JP5301979B2 - Radio base station and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent collision of signals from respective terminals. <P>SOLUTION: A radio base station 1 receives a plurality of signals transmitted from radio terminals 2A to 2D using an uplink time slot assigned to the radio terminals 2A to 2D. Next, the radio station 1 detects a time position of the plurality of received signals. Moreover, the radio base station 1 assigns a different uplink time slot from the uplink time slot assigned immediately before to at least any of radio terminals of transmission sources of two or more signals with overlapping time positions in the case where there are two or more overlapping signals in the plurality of received signals. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a radio base station that transmits signals to and from a plurality of radio terminals by time division duplex and time division multiplexing, and a communication control method in the radio base station.

  In a wireless communication system that performs time division duplex (TDD) and time division multiplexing (TDMA) communication between a plurality of wireless terminals and a wireless base station, the distance between each wireless terminal and the wireless base station is different for each wireless terminal. Different. For this reason, even though different time slots are assigned to the respective radio terminals, the radio base station may simultaneously receive burst signals from the respective radio terminals due to a propagation delay caused by a difference in distance. is there.

In order to prevent such simultaneous reception (collision) of burst signals, for example, in the techniques described in Patent Literature 1 and Patent Literature 2, a radio base station transmits a control signal for preventing collision to each radio terminal. . Each wireless terminal forcibly adjusts the transmission timing of the burst signal based on the received control signal. Such control is referred to as time alignment control.
JP 2001-169343 A JP 2002-77087 A

  However, when the wireless terminal moves from a distance to the vicinity with respect to the wireless base station, the time position (reception window) of the burst signal received by the wireless base station becomes the time even if the time alignment control as described above is performed. It may come off the front side of the slot. In addition, when the wireless terminal moves from the vicinity to the distance with respect to the wireless base station, the reception window of the burst signal received by the wireless base station) is not changed after the time slot even if the time alignment control as described above is performed. May come off to the side.

  As described above, when a burst signal whose reception timing at the radio base station is extremely delayed and a burst signal which is extremely advanced are mixed, collision of these signals occurs, and normal demodulation becomes difficult.

  In particular, in a PHS (Personal Handy Phone System) wireless communication system, a change in the distance between a wireless terminal and a wireless base station is large due to the macro cell formation, so that the above-described signal collision is likely to occur.

  In view of the above problems, an object of the present invention is to provide a radio base station and a communication control method that prevent collision of signals from each radio terminal.

  In order to solve the above-described problems, the present invention has the following features. First, the first aspect of the present invention includes a downlink time zone used for downlink communication and an uplink time zone used for uplink communication following the downlink time zone, and a plurality of the downlink time zones are provided. Frame is divided into a plurality of downlink time slots, and the uplink time slot is divided into a plurality of uplink time slots, and time division is performed with a plurality of wireless terminals using the downlink time slot and the uplink time slot. A radio base station that transmits signals by duplex and time division multiplexing, and that receives a plurality of signals transmitted using the uplink time slots assigned to the plurality of radio terminals (reception processing unit 152) ), And a time position detection unit (unique word detection unit 156 and upstream time slot allocation unit 1) that detect time positions of the plurality of signals received by the reception unit 8) and two or more signals having the same time position when there are two or more signals having the same time position among the plurality of signals received by the receiving unit. And an allocating unit (uplink time slot allocating unit 158) that allocates the uplink time slot different from the uplink time slot allocated immediately before to at least one of the wireless terminals of the transmission source And

  In such a radio base station, when the time positions of the signals received from the radio terminals are overlapped, that is, when a signal collision occurs, the radio base station of the signal transmission source radio terminal An uplink time slot different from the uplink time slot allocated until immediately before is assigned to at least one of them. As a result, the uplink time slot used for signal transmission differs depending on the wireless terminal that is the transmission source of the signal in which the collision has occurred, and the collision can be prevented.

  According to a second aspect of the present invention, the allocation unit overlaps the time position when there are two signals having the same time position among the plurality of signals received by the reception unit. The uplink time slot assigned immediately before one of the wireless terminals that are the transmission source of the two signals is the same as that of the wireless terminal that is the transmission source of the two signals whose time positions overlap. The uplink time slot assigned immediately before to the other of the wireless terminals that are the transmission source of the two signals that are assigned to the other and the time position is duplicated. The gist is to assign to one of the wireless terminals from which two signals are transmitted.

  When the time positions of two signals overlap, the time position of the front signal is out of the rear of the uplink time slot assigned to the wireless terminal that is the transmission source of the signal, and the time of the rear signal The position is at least one of the states deviated ahead of the uplink time slot assigned to the wireless terminal that is the transmission source of the signal. Therefore, by replacing the uplink time slots assigned to the wireless terminal that is the transmission source of these two signals by the wireless base station, it is possible to separate the time positions of the two overlapping signals and prevent a collision. .

