JPWO2007007662A1 - Control station, base station, slot allocation method, and radio communication system - Google Patents

Abstract

In a wireless communication system in which a plurality of cells are adjacent, a control station (base station control station) that allocates slots according to downlink transmission power of adjacent cells is provided. A base station control station (100) that manages a plurality of base stations collects downlink transmission power allocated to each slot from the base stations of each of a plurality of cells, and performs downlink communication with a mobile station. A control station acquisition unit (110) that acquires the requested transmission power required from a base station of a specific cell, and by adding the downlink transmission power of one or more cells adjacent to the specific cell for each slot, An interference power calculation unit (122) for calculating an interference power value for each slot, an allocation unit (123) for allocating requested transmission power to a slot having a small interference power value, and allocation information for allocating requested transmission power to the slot, A control station notification unit (130) for notifying a base station of a specific cell is provided.

Description

  The present invention relates to control of slot assignment in a wireless communication system in which a plurality of cells are adjacent.

  Conventionally, in a mobile communication system, communication is performed by a multiple access method in which a plurality of mobile stations are connected to one base station in a cell and wireless communication is simultaneously performed. In a mobile communication system in a multi-cell environment where a plurality of cells are expanded in a plane, a radio wave from a base station in an adjacent cell becomes an interference wave. For this reason, a communication method for avoiding interference waves is employed. For example, adjacent base stations avoid interference by using a unique spreading code for each base station, such as a communication method in which different frequency bands are used in each cell or a CDMA (Code Division Multiple Access) communication method. It is a wireless communication system.

  FIG. 24 is a diagram illustrating a frequency allocation example of a wireless communication scheme in which wireless communication is performed using different frequency bands in adjacent cells. FIG. 24 shows a typical frequency allocation example with a frequency repetition number of 3 in a regular hexagonal cell of a wireless communication system. In the figure, all frequency bandwidths are equally divided by a fixed bandwidth, and frequency bands are assigned so that the same divided frequency band is not used in adjacent cells. As a result, since the same frequency is not used in adjacent cells, it is possible to prevent deterioration in radio communication quality due to interference waves near the cell edge.

  The CDMA communication system is a communication system that is resistant to interference because a signal is multiplied by a spreading code that is different for each cell. On the other hand, if the interference power increases, the communication quality deteriorates. Therefore, it is necessary to increase the relative power ratio between the received signal power of the mobile station and the received interference power. The increase in transmission power from adjacent base stations causes interference power for mobile stations in its own cell, so the transmission rate should be set especially for mobile stations near the cell edge where interference power from adjacent base stations is large. It was necessary to increase the immunity to interference by lowering and increasing the gain due to spreading.

Further, in recent years, as the demand for high-speed mobile communication has increased, high frequency utilization efficiency, and high-speed and large-capacity communication are desired, all base stations in the communication system use the same frequency band. Research on a one-cell repetitive communication method for wireless communication has been actively conducted.
Shiro Sakata, “Wireless Ubiquitous High-Speed Wireless LAN / UWB / 3.5G Mobile Phone” Shuwa System, p. 195-210, 2004

  However, the following problems can be considered in the conventional wireless communication system described above.

  First, in a system using cell repetition by frequency division, inter-cell interference does not occur because a frequency different from that of the adjacent cell is used in the own cell, but because the frequency band is divided and used, frequency utilization efficiency is low and communication is sufficiently fast. Could not be done. Further, in the CDMA communication system, if the deterioration of the radio wave environment due to interference near the cell edge exceeds the code gain characteristic, a sufficient transmission rate cannot be obtained.

  The present invention has been made in view of such circumstances, and in a wireless communication system in which a plurality of cells are adjacent, a control station, a base station, and a slot that allocate slots according to downlink transmission power of adjacent cells The purpose is to provide an allocation method.

  (1) One aspect of a control station (base station control station) according to the present invention is a wireless communication system that uses the same frequency between a plurality of adjacent cells, and uses a frame composed of a plurality of slots in a cell. A control station that manages a plurality of base stations that communicate wirelessly with a mobile station, and collects downlink transmission power allocated to each slot from the base stations of each of a plurality of cells and for downlink communication with the mobile station. A control station acquisition unit that acquires a requested transmission power required from a base station of a specific cell, and by adding a downlink transmission power of one or more cells adjacent to the specific cell for each slot, An interference power calculation unit for calculating the interference transmission power value, an allocating unit for allocating the requested transmission power to a slot whose interference power value is smaller than a predetermined value, and scanning the requested transmission power. The allocation information allocated to Tsu bets, characterized in that it comprises a control station notification unit that notifies the base station of the particular cell.

  In this way, the control station adds the downlink transmission power of the adjacent cell to calculate the interference power value, and assigns the required transmission power required for downlink communication to the slot with the small interference power value. It is possible to adaptively allocate slots according to the downlink transmission power of the cell and reduce inter-cell interference. The technique described in Non-Patent Document 1 is written in HSDPA (High Speed Downlink Packet Access) whose specifications are approved by 3GPP (3rd Generation Partnership Project). In particular, a technique related to the present invention is a technique called “adaptive scheduling”, and is one of characteristic techniques in HSDPA. HSDPA uses a TDMA communication system as in the embodiment of the present invention, and assigns each slot in a frame based on CQI (Channel Quality Indication) which is control information indicating a propagation path state from a mobile station. . On the other hand, the difference from the present invention is that the transmission power of each slot is constant in HSDPA and there is no temporal change in interference power in adjacent cells. However, in the present invention, the transmission power of each slot is positively controlled and adjacent to each other. Interference on the cell is reduced. Also, the difference in operation at the mobile station is that HSDPA needs to return CQI for each slot, but in the present invention, information calculated from propagation loss may be returned for each frame (every time scheduling is performed). .

  (2) Also, in one aspect of the control station according to the present invention, the control station acquisition unit acquires a plurality of requested transmission powers, and the allocation unit sequentially assigns slots having a small interference power value among the plurality of slots. And a plurality of requested transmission powers are assigned to the selected slots in descending order.

  As described above, since the slots having the smaller interference power values are sequentially assigned in the descending order of the requested transmission power, the influence of the interference power of the adjacent cell can be suppressed.

  (3) Furthermore, another aspect of the control station according to the present invention is a radio communication system using the same frequency between a plurality of adjacent cells, and a mobile station in the cell using a frame composed of a plurality of slots. A control station that manages a plurality of base stations that communicate wirelessly with each other, a transmission power storage unit that stores downlink transmission power assigned to each slot in the plurality of base stations in association with cells, and a specific cell By adding the downlink transmission power of one or more adjacent cells for each slot, an interference power calculation unit for calculating an interference power value for each slot and a transmission request for the interference power value from the base station are acquired. A control station acquisition unit, and a control station notification unit that notifies the base station of the interference power value calculated by selecting the cell of the base station requested by the interference power calculation unit as the specific cell, Characterized in that it obtain.

  In this way, this control station can provide information on the interference power value to the base station that performs slot allocation by calculating the downlink transmission power of the adjacent cell as the interference power value and notifying the base station. it can. As a result, the base station can adaptively allocate slots according to the downlink transmission power of adjacent cells, and can reduce inter-cell interference.

  (4) One aspect of the base station according to the present invention is a radio communication system that uses the same frequency between a plurality of adjacent cells, and is a base station that performs radio communication with a mobile station in a cell to be controlled, A receiving unit that receives requested transmission power requested by a mobile station as downlink transmission power, a base station notification unit that notifies the requested transmission power to the control station according to claim 1, and a requested transmission power from the control station. A base station acquisition unit that acquires allocation information allocated to the slot; a scheduling unit that associates the mobile station that requested the requested transmission power with the slot using the allocation information; and a mobile station that requested the requested transmission power And a transmitter for notifying of the slot to which the requested transmission power is allocated.

  In this way, this base station calculates the downlink transmission power of an adjacent cell as an interference power value, and schedules the requested transmission power required for downlink communication to a slot with a small interference power value using the acquired allocation information. Can do. As a result, it is possible to adaptively allocate slots according to the downlink transmission power of adjacent cells to reduce inter-cell interference.

  (5) In the aspect of the base station according to the present invention, the receiving unit receives a plurality of requested transmission powers, and the scheduling unit is greater than a predetermined threshold among the received plurality of requested transmission powers. The requested transmission power is selected, and the base station notification unit notifies the selected requested transmission power.

  In this way, by notifying the control station of a part of the plurality of requested transmission powers, it is possible to adjust the communication amount and information processing amount between the control station and the base station.

