JP2011176499A - Wireless communication system, base station, repeater, and wireless communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a wireless line capacity between a repeater and a base station in accordance with a communication condition of a mobile station wirelessly connected to the repeater. <P>SOLUTION: A base station 12 wirelessly connects to a repeater wirelessly connecting to one or more mobile stations and communicates these mobile stations via the repeater. The base station 12 includes: a limitation target selection part 34 which selects one of mobile stations wirelessly communicating the base station 12 at the same timing as the repeater, as a limitation target in response to a request from the repeater for increasing the wireless line capacity between the repeater and the base station 12; and a transmission power control part 36 which reduces a wireless line capacity between the mobile station selected as the limitation target and the base station 12, and increases the wireless line capacity between the repeater and the base station 12 as much as the reduction of the wireless line capacity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless communication system, a base station, a relay device, and a wireless communication method.

  A relay device (repeater) that relays communication between a base station and a mobile station may be installed in a place where radio waves from a base station are difficult to reach directly, such as indoors and underground shopping malls. As a result, the mobile station can connect to the base station via the relay device, and the service area of the base station is expanded.

  However, when a plurality of mobile stations are wirelessly connected to the relay device, the radio channel capacity between the relay device and the base station becomes a bottleneck, and the transmission efficiency of data transmitted and received between these mobile stations and the base station decreases. It becomes easy to do. Therefore, there is a demand for a technique for increasing the radio channel capacity between the relay device and the base station according to the communication status of the mobile station wirelessly connected to the relay device.

  In this regard, the cited document 1 discloses a relay device that switches a connection destination base station by handover when the quality of a communication channel with the connection destination base station deteriorates.

JP 2001-61174 A

  However, in the relay apparatus described in the cited document 1, it is necessary that two or more base stations exist in the vicinity in order to perform the handover, and a decrease in data transmission efficiency due to the handover becomes a new problem.

  The present invention has been made in view of the above problems, and wireless communication capable of increasing the wireless channel capacity between a relay device and a base station according to the communication status of a mobile station wirelessly connected to the relay device. It is an object to provide a system, a base station, a relay device, and a wireless communication method.

  In order to solve the above problems, a wireless communication system according to the present invention wirelessly connects a base station to each of the base station and one or more mobile stations, and between the base station and the one or more mobile stations. A wireless communication system including a relay device that relays the communication of the wireless communication system, wherein the relay device has a wireless channel capacity between the relay device and the base station based on a communication status of the one or more mobile stations. Requesting means for transmitting to the base station a capacity increase request for requesting to increase the base station, in response to the capacity increase request from the relay apparatus, the base station and the base station at the same timing. Selection means for selecting any one of mobile stations performing wireless communication as a restriction target, and reducing the wireless channel capacity between the mobile station selected as the restriction target and the base station, and the reduced wireless line Characterized in that it comprises a, and bandwidth control means for increasing the radio network capacity between the only volume corresponding to the amount the relay device and the base station.

  In the present invention, in response to a capacity increase request from the relay device, the base station reduces the radio channel capacity between any of the mobile stations that perform radio communication with the own station at the same timing as the relay device, thereby relaying Precisely secure an increase in the radio channel capacity with the device. For this reason, the radio channel capacity between the relay device and the base station can be increased according to the communication status of the mobile station wirelessly connected to the relay device.

  In one aspect of the present invention, the requesting unit includes: a radio channel capacity between the relay device and the one or more mobile stations; and a radio channel capacity between the relay device and the base station. The capacity increase request may be transmitted to the base station based on the comparison result.

  According to this aspect, since the imbalance between the wireless channel capacity between the relay device and the mobile station and the wireless channel capacity between the relay device and the base station is corrected, wireless connection to the relay device is achieved. It is possible to suppress a decrease in transmission efficiency of data transmitted and received between the mobile station and the base station.

  Also, in one aspect of the present invention, the selection unit has a radio channel capacity between the base station and a mobile station that performs radio communication with the base station at the same timing as the relay apparatus, which is greater than or equal to a predetermined capacity. At least one of the mobile stations may be selected as the restriction target.

  According to this aspect, it is possible to increase the radio channel capacity between the base station and the relay device while preventing disconnection of the radio communication between the base station and the mobile station performed at the same timing as the relay device.

  In the aspect of the invention, the relay device further includes means for notifying the base station of reception quality of a downlink signal transmitted from the base station to the relay device, and the base station includes the relay device. Further comprising modulation scheme determining means for determining a modulation scheme of the downlink signal transmitted to the relay apparatus based on the reception quality of the downlink signal notified from the network, and the line capacity control means is selected as the restriction target The transmission power of the downlink signal transmitted to the mobile station may be decreased, and the transmission power of the downlink signal transmitted to the relay apparatus may be increased by the power corresponding to the decreased transmission power.

  According to this aspect, the radio channel capacity between the relay device and the base station can be increased by adjusting the transmission power distribution of the downlink signal.

  Also, in one aspect of the present invention, the line capacity control means reduces the radio channel assignment to the mobile station selected as the restriction target, and also performs the relay by an amount corresponding to the reduced radio channel assignment. The allocation of radio channels to the device may be increased.

  According to this aspect, it is possible to increase the radio channel capacity between the relay device and the base station by adjusting the radio channel allocation distribution.

