JP2013115563A - Relay device and communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relay device and a communication control method which can suppress an influence of interference due to disturbing signals.SOLUTION: A wireless communication system comprises a relay device 101, a mobile station, and a base station which transmits synchronous signals for establishing communication connection with the mobile station. The relay device 101 comprises: a mobile station side communication unit 123 for exchanging wireless signals with the mobile station; a speed detection unit 118 for detecting speed of the relay device 101; and a control unit 121 for determining whether to cause the mobile side communication unit 123 to transmit disturbing signals for disturbing the synchronous signals according to the speed detected by the speed detection unit 118.

Description

  The present invention relates to a relay device and a communication control method.

  In order for a mobile station to communicate with a base station, the mobile station needs to be located in a range (service area) where radio waves from the base station can reach. However, in urban areas where mountainous areas and high-rise buildings are lined up, there are areas where radio waves are difficult to reach due to many obstacles. In addition, there are many areas (for example, the inside of a building and the basement) where radio waves do not reach from base stations installed outdoors. In particular, in a high-speed wireless communication method such as WiMAX (Worldwide Interoperability for Microwave Access) (registered trademark) standardized based on the IEEE standard 802.16e, radio waves in a high frequency band of 2.5 GHz or more are used. Such radio waves are highly straight and have a weak property of going around obstacles. For this reason, WiMAX and the like are strongly affected by obstacles. In order to cover such a region where radio waves do not reach, a relay device (repeater) that relays radio signals between the base station and the mobile station is required.

  This relay device has the advantage that the service area can be expanded, but has the disadvantage that radio waves emitted by the relay device cause interference with other radio waves. One of the interferences caused by relay devices is between a donor node (MS (Mobile Station) unit) that communicates with a base station and a service node (BS (Base Station) unit) that communicates with a mobile station. Mutual interference (wraparound interference or self-interference) can be mentioned. For example, when the reception period of the donor node and the transmission period of the service node overlap, the transmission wave from the base station interferes with the transmission wave of the service node, and the donor node transmits the transmission wave from the base station with degraded quality. Will be received. Similarly, mutual interference also occurs when the transmission period of the donor node and the reception period of the service node overlap.

  Thus, conventionally, a wireless communication method for suppressing mutual interference has been proposed (see, for example, Patent Document 1). In this method, as shown in FIG. 4, the reception (Rx) period of the donor node and the reception period of the service node are matched within the downlink subframe period (first period) in which the base station A transmits the downlink signal. Further, the transmission (Tx) period of the donor node and the transmission period of the service node are combined within the uplink subframe period (second period) in which the base station A receives the uplink signal. As described above, the above-described mutual interference can be suppressed by controlling the transmission / reception periods of the donor node and the service node to be the same (hereinafter abbreviated as timing control). In addition, DL in FIG. 4 means a downlink (Down Link) and UL means an uplink (Up Link).

JP 2010-56711 A

  Here, as shown in FIG. 5, it is assumed that the timing-controlled service node transmits a synchronization signal of the frequency band fa to the mobile station A, and the service node and the mobile station A establish a communication connection. A base station B exists around the mobile station A, and the base station B transmits a synchronization signal of the frequency band fa for communication connection with the mobile station B. When the synchronization signal from the base station B arrives at the mobile station A at a timing different from the synchronization signal from the service node, the mobile station A may establish a communication connection with the base station B instead of the service node.

  In order to improve the connection rate between the mobile station A and the relay apparatus that can perform wireless communication in a good communication state by timing control, the service node can interfere with the synchronization signal from the base station B (preamble mask signal). ) Is transmitted in synchronization with the transmission timing of the synchronization signal of the base station B. As a result, the mobile station A cannot detect the synchronization signal from the base station B, and the mobile station A does not establish a communication connection with the base station B. Therefore, the mobile station A can connect to the service node.

  However, an interference signal from the service node may affect communication related to mobile stations other than the mobile station A. For example, as shown in FIG. 5, when the base station A and the mobile station C communicate in the frequency band fa and the radio wave from the service node reaches the mobile station C, the interference signal from the service node moves from the base station A. Interfering with signal to station C. Therefore, communication between the base station A and the mobile station C may be difficult. Such a situation is likely to occur particularly when a relay device installed in a moving vehicle or the like moves close to a mobile station that communicates in the same frequency band as the interference signal. Due to the interference by the interference signal, the throughput between the base station A and the mobile station C decreases, or the communication connection between the base station A and the mobile station C is disconnected.

  Accordingly, an object of the present invention made in view of the above problems is to provide a relay device and a communication control method capable of suppressing the influence of interference caused by a disturbing signal.

