JP2008227769A - Assignment method and base station device utilizing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration in reception characteristics caused by a signal from an uncontrolled terminal unit. <P>SOLUTION: At a control channel assignment section 36, a frame formed by the time multiplexing of a plurality of time slots is prescribed, while the time slot is formed by the frequency multiplexing of a plurality of subchannels, and one of the plurality of time slots, where a prescribed frame is formed, is identified. Then, one of the plurality of subchannels with the identified time slot formed is assigned to a control signal. A radio resource assignment section 38 preferentially assigns a subchannel, except the subchannel assigned to the control signal to the terminal unit in identified time slots. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an allocation technique, and more particularly to an allocation method for allocating a channel to a terminal apparatus and a base station apparatus using the allocation method.

In a wireless communication system, a base station device may connect a plurality of terminal devices. One of the forms when the base station apparatus connects a plurality of terminal apparatuses is TDMA / TDD. In TDMA / TDD, a frame is formed by a plurality of time slots, and a plurality of frames are continuously arranged. Further, some of the plurality of time slots included in one frame are used for the uplink, and the remaining time slots are used for the downlink. In the prior art using such TDMA / TDD, the number of time slots used for the uplink in one frame and the number of time slots used for the downlink are determined as traffic. It is set according to the difference (see, for example, Patent Document 1).
JP-A-8-186533

  In general, effective use of limited frequency resources is desired in wireless communication. In particular, as the communication speed increases, the demand is further increased. One technique for meeting this demand is the OFDMA (Orthogonal Frequency Division Multiple Access) scheme, which can be combined with the TDMA / TDD described above. OFDMA is a technique for frequency-multiplexing a plurality of terminal devices using OFDM. In such OFDMA, a subchannel is formed by a plurality of subcarriers, and a multicarrier signal is formed by a plurality of subchannels. Further, the base station apparatus performs communication with the terminal apparatus by assigning at least one subchannel to the terminal apparatus.

  On the uplink, a signal is transmitted from each of the plurality of terminal devices to the base station device, but the base station device performs batch FFT on the signals from the plurality of terminal devices. Therefore, the strength of each signal received by the base station apparatus is required to be the same value. The base station apparatus controls each of the plurality of terminal apparatuses so that each of the plurality of terminal apparatuses performs transmission power control. On the other hand, when the same frequency band is used in a plurality of base station apparatuses, signals received by the base station apparatus include those transmitted from terminal apparatuses that are not communicating, that is, not controlled. Since the base station apparatus cannot control the strength of the signal, if the strength of the signal increases, there is a possibility that the reception characteristics may deteriorate.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an allocation technique that suppresses deterioration of reception characteristics due to a signal from a terminal device that is not controlled.

  In order to solve the above problems, a base station apparatus according to an aspect of the present invention defines a frame formed by time multiplexing of a plurality of time slots while forming a time slot by frequency multiplexing of a plurality of subchannels. A survey unit that investigates the usage status of multiple time slots that form each frame in units of multiple frames, and a time slot with a low usage status based on the usage status surveyed by the survey unit A control signal indicating one of a plurality of subchannels that form a time slot that is included in a specific part to be specified and a time slot that is specified in the specific part and that should appear at intervals of the plurality of frames And an assigning unit to be assigned to

  According to this aspect, a time slot that is not used by another base station apparatus is specified, and the subchannel included in the specified time slot is assigned to the control signal. Can be prevented.

  The investigation unit measures the received power in each of a plurality of time slots as an investigation of the usage situation of the time slot, and the specific unit as a time slot with less usage situation, based on the measurement result in the investigation part, A time slot with low received power may be specified. In this case, since a time slot with low received power is specified, a time slot that is not used by another base station apparatus can be specified.

  Another aspect of the present invention is an allocation method. In this method, frames formed by time multiplexing of a plurality of time slots are defined while forming time slots by frequency multiplexing of a plurality of subchannels, and each frame is formed in units of a plurality of frames. A step of investigating the usage status of each of the plurality of time slots, a step of identifying a time slot having a low usage status based on the surveyed usage status, and an interval between the identified time slots and a plurality of frames Assigning any one of a plurality of subchannels forming time slots included in a frame to appear in the control signal to a control signal.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the deterioration of the receiving characteristic by the signal from the terminal device which is not controlled can be suppressed.

  Before describing the present invention specifically, an outline will be given first. Embodiments of the present invention relate to a communication system including a base station device and at least one terminal device. In the communication system, each frame is formed by time-division multiplexing a plurality of time slots, and each time slot is formed by frequency-division multiplexing a plurality of subchannels. Each subchannel is formed by a multicarrier signal. Here, OFDM signals are used as multicarrier signals, and OFDMA is used as frequency division multiplexing. The base station apparatus performs communication with the plurality of terminal apparatuses by assigning each of the plurality of subchannels included in each time slot to the terminal apparatus.

  On the other hand, in consideration of effective use of frequencies, the same frequency band is also used in neighboring base station apparatuses. Therefore, there is a possibility that a terminal device connected to the base station apparatus and a terminal apparatus connected to another base station apparatus are mixed in the same time slot. For this base station apparatus, since a terminal apparatus connected to another base station apparatus is not subject to control, there is a possibility that the strength of the uplink signal transmitted from the terminal apparatus is too high or there is a frequency offset. There is also. In general, this affects the uplink signal transmitted from the terminal apparatus connected to the base station apparatus. As a result, the reception characteristics of the base station apparatus deteriorate.

  The communication system forms a super frame by a plurality of frames, and assigns subchannels to control signals in units of super frames (hereinafter, control signals are also referred to as “control channels”). The control signal is a signal used to establish and maintain communication, and can be said to be highly important. Even for such a control signal, it is necessary to reduce the influence of interference as described above. In order to cope with this, the base station apparatus according to the present embodiment executes the following processing.

  The base station apparatus measures received power in each time slot included in the superframe before executing control channel allocation. When the received power is high, it can be said that most of the subchannels included in the time slot are used by other base station apparatuses. Therefore, the base station apparatus specifies a time slot with low received power and assigns one of a plurality of subchannels included in the specified time slot to the control signal.