  According to a third aspect of the present invention, when the allocation unit includes two signals having overlapping time positions among the plurality of signals received by the reception unit, Among the signals having the time position within the time zone, the uplink time zone is transmitted to the radio terminal that is the source of the signal with the shortest time difference between the front end of the time location and the front end of the uplink time slot. The time difference between the rear end of the time position and the rear end of the uplink time slot is the signal of which the time position is within the time slot of the uplink time slot. The last uplink time slot in the uplink time zone is allocated to the wireless terminal that is the shortest signal source, and the two time positions are duplicated. The second uplink time slot from the beginning of the uplink time slot is allocated to the wireless terminal that is the transmission source of the signal corresponding to the time position behind, and the time positions overlap. Assigning the second uplink time slot from the end of the uplink time zone to the wireless terminal that is the transmission source of the signal corresponding to the time position ahead of the two signals. The gist.

  As described above, the radio base station transmits the signal having the shortest time difference between the front end of the time position and the front end of the uplink time slot among the signals whose time positions are within the time slot of the uplink time slot. On the other hand, by assigning the first upstream time slot in the upstream time slot, the signal from each wireless terminal can be stored after the front end of the upstream time slot composed of a plurality of upstream time slots.

  In addition, the radio base station transmits a signal whose time position is within the time slot of the uplink time slot to the radio terminal that is the transmission source of the signal having the shortest time difference between the rear end of the time position and the rear end of the uplink time slot. On the other hand, by assigning the last uplink time slot in the uplink time slot, the signal from each wireless terminal can be stored before the rear end of the uplink time slot composed of a plurality of uplink time slots. Therefore, it is possible to prevent troubles in downlink communication using the downlink time slot.

  In addition, the radio base station assigns the first uplink time slot in the uplink time zone to the radio terminal of the signal source having the shortest time difference between the front end of the time position and the front end of the uplink time slot, The time from the rear end of the time position of the first signal to the rear end of the first upstream time slot can be made as long as possible. In addition, the radio base station transmits a signal whose time position is within the time slot of the uplink time slot to the radio terminal that is the transmission source of the signal having the shortest time difference between the rear end of the time position and the rear end of the uplink time slot. On the other hand, by assigning the last uplink time slot in the uplink time zone, the time from the front end of the time position of the last signal to the front end of the last uplink time slot can be made as long as possible.

  For this reason, the radio base station is the second from the beginning of the uplink time zone to the radio terminal that is the transmission source of the signal corresponding to the back time position among the two signals having overlapping time positions. Of the two signals that are assigned uplink time slots and have overlapping time positions, the second uplink time from the end of the uplink time zone to the wireless terminal that is the transmission source of the signal corresponding to the forward time position By assigning a slot, it is possible to reduce the possibility of a collision between a signal transmitted by the wireless terminal using the first time slot and a signal transmitted by the wireless terminal using the second time slot from the beginning. At the same time, the signal transmitted by the wireless terminal using the last time slot and the signal transmitted by the wireless terminal using the second time slot from the last are It can reduce the possibility of. In addition, it is possible to prevent a collision by separating the time positions of two overlapping signals.

  The gist of a fourth aspect of the present invention is that the time position detection unit detects a time position of a unique word included in data corresponding to the plurality of signals.

  By detecting the time position of the unique word, it is possible to determine whether the time positions of the two signals overlap based on the difference between the time positions of the unique words included in the data corresponding to the two signals. Become. Even if the radio base station cannot acquire data corresponding to the entire signal due to deterioration of the propagation environment, etc., if at least a unique word can be acquired, the time positions of the two signals overlap. It is possible to determine whether or not

  A fifth aspect of the present invention includes a measurement unit (reception quality measurement unit 154) that measures reception quality of the plurality of signals received by the reception unit, and the allocation unit is measured by the measurement unit. When the reception quality deteriorates below a predetermined level, the uplink time allocated immediately before at least one of the wireless terminals that are the transmission sources of the two or more signals whose time positions overlap each other The gist is to assign the upstream time slot different from the slot.

  Even if there is a collision in the signal, if the reception quality is good, it is not necessary to assign a new uplink time slot to the wireless terminal that is the transmission source of the signal. Therefore, the processing load can be reduced by allocating a new uplink time slot only when the reception quality is degraded.