In order to solve the above-described problems, the invention of the relay device according to the first aspect is as follows:
A relay device in a wireless communication system comprising a mobile station, a base station that transmits a synchronization signal for establishing a communication connection with the mobile station, and a relay device,
A mobile station side communication unit for transmitting and receiving radio signals to and from the mobile station;
A speed detector for detecting the speed of the relay device;
And a control unit that determines whether to cause the mobile station side communication unit to transmit an interference signal that interferes with the synchronization signal according to the speed detected by the speed detection unit.

  The invention according to a second aspect is the relay apparatus according to the first aspect, wherein the control unit stops the transmission of the jamming signal when the speed is less than a speed threshold. The side communication unit is controlled.

  Further, the invention according to a third aspect is the relay device according to the first or second aspect, wherein the control unit reduces the transmission output of the interference signal in accordance with the decrease in the speed and reduces the interference signal. The mobile station side communication unit is controlled to transmit.

  As described above, the solution of the present invention has been described as an apparatus. However, the present invention can be realized as a method, a program, and a storage medium storing the program, which are substantially equivalent thereto, and the scope of the present invention. It should be understood that these are also included.

For example, a communication control method that realizes the first aspect of the present invention as a method includes:
In a communication control method for a relay apparatus in a wireless communication system including a mobile station, a base station that transmits a synchronization signal for establishing synchronization with the mobile station, and a relay apparatus, the relay apparatus includes:
Detecting the speed of the relay device;
Determining whether to transmit to the mobile station an interference signal that interferes with the synchronization signal according to the detected speed.

  According to the relay device and the communication control method according to the present invention configured as described above, it is possible to suppress the influence of interference caused by the disturbing signal.

FIG. 1 is a schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. FIG. 2 is a functional block diagram illustrating a schematic configuration of the relay device according to the embodiment of the present invention. FIG. 3 is a flowchart showing processing of the relay device according to the embodiment of the present invention. FIG. 4 is a time chart showing a transmission / reception period of a conventional relay device. FIG. 5 is an explanatory diagram of interference caused by a conventional interference signal.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. The wireless communication system 11 includes a base station BS (BS1 and BS2), a mobile station MS (Mobile Station) (MS1 and MS2), and a relay device 101 mounted on the vehicle 103. . When the communication method of the wireless communication system 11 is WiMAX, for example, a time division duplex (TDD) method is adopted for the wireless communication system 11. The relay apparatus 101 relays a radio signal transmitted and received between the base station BS1 and the mobile station MS1 in a wireless communication method such as WiMAX. The mobile station MS1 can transmit and receive radio signals to and from the base station BS1 via the relay device 101 even if the mobile station MS1 is located outside the cell (communication area) of the base station BS1.

  Assume that the base station BS1 communicates with the relay apparatus 101 (a donor node described later) in the frequency band f1, and the mobile station MS1 communicates with the relay apparatus 101 (a service node described later) in the frequency band f2. Further, it is assumed that radio waves in the frequency band f2 from the base station BS2 reach the mobile station MS1. It is assumed that the mobile station MS2 located on the station platform 105 is communicating with the base station BS1 in the frequency band f2. The relay device 101 moves and stops. For example, it is assumed that the vehicle 103 on which the relay device 101 is mounted moves from the position P1 toward the home 105 and stops at the position P2. As the vehicle 103 moves, the relay device 101 moves and stops. When the vehicle 103 is located at the position P2, it is assumed that the radio wave in the frequency band f2 from the relay apparatus 101 (service node) reaches the mobile station MS2.

  Note that the present invention is not limited to one stop location of the vehicle 103, and there can be a plurality of homes that are stop locations. Further, in FIG. 1, two base stations BS and two mobile stations MS are described, but the present invention is not limited to this mode. For example, the number of base stations and mobile stations can be three or more.

  FIG. 2 is a functional block diagram illustrating a schematic configuration of the relay device according to the embodiment of the present invention.

  The relay apparatus 101 includes a donor node (MS unit) 111 that communicates with a base station BS, and a service node (BS unit) 113 that communicates with a mobile station MS. The relay device 101 is not limited to an integrated type as long as the relay device 101 moves, and may be a separated type. The integrated relay apparatus 101 includes a donor node 111 and a service node 113 in one housing. In the separation type relay apparatus 101, the donor node 111 and the service node 113 can be arranged independently of each other. The separated or integrated donor node 111 and the service node 113 are connected by a signal line.

  First, functional blocks of the donor node 111 will be described. The donor node 111 includes a base station side communication unit 117, a speed detection unit 118, a storage unit 119, and a control unit 121. The base station side communication unit 117, the speed detection unit 118, and the storage unit 119 are connected to the control unit 121.