  In addition, after transmitting the control signal, the base station apparatus receives a communication start request, that is, a subchannel allocation request, from the terminal apparatus. At that time, the base station apparatus allocates a subchannel of a time slot including the subchannel allocated to the control signal to the terminal apparatus. If each base station apparatus assigns control signals to different time slots, interference between control signals is reduced. In addition, the subchannel included in the time slot to which the control signal is assigned becomes difficult to be used by other base station apparatuses. As a result, by preferentially using the subchannel included in the time slot to which the control signal is allocated, it becomes difficult to allocate a terminal apparatus connected to another base station apparatus in the time slot.

  When a terminal device connected to another base station device is assigned in a time slot including a subchannel assigned to the terminal device, the terminal device connected to another base station device moves, There is also a possibility that the influence of interference becomes large. At this time, the base station apparatus requests another base station apparatus to release the subchannel assigned to the terminal apparatus. Further, when the terminal apparatus is handed over to the base station apparatus, the base station apparatus can control the terminal apparatus.

  FIG. 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. The communication system 100 includes a first terminal device 12a, a second terminal device 12b, and a third terminal device 12c, which are collectively referred to as a base station device 10 and a terminal device 12.

  The base station device 10 has a terminal device 12 connected to one end via a wireless network and a wired network (not shown) connected to the other end. Further, the terminal device 12 is connected to the base station device 10 via a wireless network. The base station apparatus 10 performs communication with the plurality of terminal apparatuses 12 by assigning communication channels to the plurality of terminal apparatuses 12. Specifically, when the terminal device 12 receives a control signal transmitted from the base station device 10, the terminal device 12 confirms the presence of the base station device 10. Further, the terminal apparatus 12 transmits a channel allocation request signal to the base station apparatus 10, and the base station apparatus 10 allocates a communication channel to the terminal apparatus 12 in response to the received request signal.

  In addition, the base station apparatus 10 transmits information on the communication channel assigned to the terminal apparatus 12, and the terminal apparatus 12 performs communication with the base station apparatus 10 while using the assigned communication channel. As a result, the data transmitted from the terminal device 12 is output to the wired network via the base station device 10 and finally received by a communication device (not shown) connected to the wired network. Data is also transmitted in the direction from the communication device to the terminal device 12. In the above description, the communication channel is specified by the combination of the subchannel and the time slot described above. In addition, since the base station apparatus 10 has a plurality of time slots and a plurality of subchannels, the base station apparatus 10 executes OFDMA using a plurality of subchannels while executing TDMA using the plurality of time slots.

  2A to 2C show a frame configuration in the communication system 100. FIG. The horizontal direction in the figure corresponds to the time axis. The frame is formed by 8 time slots. The eight time slots are composed of four upstream time slots and four downstream time slots. Here, four uplink time slots are indicated as “first uplink time slot” to “fourth uplink time slot”, and four downlink time slots are indicated as “first downlink time slot” to “fourth downlink time slot”. . Further, the illustrated frame is repeated continuously. The configuration of the frame is not limited to that shown in FIG. 2A. For example, the frame configuration may be configured by four time slots or 16 time slots. The configuration will be described with reference to FIG.

  For the sake of brevity, it is assumed that the upstream time slot and the downstream time slot have the same configuration. For this reason, only one of the uplink time slot and the downlink time slot may be described, but the same description is valid for the other time slot. Furthermore, a super frame is formed by continuing a plurality of frames shown in FIG. Here, as an example, it is assumed that a super frame is formed by “20” frames.

  FIG. 2B shows the configuration of one time slot in FIG. The vertical direction in the figure corresponds to the frequency axis. As shown in the figure, one time slot is formed by “16” subchannels from “first subchannel” to “16th subchannel”. In addition, the plurality of subchannels are frequency division multiplexed. Since each time slot is configured as shown in FIG. 2B, the above-described communication channel is specified by the combination of the time slot and the subchannel. Also, the frame configuration corresponding to one subchannel in FIG. 2B may be as shown in FIG. Note that the number of subchannels arranged in one time slot may not be “16”. Here, it is assumed that the allocation of the subchannel in the uplink time slot and the allocation of the subchannel in the downlink time slot are the same. Further, it is assumed that at least one control signal is assigned in units of superframes. For example, a control signal is assigned to one subchannel of one time slot among a plurality of downlink time slots included in a superframe. The same applies to the uplink.

  FIG. 2 (c) shows the configuration of one subchannel in FIG. 2 (b). Similar to FIG. 2A and FIG. 2B, the horizontal direction in the figure corresponds to the time axis, and the vertical direction in the figure corresponds to the frequency axis. Further, numbers “1” to “29” are assigned to the frequency axis, and these indicate subcarrier numbers. In this way, the subchannel is composed of multicarrier signals, and in particular is composed of OFDM signals. “TS” in the figure corresponds to a training symbol and is constituted by a known value. Further, it is assumed that a control signal may be included in “TS”. “GS” corresponds to a guard symbol, and no substantial signal is arranged here. “PS” corresponds to a pilot symbol, and is configured by a known value. “DS” corresponds to a data symbol and is data to be transmitted. “GT” corresponds to a guard time, and no substantial signal is arranged here.

  FIG. 3 shows an arrangement of subchannels in the communication system 100. In FIG. 3, the frequency axis is shown on the horizontal axis, and the spectrum for the time slot shown in FIG. 2B is shown. As described above, 16 subchannels from the first subchannel to the 16th subchannel are frequency division multiplexed in one time slot. Each subchannel is configured by a multicarrier signal, here, an OFDM signal.

  FIG. 4 shows the configuration of the base station apparatus 10. The base station apparatus 10 includes a first RF unit 20a, a second RF unit 20b, an NRF unit 20n, a baseband processing unit 22, a modem unit 24, an IF unit 26, a radio control unit 28, and a storage unit 30. including. Further, the radio control unit 28 includes a survey unit 32, a specifying unit 34, a control channel allocation unit 36, a radio resource allocation unit 38, a measurement unit 40, and an instruction unit 42. Further, the base station apparatus 10 is connected to the network 50.