  A sixth aspect of the present invention includes a downlink time zone used for downlink communication and an uplink time zone used for uplink communication following the downlink time zone, and the downlink time zone includes a plurality of downlink time zones. A frame that is divided into time slots and in which the uplink time slot is divided into a plurality of uplink time slots is configured, and the downlink time slots and the uplink time slots are used to perform time division duplexing with a plurality of radio terminals. And a communication control method in a radio base station that transmits signals by time division multiplexing, wherein the radio base station receives a plurality of signals transmitted using the uplink time slots assigned to the plurality of radio terminals. A step in which the radio base station detects time positions of the plurality of received signals, and the radio base station includes a plurality of the received signals. When there are two or more signals with overlapping time positions, the allocation is performed immediately before at least one of the wireless terminals that are the transmission sources of the two or more signals with overlapping time positions. And assigning the uplink time slot different from the uplink time slot.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible in a wireless base station to prevent the collision of the signal from each wireless terminal accompanying the movement of a some wireless terminal.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) the configuration of the radio communication system, (2) the operation of the radio base station, (3) the operation and effect, and (4) other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Configuration of Radio Communication System First, regarding the configuration of the radio communication system according to the embodiment of the present invention, (1.1) overall schematic configuration of radio communication system, (1.2) configuration of radio base station, (1 .3) The configuration of the wireless terminals will be described in the order.

(1.1) Overall Schematic Configuration of Radio Communication System FIG. 1 is an overall schematic configuration diagram of a radio communication system 10 according to an embodiment of the present invention.

  As shown in FIG. 1, the radio communication system 10 is a PHS radio communication system. The radio communication system 10 includes a radio base station 1, a radio terminal 2A, a radio terminal 2B, a radio terminal 2C, and a radio terminal 2D. In FIG. 1, radio terminals 2A to 2D are located in a cell 3 provided by the radio base station 1. The radio base station 1 and the radio terminals 2A to 2D transmit signals by time division duplex and time division multiplexing.

  Prior to communication with the wireless terminals 2A to 2D, the wireless base station 1 assigns time slots in the frame to the wireless terminals 2A to 2D.

    FIG. 2 is a diagram illustrating a frame configuration. As shown in FIG. 2, the frame includes a downlink time zone used for communication in the downlink direction (direction from the radio base station 1 toward the radio terminals 2A to 2D), and an uplink direction (radio terminal 2A) following the downlink time zone. To 2D to the radio base station 1), the downlink time slot is divided into four downlink time slots D1 to D4, and the uplink time slot is divided into four downlink time slots U1 to U1. It is divided into U4.

  In the initial state, the radio base station 1 assigns the downlink time slot D1 and the uplink time slot U1 to the radio terminal 2A, and assigns the downlink time slot D2 and the uplink time slot U2 to the radio terminal 2B. Further, the radio base station 1 assigns the downlink time slot D3 and the uplink time slot U3 to the radio terminal 2C, and assigns the downlink time slot D4 and the uplink time slot U4 to the radio terminal 2D. The radio terminals 2A to 2D receive signals from the radio base station 1 using the assigned downlink time slots, and transmit signals to the radio base station 1 using the assigned uplink time slots.

(1.2) Configuration of Radio Base Station Next, regarding the configuration of the radio base station 1, (1.2.1) schematic configuration of the radio base station, (1.2.2) detailed configuration of the radio base station. explain.

(1.2.1) Schematic Configuration of Radio Base Station FIG. 3 is a schematic configuration diagram of the radio base station 1. As illustrated in FIG. 3, the wireless base station 1 includes a control unit 102, a storage unit 103, a wired communication unit 104, a wireless communication unit 106, and an antenna 108.

  The control unit 102 is configured by a CPU, for example, and controls various functions provided in the radio base station 1. The storage unit 103 is configured by a memory, for example, and stores various types of information used for control and the like in the radio base station 1.

  The wired communication unit 104 communicates with a gateway server or the like in an upper network (not shown). The wireless communication unit 106 includes an RF circuit, a baseband circuit, etc., performs modulation and demodulation, encoding and decoding, etc., and transmits and receives wireless signals via the antenna 108.

(1.2.2) Detailed Configuration of Radio Base Station Next, a detailed configuration of the radio base station 1, specifically, functional block configurations of the control unit 102 and the radio communication unit 106 will be described. FIG. 4 is a functional block configuration diagram of the control unit 102 and the radio communication unit 106 of the radio base station 1.

  As illustrated in FIG. 4, the wireless communication unit 106 includes a reception processing unit 152, a reception quality measurement unit 154, and a unique word detection unit 156. In addition, the control unit 102 includes an uplink time slot allocation unit 158 and a wireless terminal transmission control unit 160.

  The reception processing unit 152 in the wireless communication unit 106 receives each signal transmitted from the wireless terminals 2A to 2D via the uplink time slot assigned to each of the wireless terminals 2A to 2D. Further, the reception processing unit 152 outputs each received signal to the reception quality measurement unit 154.

  In addition, the reception processing unit 152 demodulates and decodes each input signal to generate reception data, and each time, the reception data is sent to the unique word detection unit 154 and the reception quality measurement unit 156 in the control unit 102. Output.

