink transmission unit 120 scheduling unit 121 multiplex unit 122-a to 122-l error correction coding unit 123 -A to 123-l S / P conversion unit 124 mapping unit 125 transmission power control unit 126 IFFT unit 127 P / S conversion unit 128 GI insertion unit 129 D / A conversion unit 130 radio transmission unit 131 antenna unit 200 antenna unit 201 radio Transmitter 202 D / A converter 203 GI inserter 204 P / S Conversion unit 205 IFFT unit 206 Transmission power control unit 207 Mapping unit 208-a to 208-l S / P conversion unit 209-a to 209-l Error correction coding unit 210 Multiplex unit 211 Downlink demodulation unit 212 Wireless reception unit 213 A / D conversion unit 214 RSS measurement unit 300 Antenna unit 301 Wireless reception unit 302 A / D conversion unit 303 Synchronization unit 304 GI removal unit 305 S / P conversion unit 306 FTT unit 307 Channel estimation demapping units 308-a to 308 -L P / S conversion units 309-a to 309-l Error correction decoding unit 310 Demultiplex unit 311 Desired signal power / interference signal power measurement unit 312 Scheduling unit 313 Downlink modulation unit 314 Radio transmission unit 400 Antenna unit 401 Radio Transmission unit 402 D / A conversion unit 403 GI insertion unit 404 P / S conversion Conversion unit 405 IFFT unit 406 Transmission power control unit 407 Mapping unit 408-a to 408-l S / P conversion unit 409-a to 409-l Error correction coding unit 410 Multiplex unit 411 Downlink demodulation unit 412 Radio reception unit 700 Antenna unit 701 Radio reception unit 702 A / D conversion unit 703 Synchronization unit 704 GI removal unit 705 S / P conversion unit 706 FFT unit 707 Channel estimation demapping units 708-a to 708-l P / S conversion unit 709-a ˜709-l Error correction decoding section 710 Demultiplex section 711 Desired signal power / interference signal power measurement section 712 Scheduling section 713 Downlink modulation section 714 Wireless transmission section

Claims (21)