  As a reception process, the RF unit 20 performs frequency conversion on a radio frequency multicarrier signal received from a terminal device 12 (not shown) to generate a baseband multicarrier signal. Here, the multicarrier signal is formed as shown in FIG. 3, and corresponds to the uplink time slot of FIG. Further, the RF unit 20 outputs a baseband multicarrier signal to the baseband processing unit 22. In general, a baseband multicarrier signal is formed by an in-phase component and a quadrature component, and therefore should be transmitted by two signal lines. For the sake of clarity, a single signal line is used here. Only. The RF unit 20 also includes an AGC and an A / D conversion unit.

  As a transmission process, the RF unit 20 performs frequency conversion on the baseband multicarrier signal input from the baseband processing unit 22 to generate a radiofrequency multicarrier signal. Further, the RF unit 20 transmits a radio frequency multicarrier signal. The RF unit 20 transmits a multicarrier signal while using the same radio frequency band as the received multicarrier signal. That is, as shown in FIG. 2A, TDD (Time Division Duplex) is used. The RF unit 20 also includes a PA (Power Amplifier) and a D / A conversion unit.

  The baseband processing unit 22 inputs a baseband multicarrier signal from each of the plurality of RF units 20 as a reception operation. Since the baseband multicarrier signal is a time domain signal, the baseband processing unit 22 converts the time domain signal to the frequency domain by FFT and performs adaptive array signal processing on the frequency domain signal. To do. Further, the baseband processing unit 22 executes timing synchronization, that is, FFT window setting, and also deletes the guard interval. Since a known technique may be used for timing synchronization and the like, description thereof is omitted here. The baseband processing unit 22 outputs the result of adaptive array signal processing to the modem unit 24. As a transmission operation, the baseband processing unit 22 receives a multi-carrier signal in the frequency domain from the modulation / demodulation unit 24 and performs dispersion processing using weight vectors.

  As a transmission operation, the baseband processing unit 22 converts the frequency domain signal to the time domain by IFFT on the frequency domain multicarrier signal input from the modem unit 24, and converts the converted time domain signal to the RF unit. 20 output. The baseband processing unit 22 also adds a guard interval, but the description is omitted here. Here, the frequency domain signal includes a plurality of subchannels as shown in FIG. 2B, and each of the subchannels includes a plurality of subcarriers as in the vertical direction of FIG. 2C. For the sake of clarity, it is assumed that the signals in the frequency domain are arranged in the order of subcarrier numbers to form a serial signal.

  The modem unit 24 performs demodulation on the multi-carrier signal in the frequency domain from the baseband processing unit 22 as reception processing. The multicarrier signal converted into the frequency domain has components corresponding to each of the plurality of subcarriers as shown in FIGS. Demodulation is performed in units of subcarriers. The modem unit 24 outputs the demodulated signal to the IF unit 26. Further, the modem unit 24 performs modulation as transmission processing. The modem unit 24 outputs the modulated signal to the baseband processing unit 22 as a multi-carrier signal in the frequency domain.

  The IF unit 26 receives the demodulation result from the modulation / demodulation unit 24 as a reception process, and separates the demodulation result for each terminal device 12. The demodulation result is composed of a plurality of subchannels as shown in FIG. Therefore, when one subchannel is assigned to one terminal apparatus 12, the demodulation result includes signals from a plurality of terminal apparatuses 12. The IF unit 26 separates such a demodulation result for each terminal device 12. The IF unit 26 outputs the separated demodulation result to the network 50. At that time, the IF unit 26 performs transmission according to information for identifying the destination, for example, an IP (Internet Protocol) address.

  Further, the IF unit 26 inputs data for a plurality of terminal devices 12 from the network 50 as a transmission process. The IF unit 26 assigns data to subchannels and forms a multicarrier signal from a plurality of subchannels. That is, the IF unit 26 forms a multicarrier signal composed of a plurality of subchannels as shown in FIG. The subchannel to which data is to be assigned is determined in advance as shown in FIG. 2 (c), and an instruction related thereto is received from the radio control unit 28. The IF unit 26 outputs the multicarrier signal to the modem unit 24.

  The radio control unit 28 controls processing of each component included in the base station device 10. Here, for the sake of clarity, the contents of control by the wireless control unit 28 will be described in three parts. The three are (1) control signal allocation, (2) subchannel allocation, and (3) handover processing.

(1) Allocation of control signal The investigation unit 32 investigates the usage status of each of a plurality of time slots forming each frame in units of superframes, that is, “20” frames. That is, the investigation unit 32 investigates the usage status of “80” downlink time slots included in “20” superframes. Note that the survey unit 32 may investigate the usage status of “160” uplink time slots and downlink time slots included in “20” superframes. Here, the investigation unit 32 measures the reception power of the signal received by the RF unit 20 and the reception power in each of the plurality of time slots as an investigation of the usage situation of the time slot.

  Since a plurality of RF units 20 are provided, the investigating unit 32 measures the received power of the signals received by each of the plurality of RF units 20 and then averages the measurement results, thereby obtaining each time slot. Derived received power. Further, not only the average but also selection of one received power or other statistical processing may be executed. The investigation unit 32 stores the investigation result in the storage unit 30. As a premise of the investigation in the investigation unit 32, the radio control unit 28 receives a control signal transmitted from the other base station device 10 in advance, and is synchronized with a frame formed by the other base station device 10. Form. Since such a synchronization process may be realized by a known technique, a description thereof is omitted here.

  FIG. 5 shows a data structure of a measurement result of received power stored in the storage unit 30. As shown in the figure, the received power of “4” uplink time slots included in each of “20” frames, which are superframes, is stored. The examining unit 32 measures the received power for each of a plurality of time slots included in the superframe a plurality of times, and averages the measurement results corresponding to each time slot, thereby receiving power corresponding to the time slot. May be derived. As described above, the storage unit 30 may store the received power for the downlink time slot. Returning to FIG.