  The reception quality measurement unit 154 in the wireless communication unit 106 measures the reception quality of the received signal.

  Specifically, the reception quality measurement unit 154 inputs each signal from the reception processing unit 152. Furthermore, the reception quality measuring unit 154 measures a received signal strength (RSSI) that is a reception quality of each input signal. Alternatively, the reception quality measurement unit 154 receives the reception data from the reception processing unit 152. Further, the reception quality measuring unit 154 measures a frame error rate (FER: Flame Error Rate) which is the reception quality of each input reception data. The reception quality measuring unit 154 outputs the measured reception quality to the unique word detection unit 156 together with the corresponding reception data. Reception quality measuring section 154 outputs the measured reception quality to radio terminal transmission control section 160.

  The unique word detection unit 156 in the wireless communication unit 106 inputs reception quality and reception data corresponding to the reception quality. Furthermore, the unique word detection unit 156 determines whether any of the received reception quality has deteriorated below a predetermined level. When the reception quality has deteriorated below a predetermined level, the unique word detection unit 156 detects the time position of the unique word, which is the synchronization data included in each input received data. Further, the unique word detection unit 154 outputs the detected time position of each unique word to the unique word detection unit 156 in the control unit 102.

  The unique word detection unit 156 in the control unit 102 inputs the time position of each unique word. Furthermore, the unique word detection unit 156 determines whether or not the time position difference between the unique words included in the two consecutive received data is within a predetermined range.

  When the difference between the time positions of the unique words included in the two consecutive received data is within the predetermined range, the uplink time slot allocating unit 158 considers that the signals corresponding to the two consecutive data collide. Next, in order to prevent signal collision, uplink time slot allocating section 158 allocates immediately to at least one of the wireless terminals that are the transmission source of the signal in which the collision has occurred, among wireless terminals 2A to 2D. An upstream time slot different from the upstream time slot that has been assigned is assigned.

  Further, uplink time slot assignment section 158 outputs information on the uplink time slot newly assigned to any of radio terminals 2A to 2D (information on the uplink time slot after the change) to radio terminal transmission control section 160. To do.

  Radio terminal transmission control section 160 receives the reception quality from reception quality measurement section 154 and receives the changed uplink time slot information from uplink time slot allocation section 158. Next, radio terminal transmission control section 160 controls transmission power, modulation scheme, and frequency bandwidth for each of radio terminals 2A to 2D that are transmission sources of signals corresponding to the reception quality, according to reception quality. Control information is generated.

  Further, the radio terminal transmission control unit 160 transmits the control information and the changed uplink time slot information to the corresponding radio terminals 2A to 2D via the radio communication unit 106 and the antenna 108.

(2) Operation of Radio Base Station Next, the operation of the radio base station 1 will be described. FIG. 5 is a flowchart showing the operation of the radio base station 1. In the following, in the initial state, the radio base station 1 allocates the downlink time slot D1 and the uplink time slot U1 in the frame shown in FIG. 2 to the radio terminal 2A, and the radio terminal 2B It is assumed that the downlink time slot D2 and the uplink time slot U2 in the frame shown in FIG. In the initial state, the radio base station 1 allocates the downlink time slot D3 and the uplink time slot U3 in the frame shown in FIG. 2 to the radio terminal 2C, and the radio terminal 2D receives the frame shown in FIG. It is assumed that the downlink time slot D4 and the uplink time slot U4 are allocated.

  The radio terminals 2A to 2D transmit signals to the radio base station 1 using the assigned uplink time slots. In step S101, the radio communication unit 106 in the radio base station 1 inputs four signals transmitted from the radio terminals 2A to 2D and received by the antenna 108. Next, the wireless communication unit 106 measures reception quality for each input signal. Further, the wireless communication unit 106 determines whether any of the measured reception qualities has deteriorated below a predetermined value.

  If any of the measured reception qualities deteriorates below a predetermined value, in step S102, the wireless communication unit 106 determines the time position of the unique word (UW) included in the reception data obtained by demodulating and encoding each signal. To detect. Here, the time position of the unique word indicates the detection time of the unique word.

  FIG. 6 is a diagram illustrating a configuration of received data. The reception data shown in FIG. 6 has a bit length of 240 bits. The received data includes, in order from the top, a 4-bit long ramp time for transient response (R), a 2-bit long start symbol (SS), a 6-bit long preample (PR), a 16-bit long unique word (UW). ), 180-bit information, 16-bit CRC (Cyclic Redundancy Check), and 16-bit guard.

  Again, referring back to FIG. In step S103, the wireless communication unit 106 determines whether or not the difference between the time positions of the unique words included in the received data corresponding to the two consecutive signals is within a predetermined value.