  (6) Another aspect of the base station according to the present invention is a wireless communication system that uses the same frequency between a plurality of adjacent cells, and uses a frame composed of a plurality of slots in a cell to be controlled. A base station that performs radio communication with a mobile station, and adds the downlink transmission power of one or more cells adjacent to the cell to be controlled to each slot to add the interference power value calculated for each slot to the control station A base station acquisition unit that acquires from the receiver, a reception unit that receives the request transmission power that the mobile station requests as downlink transmission power, and a scheduling unit that allocates the request transmission power received to the slot with the acquired interference power value being small. And a transmitter that notifies the mobile station that has requested the requested transmission power of the slot to which the requested transmission power is allocated.

  In this way, this base station can acquire the interference power value and assign the requested transmission power required for downlink communication to the slot with the small interference power value. As a result, it is possible to adaptively allocate slots according to the downlink transmission power of adjacent cells to reduce inter-cell interference. Also, by allocating slots using the interference power value in the base station, the amount of information exchanged between the control station and the base station can be reduced as compared with the case of slot allocation in the control station. .

  (7) Further, another aspect of the base station according to the present invention is a radio communication system that uses the same frequency between a plurality of adjacent cells, and is a control target using a frame composed of a plurality of slots. A base station that wirelessly communicates with mobile stations in a cell and manages other base stations, and collects downlink transmission power assigned to each slot for the cells of the other base stations; and A receiving unit that receives requested transmission power requested by the mobile station as downlink transmission power, and a slot by adding the downlink transmission power of one or more cells adjacent to the cell to be controlled for each slot. An interference power calculation unit that calculates an interference power value for each, a scheduling unit that allocates the requested transmission power received to a slot having a small interference power value, and the requested transmission power To the mobile station that requested the characterized by comprising a transmitting unit for notifying the slots allocated to the request transmission power.

  As described above, this base station has a function of collecting the downlink transmission power of each cell and calculating the interference power value, and can allocate the requested transmission power to a slot having a small interference power value. Among the plurality of base stations, at least one base station has means for slot allocation using the interference power value, so that at least one base station adaptively allocates slots according to the downlink transmission power of adjacent cells. Can do. Thereby, it becomes possible to assign the slot of the own cell which is a control object according to the interference power value.

  (8) In one aspect of the base station according to the present invention, the base station acquisition unit acquires request transmission power requested by a mobile station of another cell from another base station, and the interference power calculation unit By adding the downlink transmission power of one or more cells adjacent to other cells for each slot, the interference power value for each slot is calculated, and the scheduling unit acquires the slot for which the interference power value is small. Allocation information for allocating requested transmission power is created, and the base station notification unit notifies the created allocation information to the other base station.

  In this way, when this base station acquires the requested transmission power from another base station, it calculates the interference power value for the cell of the other base station, and allocates the requested transmission power to the slot with the smaller interference power value. Can do. As a result, at least one of the plurality of base stations has means for slot allocation using the interference power value, so that at least one base station can adaptively respond to the downlink transmission power of the adjacent cell. Slots can be assigned.

  (9) In one aspect of the base station according to the present invention, the scheduling unit sequentially selects slots having a small interference power value among a plurality of slots, and assigns a plurality of requested transmission powers to the selected slots in descending order. It is characterized by.

  As described above, since the slots having the smaller interference power values are sequentially assigned in the descending order of the requested transmission power, the influence of the interference power of the adjacent cell can be suppressed.

  (10) One aspect of a slot allocation method for a control station according to the present invention is a radio communication system using the same frequency between a plurality of adjacent cells, and a mobile station in the cell using a frame composed of a plurality of slots. A slot allocation method for a control station that manages a plurality of base stations that communicate with each other wirelessly, the step of collecting downlink transmission power allocated to each slot for each of a plurality of cells from the plurality of base stations, Receiving a required transmission power required for downlink communication from a base station of a specific cell, and adding the downlink transmission power of one or more cells adjacent to the specific cell for each slot, Calculating an interference power value for each, assigning the requested transmission power to a slot having a small interference power value, and The allocation information allocates transmission power to the slot, characterized in that it comprises a step of notifying the base station of the particular cell, at least.

  Thus, in this slot allocation method, the downlink transmission power of the adjacent cell is calculated as the interference power value, and the requested transmission power required for downlink communication is allocated to the slot with the small interference power value. Inter-cell interference can be reduced by adaptively allocating slots according to link transmission power.

  (11) One aspect of a slot allocation method for a wireless communication system according to the present invention is a wireless communication system that uses the same frequency between a plurality of adjacent cells, wherein a plurality of cells in which mobile stations exist are adjacent to each other, and a plurality of slots A slot allocation method for a radio communication system using a frame comprising: a step of collecting downlink transmission power allocated to each slot from a base station of each of a plurality of cells; and Of these, the step of calculating the interference power value for each slot by adding the downlink transmission power of one or more cells adjacent to a specific cell for each slot, and the requested transmission power required as the downlink transmission power From the base station of the specific cell, and the requested transmission power to a slot with a small interference power value Characterized in that it comprises the steps of assigning, at least.

  In this way, in either the control station or the base station of this wireless communication system, the requested transmission power required for downlink communication is allocated to a slot having a small downlink transmission power in the adjacent cell, so that downlink transmission in the adjacent cell is performed. Inter-cell interference can be reduced by adaptively allocating slots according to power. In addition, since the interference power value is calculated using the downlink transmission power of the adjacent cell, slots can be allocated according to the interference power value of the adjacent cell, and interference between cells can be reduced.

  (12) In one aspect of the control station according to the present invention, the interference power calculation unit multiplies the downlink transmission power by a coefficient corresponding to an attenuation amount, and sets the downlink transmission power multiplied by the coefficient for each slot. It is characterized by adding.

  Thus, it is possible to calculate the interference power value considering the interference level of the base station.

  (13) In one aspect of the base station according to the present invention, the interference power calculation unit multiplies the downlink transmission power by a coefficient corresponding to an attenuation, and the downlink transmission power multiplied by the coefficient for each slot. It is characterized by adding.

  Thus, it is possible to calculate the interference power value considering the interference level of the base station.

  (14) In one aspect of the slot allocation method of the wireless communication system according to the present invention, the step of calculating the interference power includes multiplying the downlink transmission power by a coefficient corresponding to an attenuation amount, and multiplying the downlink power by the coefficient. The link transmission power is added for each slot.

  Thus, it is possible to calculate the interference power value considering the interference level of the base station.

  (15) According to one aspect of the wireless communication system of the present invention, a plurality of adjacent cells use the same frequency, a plurality of cells in which a mobile station exists are adjacent to each other, and a frame including a plurality of slots is used. A wireless communication system comprising a control station that manages a plurality of base stations that communicate wirelessly with mobile stations in a cell, wherein either one of the base station or the control station transfers each slot from a base station of each of a plurality of cells. The allocated downlink transmission power is collected, and the interference power value is calculated based on the downlink transmission power of one or more cells adjacent to a specific cell among the collected downlink transmission powers, and downlink transmission is performed. The requested transmission power required as power is obtained from the base station of the specific cell, and the requested transmission power is allocated to a slot having a small interference power value. To.

  In this way, in either the control station or the base station of this wireless communication system, the requested transmission power required for downlink communication is allocated to a slot having a small downlink transmission power in the adjacent cell, so that downlink transmission in the adjacent cell is performed. Inter-cell interference can be reduced by adaptively allocating slots according to power. In addition, since the interference power value is calculated using the downlink transmission power of the adjacent cell, slots can be allocated according to the interference power value of the adjacent cell, and interference between cells can be reduced.

  According to the present invention, slots can be allocated according to downlink transmission power of adjacent cells. Thereby, it becomes possible to reduce inter-cell interference.

  Next, embodiments of the present invention will be described with reference to the drawings. In the drawings, components having the same configuration or function and corresponding parts are denoted by the same reference numerals and description thereof is omitted.

(First embodiment)
Hereinafter, a first embodiment of a wireless communication system according to the present invention will be described. First, a communication method and a system configuration to which an embodiment of the present invention is applied will be described. The basic communication method in the first embodiment of the present invention is a TDMA (Time Division Multiple Access) method or an FDMA (Frequency Division Multiple Access) method.

  The TDMA system is an access system in which the same frequency band is divided into short times when data transmission / reception is performed, and wireless communication is performed by assigning the divided short time sections to different users. Normally, wireless communication is performed by repeatedly transmitting and receiving a time interval called a frame at a constant period. In the TDMA system, a time slot or TTI (Transmission Time Interval) obtained by dividing a frame into a number of frames is used. This is an access method in which a short time interval called is assigned to a plurality of mobile stations to simultaneously perform radio communication between the plurality of mobile stations and the base station.