  The base station side communication unit 117 transmits and receives radio signals to and from the base station BS via an antenna. The base station side communication unit 117 generates a baseband signal by performing amplification and down-conversion with low noise on the received radio signal, and sends the baseband signal to the control unit 121. The base station side communication unit 117 generates a radio signal by performing up-conversion and amplification on the baseband signal, and transmits the radio signal to the base station BS via the antenna.

  When the time division duplex method is adopted in the radio communication system 11, the base station side communication unit 117 receives a radio signal from the base station BS in the downlink subframe period (first period) of the base station BS, for example. Then, the radio signal is transmitted to the base station BS in the uplink subframe period (second period) of the base station BS following the first period. And the base station side communication part 117 repeats reception and transmission by repetition of the continuous 1st period and 2nd period.

  The speed detection unit 118 detects the speed (movement speed) of the relay device 101 and sends the detection result to the control unit 121, and is an acceleration sensor, for example. Further, the present invention is not limited to the speed detection unit 118 directly detecting the speed itself of the relay device 101, and the speed detection unit 118 is, for example, the vehicle 103 that moves together with the relay device 101. It can also be set as the rotational speed sensor which measures the rotational speed of a tire. The speed detection unit 118 can detect the speed of the vehicle 103 from the rotation speed and set the speed as the speed of the relay device 101. Note that the speed is not a concept that strictly includes speed and direction, but can only mean speed. In the present embodiment, the donor node 111 includes the speed detection unit 118, but the present invention is not limited to this mode. For example, the service node 113 includes a speed detection unit, and the speed detected by the speed detection unit can be handled as the speed of the relay apparatus 101.

  The storage unit 119 stores various types of information such as a speed threshold related to the speed of the relay device 101, and also functions as a work memory. The speed threshold will be described later.

  In the present embodiment, only the donor node 111 has the storage unit 119, but the present invention is not limited to this configuration. For example, only the service node 113 may have a storage unit, and the storage unit may store various information of the donor node 111 and the service node 113. Moreover, both the donor node 111 and the service node 113 have a storage unit, and each storage unit can store information on each unit associated with the storage unit.

  The control unit 121 controls and manages the entire donor node 111 and service node 113 as well as the functional blocks of the donor node 111 and service node 113. Here, the control unit 121 is configured as software executed on any suitable processor such as a CPU (Central Processing Unit), or a dedicated processor specialized for each process (for example, DSP (Digital Signal Processor)). Can also be configured. In the present embodiment, only the donor node 111 has the control unit 121, but the present invention is not limited to this configuration. For example, only the service node 113 has a control unit, and the control unit can control and manage the donor node 111 and the service node 113 as a whole. Further, both the donor node 111 and the service node 113 have a control unit, and each control unit can control and manage each unit related to the control unit.

  Next, functional blocks of the service node 113 will be described. The service node 113 includes a mobile station side communication unit 123. The mobile station side communication unit 123 is connected to the control unit 121.

  The mobile station side communication unit 123 transmits and receives radio signals to and from the mobile station MS via the antenna. The mobile station side communication unit 123 generates a baseband signal by performing amplification and down-conversion with low noise on the received radio signal, and sends the baseband signal to the control unit 121. Also, the mobile station side communication unit 123 generates a radio signal by performing up-conversion and amplification on the baseband signal, and transmits the radio signal to the mobile station MS via the antenna.

  When the time division duplex method is employed in the wireless communication system 11, the mobile station side communication unit 123 receives, for example, a wireless signal from the mobile station MS within the first period, and transmits the wireless signal to the mobile station MS. Transmit within a second period following the first period. And the mobile station side communication part 123 repeats reception and transmission by repetition of the continuous 1st period and 2nd period. The transmission period between the mobile station side communication unit 123 and the base station side communication unit 117 and the reception period between the mobile station side communication unit 123 and the base station side communication unit 117 are aligned (timing control). Interference is suppressed.

  Here, the control unit 121 of the donor node 111 will be described in more detail. In FIG. 1, mobile station MS1 receives not only radio waves in frequency band f2 from relay apparatus 101 (service node 113) but also radio waves in frequency band f2 from base station BS2. Therefore, when the mobile station MS1 receives a synchronization signal for establishing a communication connection from both the relay apparatus 101 and the base station BS2, the mobile station MS1 may be connected to the base station BS2 or may not be synchronized. In the first place, the communication connection cannot be established. In particular, when the relay apparatus 101 realizes a good communication state by timing control, the mobile station MS1 is desired to establish a communication connection with the relay apparatus 101.