  Here, the predetermined value is the maximum value of the difference between the time positions of the unique words included in the received data corresponding to the two consecutive signals when the time positions (reception windows) of the two consecutive signals overlap. is there.

  Therefore, when the difference in time position of the unique word included in the received data corresponding to the two consecutive signals is within a predetermined value, the reception windows of the two consecutive signals overlap and a signal collision occurs. Will be. On the other hand, when the difference in time position of the unique word included in the received data corresponding to two consecutive signals exceeds a predetermined value, the reception windows of the two consecutive signals do not overlap and a signal collision occurs. Will not be.

  For example, in FIGS. 7 to 9, the reception windows corresponding to two consecutive signals are reception window # 1 and reception window # 2, reception window # 2 and reception window # 3, reception window # 3 and reception window # 4. There are three pairs.

  In FIG. 7, the difference between the time positions of the two unique words corresponding to reception window # 1 and reception window # 2 exceeds a predetermined value, and reception window # 1 and reception window # 2 do not overlap. Also, the difference between the time positions of the two unique words corresponding to the reception window # 2 and the reception window # 3 exceeds a predetermined value, and the reception window # 2 and the reception window # 3 do not overlap with each other. The difference between the time positions of the two unique words corresponding to # 3 and reception window # 4 exceeds a predetermined value, and reception window # 3 and reception window # 4 do not overlap.

  On the other hand, in FIG. 8 (a) and FIG. 9 (a), the difference between the time positions of the two unique words corresponding to the reception window # 1 and the reception window # 2 exceeds a predetermined value. Reception window # 2 does not overlap. Further, the difference between the time positions of the two unique words corresponding to the reception window # 3 and the reception window # 4 exceeds a predetermined value, and the reception window # 3 and the reception window # 4 do not overlap. On the other hand, the difference between the time positions of the two unique words corresponding to reception window # 2 and reception window # 3 is within a predetermined value, and reception window # 2 and reception window # 3 overlap.

  Returning again to FIG. If it is determined in step S103 that the difference in time position of the unique word included in the reception data corresponding to two consecutive signals exceeds a predetermined value, that is, the reception windows do not overlap. If there is no signal collision, in step S104, the control unit 102 transmits transmission power and modulation for each wireless terminal 2A to 2D that is a transmission source of a signal corresponding to the reception quality, according to each reception quality. Control information for controlling the method and the frequency bandwidth is generated.

  In step S105, the control unit 102 transmits control information for each of the wireless terminals 2A to 2D to the corresponding wireless terminals 2A to 2D via the wireless communication unit 106 and the antenna 108. The radio terminals 2A to 2D receive control information. Further, the radio terminals 2A to 2D change the transmission power, the modulation scheme, and the frequency bandwidth based on the control information.

  On the other hand, when the difference in time position of the unique word included in the received data corresponding to two consecutive signals is within a predetermined value (in the case of an affirmative determination in step S103), that is, the reception window is duplicated. If there is a signal collision, in step S111, the control unit 102 allocates an uplink time slot different from the uplink time slot allocated immediately before to at least one of the wireless terminals 2A to 2D. . Further, the control unit 102 generates post-change uplink time slot information including identification information of the uplink time slot newly assigned to at least one of the radio terminals 2A to 2D.

  There are two possible methods for allocating uplink time slots. In the first method, when two reception windows are overlapped, the control unit 102 selects one of the two wireless signal transmission source wireless terminals corresponding to the two overlapping reception windows. The uplink time slot assigned immediately before is assigned to the other radio terminal, and the uplink time slot assigned immediately before for the other radio terminal is assigned to one radio terminal.

  For example, in FIG. 8A, the reception window # 2 of the signal transmitted using the uplink time slot U2 and the reception window # 3 of the signal transmitted using the uplink time slot U3 overlap. In this case, as shown in FIG. 8 (b), the control unit 102 uses the reception window # 2 as the uplink time slot U2 assigned immediately before to the wireless terminal 2B that is the transmission source of the signal corresponding to the reception window # 2. 3 is assigned to the wireless terminal 2C that is the transmission source of the signal corresponding to 3. In addition, the control unit 102 uses the uplink time slot U3 assigned immediately before to the wireless terminal 2C that is the transmission source of the signal corresponding to the reception window # 3, as the wireless terminal that is the transmission source of the signal corresponding to the reception window # 2. Assign to 2B. As a result, the reception window # 2 and the reception window # 3 do not overlap, and signal collision is prevented.

  Also, in the second method, when two reception windows overlap, the control unit 102, among signals in which the reception window falls within the time slot of the uplink time slot, the front end of the reception window and the uplink time slot The first uplink time slot in the uplink time zone is assigned to the wireless terminal that is the source of the signal with the shortest time difference from the front end. In addition, the control unit 102 determines whether the signal having the reception window within the time slot of the uplink time slot has the shortest time difference between the rear end of the reception window and the rear end of the uplink time slot. On the other hand, the last uplink time slot in the uplink time zone is allocated.