  On the other hand, in the FDMA scheme, when data is transmitted and received, a plurality of mobile stations simultaneously use a frequency band obtained by dividing a frame, which is a certain time section, into a certain bandwidth in a frequency direction called a frequency slot, thereby performing wireless communication. Is an access method for performing

  Each slot in the TDMA system and the FDMA system can simultaneously use modulation such as 64QAM, 16QAM, QPSK, and BPSK, spreading that changes the spreading factor adaptively in the frequency direction and the time axis direction. Yes, wireless communication can be performed by a method according to the propagation path environment of the mobile station assigned to each slot. Hereinafter, in the present specification, the three combinations are referred to as modulation schemes.

  Hereinafter, the frame structure of the TDMA system and the FDMA system in the embodiment of the present invention will be described. FIG. 1 is a diagram illustrating an example of a frame configuration.

  In the TDMA communication system, it is possible to divide a frame in a certain time interval in the time axis direction and assign each frame to different mobile stations for data transmission. In the present specification, the minimum unit of the divided time section is referred to as a time slot. FIG. 1A shows an example of a general TDMA frame configuration. In the case of the figure, the number of slots is eight. Generally, a control slot including information data for notifying all mobile stations such as mobile station allocation information, modulation scheme, and broadcast information of each slot is set in the slot at the head of the frame. Traffic data, mobile station specific control information, known information for propagation path estimation, etc. are assigned to other slots and transmitted.

  In the FDMA system, it is possible to divide all frequency bands of a frame of a certain short period and assign them to different mobile stations for data transmission. In addition, the minimum unit of the divided frequency section is referred to as a frequency slot in this specification. FIG. 1B shows an example of a general FDMA frame configuration. In the case of the figure, the number of slots is 12. In the TDMA system in the embodiment of the present invention, the number of slots is 16, and the first slot is a control slot including information data for notifying all mobile stations such as slot allocation information, modulation system and broadcast information of each mobile station Is set. However, the position of the control slot is not limited to that. Traffic data, mobile station specific control information, known information for propagation path estimation, etc. are assigned to other slots and transmitted.

  It is not necessary to allocate only one slot to one mobile station per TDMA communication system and FDMA communication system, and it is possible for one mobile station to occupy a plurality of slots within one frame and perform wireless communication. is there.

  FIG. 2 is a diagram showing a configuration example of a wireless communication system according to the embodiment of the present invention. The system is a system in which a base station control station (“base station control station” is also referred to as “control station”) 100, base stations 200a to 200d, and mobile stations 300a to 300l are hierarchically configured. In this specification, when there are a plurality of the same constituent elements and each is distinguished, a suffix is added to the reference numeral to distinguish each of the plurality of constituent elements. For example, in FIG. 2, the base stations 200 a, 200 b, 200 c, and 200 d distinguish a plurality of base stations, and when the base station 200 is used, indicate one or a plurality of base stations. The same applies to the mobile station 300.

  The base station control station 100 is connected to a plurality of base stations 200 and controls each base station 200. Each base station 200 is connected to a plurality of mobile stations 300 existing in the cell by wireless communication, and manages the mobile stations. Each mobile station 300 transmits and receives data based on the control information from the base station 200. Communication between the base station control station 100 and the base station 200 may be either wired communication or wireless communication. The mobile station 300 includes a portable terminal (mobile terminal) that performs wireless communication, such as a wireless device and a mobile phone.

  FIG. 3 is a block diagram illustrating a configuration example of the base station control station according to the first embodiment. As shown in FIG. 3, the base station control station 100 acquires the control information notified from each base station 200 (based on the control station acquisition unit 110), and the control information notified from each base station 200, A control information processing unit 120 that controls each base station 200 and a control station notification unit 130 that notifies (transmits) the control result controlled by the control information processing unit 120 to each base station 200 are provided. The control information includes requested transmission power requested by the mobile station 300 for transmission, downlink transmission power when the base station 200 transmits data to the mobile station 300, and other information exchanged with each base station 200. In addition, the control result includes, for example, allocation information described later, as a result of control by the control information processing unit 120.

  The control information processing unit 120 includes a transmission power storage unit 121, an interference power calculation unit 122, and an allocation unit 123. The transmission power storage unit 121 stores, for each of a plurality of cells managed by the control station 100, transmission power information in which the downlink transmission power assigned to each slot is associated with each cell. The downlink transmission power of each cell is notified to the base station control station 100 from each base station 200 arranged in the cell. The transmission power information is stored in association with a cell identifier for identifying a cell. Allocation unit 123 performs slot allocation using the transmission power information stored in transmission power storage unit 121 and the requested transmission power acquired from base station 200. The transmission power storage unit 121 may be an area that temporarily stores transmission power information. For example, it may be a storage area secured only when slot allocation is performed. Therefore, it is sufficient that a mechanism for ensuring a storage area for storing transmission power information is provided.

  The interference power calculation unit 122 calculates the interference power value for each slot by adding the downlink transmission power of one or more cells adjacent to the specific cell for each slot. The interference power here is the sum of transmission power for each slot in consideration of the distance between each adjacent base station and the own base station, and is different from the interference power received by each mobile station in the cell. .

  The allocating unit 123 uses the interference power value calculated by the interference power calculating unit 122 to allocate the requested transmission power received to a slot whose interference power value is smaller than a predetermined value. In the present embodiment, the slots are assigned in order of increasing interference power value in order of increasing (high) requested transmission power. The allocating unit 123 creates allocation information in which the requested transmission power is associated with the slot number of the allocated slot.

  FIG. 4 is a block diagram illustrating a configuration example of the base station according to the first embodiment. The base station 200 notifies the base station control station 100 of control information such as requested transmission power and downlink transmission power to the base station control station 100 (base station control unit 100), and performs base station control using the control information. A base station acquisition unit 220 that acquires (receives) a control result controlled by the station 100, a transmission unit 230 that transmits radio data to the mobile station 300, a reception unit 240 that receives radio data from the mobile station 300, a base The mobile station control unit 250 that processes information notified from the station control station 100 and each mobile station 300 is provided, and wireless data is transmitted to and received from each mobile station 300 via the antenna unit 260. In addition, the mobile station control processing unit 250 includes a scheduling unit 251 and a power control unit 252. The scheduling unit 251 assigns the mobile station 300 to each slot. In the present embodiment, each mobile station 300 is allocated to a slot using allocation information notified from the base station control station 100. Details will be described later. The power control unit 252 controls the downlink transmission power of each slot based on the result of the scheduling unit 251.

  FIG. 5 is a block diagram illustrating a configuration example of the mobile station according to the first embodiment. The mobile station 300 includes a receiving unit 310 that receives wireless data transmitted from the base station 200, a transmitting unit 320 that transmits wireless data to the base station 200, and an information processing unit 330 that processes the received wireless data. Wireless data is transmitted and received from the antenna unit 340. Furthermore, the mobile station 300 includes a received power measuring unit 350 that measures the received power level of the radio data transmitted from the base station 200 in the downlink (downlink), and the propagation path quality information calculated from the measurement result is obtained. The base station 200 is notified by uplink (uplink direction) wireless communication.

  The procedure and operation of slot allocation in the first embodiment of the present invention will be described below. The outline of the slot allocation method of the first embodiment is as follows. Here, as shown in FIG. 2, the mobile station 300 installed in each of a plurality of cells, the plurality of base stations 200 that control the mobile stations 300 existing in each cell, and the base station control that manages the plurality of base stations 200 A wireless communication system composed of the station 100 is used. The plurality of base stations 200 determines downlink transmission power in consideration of downlink propagation path quality information received from each mobile station 300, and the base station control station 100 receives the determined downlink transmission power and The downlink transmission power of the slot used by each mobile station 300 is adaptively allocated so as to reduce the amount of interference due to radio waves from the cell.

  In addition, the slot to which the base station control station 100 allocates the requested transmission power is a slot that only requires a certain amount of downlink transmission power in order to reduce the amount of information between the base station control station 100 and the base station 200. Make assignments. The threshold value of requested transmission power for performing transmission power allocation work is an element related to increase / decrease in the amount of information such as the number of base stations to be controlled and the number of slots, that is, the amount of information between the base station control station 100 and a plurality of base stations 200 It is desirable to determine the information processing ability.