A communication slot specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band is assigned to each terminal device to be controlled, and is assigned to each terminal device. A control station apparatus that performs uplink communication based on the communication slot assignment,
A receiving unit for receiving information from each terminal device;
Based on the received information, a transmission power determining unit that determines transmission power for each terminal device when each terminal device performs uplink communication;
A group of terminal devices is formed based on transmission power determined for each terminal device, and communication is performed by allocating communication slots of the same time channel or the same frequency channel to terminal devices belonging to the same group. A scheduling unit for generating slot allocation information;
A control station apparatus comprising: a transmission unit that transmits the generated communication slot allocation information to each terminal apparatus. A communication slot specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band is assigned to each terminal device to be controlled, and is assigned to each terminal device. A control station apparatus that performs uplink communication based on the communication slot assignment,
A receiving unit for receiving information including position information of each terminal device from each terminal device;
A group of terminal devices is formed based on the received location information of each terminal device, and communication slots of the same time channel or the same frequency channel are allocated to terminal devices belonging to the same group, A scheduling unit for generating allocation information;
A control station apparatus comprising: a transmission unit that transmits the generated communication slot allocation information to each terminal apparatus. The location information received by the receiving unit is a control station identifier,
The scheduling unit includes
The control station apparatus according to claim 2, wherein a group of terminal apparatuses is formed based on the received control station identifier. Based on the received information, the terminal device further includes a transmission power determining unit that determines transmission power for each terminal device when performing uplink communication,
The scheduling unit includes
Within the formed group, further form a subgroup based on transmission power determined for each terminal device,
4. The control according to claim 2, wherein communication slot allocation information is generated by allocating communication slots of the same time channel or the same frequency channel to terminal devices belonging to the same subgroup. Station equipment. Further comprising an acquisition unit for acquiring information about the communication environment in each time channel or each frequency channel from the information received by the reception unit;
The scheduling unit includes
According to the information on the communication environment, communication slot allocation information is generated by allocating communication slots of the same time channel or the same frequency channel to terminal devices belonging to the same group or the same subgroup. The control station apparatus according to any one of claims 1 to 4. The receiver is
Receiving communication slot allocation information generated by another control station device from each terminal device;
The scheduling unit includes
According to the received communication slot allocation information, communication slot allocation information is generated by allocating communication slots of the same time channel or the same frequency channel to terminal devices belonging to the same group or the same subgroup. The control station apparatus according to claim 1, wherein: Further comprising an acquisition unit for acquiring information about the communication environment in each time channel or each frequency channel from the information received by the reception unit;
The receiver is
Receiving communication slot allocation information generated by another control station device from each terminal device;
The scheduling unit includes
According to the information on the communication environment and the received communication slot allocation information, the communication slot of the same time channel or the same frequency channel is allocated to terminal devices belonging to the same group or the same subgroup, 5. The control station apparatus according to claim 1, wherein allocation information is generated. The scheduling unit includes
A plurality of levels are determined by dividing the magnitude of the transmission power of the terminal devices belonging to the group into a plurality of numerical ranges, and the level to which the determined transmission power belongs belongs to each terminal device to be controlled The control station apparatus according to claim 4, wherein the subgroup is formed by specifying The scheduling unit includes
Information on interference power in each time channel or each frequency channel is extracted from information on the communication environment, and each terminal device in the group or subgroup to which the terminal device having the relatively large transmission power belongs. The communication station allocation information is generated by allocating a communication slot of a time channel or a frequency channel with relatively low interference power to the control station. apparatus. The scheduling unit includes
No other control station device is assigned to a terminal device that is a control target for each terminal device in a group or subgroup to which a terminal device having a relatively large amount of transmission power belongs. Allocate communication slots of time channel or frequency channel with first priority,
For each terminal device in a group or subgroup to which a terminal device having a relatively large transmission power is determined, another control station device is connected to the group around the other control station device. Assigns communication slots of time channels or frequency channels assigned to terminal devices located on different sides with second priority,
A communication slot of a time channel or a frequency channel with a relatively small interference power is assigned to each terminal device in the group or subgroup to which the terminal device having the relatively large transmission power belongs. Assign with priority,
8. The control station apparatus according to claim 6, wherein communication slot allocation information is generated. The scheduling unit includes
There are two or more subgroups belonging to the same group,
When there is an empty communication slot in the time channel or frequency channel assigned to another subgroup to which a terminal device that requires transmission power larger than the transmission power required by a terminal device belonging to a certain subgroup exists The control station apparatus according to any one of claims 3 to 10, wherein a terminal apparatus belonging to a subgroup with low transmission power is allocated to the vacant communication slot. The scheduling unit includes
There are two or more subgroups belonging to the same group,
When there is an empty communication slot in the time channel or frequency channel assigned to another subgroup to which a terminal device that requires transmission power smaller than the transmission power required by a terminal device that belongs to a certain subgroup exists The control station apparatus according to any one of claims 3 to 10, wherein a terminal apparatus belonging to a subgroup with a large transmission power is allocated to the vacant communication slot.   The control station apparatus according to claim 11 or 12, wherein the scheduling unit changes at least one of transmission power and a modulation scheme when allocating the terminal apparatus to the vacant communication slot.   The scheduling unit is based on information about a communication environment acquired by the acquisition unit when allocating communication slots in the same time channel or the same frequency channel to terminal devices belonging to the same group or subgroup. 8. The control station apparatus according to claim 5, wherein a communication slot to be allocated for each terminal apparatus is specified and communication slot allocation information is generated. The allocation of the communication slot to each terminal device is as follows:
Starting from a communication slot with relatively low interference power,
15. The control station apparatus according to claim 14, wherein the control station apparatus performs in order from a terminal apparatus having a relatively large reception signal power to interference and noise power ratio in each communication slot. A terminal device including a transmission / reception unit that performs wireless communication with the control station device according to any one of claims 2 to 15,
The transmission / reception unit wirelessly transmits information indicating a base station identifier received from another control station apparatus that is not a connection destination to a control station apparatus that is a connection destination.   When the received power of a signal received from another control station device that is not a connection destination is equal to or greater than a certain threshold, the transmission / reception unit transmits information indicating the base station identifier of the control station device to the connection destination control station device. The terminal apparatus according to claim 16, wherein the terminal apparatus wirelessly transmits.   The terminal apparatus according to claim 16, wherein the transmission / reception unit wirelessly transmits communication slot allocation information received from another control station apparatus that is not a connection destination to a control station apparatus that is a connection destination.   A wireless communication system comprising: the control station apparatus according to any one of claims 2 to 15; and the terminal apparatus according to any one of claims 16 to 18. A scheduling method for allocating a communication slot specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band for each terminal device to be controlled,
Receiving information from each of the terminal devices;
Determining, for each terminal device, transmission power when each terminal device performs uplink communication based on the received information;
Forming a group of terminal devices based on transmission power determined for each terminal device;
Allocating communication slots of the same time channel or the same frequency channel to terminal devices belonging to the same group. A scheduling method for allocating a communication slot specified by one or more time channels defined by a certain time length and one or more frequency channels defined by a certain frequency band for each terminal device to be controlled,
Receiving information including location information of each terminal device from each terminal device;
Determining, for each terminal device, transmission power when each terminal device performs uplink communication based on the received information;
Forming a group of terminal devices based on the received location information of each terminal device;
Allocating communication slots of the same time channel or the same frequency channel to terminal devices belonging to the same group.

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