  The base station according to the present invention is a base station that is wirelessly connected to a relay device that is wirelessly connected to each of one or more mobile stations, and communicates with the one or more mobile stations via the relay device, When a request is made from the relay device to increase the radio channel capacity between the relay device and the base station, any mobile station that performs radio communication with the base station at the same timing as the relay device is restricted. Selecting means for selecting as a target, and reducing the radio channel capacity between the base station and the mobile station selected as the restriction target, and the relay device and the capacity corresponding to the reduced radio channel capacity Circuit capacity control means for increasing the capacity of the radio channel with the base station.

  The relay device according to the present invention is a relay device that wirelessly connects to each of a base station and one or more mobile stations, and relays communication between the base station and the one or more mobile stations, In response to a capacity increase request from a relay device, selection means for selecting any of the mobile stations that perform radio communication with the base station at the same timing as the relay device, and the mobile station selected as the restriction target A channel capacity control means for decreasing the radio channel capacity between the relay station and the base station by a capacity corresponding to the decreased radio channel capacity, and , Including a request means for transmitting the capacity increase request based on the communication status of the one or more mobile stations.

  In addition, the wireless communication method according to the present invention is a relay that wirelessly connects a base station to each of the base station and one or more mobile stations, and relays communication between the base station and the one or more mobile stations. A wireless communication method in a wireless communication system including the device, wherein the relay device increases a radio channel capacity between the relay device and the base station based on a communication status of the one or more mobile stations. Transmitting a capacity increase request to request to the base station, and the base station performs wireless communication with the base station at the same timing as the relay apparatus in response to the capacity increase request from the relay apparatus Selecting one of the mobile stations as a restriction target, and the base station reduces the radio channel capacity between the mobile station selected as the restriction target and the base station, and Characterized in that it comprises the steps of: increasing the wireless network capacity between only capacity according to the bandwidth the relay device and the base station.

It is a figure which shows the structure of the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the TDD frame structure which concerns on this embodiment. It is a figure which shows an example of the transmission power (transmission spectrum) of the downlink signal transmitted from a base station. It is a figure which shows an example of the reception power (reception spectrum) of the downlink signal transmitted with the transmission power shown to FIG. 3A. It is a figure which shows an example of the transmission power of the downlink signal transmitted from a base station according to the high speed mode request | requirement from a relay apparatus. It is a figure which shows an example of the reception power of the downlink signal transmitted with the transmission power shown to FIG. 4A. It is a functional block diagram of the base station which concerns on this embodiment. It is a figure which shows an example of the table which defined the correspondence of CNR and a modulation system. It is a figure which shows an example of the adjustment process of the radio channel capacity in the base station which concerns on this embodiment. It is a functional block diagram of the relay apparatus which concerns on this embodiment. It is a figure which shows an example of the high-speed mode request process in the relay apparatus which concerns on this embodiment. It is a figure which shows an example of the adjustment process of the allocation allocation of the slot (radio channel) in the base station which concerns on this embodiment.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a wireless communication system 10 according to an embodiment of the present invention. As shown in FIG. 1, the wireless communication system 10 includes a base station 12, a plurality of mobile stations 14, and a relay device 16 installed in a cover area 18-1 of the base station 12. .

  The base station 12 wirelessly communicates with each of the mobile station 14 (in this case, the mobile stations 14-1 to 14-5) and the relay device 16 located in the cover area 18-1 of the own station by the OFDMA method and the TDMA / TDD method. Communicate. The mobile station 14 corresponds to a mobile phone, a communication card, a portable information terminal with a built-in communication function, and the like.

  The relay device 16 is wirelessly connected to the base station 12 and wirelessly connected to the mobile station 14 (here, the mobile stations 14-6 and 14-7) located in the cover area 18-2 of the own device. The relay device 16 operates as a mobile station with respect to the base station 12 and operates as a base station with respect to the mobile station 14, so that the mobile station is located within the cover area 18-2 with the base station 12. 14 is relayed. As a result, the mobile station 14 located within the cover area 18-2 of the relay device 16 can be connected to the base station 12 via the relay device 16. That is, the service area of the base station 12 is expanded to a range including the cover area 18-1 and the cover area 18-2.

  FIG. 2 is a diagram illustrating an example of a TDD frame configuration in the wireless communication system 10 (horizontal axis: symbol (time), vertical axis: subchannel (frequency)). As shown in FIG. 2, in the wireless communication system 10, the base station 12 transmits a radio signal to the mobile station 14 and / or the relay device 16 in one TDD frame, and the base station 12 transmits the mobile station 14. And / or an uplink subframe for receiving a radio signal transmitted from the relay device 16, a guard time TTG (Transmit Transition Gap) for the base station 12 to switch from transmission to reception, and the base station 12 to switch from reception to transmission Guard time RTG (Receive Transition Gap).

  The minimum unit of the radio channel that the base station 12 allocates to the mobile station 14 or the relay device 16 is called a “slot”, and each slot is determined in the time direction with one of a plurality of subchannels defined in the frequency direction. Belonging to any one of a plurality of OFDM symbols. Note that each of the plurality of subchannels includes a plurality of subcarriers.

  Among these, the slot of the uplink subframe is used as a data burst (in this case, uplink bursts # 1 to 6) assigned to the mobile station 14 or the relay device 16 for uplink data transmission, a ranging subchannel, and the like.

  On the other hand, the slot of the downlink subframe is a data burst (here, downlink burst # 1 to 6), preamble, FCH (Frame Control Header) assigned to the mobile station 14 or the relay device 16 for downlink data transmission. DL-MAP (Downlink Map) indicating slot allocation in the downlink subframe, UL-MAP (Uplink Map) indicating slot allocation in the uplink subframe, and the like. The base station 12 can change the slot assignment for each frame by DL-MAP and UL-MAP.