  After the above processing, the base station 200 uses the allocation information notified from the base station control station 100 to allocate a slot to the mobile station 300 that requires a downlink transmission power larger than the threshold value. A slot is allocated to the mobile station 300 that requires downlink transmission power equal to or less than the threshold. Base station 200 schedules data for each mobile station 300 based on the allocation result (allocation information), and transmits radio data. Details of allocation when adaptive slot allocation is performed by the base station control station 100 will be described below.

  In the following description, as an aspect of the present invention, the slot allocation method is applied to a wireless communication system of a mobile phone, and a terminal (mobile terminal) is used as an example of the mobile station 300. The slot configuration according to the first embodiment will be described by taking the slot configuration in the TDMA system shown in FIG. 1A as an example. However, the same effect can be obtained by treating the slots in the frequency direction in the FDMA system as described above as slots in the time axis direction of the TDMA system. The configuration of the wireless communication system is the same as in FIG.

  The first embodiment is a system in which each base station 200 is synchronized, that is, a system that is designed so that the timing at which each base station 200 transmits a frame is the same. As for the synchronization method, a synchronization method using GPS (Global Positioning System) is generally well known, but the description is omitted here. Next, the cell arrangement status used for the description of the present embodiment will be described.

FIG. 6 is a diagram showing a typical example of a cell and a terminal arrangement existing in the cell. FIG. 6 illustrates a case where terminals A to F exist in the cell 1. In cell 1, base station 200a is arranged. FIG. 7 is a diagram showing the relative relationship between the magnitudes of requested transmission powers for the terminals A to F in the cell 1. FIG. 7 is an example in which the required transmission power of terminal F is the maximum and the required transmission power of terminal D is the minimum. The threshold value P _TH is a threshold value for determining whether or not the base station control station 100 sets the downlink transmission power. A terminal that requires downlink transmission power larger than the threshold value P _TH sets the downlink transmission power by the base station control station 100. It is desirable to change the value of the threshold value _PTH in relation to the cell size, the information processing amount between the base station 200 and the base station control station 100, and the like. FIG. 8 is a diagram illustrating a frame configuration example used in the first embodiment. In the frame configuration shown in FIG. 8, the total number of slots is 16, the number of control slots (slot number 0), the number of time slots is 15, and the same frequency band is used in all cells.

  FIG. 9 is a diagram illustrating a relationship between a plurality of cells and terminal arrangement. FIG. 9 shows a state where the cell 1 shown in FIG. 6 is adjacent to the cell 2 and the cell 3. In the cell 2, the base station 200b and the terminals H to N are arranged, and in the cell 3, the base station 200c and the terminals O to U are arranged. Here, regarding cell 2 and cell 3 in FIG. 9, it is assumed that slot allocation has already been performed by the same method as in the first experimental mode of the present invention. FIG. 10 shows the relative relationship between the magnitudes of the requested transmission powers for the terminals H to N in the cell 2. FIG. 11 shows the relative relationship between the magnitudes of requested transmission power for the terminals O to U in the cell 3. Assume that the terminals of each cell are in the slot allocation status as shown in FIGS. FIG. 12 is a diagram illustrating the slot allocation status of each terminal H to N in the cell 2, and FIG. 13 is a diagram illustrating the slot allocation status of each terminal O to U in the cell 3. Hereinafter, an example will be described in which slot allocation is performed based on the propagation path status of each terminal (mobile station 300) in cell 1 of FIG. That is, the cell 1 corresponds to a specific cell. The specific cell is a cell (slot allocation request cell) in which a base station requesting slot allocation exists.

  Next, downlink radio data slot allocation (scheduling) will be described. FIG. 14 is a sequence diagram illustrating an example of slot allocation in the first embodiment. FIG. 14 shows a sequence among the base station control station 100, the base station 200, and the mobile station 300. The operation of the mobile station 300 shows the operation of each of the terminals A to G. In the description of the operation, when the mobile station 300 of the cell 1 is described, it means all of the terminals A to G or any one or more terminals.

  First, for the cell 2 and the cell 3, the base station control station 100 acquires the downlink transmission power from each base station 200 (here, the base stations 200b and 200c) for each of the cells 2 and 3, and The downlink transmission power is stored in the transmission power storage unit 121 (step S10). This operation is performed when the downlink transmission power is notified from each base station 200 after the slot assignment of the cell 2 and the cell 3 or before the slot assignment of the cell 1 is performed by the base station control station 100. Implement by collecting.

  Each base station 200 periodically transmits control information to the mobile station 300 (step S11). When a communication request is generated in the mobile station 300 in the cell 1 and a slot allocation opportunity is obtained, each mobile station 300 receives a control signal periodically transmitted from the base station 200. Each mobile station 300 measures the received power level of the received signal (step S12), and further demodulates the received signal (step S13) to obtain control information (control signal) transmitted from the base station 200 (step S13). Step S14). The control information is transmitted from the base station 200 at regular intervals, and the downlink transmission power is set to the power and modulation scheme that can be received even when the mobile station 300 is located near the cell edge. It is assumed that the control information transmitted in the control slot includes transmission power of the control slot that transmitted the control information and slot allocation information of each mobile station 300.

  Next, the mobile station 300 calculates a propagation loss, which is the amount of radio wave attenuation in the propagation path, from the downlink transmission power and reception power level obtained from the demodulated signal. An expression for calculating the propagation loss is shown below.

Propagation loss = downlink transmission power-reception power level (Equation 1)
The mobile station 300 derives the required transmission power and the modulation scheme based on the propagation loss obtained from Equation 1 (step S15). Detailed description regarding the derivation of the required transmission power and the modulation scheme is omitted. The mobile station 300 notifies the requested transmission power and modulation scheme to the base station 200 through uplink transmission (step S17). At this time, if the mobile station 300 performs continuous communication with the base station 200, the request transmission power notification method is a difference value from the power level currently used for downlink transmission with the base station, or It is also possible to notify by a bit indicating increase / decrease. The base station 200 is notified of the required transmission power and modulation scheme from the mobile station 300, and acquires the channel quality information of each mobile station 300. During this time, the base station 200 transmits data to the already assigned terminals (step S16).

Next, in the base station 200, the scheduling unit 251 acquires information on the requested transmission power and the modulation scheme, compares the requested transmission power of each mobile station 300 with the threshold value _PTH, and needs to be scheduled by the base station control station 100. A mobile station is determined (step S18). Specifically, the scheduling unit 251 extracts the mobile station 300 that requires a required transmission power that is greater than the threshold value _PTH . The base station notifying unit 210 notifies the base station control station 100 of the number of assigned slots (the number of extracted mobile stations 300) and the respective requested transmission power (step S19).

Here, _PTH is a threshold value set for the requested transmission power of the mobile station as described above, but it is preferable to set a downlink transmission power corresponding to the mobile station 300 having a large requested transmission power. Necessary for communication. Therefore, the radio data transmitted toward a mobile station having a large required transmission power has a large downlink transmission power and a large interference with adjacent cells. Therefore, the value for determining whether to separate the mobile station that requires downlink transmission power that causes large interference from the mobile station that does not, is _PTH , and the setting is changed depending on the value of the set cell radius, that is, the proximity of adjacent cells. It should be a value. The base on the value of P for the mobile station _{that TH} treatment with a base station controller 100 as to set low is increased, i.e. P _TH from becoming much information amount notified to the base station controller 100 from the base station 200 It is possible to manipulate the amount of information with the station control station.

  The control station acquisition unit 110 of the base station control station 100 acquires the number of assigned slots and the requested transmission power from the base station 200. In the base station control station 100, the interference power calculation unit 122 calculates the interference power value, and the allocation unit 123 uses the information from the base station 200 and the transmission power information stored in the transmission power storage unit 121 to determine the slot power. Downlink transmission power allocation is performed (step S20).

  FIG. 15 is a diagram illustrating a sum of downlink transmission power for each slot of a plurality of cells. FIG. 15 illustrates an example in which the cell 2 assigns downlink transmission power to the slot numbers 1 to 7 and the cell 3 assigns downlink transmission power to the slot numbers 9 to 15. As shown in FIG. 15, the interference power calculation unit 122 calculates the interference power value for each slot by adding the downlink transmission power of each base station of the adjacent cell for each slot. In the present embodiment, the case where the transmission waves from the base stations of the cell 2 and the cell 3 are handled as interference waves is shown, but the calculation can be performed in the same way even when there are three or more adjacent base stations causing interference. However, a coefficient corresponding to the attenuation is set in advance for a base station whose interference level is lower than the base station of the nearest cell due to a difference in physical distance from the cell being assigned at this time or a topographical obstacle. It is desirable. Therefore, in order to add the downlink transmission power of each base station in the adjacent cell for each slot, the downlink transmission power is multiplied by a coefficient corresponding to the attenuation set in advance for each base station. Adding as transmission power is also included. Also, in this embodiment, there are no slots used simultaneously in cell 2 and cell 3, but when there are slots used simultaneously by two base stations, the sum of the downlink transmission power of cell 2 and cell 3 Is treated as the total interference power value of the slot.