  Furthermore, the control unit 102 transmits the second uplink signal from the beginning of the uplink time period to the wireless terminal that is the transmission source of the signal corresponding to the backward reception window, out of the two signals having overlapping reception windows. The second uplink time slot from the end of the uplink time slot to the radio terminal that is the source of the signal corresponding to the forward reception window, of the two signals to which the time slots are assigned and the reception windows overlap. Assign.

  For example, in FIG. 9A, the reception window # 2 of the signal transmitted using the uplink time slot U2 and the reception window # 3 of the signal transmitted using the uplink time slot U3 overlap. The reception window # 1 of the signal transmitted using the uplink time slot U1 is within the time zone of the uplink time slot U1, and the reception window # 4 of the signal transmitted using the uplink time slot U4 is It is within the time slot of the upstream time slot U4.

  Further, when the reception window # 1 and the reception window # 4 are compared, the time difference between the front end of the reception window # 4 and the front end of the time slot U4 is larger than the time difference between the front end of the reception window # 1 and the front end of the time slot U1. short. On the other hand, the time difference between the rear end of reception window # 1 and the rear end of time slot U1 is shorter than the time difference between the rear end of reception window # 4 and the rear end of time slot U4.

  In this case, as shown in FIG. 9B, the control unit 102 assigns the uplink time slot U1 that is the first uplink time slot to the radio terminal 2D that is the transmission source of the signal corresponding to the reception window # 4. At the same time, the uplink time slot U4, which is the last uplink time slot, is allocated to the wireless terminal 2A that is the transmission source of the signal corresponding to the reception window # 1.

  Further, as shown in FIG. 9C, the control unit 102 transmits the wireless terminal 2C that is the transmission source of the signal corresponding to the rear receiving window # 3 among the overlapping receiving windows # 2 and # 3. Is assigned the uplink time slot U2 that is the second uplink time slot from the beginning, and the second uplink time from the end to the wireless terminal 2B that is the transmission source of the signal corresponding to the forward reception window # 2. An uplink time slot U3, which is a slot, is allocated.

  Returning again to FIG. In step S112, the control unit 102 controls the transmission power, the modulation scheme, and the frequency bandwidth for each of the wireless terminals 2A to 2D that are the transmission sources of signals corresponding to the reception quality, according to each reception quality. Generate control information.

  In step S113, the control unit 102 transmits the control information for each of the wireless terminals 2A to 2D and the changed uplink time slot information for each of the wireless terminals 2A to 2D via the wireless communication unit 106 and the antenna 108. Transmit to terminals 2A to 2D. The radio terminals 2A to 2D receive the control information and the changed uplink time slot information. Furthermore, the radio terminals 2A to 2D change the transmission power, the modulation scheme, and the frequency bandwidth based on the control information, and use the uplink time slot specified by the changed uplink time slot information to In response to this, a signal is transmitted.

  Thereafter, in step S114, the wireless communication unit 106 is used to transmit a signal corresponding to the received data for the unique word included in the received data obtained by demodulating and encoding each signal from the wireless terminals 2A to 2D. The time position in the time zone of the uplink time slot is detected.

  Further, in step S115, the wireless communication unit 106 determines whether or not the time position difference between the unique words included in the two consecutive received data is within a predetermined value.

  When it is determined that the time difference between the unique words included in two consecutive received data exceeds a predetermined value, that is, the reception windows do not overlap and no signal collision occurs. In this case, the operation after the determination as to whether or not the reception quality in step S101 has deteriorated below a predetermined value is repeated.

  On the other hand, when it is determined that the time position difference between the unique words included in the two consecutive received data is within a predetermined value, that is, the reception windows overlap and a signal collision occurs. In this case, the operations after the generation of the uplink time slot information and the changed uplink time slot information in step S111 are repeated again.

(3) Operation / Effect In the radio communication system 10 according to the embodiment of the present invention, the radio terminals 2A to 2D transmit signals using uplink time slots assigned to themselves. The radio base station 1 receives this signal and obtains received data by demodulation and decoding. Further, the radio base station 1 detects the time position of the unique word included in the received data, and when the difference between the time positions of the unique words included in the two consecutive received data is within a predetermined value, And the uplink time slot allocated immediately before at least one of the wireless terminals that transmitted the signal among the wireless terminals 2A to 2D. A different uplink time slot is assigned.

  Specifically, in the first method, when two reception windows are overlapped, the radio base station 1 determines whether the wireless terminal that is the transmission source of the two signals corresponding to the two reception windows overlapped with each other. Of these, the uplink time slot assigned immediately before to one wireless terminal is assigned to the other wireless terminal. Further, the radio base station 1 assigns the uplink time slot assigned immediately before to the other radio terminal to one radio terminal.