  The identifying unit 34 identifies a time slot with a small usage state based on the usage state investigated by the examining unit 32. This corresponds to specifying a time slot with low reception power while referring to reception power stored in the storage unit 30. As shown in FIG. 3, each time slot is formed by a plurality of subchannels. Therefore, a time slot with low received power is the number of subchannels used by another base station apparatus 10 (not shown). Corresponds to a time slot including a subchannel allocated to a terminal device 12 (not shown) that is far away. It can also be said that the time slot has a small number of communication channels used by other base station apparatuses 10. In the present embodiment, it is desirable to specify a time slot to which no subchannel is assigned by another base station apparatus 10. The identifying unit 34 outputs information regarding the identified time slot to the control channel allocating unit 36.

  The control channel allocating unit 36 includes a plurality of subchannels that form the time slots specified in the control channel allocating unit 36 and included in frames that should appear at intervals of “20” frames. Assign one of them to the control signal. That is, the control channel allocation unit 36 arranges one control signal per superframe. Here, the control channel allocating unit 36 selects a predetermined fixed subchannel like the first subchannel. As described above, since the subchannel assignment in the uplink and the subchannel assignment in the downlink are symmetric, control signals are assigned to the uplink time slot and the downlink time slot. The modulation / demodulation unit 24 transmits the assigned control signal from the RF unit 20.

  FIG. 6 shows an outline of control signal allocation by the control channel allocation unit 36. The horizontal axis of the figure corresponds to time, and a plurality of frames are shown. “DL” indicates a downlink time slot, and “UL” indicates an uplink time slot. The numbers such as “1” and “2” shown at the bottom correspond to the time slot numbers. The vertical axis of the figure corresponds to the frequency, and among the “16” subchannels in FIG. 2B, “4” subchannels are shown. Here, “# 1C” is shown in one subchannel in the second downlink time slot of the first frame. “# 1C” corresponds to a control signal in the first base station apparatus 10a (not shown). In a frame “20” frames after that frame, “# 1C” is reassigned to one subchannel of the second downlink time slot. Here, illustration of the control signal in the uplink time slot is omitted. On the other hand, “# 2C” is indicated in one sub-channel in the fourth downlink time slot of the second frame. “# 2C” corresponds to a control signal in the second base station apparatus 10b (not shown). Returning to FIG.

(2) Subchannel allocation The subchannel allocation corresponds to the processing after the control signal is allocated. As described above, the control channel allocation unit 36 identifies one frame per superframe and further identifies one of a plurality of time slots that form the identified frame. Furthermore, the control channel allocation unit 36 allocates one of a plurality of subchannels forming the identified time slot to the control signal. That is, the control channel allocating unit 36 forms the specified time slot after specifying the time slots having the same relative timing in the frames in the frames that should appear at intervals of “20” frames. Any one of the plurality of subchannels is assigned to the control signal. Here, the time slots having the same relative timing in the frame correspond to time slots identified by the same time slot number.

  A terminal device 12 (not shown) receives a control signal from the base station device 10 and recognizes the presence of the base station device 10. Further, the terminal device 12 transmits an allocation request to the base station device 10 when desiring to connect to the base station device 10. At that time, for example, a control channel in an uplink time slot is used. The radio resource allocation unit 38 receives an allocation request via the RF unit 20 or the like. The radio resource allocation unit 38 preferentially allocates to the terminal device 12 subchannels other than the subchannel to which the control signal is allocated among the time slots specified by the control channel allocation unit 36, that is, the time slot to which the control signal is allocated.

  That is, if there is an empty subchannel in the time slot to which the control signal is allocated, the radio resource allocation unit 38 allocates the subchannel to the terminal device 12. As described above, there is only one time slot to which a control signal is assigned per superframe. Therefore, there is a possibility that the transmission rate desired by the terminal device 12 cannot be satisfied only by the assigned subchannel. In order to cope with this, the radio resource allocation unit 38 further executes the following processing.

  The radio resource allocating unit 38, in a frame that should appear at a frame interval shorter than the interval of “20” frames, has a time slot in which the relative timing in the frame is the same as the time slot to which the control signal is allocated. Is identified. For example, frames that should appear at frame intervals such as “2” and “4” are specified. In FIG. 6, since the control signal is allocated to the second time slot, the radio resource allocation unit 38 identifies the second time slot in the identified frame. In order to clarify the following description, here, the time slot specified as described above and the time slot to which the control signal is assigned are referred to as “management slot”. Finally, the radio resource allocation unit 38 preferentially allocates each of the plurality of subchannels forming the management slot to the terminal device 12.

  The control channel is always assigned by each base station apparatus 10, and they are generally assigned so that no collision occurs between the base station apparatuses 10. Based on such a situation, here, a management slot is defined with reference to the control channel, and resource management of subchannels in the management slot is performed. In addition, when subchannels are allocated according to the required transmission rate, time slots included in frames at a predetermined number of intervals from the frame including the control channel are targeted for allocation. Here, the predetermined number of intervals is defined to be shorter than the superframe interval. Such a time slot is also a management channel. That is, depending on the required transmission rate, several stages of allocation are defined for the number of time lots to be allocated. Therefore, fewer subchannels must be reassigned when changing the assignment method.

  FIG. 7 shows an overview of allocation by the radio resource allocation unit 38. Since the display of the horizontal axis, the vertical axis, and the numbers at the bottom, “# 1C” and “# 2C” in FIG. 7 is the same as in FIG. 6, the description is omitted here. A management slot 200, a management slot 202, a management slot 212, and a management slot 214 are provided in a frame including a subchannel to which a control signal is assigned. As an example, the management slot 208 and the management slot 210 are provided at intervals of “2” frames from the frame including the subchannel to which the control signal is assigned. Note that any of the management slots uses the second time slot. The radio resource allocation unit 38 allocates the subchannels included in these management slots to the terminal device 12. On the other hand, each base station apparatus 10 is provided with a management slot. In FIG. 7, management slots provided by other base station apparatuses 10 are indicated as other slots 204, other slots 206, other slots 216, and other slots 218. Returning to FIG.

  The radio resource allocating unit 38, if any of the plurality of subchannels forming the management slot is allocated by another base station apparatus 10, another time slot in the same frame as the management time slot Identify again. The management slot here corresponds to a management slot to which no control signal is assigned. For example, when the management slot is already under the management of another base station apparatus 10, a time slot that is not under the management of any base station apparatus 10 is specified in the same frame. The identified time slot is set as a management slot in the frame. The radio resource allocation unit 38 sets management slots in units of superframes. Therefore, when the management slot is moved in a predetermined frame, the radio resource allocating unit 38 uses a frame having the same timing as the frame including the moved management slot in the next superframe. Move the management slot.