  Next, the allocation unit 123 of the base station control station 100 allocates slots in the order of the largest required transmission power (step S20). FIG. 16 is a flowchart showing an example of the slot allocation procedure. The control station acquisition unit 110 acquires the requested transmission power from the base station 200 (step S31) and passes it to the allocation unit 123. The allocating unit 123 first determines a slot that requires the largest requested transmission power (step S32). In the determination method, the selected slot is assigned to an unassigned slot having the smallest sum of downlink transmission powers (that is, interference power values) of adjacent base stations that become interference waves. The mobile station 300 that has requested the largest requested transmission power is assigned in order from the slot used, and the next largest requested transmission power is the lowest among the slots other than the slots that have already been assigned to the largest requested transmission power. The slot is assigned (step S33). That is, the slots are assigned to slots having a lower interference power value in order from the slot having the highest downlink transmission power. Thereafter, the process is continued until there is no slot to which the above work is assigned (step S34).

  When the allocation is completed, the transmission power information (allocation information and scheduling information) set for each slot is notified to the base station (step S35, step S21 in FIG. 14).

Next, the base station 200 performs scheduling of the mobile station 300 (step S22). A method for assigning each mobile station in the base station 200 will be described with reference to the flowchart of FIG. FIG. 17 is a flowchart illustrating an example of a procedure in which the base station assigns a mobile station to each slot. Base station 200 allocates slots used by each mobile station 300 based on allocation information for allocating requested transmission power to each slot acquired from base station control station 100. In the allocation information, the slot number and the requested transmission power are associated with each other. Accordingly, the base station 200 associates the mobile station 300 that has requested the requested transmission power with the slot number. Further, in base station 200, the requested transmission power set for the slot is used as downlink transmission power used in downlink communication with mobile station 300. Scheduling section 251 performs allocation from mobile station 300 having a required transmission power greater than threshold value _PTH , which is a determination criterion for allowing base station control station 100 to perform allocation as a first stage. Scheduling section 251 of base station 200, requesting performs slot assignment transmission power to the mobile station 300 in descending order of required transmit power within the threshold P _TH is larger than the mobile station 300, then the second step, required transmission power _Are allocated to the mobile station 300 in the order of the required transmission power among the mobile stations 300 having a threshold _PTH smaller than (low). Specifically, the following procedure is performed.

As a first stage, the scheduling unit 251 selects the mobile station 300 that has requested the requested transmission power most among the unassigned mobile stations 300 (step S41). Next, in the case of the mobile station 300 whose requested transmission power is larger than the threshold value _PTH (Yes in step S42), in the allocation information acquired from the base station control station 100, the slot satisfying the requested transmission power of the selected mobile station. To the slot with the largest required transmission power (step S43). In order, the mobile station with the highest required transmission power is assigned to the slot with the highest required transmission power among the unallocated slots (step S41 to step S43). Regarding the above steps, the requested transmission power requested by the mobile station is determined by the base station control station 100 and notified to the base station 200 as allocation information. Therefore, since any slot in the frame is set to the required transmission power, the mobile station 300 having the largest propagation loss can be selected to correspond to that slot.

Next, as a second stage, the mobile stations whose requested transmission power is _PTH or lower are assigned in order. A slot is assigned by the base station control station 100 for the requested transmission power greater than the threshold value P _TH , but no slot is assigned by the base station control station 100 for a requested transmission power less than or equal to the threshold value P _TH . For this reason, in the case of the mobile station 300 that requested the requested transmission power to be equal to or less than the threshold value _PTH (No in step S42), the scheduling unit 251 starts with the largest requested transmission power that is not assigned the slot selected in step S41. In order, a slot to be allocated is selected from the remaining slots other than the slot allocated in the first stage (step S44). The above procedure is repeated until there is no unassigned mobile station (if step S45 is No, step S41, step S42, and step S44 are repeated).

  The scheduling unit 251 uses the requested transmission power assigned to each slot as the downlink transmission power. The slot allocation result is notified by the transmission unit 230 to the mobile station 300 in the cell through the control slot (step S46, step S24 in FIG. 14). Thereafter, the allocated data is transmitted in the downlink by a desired modulation method (step S47, step S25 in FIG. 14).

  In addition, after the allocation of the downlink transmission power (requested transmission power) at the base station 200 is completed, the base station notification unit 210 associates the downlink transmission power allocated to each slot with the slot number and performs base station control. The station 100 is notified (step S23 in FIG. 14). However, this procedure does not matter in the order of the control information transmission and data transmission procedure to each mobile station 300. In the base station control station 100 that has received the notification, the control station acquisition unit 110 acquires downlink transmission power, and the transmission power storage unit 121 as transmission power information in which the acquired downlink transmission power is associated with a cell (cell identifier). Write to. Note that the update of the transmission power information is not limited to the case where the transmission power information is notified from the base station 200. Even when a downlink transmission power notification is regularly received from each base station 200 or when a downlink allocation request is received from the base station 200, the downlink transmission power is collected from each base station 200. Good.

The result of slot allocation performed as described above is shown in FIG. The upper part of FIG. 18 is a diagram showing the value of downlink transmission power for each slot for each cell, and the lower part of FIG. 18 is a frame configuration diagram showing the result of the slot assignment of cell 1. Specifically, when _PTH is set as shown in FIG. 7, the terminal A, terminal B, and terminal F set the downlink transmission power in the base station control station 100. Base station 200a arranged in cell 1 reports to base station control station 100 the number of slots used by terminal A, terminal B, and terminal F and their required transmission power. At this time, the base station control station 100 collects downlink transmission power information from the base stations 200b and 200c of the adjacent cell 2 and cell 3 (or reads the collected transmission power information from the transmission power storage unit 121), and Calculate the sum for each. In the calculation, a value that corrects the distance between the base station 200a and the base stations 200b and 200c serving as the peripheral interference stations is taken into account, but in this case, since the cell 2 and the cell 3 are equidistant from the base station, no correction is performed. good.

  Using the sum of the downlink transmission power shown in FIG. 15, the request slots are assigned from the slot 8 with the smallest sum. Next, the requested transmission power is assigned to slot 7. Finally, the requested transmission power is assigned to slot 6. Allocation information including three slot numbers and power information is notified to base station 200, and base station 200 performs slot allocation for each terminal. The slot allocation in the base station 200a is started from the terminal having the large required transmission power, and specifically, the terminals F, A, B, E, C, G, and D are in this order. The slot allocation is selected from slots that satisfy the required downlink transmission power of each terminal.

  Thus, according to the slot allocation of the first embodiment, in the radio communication system composed of a plurality of cells, the requested transmission power derived from the propagation path status of each mobile station 300 is changed to the transmission power status of the adjacent cell. Accordingly, adaptively assigning the slots to the slots makes it possible to suppress a deterioration in wireless communication quality due to interference waves from adjacent cells. Further, by using a slot having a small interference power value, it is possible to suppress excessive power consumption for improving quality.

  Note that the transmission power allocation as described above is not necessarily performed every frame.

  Further, in the present embodiment, for the requested transmission power smaller than the threshold, the requested transmission power is allocated to an unallocated slot in the base station 200. This is based on the premise that the requested transmission power below the threshold is less affected by interference.

  Further, when it is desired to assign a plurality of slots to one mobile station 300 for the number of slots and the requested transmission power that the base station 200 notifies to the base station control station 100, so as to assign a plurality of slots to one requested transmission power, It is also possible to notify the base station control station 100.

(Second Embodiment)
Next, a second embodiment of the wireless communication system according to the present invention will be described. This embodiment is different from the first embodiment in that the slot transmission power allocation work is performed by the base station.

  This embodiment uses the TDMA communication system and the FDMA communication system as in the first embodiment. The description of the TDMA communication system and the FDMA communication system used in this embodiment is the same as that of the first embodiment, and will be omitted. The system configuration of this embodiment is also the same as that shown in FIG.

  The base station control station and the base station are different from those in the first embodiment. FIG. 19 is a block diagram illustrating a configuration example of a base station control station according to the second embodiment. FIG. 20 is a block diagram illustrating a configuration example of a base station according to the second embodiment. The control information processing unit 420 of the base station control station 400 in FIG. 19 has a configuration obtained by removing the allocation unit 123 from the control information processing unit 120 in FIG. The base station 500 in FIG. 20 has a configuration in which the same function as the allocation unit 123 is added to the scheduling unit 551 of the mobile station control unit 550 and the adjacent cell information storage unit 553 is added to the scheduling unit 551.