  Note that a TDD frame configuration similar to the TDD frame configuration shown in FIG. 2 is also used between the relay device 16 operating as a base station and the mobile station 14 wirelessly connected to the relay device 16.

  In the following, as shown in FIG. 2, uplink burst # 1 and downlink burst # 1 are assigned to mobile station 14-1, and uplink burst # 2 and downlink burst # 2 are assigned to relay device 16, respectively. 14-1 is performing wireless communication with the base station 12 at the same timing as the relay device 16.

  FIG. 3A is a diagram illustrating an example of transmission power (transmission spectrum) of a downlink signal transmitted from the base station 12 to the mobile station 14 and the relay device 16 via the downlink bursts # 1 and # 2, respectively. In the example shown in FIG. 3A, the transmission power is constant for all subcarriers (burst average power is Pa [dBm]), and the downlink signal transmission power transmitted to the mobile station 14-1 is transmitted to the relay device 16. It is equal to the transmission power of the downlink signal.

  FIG. 3B is a diagram illustrating an example of reception power (reception spectrum) in the mobile station 14 and the relay device 16 of the downlink signal transmitted with the transmission power illustrated in FIG. 3A. Since the relay device 16 is installed at a location farther from the base station 12 than the mobile station 14-1 (see FIG. 1), the received power of the downlink signal transmitted from the base station 12 at the relay device 16 is Lower than that in 14-1. In addition, the CNR (Carrier to Noise Ratio) of the downlink signal in the relay device 16 is also lower than that in the mobile station 14-1.

  When the CNR of the downlink signal is reduced, it is necessary to apply a modulation scheme with low transmission efficiency to the downlink signal, and the downlink capacity is reduced. For this reason, when a plurality of mobile stations 14 are wirelessly connected to the relay device 16, the downlink capacity between the relay device 16 and the base station 12 becomes a bottleneck and is transmitted from the base station 12 to the mobile stations 14. Data transmission efficiency tends to decrease.

  Accordingly, in such a case, in the wireless communication system 10, the base station 12 performs wireless communication with the own station at the same timing as the relay device 16 in response to a request (high-speed mode request) from the relay device 16. By reducing the downlink capacity with any of the mobile stations 14-1 (here, the mobile station 14-1), an increase in the downlink capacity with the relay apparatus 16 is preferentially secured.

  For example, if the downlink capacity between the relay device 16 and the mobile stations 14-6 and 14-7 greatly exceeds the downlink capacity between the relay device 16 and the base station 12, the base station 12 In response to the high-speed mode request from 16, as shown in FIG. 4A, the transmission power of the downlink signal transmitted to the mobile station 14-1 that performs radio communication with the own station at the same timing as the relay device 16 is reduced, and The transmission power of the downlink signal transmitted to the relay device 16 is increased by the power corresponding to the decreased transmission power (burst average power is maintained at Pa [dBm]).

  As a result, as shown in FIG. 4B, the reception power of the downlink signal transmitted from the base station 12 in the relay device 16 increases, and the CNR of the downlink signal in the relay device 16 also increases.

  As described above, in the wireless communication system 10, the downlink capacity between the relay device 16 and the mobile stations 14, the relay device 16, according to the communication status of one or more mobile stations 14 wirelessly connected to the relay device 16. And the downlink capacity between the base station 12 and the base station 12 are corrected, so that a decrease in transmission efficiency of data transmitted from the base station 12 to the mobile station 14 via the relay device 16 is suppressed. can do.

  Hereinafter, a configuration of the base station 12 and the relay device 16 for realizing the above processing will be specifically described.

[Configuration of base station 12]
FIG. 5 is a functional block diagram of the base station 12. As shown in FIG. 5, the base station 12 includes an antenna 20, a receiving unit 22, a demodulating unit 24, a control unit 26 (a message analyzing unit 28, a channel allocating unit 30, a modulation scheme determining unit 32, a restriction target selecting unit 34, a transmission The power control unit 36, the message generation unit 38), the storage unit 40, the modulation unit 42, and the transmission unit 44 are configured.

  The antenna 20 receives a radio signal transmitted from the mobile station 14 and / or the relay device 16 and outputs the received radio signal to the receiving unit 22. Further, the antenna 20 transmits the radio signal supplied from the transmission unit 44 to the mobile station 14 and / or the relay device 16. Note that reception and transmission of radio signals are switched in time division so as to correspond to the uplink subframe and the downlink subframe shown in FIG.

  The receiving unit 22 includes a low noise amplifier, a frequency converter, a band pass filter, and an A / D converter. The receiving unit 22 amplifies the radio signal input from the antenna 20 with a low noise amplifier, then down-converts it to an intermediate frequency signal, converts it to a digital signal, and then outputs it to the demodulating unit 24.

  The demodulator 24 includes an FFT (Fast Fourier Transform) unit, a serial-parallel converter, a parallel-serial converter, and an error detection unit. The demodulator 24 converts the digital signal input from the receiver 22 into serial / parallel conversion, removal of GI (Guard Interval), primary demodulation (fast Fourier transform), parallel / serial conversion, time division separation processing, secondary demodulation ( Symbol demapping), decoding, error detection, and the like are performed, and the obtained received data is output to the control unit 26.

  The control unit 26 includes, for example, a CPU and a program that controls the operation of the CPU, and controls each unit of the base station 12. In particular, the control unit 26 functionally includes a message analysis unit 28, a channel allocation unit 30, a modulation scheme determination unit 32, a restriction target selection unit 34, a transmission power control unit 36, and a message generation unit 38, and the base station 12 Controls the modulation method and transmission power of the downlink signal to be transmitted.