  By managing the subchannels in one time slot by one base station apparatus 10, transmission power control works effectively. When the management slot is moved, the radio resource assignment unit 38 notifies the terminal device 12 of the movement in the control signal and the already assigned subchannel. Further, in order to confirm such notification, after detecting time slot allocation, the radio resource allocation unit 38 may perform management slot movement after the superframe period has elapsed.

  At that time, the radio resource allocation unit 38 investigates the allocation status for each of the other time slots in the same frame as the management time slot, and specifies the time slot again according to the examination result. The allocation status, that is, whether the time slot is under the control of another base station apparatus 10 is identified as follows. The radio resource allocation unit 38 observes all uplink time slots or all subchannels included in the uplink time slots. Here, the observation is realized by measuring the received power. In addition, when the received power does not exceed the threshold value, the radio resource allocation unit 38 determines that the time slot or the subchannel is free. This is provided as an essential function for creating a ranging map, that is, a TCH monitor, and corresponds to the use of the function. Further, the radio resource allocation unit 38 concludes that the slot determined that all the subchannels are empty is an empty management slot. On the other hand, it is concluded that the time slot in which at least one subchannel is used is already managed by another base station apparatus 10.

  When all the time slots in the frame are allocated or managed by another base station apparatus 10, the radio resource allocation unit 38 measures the received power of the control signal in the downlink time slot, A time slot with the smallest received power may be set as a sub management slot, and subchannels may be allocated therein. Such a time slot can be said to be a time slot under the control of another base station apparatus 10 installed at a relatively far distance from the base station apparatus 10. Therefore, the influence of the uplink signal of the base station apparatus 10 to which the subchannel is allocated by the radio resource allocation unit 38 on another base station apparatus 10 is reduced.

  FIG. 8 shows another outline of allocation by the radio resource allocation unit 38. Since the display of the horizontal axis, the vertical axis, and the numbers at the bottom, “# 1C” and “# 2C” in FIG. 8 are the same as those in FIG. 6, the description thereof is omitted here. In FIG. 8, as in FIG. 7, a management slot 240 and a management slot 242 are set. However, the other slot 248 is already used by the other base station apparatus 10 in the two frames after the frame in which these management slots are arranged. Further, another slot 250 following the other slot 248 is already used. Therefore, the radio resource allocation unit 38 sets the first downlink time slot as the management slot 246. At that time, the radio resource allocating unit 38 allocates to the terminal device 12 a subchannel that has been allocated so far, for example, the same subchannel as the third subchannel. Further, the radio resource allocation unit 38 sets the management slot 252 so that the uplink of this frame is also symmetric with the downlink.

  Further, in the subsequent frame, other slots 254 to 284 are already used for other base station apparatuses 10. In that case, the radio | wireless resource allocation part 38 moves the time slot which should be allocated to the terminal device 12 to a 1st downlink time slot. In addition, when the third subchannel in the first downlink time slot has already been used, the radio resource allocation unit 38 allocates the fourth subchannel to the terminal device 12. The same applies to the uplink. Returning to FIG.

  After setting the management slot, the radio resource allocation unit 38, if a non-allocated time slot occurs in the same frame as the set time slot, re-assigns a time slot that has not been allocated in the frame. Identify. Further, the radio resource allocation unit 38 sets the identified time slot as a management slot. That is, when an unmanaged unused time slot occurs in the same frame as the moved management slot, the radio resource allocation unit 38 secures the time slot as a management slot.

(3) Handover processing As described above, the radio resource allocation unit 38 allocates at least one of the plurality of subchannels in which the time slots are formed and the frequency-multiplexed subchannels to the terminal device 12. .

  The measurement unit 40 is another terminal device 12 assigned to a subchannel other than the subchannel assigned to the terminal device 12, and another terminal device to which a subchannel is assigned by another base station device 10 (not shown). The received power of the signal from 12 is measured. That is, the measurement unit 40 measures the power of the signal received from the non-communication terminal device 12 based on the signal received by the RF unit 20 and the subchannel unit signal output from the baseband processing unit 22. To do. Note that the signal from another terminal apparatus 12 received by the measurement unit 40 includes information on the other base station apparatus 10 that is the destination of the signal. The measurement unit 40 outputs the information to the instruction unit 42.

  If the reception power measured by the measurement unit 40 is greater than the threshold value, the instruction unit 42 instructs the release of the subchannel assigned to another terminal device 12. Instruction processing will be described in more detail here. The IF unit 26 is connected to another base station apparatus 10 (not shown) via the network 50. The instruction unit 42 determines that the received power measured by the measurement unit 40 has become larger than the threshold, and then refers to the information included in the signal received by the measurement unit 40, whereby another base station device 10. Is identified. The instruction unit 42 outputs a request for releasing another terminal device 12 to the other identified base station device 10 via the IF unit 26 and the network 50. The other terminal device 12 is specified by specifying the time slot and subchannel assigned to the other terminal device 12.

  The other base station apparatus 10 that has received the request via the network 50 identifies another terminal apparatus 12 based on the information on the time slot and the subchannel included in the instruction. Also, the other base station apparatus 10 releases the subchannel assigned to the identified other terminal apparatus 12. Note that the release process may be realized by a known technique, and thus the description thereof is omitted here. The terminal apparatus 12 whose subchannel is released detects the base station apparatus 10 that is a new connection destination, and executes a handover to the detected base station apparatus 10.

  That is, the instruction unit 42 causes the base station apparatus 10 to perform handover when the received power from the terminal apparatus 12 under the control of another base station apparatus 10 increases. As a result, one base station apparatus 10 manages subchannels in one time slot, so that transmission power control works effectively.