  The interference power calculation unit 122 of the base station control station 400 adds, for each slot, downlink transmission power of one or more cells adjacent to a cell other than the base station that has received the transmission of interference power information. The interference power value is calculated. The scheduling unit 551 of the base station 500 performs slot allocation using the interference power value acquired from the base station control station 400 and the requested transmission power received from the mobile station 300. Although the slot allocation procedure will be described later, it is generally the same as the procedure of the allocation unit 123 of the first embodiment. The adjacent cell information storage unit 553 is a storage area for storing information related to adjacent cells. In the present embodiment, the interference power value is stored as neighboring cell information. Note that the neighboring cell information storage unit 553 may be an area that temporarily stores neighboring cell information. For example, it may be a storage area secured only when slot allocation is performed. Therefore, it is only necessary to provide a mechanism for securing a storage area for storing adjacent cell information.

  Since the block function related to the mobile station is the same as that of the first embodiment, the description thereof is omitted.

  The procedure and operation of slot allocation in the second embodiment will be described below. FIG. 21 is a sequence diagram illustrating an example of slot allocation in the second embodiment. Compared with FIG. 14 which is the sequence diagram of the first embodiment, there is a difference that each base station 500 in each cell performs slot allocation and mobile station allocation of each slot of the radio communication frame.

  In the following explanation, scheduling examples of downlink radio data in the example of the cell arrangement and the required transmission power of the cell 1 shown in FIGS. 6 to 9 will be explained as in the first embodiment. As for the cell 2 and the cell 3 in FIG. 9, it is assumed that channel allocation has already been performed by the same method as in the present experimental mode (or the first embodiment), as in the first embodiment. It is assumed that the relative relationship between the requested transmission powers of the mobile stations 300 of the cell 2 and the cell 3 is as shown in FIGS. 10 and 11, and the allocation status of each channel is as shown in FIGS. It is assumed that the allocation status has been reached.

  First, the base station control station 400 collects transmission power information from each base station 500 as in FIG. 14 (step S50). When a communication request is generated from the terminal A in the cell 1 at the terminal G and a slot allocation opportunity is obtained, first, as shown in FIG. 20, a control signal periodically transmitted from the base station is transmitted to the mobile station 300 ( Each of terminals A to G) performs reception (step S51). Each mobile station 300 measures the received power level of the received signal (step S52) and further demodulates the received signal (step S53) to obtain control information (transmission power information) transmitted from the base station 500. (Step S54). The control signal is transmitted from the base station 500 at regular intervals, and the transmission power is set to the power and modulation scheme that can be received even when the mobile station 300 is located near the cell edge. It is assumed that the control information transmitted in the control slot includes transmission power of the control slot that transmitted the control information and slot allocation information of each mobile station. Next, the propagation loss of the radio wave in the propagation path is calculated from the transmission power and reception power level obtained from the demodulated signal. The mobile station derives the required transmission power and modulation scheme based on the above-described propagation loss (step S55), and notifies the base station 500 of the result via the uplink.

  The base station 500 obtains the required downlink transmission power of each mobile station 300 required in the slot allocation method (step S57). During this time, the base station 500 transmits data to terminals that have already been assigned (step S56).

  The base station 500 receives the interference power value of each slot based on the downlink transmission power of the neighboring base station 500 from the base station control station 400 (step S58) and stores it in the neighboring cell information storage unit 553. The interference power value is calculated in the same manner as in the first embodiment, and the interference level of the base station 500 of the adjacent cell serving as the interference station is lower than the base station 500 of the nearest cell due to factors such as physical distance or topographical obstacle. As for base station 500, it is desirable to set a coefficient corresponding to the attenuation amount in advance.

  Next, scheduling section 551 of base station 500 performs slot allocation in the order of the largest required transmission power (step S59). FIG. 22 is a flowchart showing an example of the slot assignment operation used by the mobile station 300 in the base station 500. Scheduling section 551 assigns slots in the order of the largest required transmission power. For this reason, the mobile station that has requested the largest required transmission power is selected from the mobile stations 300 to which no slot is assigned (step S71). In the allocation method, the selected requested transmission power is allocated to the unallocated slot having the smallest interference power value, which is the sum of the transmission powers of adjacent base stations 500 serving as interference waves (step S72). The mobile station that has the highest requested transmission power is assigned in order from the mobile station that requires the largest requested transmission power, and the slot of the mobile station that has the next largest requested transmission power is the most slot other than the slot that is used by the mobile station that requires the largest requested transmission power. It is assigned to the slot where the sum of interference power values is low. Thereafter, the process is continued until there is no slot to which the above work is assigned (step S73).

  The slot allocation result is reported to the mobile station in the cell through the control slot (step S74). Thereafter, the allocated data is transmitted in the downlink (step S75).

  In addition, after allocation of downlink transmission power at base station 500 is completed, transmission power allocation information is notified to base station control station 400. However, this procedure is possible even after the control information transmission and data transmission procedure to each mobile station 300.

  The result of the assignment performed as described above is the same as in FIG. Specifically, the base station performs downlink transmission power setting and slot allocation in the order of terminal F, terminal A, terminal B, terminal E, terminal C, terminal G, and terminal D. At this time, the base station control station 400 collects downlink transmission power information from the base stations of the neighboring base stations cell 2 and cell 3, and calculates the sum of each slot as an interference power value (interference power calculation). Unit 122). The calculated interference power value is notified to the base station 500 to be allocated. Allocation at base station 500 is such that mobile station 300 with the highest required transmission power is assigned to the slot with the smallest interference power value for each slot.

  In the first embodiment, allocation of requested transmission power below a threshold is performed in the base station 200 without using transmission power information (interference power value). May result different from FIG. Here, only cases where similar results are obtained are shown.

  Thus, according to the slot allocation of the second embodiment, in the radio communication system composed of a plurality of cells, the requested transmission power derived from the propagation path status of each mobile station 300 is changed to the transmission power status of the adjacent cell. Therefore, adaptive allocation to slots can suppress degradation of wireless communication quality due to interference waves from adjacent cells, and use of slots with small interference power values can increase excessive quality. Power consumption can be reduced. Furthermore, compared to the first embodiment, there is an advantage that the amount of information exchanged between the base station control station 400 and the base station 500 is small, and the time required for allocation can be shortened.

  In the present embodiment, the case where base station control station 400 notifies base station 500 of the interference power value calculated from the transmission power information has been described, but in the case of transmitting transmission power information itself to base station 200. There may be. In this case, although the amount of information notified from the base station control station 400 to the base station 200 increases, the processing amount of the base station control station 400 itself decreases. Also, the neighboring cell information storage unit 553 stores transmission power information.

  Furthermore, the base station control station 400 of the present embodiment may be configured to include the allocation unit 123. For example, the base station control station 100 shown in FIG. 3 may accept a request for sending an interference power value from the base station 500 and notify the interference power value. When the base station control station 100 shown in FIG. 3 also has a function of accepting an interference power value transmission request, the base station 200 shown in FIG. 4 and the base station 500 shown in FIG. It will be good.

(Third embodiment)
In the third embodiment, an example in which the basic allocation method is the same as that in the first embodiment and the second embodiment, but the frame configuration used for communication is different will be described.

  The frame configuration of the present embodiment is a communication method having both characteristics of the TDMA method and the FDMA method, and is a communication method generally used in a multicarrier communication method. The description of the TDMA method and the FDMA method has been described in the first embodiment, and will be omitted.

  FIG. 23 is a diagram illustrating an example of a multicarrier / (TDMA, FDMA) two-dimensional frame configuration that is a target of the third embodiment. In FIG. 23, the vertical axis represents frequency and the horizontal axis represents time. In FIG. 23, one of the squares is a minimum unit used for data transmission, and in the present embodiment, this is called a slot. Among the slots, the hatched square is the control slot (T0). In the case of this figure, it means that there are 9 slots in the time direction and 12 slots in the frequency direction in one frame, which means that there are a total of 108 slots (of which 12 slots are control slots). ing.

  When performing wireless data communication from a base station to a mobile station, the base station can also transmit data by assigning each small square (slot) in FIG. 23 shown in the description of the frame configuration to a separate mobile station. It is also possible to perform radio communication by assigning all slots to one mobile station.