  The storage unit 40 is composed of, for example, a semiconductor memory element, and stores a program, data, a table shown in FIG. FIG. 6 is a diagram illustrating an example of a table defining a correspondence relationship between CNR and modulation scheme.

  Here, the functional configuration of the control unit 26 will be described in more detail.

  The message analysis unit 28 identifies various messages from the mobile station 14 and / or the relay device 16 included in the reception data input from the demodulation unit 24 based on the configuration of the uplink subframe illustrated in FIG. Analyze the message content. For example, the message analysis unit 28 identifies a connection request message from the mobile station 14 and / or the relay device 16 and distinguishes whether the transmission source is the mobile station 14 or the relay device 16 from the connection request message. To obtain a terminal ID. Further, the message analysis unit 28 identifies a message including the high speed mode request from the relay device 16. This high speed mode request is a capacity increase request for requesting to increase the radio channel capacity between the relay device 16 and the base station 12. The message analysis unit 28 also receives a downlink signal (from the base station 12 to the mobile station 14 via the downlink burst) detected by the mobile station 14 and / or the relay device 16 from the reception data input from the demodulation unit 24. (Or a radio signal transmitted to the relay device 16).

  The channel allocation unit 30 allocates slots (radio channels) to the mobile station 14 and / or the relay device 16. That is, the channel allocator 30 sets at least one slot included in the downlink subframe as a downlink burst and at least one slot included in the uplink subframe as an uplink burst to the mobile station 14 and / or the relay device 16. assign. At this time, the channel allocation unit 30 may determine the downlink burst and the uplink burst to be allocated to the mobile station 14 and / or the relay device 16 based on the amount of data transmitted and received and the priority according to the communication type. Good.

  The modulation scheme determination unit 32 receives the CNR of the downlink signal (radio signal transmitted from the base station 12 to the mobile station 14 and / or the relay device 16 via the downlink burst) notified from the mobile station 14 and / or the relay device 16. Based on the above, a downlink burst modulation scheme in the next frame (or later) is determined. Also, the modulation scheme determination unit 32 determines the next frame (or later) based on the CNR of the uplink signal (the radio signal transmitted from the mobile station 14 and / or the relay device 16 to the base station 12 via the uplink burst). Determines the uplink burst modulation method in.

  In determining the modulation method, for example, the correspondence relationship between the CNR and the modulation method stored in the storage unit 40 (a modulation method having a high transmission efficiency corresponds to a high CNR, and a transmission efficiency is low to a low CNR. A table (see FIG. 6) defining a modulation method is used. Other than CNR, RSSI (Received Signal Strength Indication), SINR (Signal to Interference and Noise Ratio), FER (Frame Error Rate), etc. May be used. These received qualities are the complex symbol sequence obtained by the primary demodulation (fast Fourier transform) in the demodulator 24, the error detection result in the demodulator 24, and the information fed back from the mobile station 14 and / or the relay device 16. And so on.

  In response to a high-speed mode request from the relay device 16, the restriction target selection unit 34 selects any of the mobile stations 14 that perform wireless communication with the base station 12 at the same timing as the relay device 16 as a restriction target. Here, of the mobile stations 14 that perform radio communication with the base station 12 at the same timing as the relay device 16, the restriction target selection unit 34 has a radio channel capacity with the base station 12 that is greater than or equal to a predetermined capacity. May be selected as a restriction target.

  For example, the restriction target selecting unit 34 has the modulation scheme with the lowest modulation efficiency assigned to the base station 12 among the mobile stations 14 that perform radio communication with the base station 12 at the same timing as the relay device 16. What is not (QPSK in the example shown in FIG. 6) may be selected as a restriction target. When there are a plurality of restriction target candidates, it is preferable that the restriction target selecting unit 34 selects the mobile station 14 to which a downlink burst having a modulation scheme with higher transmission efficiency is assigned as the restriction target.

  The transmission power control unit 36 reduces the radio channel capacity between the mobile station 14 and the base station 12 selected as the restriction target by the restriction target selection unit 34, and only the capacity corresponding to the reduced radio channel capacity. The radio channel capacity between the relay device 16 and the base station 12 is increased. Specifically, the transmission power control unit 36 reduces the transmission power of the downlink signal transmitted to the mobile station 14 selected as the restriction target in response to the high speed mode request from the relay device 16 and reduces the transmission power. The transmission unit 44 is controlled to increase the transmission power of the downlink signal transmitted to the relay device 16 by the power corresponding to the transmission power.

  In addition, if the transmission power of the downlink signal is increased or decreased so that the burst average power is constant before and after the adjustment, the linearity of the signal in the transmission unit 44 is easily maintained. Further, the amount of decrease and increase in the transmission power of the downlink signal may be a predetermined fixed value, or the amount of data transmitted / received between the base station 12 and the mobile station 14 and / or the relay device 16. It may be a variable value according to the amount.

  The message generation unit 38 generates control messages and transmission data addressed to the mobile station 14 and / or the relay device 16, and outputs them to the modulation unit 42 so that they are transmitted based on the configuration of the downlink subframe illustrated in FIG. To do. For example, the message generation unit 38 includes a DL-MAP indicating a downlink burst determined by the channel allocation unit 30, a UL-MAP indicating an uplink burst determined by the channel allocation unit 30, and a downlink determined by the modulation scheme determination unit 32. A control message including the burst modulation scheme and the uplink burst modulation scheme determined by the modulation scheme determination unit 32 is generated and output to the modulation unit 42.