  9A to 9C show an outline of processing in the instruction unit 42. FIG. FIG. 9A shows a configuration example of the communication system 100 for explaining the handover process. As the base station apparatus 10, a first base station apparatus 10a and a second base station apparatus 10b are installed, the first base station apparatus 10a forms a first area 70, and the second base station apparatus 10b is a second base station apparatus 10b. Area 72 is formed. In addition, the second terminal device 12b and the fifth terminal device 12e are also illustrated. In the initial state, the second terminal device 12b is connected to the second base station device 10b, and the fifth terminal device 12e is connected to the first terminal device 12e. It is assumed that it is connected to the base station apparatus 10a. Furthermore, the second terminal apparatus 12b is moving in the direction of the arrow, that is, in the direction from the second base station apparatus 10b to the first base station apparatus 10a.

  FIG. 9B shows time slot and subchannel allocation in the initial state. Here, the uplink time slot is the subject of the description. Assume that the second uplink time slot is the management slot of the first base station apparatus 10a in FIG. Further, “2” shown in the third subchannel of the management slot corresponds to the second terminal apparatus 12b shown in FIG. 9A, and “5” is shown in FIG. 9A. This corresponds to the fifth terminal device 12e. Further, “1”, “3”, and “4” in other time slots correspond to the first terminal device 12a, the third terminal device 12c, and the fourth terminal device 12d that are not shown in FIG. However, the description about these is abbreviate | omitted here. In the state of FIG. 9B, the first base station apparatus 10a can control the transmission power of the fifth terminal apparatus 12e, but cannot control the transmission power of the second terminal apparatus 12b. Therefore, the signal received from the second terminal device 12b may cause interference.

  FIG. 9 (c) shows time slot and subchannel allocation in the state following FIG. 9 (b). This corresponds to a state in which the second terminal apparatus 12b is handed over from the second base station apparatus 10b to the first base station apparatus 10a in FIG. 9A. As illustrated, the first base station apparatus 10a allocates the second subchannel to the second terminal apparatus 12b. Moreover, the 1st base station apparatus 10a can also control the transmission power of the 2nd terminal device 12b.

  FIG. 10 shows an overview of received power in the communication system 100. Here, for the sake of clarity, it is assumed that transmission power control is not performed before handover. FIG. 10 assumes the case where the second terminal apparatus 12b moves as shown in FIG. 9A, and shows received power at the first base station apparatus 10a and the second base station apparatus 10b at that time. Time is shown on the horizontal axis, and received power is shown on the vertical axis. The signal transmission direction corresponding to the received power is shown on the left side of the figure. For example, “second terminal device → second base station device” is changed from the second terminal device 12b to the second base station device 10b. It corresponds to the signal transmitted to Since the second terminal apparatus 12b is moving in the direction from the second base station apparatus 10b to the first base station apparatus 10a, the received power in the second base station apparatus 10b decreases as time passes, The received power in one base station apparatus 10a increases with time.

  On the other hand, since the fifth terminal apparatus 12e is not moving, the reception power is almost constant. Note that when the received power from the second terminal device 12b in the first base station device 10a increases, the first base station device 10a increases the received power from the second terminal device 12b to match the fifth terminal device 12e. The balance may be maintained by increasing the transmission power. Further, when the received power from the second terminal apparatus 12b in the first base station apparatus 10a increases, as described above, the first base station apparatus 10a changes the second terminal apparatus 12b to the second base station apparatus 10b. Request to be handed over. When the second terminal apparatus 12b is handed over to the first base station apparatus 10a, the first base station apparatus 10a can control the transmission power of the second terminal apparatus 12b. Therefore, as indicated by a thick line, the received power from the second base station apparatus 10b in the first base station apparatus 10a approaches a constant value.

  FIG. 11 shows another outline of received power in the communication system 100. FIG. 11 corresponds to FIG. 10 when transmission power control before handover is taken into consideration. A dotted line in FIG. 11 shows a case where transmission power control is not executed, which is the same as FIG. Also, the solid line in FIG. 11 is a case where transmission power control is executed. Since the first base station apparatus 10a requests the second base station apparatus 10b to execute handover, the second base station apparatus 10b performs handover of received power from the second terminal apparatus 12b as shown in the figure. Even if the threshold is not reached, the handover is executed. Note that, as a handover destination time slot, the same time slot as that used for communication is used in principle.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a communication function loaded in the memory. Describes functional blocks realized by collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The operation of the communication system 100 configured as above will be described. FIG. 12 is a flowchart showing a control signal allocation procedure in the base station apparatus 10. The examining unit 32 measures the received power in the time slot over the superframe (S10). If the measurement is not completed (N in S12), the process returns to Step 10. When the measurement is completed (Y in S12), the specifying unit 34 selects a time slot with low received power (S14). The control channel allocation unit 36 allocates a control signal to the selected time slot (S16).

  FIG. 13 is a flowchart showing an allocation procedure in the base station apparatus 10. If control signal allocation by the control channel allocation unit 36 has not been completed (N in S30), the radio resource allocation unit 38 stands by. On the other hand, if the control channel allocation by the control channel allocation unit 36 has been completed (Y in S30), the radio resource allocation unit 38 sets a management slot (S32). When there is a subchannel allocated by another base station apparatus 10 in the management slot (Y in S34), if there is a time slot not allocated in the same frame (Y in S38), a radio resource allocation unit 38 uses the time slot (S40). On the other hand, if there is no unassigned time slot in the same frame (N in S38), the radio resource allocating unit 38 uses a time slot with low received power (S42).

  If there is no subchannel allocated by another base station apparatus 10 in the management slot (N in S34), if there is an empty subchannel (Y in S36), the radio resource allocation unit 38 uses the empty subchannel. (S44). On the other hand, when there is no free subchannel (N in S36), if there is a time slot not allocated in the same frame (Y in S38), the radio resource allocation unit 38 uses the time slot (S40). . On the other hand, if there is no unassigned time slot in the same frame (N in S38), the radio resource allocating unit 38 uses a time slot with low received power (S42).

  FIG. 14 is a flowchart showing a time slot moving procedure in the base station apparatus 10. When there is a subchannel allocated by another base station apparatus 10 in the time slot (Y in S60) and there is an unused time slot in the same frame (Y in S62), the radio resource allocation unit 38 Moves the management slot to the time slot (S64). When there is no subchannel allocated by another base station apparatus 10 in the time slot (N in S60), or when there is no time slot not used in the same frame (N in S62), the process ends. Is done.