  In the present embodiment, the method of allocating transmission power at the base station control station shown in the first embodiment using the above frame configuration or the method of allocating slots at the base station shown in the second embodiment is used. Wireless data communication.

  Thus, according to the slot allocation of the third embodiment, in a wireless communication system composed of a plurality of cells using the same frequency, the requested transmission power derived from the propagation path status of each mobile station is By adaptively allocating to slots according to the transmission power status, it is possible to suppress degradation of wireless communication quality due to interference waves from adjacent cells, and to improve quality by using slots with small interference power values. Therefore, excessive power consumption can be suppressed.

(Fourth embodiment)
In the fourth embodiment, a mode in which any one of the base stations 200 has a slot allocation function will be described. For example, in FIG. 2, a case where the base station 200b has a slot assignment function and the other base stations 200a, 200c, and 200d do not have a slot assignment function will be described as an example. The base stations 200a, 200c, and 200d exchange with the base station 200b the portions that were exchanged with the base station control stations 100 and 400 in the first embodiment and the second embodiment. That is, the base stations 200a, 200c, and 200d communicate with the base station 200b in steps S19, S21, and S23 in FIG. 14, or steps S58 and S60 in FIG. The base station 200b having the slot assignment function has at least the following components. A transmission power storage unit serving as a storage area for storing transmission power information is included in the configuration of the base station 200 of FIG. Other components are the same, but it is necessary to add a function of slot allocation from another base station 200 to the function of the scheduling unit 251. That is, the scheduling unit 251 needs to have a function of performing slot allocation requested from another base station 200.

  When the requested transmission power is received from the mobile station 300 in the own cell that is the control target, the scheduling unit 251 uses the transmission power information to bring down one or more cells adjacent to the own cell that is the control target. By adding the link transmission power for each slot, the interference power value for each slot is calculated, and the received requested transmission power is assigned to a slot whose interference power value is smaller than a predetermined value.

  In addition, when the base station acquisition unit 220 acquires the requested transmission power of the mobile station controlled by the other base station 200 from the other base station 200, the slot allocation of another cell is performed as follows. The scheduling unit 251 calculates the interference power value for each slot by adding the downlink transmission power of one or more cells adjacent to another cell for each slot using the transmission power information, and the interference power Allocation information for allocating the requested transmission power acquired to a slot whose value is smaller than a predetermined value is created. The created allocation information is notified to other base stations by the base station notification unit 210. In addition, although the case where the base station 200b has a slot assignment function has been described above, a plurality of base stations may have a slot assignment function. Further, all base stations may have a slot allocation function.

  Thus, in the present embodiment, a configuration is adopted in which a specific base station has a function of collecting transmission power information, a function of calculating an interference power value, and a function of assigning a slot using the interference power value. Can do. In this case, it is possible to adopt a configuration in which each base station has a function of allocating slots using the interference power value. In this case, the base station 500 (FIG. 20) described in the second embodiment is used. . In this way, it is possible to reduce interference between adjacent cells.

  As described above, in each of the above embodiments, the plurality of mobile stations report the setting value of the downlink transmission power used for transmission to the base station control station or the base station, and the base station control station or the base station is reported. Based on the setting value of the downlink transmission power, the setting value of the downlink transmission power of the base station is determined, and allocation is performed so that the amount of interference between the plurality of base stations is minimized. Thereby, in consideration of the transmission power of the adjacent cell, the base station control station or the base station can allocate the transmission power of the slot so that the interference power value of the mobile station of the own cell becomes smaller. As a result, each mobile station can perform good reception in a state where the amount of interference from adjacent base stations is minimized while being repeated by one cell. In particular, it is possible to reduce interference between cells in a wireless communication system that uses the same frequency between a plurality of adjacent cells.

  Further, as described in Non-Patent Document 1, in HSDPA (High-Speed Downlink Packet Access) standardized by 3GPP, the transmission power is basically constant, the modulation scheme and the error correction coding rate. Is selected dynamically, aiming at the maximum transmission rate adapted to the downlink propagation state. In this method, since the transmission power from the base station is always constant, the value of the interference power can be basically treated as constant, but also when the distance between the base station and the mobile station is short Since transmission is performed with a constant transmission power, transmission is performed using a surplus transmission power to a mobile station in a sufficiently good reception environment. According to the preferred embodiment of the present invention, the effect of controlling the downlink transmission power to an appropriate value for the mobile station is not only the reduction of the excessive transmission power of the base station, but also to the adjacent cell. There is also an effect of reducing the influence. That is, by reducing the transmission power, it becomes difficult for a signal to reach the adjacent cell from the own cell, and as a result, the power of the interference signal for the adjacent cell can be reduced.

  Further, in each of the above embodiments, as one aspect of a preferred radio communication system (radio cellular system), a one-cell repetition method in which the same frequency is used in adjacent cells is adopted, and the cell is controlled by one cell. A plurality of base stations are controlled by the control station, the mobile station is assigned at least a slot, and transmission power control is performed for the downlink from the base station to the mobile station. It has been explained that a control station or a base station having at least a part of functions of the control station, which is effectively applied to a wireless communication system to be made, includes at least a component (means) for performing the following functions . (1) Function (information collecting means) for collecting downlink transmission power information allocated to each slot from each of the base stations having jurisdiction over a plurality of adjacent cells, (2) Based on the collected transmission power information A function (interference information generating means) for generating information (interference information, interference power value) indicating the interference status for each slot, and (3) information indicating the interference status for each slot when downlink communication is performed. Based on the above, a function (allocation means) for dynamically (adaptively) allocating a slot having a low interference level to a communication destination mobile station. That is, in either or both of the control station and the base station of the wireless communication system, downlink transmission power information notified from the mobile station is collected via the base station of each cell (information collecting means), and the collected downlink A function of generating interference information by adding transmission power information for each slot and calculating a sum (interference information generating means), and using the generated interference information, adaptively assigning a mobile station to a slot (allocating means) To implement. The specific functions implemented in the control station or base station are as described in the above embodiment, and it is sufficient if the above functions are implemented as a whole wireless communication system, regardless of whether the control station or base station implements it. This is also shown in the above embodiments. Further, other functions performed by the control station or the base station are also described in the examples shown in the above embodiments.

  In each of the above-described embodiments, the description has been made on the assumption that slot allocation is performed independently for each cell. This is because it is preferable that each base station under the control of the base station performs the reassignment work at a different time because the base station control station and the base station control are assigned with reference to neighboring base station information. Based. In particular, when the allocation is performed simultaneously in adjacent base stations, the interference situation changes simultaneously in the post-allocation frame, which may affect the radio communication quality. For this reason, it is desirable to prevent a phenomenon in which slot allocation is simultaneously performed for a plurality of cells. In addition, at the time of transmission power allocation in the base station control station and the base station, it is preferable to perform power allocation in consideration of degradation due to interference waves from adjacent cells.

  Also, in each of the above embodiments, the mobile station can increase the downlink transmission power by intentionally increasing the required transmission power for transmission. For example, in the case of emergency contact or when it is desired to construct an emergency contact network in the event of a disaster, the required transmission power can be increased particularly. In particular, a mobile station with high publicity such as used in a disaster can be provided with an emergency mode or the like, and a function for increasing the required transmission power can be added by changing the mode. Alternatively, instead of changing the mode, a special switch may be provided and a function may be added by increasing the required transmission power by pressing the switch.

It is a figure which shows an example of a frame structure. FIG. 1A is a diagram illustrating an example of a general TDMA frame configuration. FIG. 1B is a diagram showing an example of a general FDMA frame configuration. It is the figure which showed the structural example of the radio | wireless communications system of 1st Embodiment. It is a block diagram which shows the structural example of the base station control station of 1st Embodiment. It is a block diagram which shows the structural example of the base station of 1st Embodiment. It is a block diagram which shows the structural example of the mobile station of 1st Embodiment. It is the figure which showed the typical example about the terminal arrangement | positioning which exists in a cell and a cell. It is a figure which shows the relative relationship of the magnitude | size of request | requirement transmission power regarding each terminal AF in the cell 1. FIG. It is a figure which shows the example of a frame structure used in 1st Embodiment. It is a figure which shows the relationship between a cell and terminal arrangement | positioning. It is a figure which shows the relative relationship of the magnitude | size of request | requirement transmission power regarding each terminal HN in the cell 2. FIG. It is a figure which shows the relative relationship of the magnitude | size of request | requirement transmission power regarding each terminal OU in the cell 3. FIG. FIG. 4 is a diagram showing a slot allocation situation of each terminal H to N in the cell 2. FIG. 4 is a diagram showing a slot allocation situation of each terminal OU in the cell 3. It is a sequence diagram which shows an example of the slot allocation in 1st Embodiment. It is a figure which shows the sum of the transmission power for every slot of each of several cells. It is a flowchart which shows an example of a slot allocation procedure. It is a flowchart which shows an example of the procedure in which a base station allocates a mobile station to each slot. It is a figure which shows an example of the result of the slot allocation of 1st Embodiment. It is a block diagram which shows the structural example of the base station control station of 2nd Embodiment. It is a block diagram which shows the structural example of the base station of 2nd Embodiment. It is a sequence diagram which shows an example of the slot allocation in 2nd Embodiment. It is a flowchart which shows an example of the allocation operation | movement of the slot which the mobile station uses in a base station. It is a figure which shows an example of the multi-carrier / (TDMA, FDMA) two-dimensional frame structure used as the object of 3rd Embodiment. It is a figure which shows the frequency allocation example of the radio | wireless communication system which performs radio | wireless communication using a different frequency band in an adjacent cell.