  The modulation unit 42 includes an IFFT (Inverse Fast Fourier Transform) unit, a serial-parallel converter, a parallel-serial converter, and an encoding circuit. The modulation unit 42 adds error detection code to the control message and transmission data addressed to the mobile station 14 and / or the relay device 16 input from the control unit 26, encodes, primary modulation (symbol mapping), time division multiplexing. Processing, serial / parallel conversion, secondary modulation (inverse fast Fourier transform), addition of GI, parallel / serial conversion, and the like are performed, and the obtained digital signal is output to the transmitter 44.

  The transmission unit 44 includes a power amplifier, a frequency converter, a band pass filter, and a D / A converter. The transmission unit 44 converts the digital signal input from the modulation unit 42 into an analog signal, then up-converts the digital signal into a radio signal, amplifies the signal to a transmission output level with a power amplifier, and supplies the signal to the antenna 20.

[Operation of base station 12]
Next, a part of the operation of the base station 12 will be described with reference to FIG. FIG. 7 is a diagram illustrating an example of adjustment processing of the radio channel capacity in the base station 12. This process is executed after wireless communication with the relay device 16 is started.

  As shown in FIG. 7, first, the base station 12 acquires the CNR of a downlink signal (a radio signal transmitted from the base station 12 to the relay device 16) notified from the relay device 16 (S100). Next, the base station 12 determines a downlink burst to be assigned to the relay device 16 and sets a modulation method for the downlink signal to be transmitted to the relay device 16 via the downlink burst based on the CNR of the downlink signal acquired in S100. Determine (S102).

  If there is a request for the high speed mode from the relay device 16 (S104: Y), the base station 12 determines whether there is a mobile station 14 that is performing radio communication with the base station 12 at the same timing as the relay device 16. Is confirmed (S106). If there is a mobile station 14 that is performing radio communication with the base station 12 at the same timing as the relay device 16 (S106: Y), the base station 12 transmits a downlink signal to be transmitted to the mobile station 14 (candidate for restriction). A modulation method is acquired, and it is confirmed whether or not the modulation method is the modulation method with the lowest transmission efficiency (S108). If the modulation scheme is not the lowest modulation scheme (S108: N), the base station 12 selects at least one of the mobile stations 14 as a restriction target, and the mobile station selected as the restriction target. The transmission power of the downlink signal transmitted to 14 is reduced (S110).

  Thereafter, the base station 12 increases the transmission power of the downlink signal transmitted to the relay device 16 by the power corresponding to the transmission power decreased in S110 (S112). Note that if there is no mobile station 14 that is performing radio communication with the base station 12 at the same timing as the relay device 16 (S106: N), the base station 12 may not exceed the upper limit of the average transmission power. The transmission power of the downlink signal to be transmitted is increased (S112).

  After S112 or when there is no request for the high speed mode from the relay device 16 (S104: N), the base station 12 repeatedly executes the processing from S100 until the communication with the relay device 16 ends (S114). Thereby, in response to the high-speed mode request from the relay device 16, the received power of the downlink signal transmitted from the base station 12 in the relay device 16 increases, and the CNR of the downlink signal in the relay device 16 also increases. As a result, when the modulation method of the downlink signal transmitted from the base station 12 to the relay device 16 is changed to one with higher transmission efficiency, the downlink capacity between the relay device 16 and the base station 12 also increases.

[Configuration of Relay Device 16]
FIG. 8 is a functional block diagram of the relay device 16. As shown in FIG. 8, the relay device 16 includes antennas 50-1 and 50-2, transmission / reception units 52-1 and 52-2, modulation / demodulation units 54-1 and 54-2, a control unit 56 (message analysis unit 58, A channel allocation unit 60, a modulation scheme determination unit 62, a channel capacity calculation unit 64, a high-speed mode request unit 66, a message generation unit 68), and a storage unit 70 are configured.

  Among these, the antenna 50-1, the transmitting / receiving unit 52-1, and the modem unit 54-1 are configured to be used for wireless communication with the base station 12 (because the relay device 16 operates as a mobile station with respect to the base station 12). The antenna 50-2, the transmission / reception unit 52-2, and the modulation / demodulation unit 54-2 are used for wireless communication with the mobile station 14 (the relay device 16 serves as a base station for the mobile station 14). Configuration for operation).

  That is, a radio signal transmitted from the base station 12 is received by the antenna 50-1, and is transmitted through the transmission / reception unit 52-1, the modulation / demodulation unit 54-1, the control unit 56, the modulation / demodulation unit 54-2, and the transmission / reception unit 52-2. Via the antenna 50-2 to the mobile station 14 wirelessly connected to the relay device 16. Conversely, a radio signal transmitted from the mobile station 14 that is wirelessly connected to the relay device 16 is received by the antenna 50-2, and is transmitted / received to the transmitting / receiving unit 52-2, the modem unit 54-2, the control unit 56, and the modem unit 54. -1 and the transmission / reception unit 52-1, the relay device 16 is transmitted to the base station 12 wirelessly connected from the antenna 50-1.

  The antennas 50-1 and 50-2 receive radio signals transmitted from the base station 12 and the mobile station 14, and output the received radio signals to the transmission / reception units 52-1 and 52-2, respectively. The antennas 50-1 and 50-2 transmit the radio signals supplied from the transmission / reception units 52-1 and 52-2 to the base station 12 and the mobile station 14, respectively. Note that reception and transmission of radio signals by the antenna 50-1 (reception and transmission of radio signals by the antenna 50-2) are switched in a time division manner.