  When reception windows of two consecutive signals overlap, a state in which the reception window of the front signal is out of the rear side of the upstream time slot used for transmission of the signal and the reception window of the rear signal are The state is at least one of the states deviated in front of the corresponding upstream time slot used for transmission of the signal. In this case, by adopting the first method, it is possible to separate the reception windows of the two overlapping signals and prevent a collision.

  Alternatively, in the second method, when the two reception windows overlap, the radio base station 1 determines that the front end of the reception window and the upstream time slot out of the signals in which the reception window falls within the time slot of the upstream time slot. The first uplink time slot in the uplink time slot is allocated to the wireless terminal that is the transmission source of the signal having the shortest time difference from the front end. Also, the radio base station 1 is a radio terminal that is a transmission source of a signal having the shortest time difference between the rear end of the reception window and the rear end of the uplink time slot among the signals having the reception window within the time slot of the uplink time slot. Is assigned the last uplink time slot in the uplink time zone. Furthermore, the radio base station 1 transmits the second signal from the beginning of the uplink time period to the radio terminal that is the transmission source of the signal corresponding to the rear reception window, out of the two signals having the same reception window. Of the two signals with an uplink time slot allocated and the reception window overlapping, the second uplink time from the end of the uplink time zone to the wireless terminal that is the transmission source of the signal corresponding to the front reception window Assign a slot.

  By adopting the second method, the signals from the radio terminals 2A to 2D can be stored after the front end of the upstream time slot composed of a plurality of upstream time slots and before the rear end, It is possible to prevent troubles in the downstream communication used. Furthermore, the time from the rear end of the reception window of the first signal to the rear end of the first uplink time slot can be made as long as possible, and the front end of the reception window of the last signal can be The time to the front end can be made as long as possible.

  For this reason, the radio base station 1 is the second from the beginning of the uplink time zone to the radio terminal that is the transmission source of the signal corresponding to the rear reception window, out of the two signals with overlapping reception windows. Of the two signals having the same reception time window and the overlapping reception window, the second uplink signal from the end of the upstream time period is transmitted to the wireless terminal that is the transmission source of the signal corresponding to the front reception window. By assigning the time slot, it is possible to reduce the possibility that a signal transmitted by the wireless terminal using the first time slot and a signal transmitted by the wireless terminal using the second time slot from the beginning collide with each other. And the signal transmitted by the wireless terminal using the last time slot and the second time slot from the last by the wireless terminal. A signal transmitted There are can reduce the possibility of collision. In addition, it is possible to prevent a collision by separating the time positions of two overlapping signals.

  Further, the radio base station 1 detects the time position of the unique word included in the received data corresponding to the signals from the radio terminals 2A to 2D, and based on the difference in the time position of the unique word, the reception window overlaps, Determines the collision of signals. Therefore, even if the wireless base station 1 cannot acquire the received data corresponding to the entire signal due to the deterioration of the propagation environment or the like, if at least the unique word can be acquired, the reception window will overlap. It can be determined whether or not.

  Also, the radio base station 1 measures the reception quality of the signals from the radio terminals 2A to 2D, and only when any one of the reception qualities is deteriorated below a predetermined value, the radio terminals 2A to 2A An uplink time slot different from the uplink time slot assigned immediately before is assigned to 2D. Even if there is a collision in the signal, if the reception quality is good, it is necessary to allocate an uplink time slot different from the uplink time slot allocated immediately before to the wireless terminal that is the transmission source of the signal. Absent. Therefore, the processing load can be reduced by assigning an uplink time slot different from the uplink time slot assigned immediately before, when the radio base station 1 has deteriorated reception quality.

(4) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the above-described embodiment, as illustrated in FIGS. 2 and 7 to 9, the case where the uplink time slot is divided into four uplink time slots has been described as an example, but is divided into more uplink time slots. Even in this case, the present invention can be similarly applied. For example, when the above-described second method is adopted at the time of uplink time slot allocation, the second method transmits the first and second from the beginning to the wireless terminals 2A to 2D that are the transmission sources of the four signals. And the last and second last 4 uplink time slots are allocated, but for the wireless terminal that is the source of other signals (signals whose reception window is within the time slot of the uplink time slot) The remaining uplink time slots are allocated.