  FIG. 15 is a sequence diagram illustrating a handover procedure in the communication system 100. The second terminal apparatus 12b and the second base station apparatus 10b perform communication (S80). Further, when the signal transmitted from the second terminal apparatus 12b to the second base station apparatus 10b reaches the first base station apparatus 10a, the second terminal apparatus 12b interferes with the first base station apparatus 10a ( S82). When the interference power increases, the first base station apparatus 10a (S84). An instruction to release the second terminal device 12b is given (S86). The instruction is transmitted from the first base station apparatus 10a to the second base station apparatus 10b (S88). When receiving the instruction (S90), the second base station apparatus 10b releases the second terminal apparatus 12b (S92). The second terminal apparatus 12b requests the first base station apparatus 10a for handover (S94). The second terminal apparatus 12b and the first base station apparatus 10a perform communication (S96).

  According to the embodiment of the present invention, a time slot that is not used by another base station apparatus is identified, and a subchannel included in the identified time slot is assigned to a control signal. Deterioration of reception characteristics due to signals can be suppressed. Moreover, since the time slot with low received power is specified, it is possible to specify a time slot that is not used by another base station apparatus.

  Since the time slot including the subchannel assigned to the control signal is set as a management slot and the subchannel of the management slot is preferentially assigned to the terminal device, the terminal device communicating with other base station devices in the management slot Can be difficult to contain. In addition, since it is difficult to include terminal devices communicating with other base station devices, it is possible to suppress deterioration in reception characteristics due to signals from terminal devices that are not controlled. Further, since a time slot to which no control signal is assigned is also used as a management slot and a subchannel in such a management slot is assigned to a terminal device, the transmission rate for the terminal device can be improved.

  In addition, if the management slot is assigned by another base station apparatus, another time slot in the same frame as the management slot is specified again as the management slot. Deterioration of reception characteristics can be suppressed. In addition, since the management slot is specified again according to the received power, it is possible to suppress deterioration of reception characteristics due to a signal from a terminal device that is not controlled. In addition, when a time slot that has not been assigned occurs, the time slot is specified again as a management slot, so that it is possible to suppress deterioration in reception characteristics due to a signal from a terminal device that is not controlled.

  In addition, if another terminal device assigned by another base station device exists in the time slot to which the terminal device is assigned, and the received power of a signal from another terminal device increases, the terminal device is assigned to another terminal device. Since the release of the designated subchannel is instructed, it is possible to suppress deterioration of reception characteristics due to a signal from a terminal device that is not controlled. In addition, since a release request is output to another base station apparatus via the network, it is possible to reliably instruct the release of the subchannel. Moreover, since it requests | requires that another terminal device is handed over to this base station apparatus, the deterioration of the receiving characteristic by the signal from the terminal device which is not controlled can be suppressed.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the radio resource allocation unit 38 measures the reception power of the uplink time slot in order to identify the allocation status, that is, whether the time slot is under the management of another base station apparatus 10. However, the present invention is not limited to this. For example, the radio resource allocation unit 38 may periodically exchange management slot information with another base station device 10 via the IF unit 26. According to this modification, it is possible to reliably identify whether the time slot is under the control of another base station apparatus 10.

  In the present embodiment, the instruction unit 42 outputs a request for releasing another terminal device 12 to another base station device 10 via the IF unit 26. However, the present invention is not limited to this. For example, the instruction unit 42 may output a request to hand over another terminal device 12 to the base station device 10 in addition to a request to release another terminal device 12. . The other base station apparatus 10 disconnects the connection with another terminal apparatus 12 while designating the handover destination to the terminal apparatus 12 in response to the request. According to this modification, a handover can be reliably executed.

  In the present embodiment, the examining unit 32 measures the received power of the received signal, and the identifying unit 34 identifies a time slot with a low received power as a time slot with less usage status. However, the present invention is not limited to this. For example, the examining unit 32 may measure the received power to interference power ratio with respect to the received signal. Further, the examining unit 32 is not limited to the ratio of received power to interference power, and may measure the amount of effective signal components included in the received signal. For these measurements, a known technique may be used. Furthermore, the specifying unit 34 specifies a time slot having a low reception power to interference power ratio as a time slot having a low usage status. According to this modification, even when the received power is substantially equal, a time slot with a low received power to interference power ratio can be selected, and it is specified whether the time slot is under the control of another base station apparatus 10 it can.

In addition, the Example of this invention may be specified by the following items.
(Item 1-1)
While a time slot is formed by frequency multiplexing of a plurality of subchannels, a frame formed by time multiplexing of a plurality of time slots is defined, and one of a plurality of time slots forming a predetermined frame is specified. A first assigning unit that assigns one of a plurality of subchannels forming the identified time slot to the control signal;
A second allocation unit that preferentially allocates a subchannel other than the subchannel allocated to the control signal among the time slots specified in the first allocation unit;
A base station apparatus comprising:

(Item 1-2)
The first assigning unit identifies a plurality of subchannels forming the identified time slot after identifying the time slots having the same relative timing in the frame in the frames that should appear at intervals of the plurality of frames. Assign one of them to the control signal,
The second allocating unit is configured such that, in a frame that should appear at a frame interval shorter than the interval between the plurality of frames, the relative timing in the frame is the same as the time slot specified by the first allocating unit. The base station apparatus according to (Item 1-1), wherein after specifying a slot, each of a plurality of subchannels forming the specified time slot is preferentially assigned to a terminal apparatus.

(Item 1-3)
The second assigning unit, if any of the plurality of subchannels forming the specified time slot is assigned by another base station apparatus, another second station in the same frame as the specified time slot The base station apparatus according to (Item 1-2), wherein the time slot is specified again.

(Item 1-4)
The second allocating unit investigates an allocation situation for each of the other time slots in the same frame as the identified time slot, and identifies the time slot again according to the survey result ( Item 1-3) Base station apparatus.

(Item 1-5)
The second assigning unit, after identifying the time slot, re-identifies the time slot if an unassigned time slot occurs in the same frame as the identified time slot ( Item 1-3) or base station apparatus according to (Item 1-4).