  The transmission / reception units 52-1 and 52-2 include a low noise amplifier, a power amplifier, a frequency converter, a band pass filter, an A / D converter, and a D / A converter. The transmission / reception units 52-1 and 52-2 amplify the radio signals input from the antennas 50-1 and 50-2 using a low noise amplifier, down-convert them into intermediate frequency signals, and further convert them into digital signals. Are output to the modems 54-1 and 54-2, respectively. The transmission / reception units 52-1 and 52-2 convert the digital signals input from the modulation / demodulation units 54-1 and 54-2 into analog signals, and then up-convert them into radio signals, and transmit power levels with a power amplifier. And then supplied to the antennas 50-1 and 50-2.

  The modems 54-1 and 54-2 include an FFT unit, an IFFT unit, a serial-parallel converter, a parallel-serial converter, an error detection unit, and an encoding circuit. The modulation / demodulation units 54-1 and 54-2 convert the digital signals input from the transmission / reception units 52-1 and 52-2 to serial / parallel conversion, GI removal, primary demodulation (fast Fourier transform), parallel / serial conversion, Time division separation processing, secondary demodulation (symbol demapping), decoding, error detection, and the like are performed, and the obtained received data is output to the control unit 56. The modulation unit 42 adds error detection codes to the control message and transmission data addressed to the base station 12 and the mobile station 14 and transmission data input from the control unit 56, encodes, primary modulation (symbol mapping), time division multiplexing processing, Serial-parallel conversion, secondary modulation (inverse fast Fourier transform), GI addition, parallel-serial conversion, and the like are performed, and the obtained digital signals are output to the transmission / reception units 52-1 and 52-2, respectively.

  The control unit 56 includes, for example, a CPU and a program that controls the operation of the CPU, and controls each unit of the relay device 16. In particular, the control unit 56 functionally includes a message analysis unit 58, a channel allocation unit 60, a modulation scheme determination unit 62, a channel capacity calculation unit 64, a high-speed mode request unit 66, and a message generation unit 68. Processing for requesting the base station 12 to increase the radio channel capacity between the relay device 16 and relaying communication between the base station 12 and one or more mobile stations 14 wirelessly connected to the relay device 16 Control, etc.

  The storage unit 70 is composed of, for example, a semiconductor memory element, and stores programs and data necessary for the operation of the relay device 16, the table shown in FIG.

  Here, the functional configuration of the control unit 56 will be described in more detail.

  Based on the uplink subframe configuration illustrated in FIG. 2, the message analysis unit 58 performs various operations from the base station 12 and the mobile station 14 included in the received data input from the modems 54-1 and 54-2. Identify each message and analyze the contents of the message. For example, the message analysis unit 58 identifies the control message from the base station 12 from the received data input from the modulation / demodulation unit 54-1, the downlink burst allocated from the base station 12 based on the control message, and the downlink burst. To obtain the modulation scheme of the downlink signal transmitted from the base station 12 via the. Further, the message analysis unit 58 relays the downlink signal detected by the mobile station 14 from the reception data input from the modem unit 54-2 (via the downlink burst assigned to the mobile station 14 by the relay device 16). The CNR of the radio signal transmitted from the device 16 to the mobile station 14 is acquired.

  The channel assignment unit 60 assigns a slot (wireless channel) to the mobile station 14 wirelessly connected to the relay device 16. That is, the channel allocation unit 60 allocates to the mobile station 14 at least one slot included in the downlink subframe as a downlink burst and at least one slot included in the uplink subframe as an uplink burst. At this time, the channel allocation unit 60 may determine the downlink burst and the uplink burst allocated to the mobile station 14 based on the amount of data transmitted / received by the mobile station 14 and the priority according to the communication type.

  The modulation scheme determination unit 62 receives the CNR of the downlink signal notified from the mobile station 14 (the radio signal transmitted from the relay apparatus 16 to the mobile station 14 via the downlink burst assigned to the mobile station 14 by the relay apparatus 16). Based on the above, a downlink burst modulation scheme in the next frame (or later) is determined. In addition, the modulation scheme determination unit 62 determines the next based on the CNR of the uplink signal (the radio signal transmitted from the mobile station 14 to the relay device 16 via the uplink burst assigned by the relay device 16 to the mobile station 14). Determine the modulation method of the upstream burst in the frame (or later).

  In determining the modulation method, for example, the correspondence between the CNR and the modulation method stored in the storage unit 70 (a high CNR corresponds to a modulation method with high transmission efficiency, and a low CNR has low transmission efficiency) A table (see FIG. 6) defining a modulation method is used. Note that other reception qualities such as RSSI, SINR, and FER may be used instead of CNR.

  The line capacity calculation unit 64 includes a radio line capacity between the relay apparatus 16 and one or more mobile stations wirelessly connected to the relay apparatus 16, and a radio line capacity between the relay apparatus 16 and the base station 12. , Is calculated. For example, the channel capacity calculation unit 64 assigns to each mobile station 14 based on the number of slots constituting the downlink burst allocated to each mobile station 14 and the modulation scheme of the downlink signal transmitted via the downlink burst. The transmission rate of the downlink signal to be transmitted (transmission rate on the mobile station side) is calculated. In addition, the channel capacity calculation unit 64 receives the number of slots constituting the downlink burst allocated from the base station 12 and the modulation scheme of the downlink signal transmitted via the downlink burst from the base station 12. The transmission rate of the downlink signal to be transmitted (base station side transmission rate) is calculated.