  In the above-described embodiment, the case where two signals collide has been described. However, the present invention can be similarly applied to a case where three or more signals collide. In this case, for example, the radio base station 1 derives all the allocation patterns of the uplink time slots for the signal, and identifies the allocation pattern in which the reception windows do not overlap among these allocation patterns.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a figure which shows the structure of the flame | frame which concerns on embodiment of this invention. It is a schematic block diagram of the radio base station which concerns on embodiment of this invention. It is a functional block block diagram of the control part and radio | wireless communication part in a wireless base station based on embodiment of this invention. It is a flowchart which shows the operation | movement of the wireless base station which concerns on embodiment of this invention. It is a figure which shows the structure of the reception data which concern on embodiment of this invention. It is a figure which shows an example of the correspondence of the uplink time slot and reception window which concern on embodiment of this invention. It is a figure which shows the 1st example of allocation of the uplink time slot which concerns on embodiment of this invention. It is a figure which shows the 2nd example of allocation of the uplink time slot which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Wireless base station, 2A-2C ... Wireless terminal, 3 ... Cell, 10 ... Wireless communication system, 102 ... Control part, 103 ... Memory | storage part, 104 ... Wired communication part, 106 ... Wireless communication part, 108 ... Antenna, 152 ... reception processing unit, 154 ... reception quality measurement unit, 164 ... unique word detection unit, 158 ... uplink time slot allocation unit, 160 ... wireless terminal transmission control unit

Claims (6)

A downlink time zone used for downlink communication and an uplink time zone used for uplink communication following the downlink time zone, and the downlink time zone is divided into a plurality of downlink time slots, and the uplink time zone A frame in which a band is divided into a plurality of uplink time slots is configured, and signals are transmitted to and from a plurality of wireless terminals by time division duplex and time division multiplexing using the downlink time slots and the uplink time slots. A wireless base station,
A receiving unit for receiving a plurality of signals transmitted using the uplink time slots assigned to the plurality of wireless terminals;
A time position detecting unit for detecting time positions of the plurality of signals received by the receiving unit;
Of the plurality of signals received by the receiving unit, when there are two or more signals with overlapping time positions, the source of two or more signals with overlapping time positions the radio base station and a allocation unit for allocating a different said uplink time slots to at least to either the uplink time slot that has been allocated immediately before the wireless terminal.   The allocating unit transmits the two signals having overlapping time positions when there are two signals having overlapping time positions among the plurality of signals received by the receiving unit. The uplink time slot assigned immediately before to one of the original wireless terminals is assigned to the other of the wireless terminals as the transmission source of the two signals whose time positions overlap, and the time position The uplink time slot assigned immediately before to the other of the radio terminals of the two signals that are overlapping is the radio of the source of the two signals that are overlapping in time position The radio base station according to claim 1, which is assigned to one of the terminals.   The allocating unit is configured such that when there are two signals having the same time position among the plurality of signals received by the receiving unit, the time position falls within the time slot of the uplink time slot. The first uplink time slot of the uplink time slot for the wireless terminal that is the source of the signal with the shortest time difference between the front end of the time position and the front end of the uplink time slot. Among the signals whose time positions are within the time slot of the upstream time slot, the transmission source of the signal having the shortest time difference between the rear end of the time position and the rear end of the upstream time slot The last uplink time slot in the uplink time slot is allocated to the wireless terminal, and the two signals having the overlapping time positions are behind the two signals. The second uplink time slot from the beginning of the uplink time zone is allocated to the wireless terminal that is the transmission source of the signal corresponding to the inter-position, and the two signals having the overlapping time positions are allocated. The radio according to claim 1 or 2, wherein the second uplink time slot from the end of the uplink time zone is allocated to the radio terminal that is a transmission source of the signal corresponding to the time position ahead. base station.   The radio base station according to any one of claims 1 to 3, wherein the time position detection unit detects a time position of a unique word included in data corresponding to the plurality of signals. A measurement unit that measures reception quality of the plurality of signals received by the reception unit;
When the reception quality measured by the measurement unit is deteriorated below a predetermined level, the allocating unit is provided to at least one of the wireless terminals that are the transmission sources of two or more signals having overlapping time positions. On the other hand, the radio base station according to any one of claims 1 to 4, wherein the uplink time slot different from the uplink time slot allocated immediately before is allocated. A downlink time zone used for downlink communication and an uplink time zone used for uplink communication following the downlink time zone, and the downlink time zone is divided into a plurality of downlink time slots, and the uplink time zone A frame in which a band is divided into a plurality of uplink time slots is configured, and signals are transmitted to and from a plurality of wireless terminals by time division duplex and time division multiplexing using the downlink time slots and the uplink time slots. A communication control method in a radio base station,
The radio base station receiving a plurality of signals transmitted using the uplink time slots assigned to the plurality of radio terminals;
The radio base station detecting time positions of the received signals;
The radio base station transmits two or more signals with overlapping time positions when there are two or more signals with overlapping time positions among the plurality of received signals. Allocating the uplink time slot different from the uplink time slot allocated immediately before to at least one of the original wireless terminals.

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