(Item 1-6)
While a time slot is formed by frequency multiplexing of a plurality of subchannels, a frame formed by time multiplexing of a plurality of time slots is defined, and one of a plurality of time slots forming a predetermined frame is specified. And assigning one of a plurality of subchannels forming the identified time slot to the control signal;
A step of preferentially allocating a subchannel other than the subchannel allocated to the control signal among the identified time slots to the terminal device;
An allocation method comprising:

(Item 1-7)
While a time slot is formed by frequency multiplexing of a plurality of subchannels, a frame formed by time multiplexing of a plurality of time slots is defined, and one of a plurality of time slots forming a predetermined frame is specified. And assigning one of a plurality of subchannels forming the identified time slot to the control signal;
A step of preferentially allocating a subchannel other than the subchannel allocated to the control signal among the identified time slots to the terminal device;
A program that causes a computer to execute.

(Item 2-1)
An allocating unit that allocates at least one of the plurality of subchannels in which the time slots are formed and the frequency-multiplexed subchannels to the terminal device;
Received power of signals from another terminal apparatus that is assigned to a subchannel other than the subchannel assigned to the terminal apparatus by the assigning unit and to which a subchannel is assigned by another base station apparatus A measurement unit for measuring
If the reception power measured by the measurement unit is increased, an instruction unit for instructing release of a subchannel allocated to another terminal device;
A base station apparatus comprising:

(Item 2-2)
A connection unit for connecting to another base station device via a wired network;
The signal from another terminal device received by the measurement unit includes information on another base station device that is the destination of the signal,
The instructing unit identifies another base station device based on information included in the signal received by the measurement unit, and releases another terminal device to the other base station device via the connection unit. The base station apparatus according to (Item 2-1), wherein a request to do so is output.

(Item 2-3)
The instruction unit outputs a request to hand over another terminal device to the base station device in addition to a request to release another terminal device (Item 2-2) Base station equipment.

(Item 2-4)
Assigning to a terminal device at least one of a plurality of subchannels in which time slots are formed and frequency-multiplexed;
Measure the received power of a signal from another terminal device assigned to a subchannel other than the subchannel assigned to the terminal device and to which a subchannel is assigned by another base station device Steps,
If the measured received power increases, instructing the release of the subchannel allocated to another terminal device;
An allocation method comprising:

(Item 2-5)
Assigning to a terminal device at least one of a plurality of subchannels in which time slots are formed and frequency-multiplexed;
Measure the received power of a signal from another terminal device assigned to a subchannel other than the subchannel assigned to the terminal device and to which a subchannel is assigned by another base station device Steps,
If the measured received power increases, instructing the release of the subchannel allocated to another terminal device;
A program that causes a computer to execute.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. It is a figure which shows the frame structure in the communication system of FIG. It is a figure which shows the frame structure in the communication system of FIG. It is a figure which shows the frame structure in the communication system of FIG. It is a figure which shows arrangement | positioning of the subchannel in the communication system of FIG. It is a figure which shows the structure of the base station apparatus of FIG. FIG. 5 is a diagram illustrating a data structure of a measurement result of received power stored in a storage unit in FIG. 4. FIG. 5 is a diagram showing an overview of control signal allocation by a control channel allocation unit in FIG. 4. FIG. 5 is a diagram showing an overview of assignment by a radio resource assignment unit in FIG. 4. It is a figure which shows another outline | summary of the allocation by the radio | wireless resource allocation part of FIG. FIGS. 9A to 9C are diagrams showing an outline of processing in the instruction unit of FIG. It is a figure which shows the outline | summary of the received power in the communication system of Fig.9 (a). It is a figure which shows another outline | summary of the received power in the communication system of Fig.9 (a). 6 is a flowchart showing a control signal allocation procedure in the base station apparatus of FIG. It is a flowchart which shows the allocation procedure in the base station apparatus of FIG. 5 is a flowchart showing a time slot movement procedure in the base station apparatus of FIG. FIG. 10 is a sequence diagram showing a handover procedure in the communication system of FIG.

Explanation of symbols

  10 base station apparatus, 12 terminal apparatus, 20 RF section, 22 baseband processing section, 24 modulation / demodulation section, 26 IF section, 28 radio control section, 30 storage section, 32 investigation section, 34 identification section, 36 control channel allocation section, 38 radio resource allocation unit, 40 measurement unit, 42 instruction unit, 50 network, 100 communication system.

Claims (4)

Frames formed by time multiplexing of a plurality of time slots are defined while forming time slots by frequency multiplexing of a plurality of subchannels, and a plurality of time slots forming each frame in units of a plurality of frames A survey department to investigate the usage status of each
Based on the usage situation investigated in the investigation part, a specific part that identifies a time slot with less usage situation;
An allocating unit that allocates, to the control signal, any one of a plurality of subchannels that are time slots specified by the specifying unit and that form time slots included in frames that should appear at intervals of a plurality of frames; ,
A base station apparatus comprising: The survey unit measures received power in each of a plurality of time slots as a survey of time slot usage.
The base station apparatus according to claim 1, wherein the specifying unit specifies a time slot with low reception power based on a measurement result of the investigation unit as a time slot with less usage status. Frames formed by time multiplexing of a plurality of time slots are defined while forming time slots by frequency multiplexing of a plurality of subchannels, and a plurality of time slots forming each frame in units of a plurality of frames Steps to investigate the usage of each
Based on the surveyed usage, identifying a time slot with low usage,
Assigning to the control signal any one of a plurality of subchannels that form a time slot included in a frame that is the identified time slot and should appear at intervals of the plurality of frames;
An allocation method comprising: Frames formed by time multiplexing of a plurality of time slots are defined while forming time slots by frequency multiplexing of a plurality of subchannels, and a plurality of time slots forming each frame in units of a plurality of frames Steps to investigate the usage of each
Based on the surveyed usage, identifying a time slot with low usage,
Assigning to the control signal any one of a plurality of subchannels that form a time slot included in a frame that is the identified time slot and should appear at intervals of the plurality of frames;
A program that causes a computer to execute.

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