Explanation of symbols

100, 400 Base station control station 110 Control station acquisition unit 120, 420 Control information processing unit 121 Transmission power storage unit 122 Interference power calculation unit 123 Allocation unit 130 Control station notification unit 200, 200a to 200d, 500 Base station 210 Base station notification Unit 220 base station acquisition unit 230 transmission unit 240 reception unit 250, 550 mobile station control unit 251, 551 scheduling unit 252 power control unit 260 antenna unit 300, 300a to 300l mobile station 310 reception unit 320 transmission unit 330 information processing unit 340 antenna Unit 350 received power measurement unit 553 neighbor cell information storage unit

Claims (15)

In a wireless communication system that uses the same frequency between a plurality of adjacent cells, a control station that manages a plurality of base stations that wirelessly communicate with mobile stations in a cell using a frame composed of a plurality of slots,
Acquire the downlink transmission power allocated to each slot from each base station of multiple cells and acquire the required transmission power required for downlink communication with the mobile station from the base station of a specific cell And
An interference power calculation unit that calculates an interference power value for each slot by adding the downlink transmission power of one or more cells adjacent to the specific cell for each slot;
An allocating unit that allocates the requested transmission power to a slot in which the interference power value is smaller than a predetermined value;
A control station, comprising: a control station notifying unit that notifies the base station of the specific cell of allocation information in which the requested transmission power is allocated to a slot. The control station acquisition unit acquires a plurality of request transmission powers,
2. The control station according to claim 1, wherein the allocating unit sequentially selects a slot having a small interference power among a plurality of slots, and allocates a plurality of requested transmission powers to the selected slot in a descending order. In a wireless communication system that uses the same frequency between a plurality of adjacent cells, a control station that manages a plurality of base stations that wirelessly communicate with mobile stations in a cell using a frame composed of a plurality of slots,
A transmission power storage unit that stores downlink transmission power assigned to each slot in a plurality of base stations in association with cells;
An interference power calculation unit that calculates an interference power value for each slot by adding the downlink transmission power of one or more cells adjacent to a specific cell for each slot;
A control station acquisition unit for acquiring a transmission request for the interference power value from a base station;
A control station notifying section for notifying the base station of an interference power value calculated by selecting the cell of the base station requested to be sent by the interference power calculating section as the specific cell; . In a wireless communication system using the same frequency between a plurality of adjacent cells, a base station that wirelessly communicates with a mobile station in a cell to be controlled,
A receiver that receives the requested transmission power that the mobile station requests as downlink transmission power;
A base station notifying unit for notifying the requested transmission power to the control station according to claim 1;
A base station acquisition unit for acquiring allocation information in which requested transmission power is allocated to slots from the control station;
A scheduling unit that associates the mobile station that requested the requested transmission power with the slot using the allocation information;
A base station comprising: a transmission unit that notifies a mobile station that has requested the requested transmission power of a slot to which the requested transmission power is allocated. The receiving unit receives a plurality of requested transmission powers,
The scheduling unit selects a request transmission power that is greater than a predetermined threshold among the plurality of received request transmission powers,
The base station according to claim 4, wherein the base station notification unit notifies the selected requested transmission power. In a wireless communication system that uses the same frequency between a plurality of adjacent cells, a base station that wirelessly communicates with a mobile station in a cell to be controlled using a frame composed of a plurality of slots,
A base station acquisition unit that acquires, from the control station, an interference power value calculated for each slot by adding the downlink transmission power of one or more cells adjacent to the cell to be controlled for each slot;
A receiving unit that receives request transmission power that the mobile station requests as downlink transmission power; and
A scheduling unit that allocates the received request transmission power to the slot having the acquired interference power value being small;
A base station comprising: a transmission unit that notifies a mobile station that has requested the requested transmission power of a slot to which the requested transmission power is allocated. A wireless communication system that uses the same frequency between a plurality of adjacent cells, and that uses a frame composed of a plurality of slots to wirelessly communicate with mobile stations in a cell to be controlled and to manage other base stations Station,
A base station acquisition unit that collects downlink transmission power assigned to each slot for cells of other base stations;
A receiving unit that receives request transmission power that the mobile station requests as downlink transmission power; and
An interference power calculation unit that calculates an interference power value for each slot by adding the downlink transmission power of one or more cells adjacent to the cell to be controlled for each slot;
A scheduling unit that allocates the requested transmission power received to a slot having a small interference power value;
A base station comprising: a transmission unit that notifies a mobile station that has requested the requested transmission power of a slot to which the requested transmission power is allocated. The base station acquisition unit acquires a request transmission power requested by a mobile station of another cell from another base station,
The interference power calculation unit calculates the interference power value for each slot by adding the downlink transmission power of one or more cells adjacent to the other cell for each slot,
The scheduling unit creates allocation information for allocating the requested transmission power acquired to a slot having a small interference power value,
The base station according to claim 7, wherein the base station notification unit notifies the created allocation information to the other base station.   9. The scheduling unit according to claim 6, wherein the scheduling unit sequentially selects slots having a small interference power value among a plurality of slots, and assigns a plurality of request transmission powers to the selected slots in descending order. Base station as described in. In a radio communication system that uses the same frequency between a plurality of adjacent cells, a slot assignment method for a control station that manages a plurality of base stations that perform radio communication with mobile stations in the cell using a frame composed of a plurality of slots. There,
Collecting downlink transmission power assigned to each slot for each of a plurality of cells from a plurality of base stations;
Receiving requested transmission power required for downlink communication with a mobile station from a base station of a specific cell;
Calculating an interference power value for each slot by adding the downlink transmission power of one or more cells adjacent to the specific cell for each slot;
Allocating the requested transmission power to a slot having a small interference power value;
Notifying the base station of the specific cell of the allocation information for allocating the requested transmission power to the slot. A wireless communication system that uses the same frequency between a plurality of adjacent cells, a slot allocation method for a wireless communication system that uses a frame composed of a plurality of slots adjacent to a plurality of cells in which a mobile station exists,
Collecting downlink transmit power assigned to each slot from a base station of each of a plurality of cells;
Calculating an interference power value by adding the downlink transmission power of one or more cells adjacent to a specific cell among the collected downlink transmission powers for each slot;
Obtaining requested transmission power required as downlink transmission power from the base station of the specific cell;
Allocating the requested transmission power to a slot having a small interference power value.   The interference power calculation unit multiplies the downlink transmission power by a coefficient corresponding to an attenuation, and adds the downlink transmission power multiplied by the coefficient for each slot. The listed control station.   The base station according to claim 7, wherein the interference power calculation unit multiplies the downlink transmission power by a coefficient corresponding to an attenuation amount, and adds the downlink transmission power multiplied by the coefficient for each slot. .   11. The step of calculating the interference power includes multiplying the downlink transmission power by a coefficient corresponding to an attenuation amount, and adding the downlink transmission power multiplied by the coefficient for each slot. Item 12. The slot allocation method according to Item 11. Uses the same frequency between multiple adjacent cells, manages multiple base stations that are adjacent to multiple cells in which a mobile station exists, and that communicate wirelessly with mobile stations in the cell using a frame composed of multiple slots A wireless communication system comprising a control station for
By either the base station or the control station,
Collect the downlink transmit power allocated to each slot from the base station of each of multiple cells,
Of the collected downlink transmission power, calculate the interference power value for each slot based on the downlink transmission power of one or more cells adjacent to a specific cell,
Obtaining requested transmission power required as downlink transmission power from the base station of the specific cell;
A wireless communication system, wherein the requested transmission power is allocated to a slot having a small interference power value.

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