  Therefore, the control unit 121 controls the mobile station side communication unit 123 to transmit an interference signal (preamble mask signal) that interferes with the synchronization signal from the base station BS2 in accordance with the transmission timing of the synchronization signal. As a result, the mobile station MS1 cannot detect the synchronization signal from the base station BS2, and establishes a communication connection with the relay apparatus 101.

  The jamming signal is used to ensure the establishment of a communication connection between the relay apparatus 101 and the mobile station MS1, and the jamming signal is communicated in the same frequency band f2 as the jamming signal. May be adversely affected. In the present embodiment, when the vehicle 103 is located at the position P2, the interference signal from the relay apparatus 101 (service node 113) interferes with the synchronization signal in the frequency band f2 from the base station BS1 to the mobile station MS2. The longer the interference caused by the disturbing signal from the relay apparatus 101 (service node 113) occurs, the lower the throughput in communication between the mobile station MS2 and the base station BS1, and the possibility of disconnecting the communication connection itself. Will also increase.

  Therefore, the control unit 121 determines whether to cause the mobile station side communication unit 123 to transmit an interference signal that interferes with the synchronization signal, according to the speed detected by the speed detection unit 118. For example, when the speed detected by the speed detection unit 118 is less than the speed threshold value stored in the storage unit 119, the mobile station side communication unit 123 is controlled to stop transmission of the interference signal, and the speed is equal to or higher than the speed threshold value. Then, the mobile station side communication unit 123 can be controlled to transmit the interference signal. As the speed threshold is larger, the transmission of the jamming signal is stopped at a stage where the mobile station MS2 continues to be affected by the interference by the jamming signal. Therefore, the speed threshold value is an item that can be arbitrarily set according to the time during which the mobile station MS2 is allowed to continue to be affected by the interference caused by the interference signal. The allowable time is determined in consideration of the reception quality value of the mobile station MS2 that is reduced by the interference signal, the modulation / demodulation method that can be used for communication of the mobile station MS2, the throughput that the mobile station MS2 wants to realize, and the like. The reception quality value is, for example, CINR (Carrier to Interference and Noise Ratio) or SINR (Signal to Interference and Noise Ratio). In addition, when there are a plurality of mobile stations that are affected by the jamming signal, the speed threshold can be set by comprehensively considering the allowable time of the jamming signal influence in these mobile stations.

  In addition, when the control unit 121 determines to cause the mobile station side communication unit 123 to transmit the interference signal, the control unit 121 can further control the transmission output of the interference signal according to the speed of the relay device 101. For example, as the speed of the relay apparatus 101 decreases, the mobile station side communication unit 123 can be controlled to transmit the interference signal with a small transmission output continuously or stepwise. As the transmission output of the jamming signal becomes smaller, the influence of interference caused by the jamming signal can be reduced.

  Next, a method in which the relay apparatus 101 (control unit 121) controls transmission of an interference signal will be described with reference to FIGS. FIG. 3 is a flowchart showing processing of the relay device according to the embodiment of the present invention. The vehicle 103 moves from the position P1 to the position P2, and stops at the position P2. Then, it is assumed that the vehicle 103 at the position P1 is moving at a speed equal to or higher than the speed threshold.

  The speed detection unit 118 detects the speed of the relay device 101 regularly or irregularly (step S101). And if the speed detection part 118 sends a detection result to the control part 121, the control part 121 will compare the detected speed with the speed threshold value memorize | stored in the memory | storage part 119 (step S102).

  When the detected speed is equal to or higher than the speed threshold (Yes in step S102), the control unit 121 determines that the influence of the interference signal on the communication related to the mobile station MS2 is small, and transmits the interference signal to the mobile station side communication unit 123. Decide to send. That is, the mobile station side communication unit 123 is controlled to transmit the interference signal (step S103). As long as the detected speed is equal to or higher than the speed threshold, the processes in steps S101 to S103 are repeated, and the interference signal is continuously transmitted. Further, the control unit 121 can also control the mobile station side communication unit 123 so that the transmission output of the interference signal decreases as the detected speed decreases.

  In order to stop at the position P2, the vehicle 103 decreases the speed as it approaches the position P2. Therefore, the speed of the relay device 101 is less than the speed threshold at any location between the position P1 and the position P2 of the vehicle 103.