  The high-speed mode request unit 66 includes a radio channel capacity between the relay device 16 and one or more mobile stations wirelessly connected to the relay device 16, and a radio channel capacity between the relay device 16 and the base station 12. Based on the comparison result of, a high-speed mode request (capacity increase request) is transmitted to the base station 12 for requesting an increase in the radio channel capacity between the relay device 16 and the base station 12.

  For example, the high-speed mode request unit 66 compares the mobile station side transmission rate calculated by the channel capacity calculation unit 64 with the base station side transmission rate, and the mobile station side transmission rate increases a predetermined coefficient multiple of the base station side transmission rate. The high-speed mode request may be transmitted at a timing exceeding this. In this way, when the downlink capacity between the relay device 16 and the mobile station 14 greatly exceeds the downlink capacity between the relay device 16 and the base station 12, the imbalance between them is corrected. Therefore, it is possible to suppress a decrease in transmission efficiency of data transmitted from the base station 12 to the mobile stations 14 via the relay device 16.

  The message generation unit 68 generates control messages and transmission data addressed to the base station 12 and the mobile station 14 and transmits / receives them based on the configuration of the downlink subframe as illustrated in FIG. , 54-2. For example, the message generation unit 68 generates a control message including the high speed mode request and outputs the control message to the modem unit 54-1. In addition, the message generation unit 68 includes a DL-MAP indicating a downlink burst determined by the channel allocation unit 60, a UL-MAP indicating an uplink burst determined by the channel allocation unit 60, and a downlink determined by the modulation scheme determination unit 62. A control message including the burst modulation scheme, the uplink burst modulation scheme determined by the modulation scheme determination section 62, and the like are generated and output to the modulation / demodulation section 54-2.

[Operation of Relay Device 16]
Next, a part of the operation of the relay device 16 will be described with reference to FIG. FIG. 9 is a diagram illustrating an example of high-speed mode request processing in the relay device 16.

  As shown in FIG. 9, the relay device 16 first transmits a downlink signal (a radio signal transmitted from the relay device 16 to the mobile station 14) notified from one or more mobile stations 14 wirelessly connected to the relay device 16. A CNR is acquired (S200). Next, the relay device 16 determines a downlink burst to be assigned to each mobile station 14 and modulates a downlink signal to be transmitted to each mobile station 14 via the downlink burst based on the CNR of the downlink signal acquired in S200. A method is determined (S202). Then, the relay device 16 transmits to the mobile stations 14 based on the number of slots constituting the downlink burst allocated to each mobile station 14 and the modulation scheme of the downlink signal transmitted via the downlink burst. The downlink signal transmission rate (mobile station side transmission rate) is calculated (S204).

  Next, the relay device 16 acquires the downlink burst allocated from the base station 12 and the modulation method of the downlink signal transmitted via the downlink burst (S206). Then, the relay device 16 is transmitted from the base station 12 based on the number of slots constituting the downlink burst allocated from the base station 12 and the modulation method of the downlink signal transmitted via the downlink burst. The downlink signal transmission rate (base station side transmission rate) is calculated (S208).

  Thereafter, the relay device 16 compares the mobile station side transmission rate calculated in S204 with the base station side transmission rate calculated in S208, and whether or not a request for the high speed mode is necessary based on the comparison result. If it is determined that the request for the high speed mode is necessary (S210: Y), the high speed mode request is transmitted to the base station 12 (S212). For example, the relay device 16 may determine that the request for the high speed mode is necessary when the mobile station side transmission rate exceeds a predetermined coefficient multiple of the base station side transmission rate.

  According to the wireless communication system 10 described above, the base station 12 performs the wireless communication with the mobile station 14 at the same timing as the relay apparatus 16 according to the high speed mode (capacity increase request) from the relay apparatus 16. By decreasing the downlink capacity with either one, an increase in downlink capacity with the relay device 16 is preferentially secured. Therefore, the downlink capacity between the relay device 16 and the base station 12 can be increased according to the communication status of one or more mobile stations 14 wirelessly connected to the relay device 16. That is, since the imbalance between the downlink capacity between the relay apparatus 16 and the mobile station 14 and the downlink capacity between the relay apparatus 16 and the base station 12 is corrected, the relay apparatus 16 is Thus, it is possible to suppress a decrease in transmission efficiency of data transmitted from the base station 12 to the mobile stations 14 via the base station 12.

  The present invention is not limited to the above embodiment.

  For example, in the above embodiment, the base station 12 increases the downlink capacity between the relay device 16 and the base station 12 by adjusting the transmission power distribution of the downlink signal, but the base station 12 The radio channel capacity between the relay device 16 and the base station 12 may be increased by adjusting the allocation distribution of slots (radio channels).

  FIG. 10 is a diagram illustrating an example of slot (radio channel) allocation distribution adjustment processing in the base station.

  As shown in FIG. 10, first, when there is a high speed mode request from the relay device 16, the base station 12 checks whether there is an empty slot that can be allocated to the relay device 16 (S300). If there is no free slot that can be allocated to the relay device 16 (S300: N), the base station 12 has a mobile station 14 that is performing radio communication with the base station 12 at the same timing as the relay device 16. It is confirmed whether or not (S302). Here, if there is a mobile station 14 that is performing radio communication with the base station 12 at the same timing as the relay device 16 (S302: Y), the base station 12 assigns a slot to the mobile station 14 (candidate for restriction). It is confirmed whether or not the number can be reduced (for example, whether the downlink burst and / or the uplink burst is composed of two or more slots) (S304).

  When the number of slots allocated to the mobile station 14 can be reduced (S304: Y), the base station 12 selects at least one of the mobile stations 14 as a restriction target, and the mobile station 14 selected as the restriction target. The number of slots allocated to is reduced (S306).

  Thus, when an empty slot that can be allocated to the relay device 16 is secured (S306 or S300: Y), the base station 12 increases the number of slots allocated to the relay device 16 as a downlink burst and / or an uplink burst (S308). ).

  Even in this case, the radio channel capacity between the relay device 16 and the base station 12 can be increased according to the communication status of the mobile station 14 wirelessly connected to the relay device 16.

  The present invention is not limited to a wireless communication system that employs OFDMA and TDMA / TDD, but can be widely applied to all wireless communication systems including a base station, a relay device, and a plurality of mobile stations that are wirelessly connected to them. is there.

  10 wireless communication system, 12 base station, 14 mobile station, 16 relay device, 18 cover area, 20, 50 antenna, 22 receiving unit, 24 demodulating unit, 26, 56 control unit, 28, 58 message analyzing unit, 30, 60 Channel allocation unit, 32, 62 Modulation method determination unit, 34 Restriction target selection unit, 36 Transmission power control unit, 38, 68 Message generation unit, 40, 70 Storage unit, 42 Modulation unit, 44 Transmission unit, 52 Transmission / reception unit, 54 Modulation / demodulation unit, 64 channel capacity calculation unit, 66 high-speed mode request unit.

Claims (8)

A base station,
A relay apparatus that wirelessly connects to each of the base station and the one or more mobile stations, and relays communication between the base station and the one or more mobile stations;
A wireless communication system comprising:
The relay device transmits a capacity increase request for requesting the base station to increase a radio channel capacity between the relay device and the base station based on a communication status of the one or more mobile stations. Including
The base station
In response to the capacity increase request from the relay device, selection means for selecting any of the mobile stations that perform radio communication with the base station at the same timing as the relay device;
The radio channel capacity between the mobile station selected as the restriction target and the base station is reduced, and the radio channel between the relay apparatus and the base station is reduced by a capacity corresponding to the reduced radio channel capacity. Circuit capacity control means for increasing capacity;
including,
A wireless communication system. The wireless communication system according to claim 1, wherein
The request means increases the capacity based on a comparison result between a radio channel capacity between the relay device and the one or more mobile stations and a radio channel capacity between the relay device and the base station. Sending a request to the base station;
A wireless communication system. The wireless communication system according to claim 1 or 2,
The selection means restricts at least one of the mobile stations that perform radio communication with the base station at the same timing as the relay apparatus, and has a radio channel capacity with the base station that is greater than or equal to a predetermined capacity. Select as a target
A wireless communication system. In the radio | wireless communications system in any one of Claim 1 to 3,
The relay device further includes means for notifying the base station of reception quality of a downlink signal transmitted from the base station to the relay device,
The base station further includes a modulation scheme determining means for determining a modulation scheme of a downlink signal transmitted to the relay device based on reception quality of the downlink signal notified from the relay device;
The line capacity control means reduces a transmission power of a downlink signal transmitted to the mobile station selected as the restriction target, and transmits a downlink signal transmitted to the relay apparatus by a power corresponding to the reduced transmission power. Increase the transmit power of the
A wireless communication system. In the radio | wireless communications system in any one of Claim 1 to 3,
The line capacity control means decreases the radio channel assignment to the mobile station selected as the restriction target and increases the radio channel assignment to the relay apparatus by an amount corresponding to the reduced radio channel assignment. ,
A wireless communication system. A base station that wirelessly connects to a relay device that wirelessly connects to each of the one or more mobile stations, and communicates with the one or more mobile stations via the relay device;
When a request is made from the relay device to increase the radio channel capacity between the relay device and the base station, any mobile station that performs radio communication with the base station at the same timing as the relay device is restricted. Selection means to select as a target,
The radio channel capacity between the mobile station selected as the restriction target and the base station is reduced, and the radio channel between the relay apparatus and the base station is reduced by a capacity corresponding to the reduced radio channel capacity. Circuit capacity control means for increasing capacity;
A base station comprising: A relay device that wirelessly connects to each of a base station and one or more mobile stations, and relays communication between the base station and the one or more mobile stations,
In response to a capacity increase request from the relay device, a selection unit that selects any of the mobile stations that perform radio communication with the base station at the same timing as the relay device,
The radio channel capacity between the mobile station selected as the restriction target and the base station is reduced, and the radio channel between the relay device and the base station is reduced by a capacity corresponding to the reduced radio channel capacity. Circuit capacity control means for increasing capacity;
Request means for transmitting the capacity increase request to the base station including the one or more mobile stations based on the communication status of the one or more mobile stations,
A relay device comprising: A base station,
A relay apparatus that wirelessly connects to each of the base station and the one or more mobile stations, and relays communication between the base station and the one or more mobile stations;
A wireless communication method in a wireless communication system including:
The relay apparatus transmitting to the base station a capacity increase request for requesting to increase a radio channel capacity between the relay apparatus and the base station based on a communication status of the one or more mobile stations; ,
In response to the capacity increase request from the relay device, the base station selects any of mobile stations that perform radio communication with the base station at the same timing as the relay device;
The base station reduces the radio channel capacity between the mobile station selected as the restriction target and the base station, and the relay device and the base station have a capacity corresponding to the reduced radio channel capacity. Increasing the wireless link capacity between
A wireless communication method comprising:

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