  When the speed detected by the speed detection unit 118 becomes less than the speed threshold (No in step S102), the control unit 121 determines that the interference signal has a great influence on the communication related to the mobile station MS2, and determines that the interference signal is on the mobile station side. It determines not to make the communication part 123 transmit. That is, the mobile station side communication unit 123 is controlled to stop transmission of the interference signal (step S104). When the vehicle 103 stops at the position P2 and starts moving toward the next station, the speed of the relay device 101 increases. When the speed of the relay apparatus 101 becomes equal to or higher than the speed threshold (Yes in Step S102), the control unit 121 controls the mobile station side communication unit 123 to resume transmission of the interference signal (Step S103). .

  As described above, in the present embodiment, the control unit 121 of the relay apparatus 101 determines whether to cause the mobile station side communication unit 123 to transmit an interference signal that interferes with the synchronization signal, according to the speed detected by the speed detection unit 118. To do. Thereby, the control part 121 can make the mobile station side communication part 123 stop a disturbance signal according to speed, and can remove the influence of the interference resulting from a disturbance signal. Since the interference signal does not interfere with the communication related to the mobile station MS2, it is possible to prevent the throughput of the communication related to the mobile station MS2 from being lowered.

  Moreover, in this embodiment, the control part 121 can control the mobile station side communication part 123 so that transmission of an interference signal may be stopped, when speed becomes less than a speed threshold value. When the speed of the relay apparatus 101 is reduced, the change in the position of the relay apparatus 101 is reduced, so that the time during which an interference signal from the relay apparatus 101 (service node 113) continues to reach the mobile station MS2 becomes longer. Therefore, the influence of interference caused by the disturbing signal is received for a long time. By determining a speed threshold corresponding to the time during which the mobile station MS2 can be affected by the jamming signal, the control unit 121 transmits and stops the jamming signal based only on the comparison between the speed and the speed threshold. Judgment can be made. The processing efficiency can be improved as compared with the case where the judgment criteria for transmission and stop of the interference signal are changed according to the radio wave environment around the changing relay device 101.

  Moreover, in this embodiment, the control part 121 can control the mobile station side communication part 123 so that the transmission output of a disturbance signal may be made small and a disturbance signal may be transmitted according to the fall of speed. As the speed decreases, the influence of interference due to jamming signals on the mobile station MS2 increases. Therefore, even when the jamming signal is transmitted, the influence of the synchronization signal from the base station BS2 on the connection between the relay apparatus 101 and the mobile station MS1 is suppressed by lowering the jamming signal transmission output according to the decrease in speed. Thus, it is possible to suppress the influence of interference caused by the disturbing signal received by the mobile station MS2.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention.

  For example, functions included in each member, each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined or divided into one. Is possible.

  In the description of the embodiment of the present invention described above, for example, the meaning of the technical idea of the expression such as the threshold “more than” or the threshold “less than” is not necessarily a strict meaning, and depending on the specifications of the relay device, The meaning of including or not including the reference value is included. For example, the threshold “above” may imply not only the case where the value to be compared with the threshold reaches the threshold but also the case where the threshold is exceeded. Further, for example, “less than the threshold value” can imply not only when the value to be compared with the threshold value is below the threshold value but also when the threshold value is reached, that is, when the threshold value is below the threshold value.

DESCRIPTION OF SYMBOLS 11 Wireless communication system 101 Relay apparatus 103 Vehicle 105 Home 111 Donor node 113 Service node 117 Base station side communication part 118 Speed detection part 119 Storage part 121 Control part 123 Mobile station side communication part BS1, BS2 Base station MS1, MS2 Mobile station f1 , F2 frequency band P1, P2 position

Claims (4)

A relay device in a wireless communication system comprising a mobile station, a base station that transmits a synchronization signal for establishing a communication connection with the mobile station, and a relay device,
A mobile station side communication unit for transmitting and receiving radio signals to and from the mobile station;
A speed detector for detecting the speed of the relay device;
A relay apparatus comprising: a control unit that determines whether an interference signal that interferes with the synchronization signal is transmitted to the mobile station side communication unit according to a speed detected by the speed detection unit. The relay device according to claim 1, wherein the control unit includes:
The relay apparatus, wherein when the speed becomes less than a speed threshold, the mobile station side communication unit is controlled to stop transmission of the interference signal. The relay device according to claim 1 or 2, wherein the control unit includes:
The relay apparatus, wherein the mobile station side communication unit is controlled to transmit the jamming signal by reducing a transmission output of the jamming signal according to the decrease in the speed. In a communication control method for a relay apparatus in a wireless communication system including a mobile station, a base station that transmits a synchronization signal for establishing synchronization with the mobile station, and a relay apparatus, the relay apparatus includes:
Detecting the speed of the relay device;
Determining whether to transmit to the mobile station an interference signal that interferes with the synchronization signal according to the detected speed.

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