JP5490075B2 - Radio relay apparatus and control method - Google Patents

Description

  The present invention relates to a radio relay apparatus and control method for relaying data transmitted and received between a radio base station and a radio terminal.

  Conventionally, a wireless relay device that relays data transmitted and received between a wireless base station and a wireless terminal has been widely used. A wireless terminal communicates with a wireless base station via a wireless relay device, and is located outside the range of a cell (communication area) formed by the wireless base station or in a peripheral portion (so-called self-ringing) of the cell. Even so, it can communicate with the radio base station.

  Such a wireless relay device includes a first wireless communication unit configured to perform wireless communication with a wireless base station, a second wireless communication unit configured to perform wireless communication with a wireless terminal, And a control unit that controls the first wireless communication unit and the second wireless communication unit.

  In addition, a time division duplex (TDD) method is known as one method for realizing bidirectional communication in a wireless communication system. In the TDD scheme, a downlink period in which communication from a radio base station to a radio terminal is performed and an uplink period in which communication from the radio terminal to the radio base station is performed are provided in a time division manner in a communication frame.

  When a radio relay apparatus is used in a radio communication system that employs the TDD scheme, in the downlink period, the radio signal from the radio base station is received by the first radio communication unit and at the same time from the second radio communication unit to the radio terminal. Since the radio signal is transmitted to the first radio communication unit, the first radio communication unit is affected by the radio signal transmitted by the second radio communication unit. Further, in the uplink period, the first radio communication unit transmits the radio signal from the first radio communication unit to the radio base station at the same time when the second radio communication unit receives the radio signal from the radio terminal. The second radio communication unit is affected by interference by the radio signal to be transmitted.

  In order to solve such a problem, the period during which the radio signal is transmitted from the second radio communication unit to the radio terminal is shifted from the downlink period to the uplink period, and the second radio communication unit transmits the radio signal from the radio terminal. There has been proposed a radio relay apparatus configured to shift a reception period from an uplink period to a downlink period (see Patent Document 1).

JP 2010-56711 A

  By the way, the radio base station and the second radio communication unit of the radio relay apparatus transmit a synchronization signal that is a radio signal used for establishing synchronization by the radio terminal at a predetermined timing in the downlink period. The wireless terminal searches for a synchronization signal when starting wireless communication and establishes synchronization with the transmission source of the synchronization signal when the synchronization signal is successfully received, thereby connecting to the transmission source of the synchronization signal. To do.

  However, since the radio relay apparatus described in Patent Document 1 shifts the period during which a radio signal is transmitted to the radio terminal to the uplink period, the radio terminal adjacent to the radio relay apparatus receives a synchronization signal from the radio base station. (Hereinafter, the first synchronization signal) and the synchronization signal from the radio relay apparatus (hereinafter, the second synchronization signal) are received at different timings.

  A wireless terminal in proximity to the wireless relay device can perform wireless communication in a good communication state by connecting to the wireless relay device, but by receiving the first synchronization signal and the second synchronization signal at different timings. There is a problem that communication with a good communication state cannot be realized because the wireless base station is connected or the synchronization destination becomes uncertain and synchronization cannot be established.

  Therefore, an object of the present invention is to provide a wireless relay device and a control method that can increase the probability that a wireless terminal in the vicinity of the wireless relay device is connected to the wireless relay device.

  In order to solve the above-described problems, the present invention has the following features. First, a feature of the wireless relay device according to the present invention is a wireless relay device used in a wireless communication system in which a wireless base station transmits a synchronization signal, which is a wireless signal used for establishing synchronization by a wireless terminal, at a predetermined timing. A first wireless communication unit that performs wireless communication with the wireless base station, a second wireless communication unit that performs wireless communication with the wireless terminal, and the first wireless communication unit and the second wireless communication unit. A communication frequency band having the highest radio quality level measured for the first radio communication unit among a plurality of communication frequency bands that can be used by the radio relay device. The communication frequency band set for the first wireless communication unit and having the lowest wireless quality level measured for the first wireless communication unit among the plurality of communication frequency bands is set for the second wireless communication unit. Set, and summarized in that for controlling the second wireless communication unit to the interference signal is a radio signal for interfering with the synchronization signal transmitted in the predetermined timing.

  The control method according to the present invention is characterized in that in the radio relay apparatus according to the above feature, a radio base station transmits a synchronization signal, which is a radio signal used for establishing synchronization by a radio terminal, at a predetermined timing. A method for controlling a radio relay apparatus, comprising: a first radio communication unit that performs radio communication with the radio base station; and a second radio communication unit that performs radio communication with the radio terminal, Among the plurality of communication frequency bands that can be used by the wireless relay device, a communication frequency band having the highest wireless quality level measured for the first wireless communication unit is set for the first wireless communication unit, Of the communication frequency bands, the step of setting the communication frequency band having the lowest radio quality level measured for the first radio communication unit for the second radio communication unit, and the synchronization signal And summarized in that has a step of controlling the second wireless communication unit to transmit a jamming signal is a radio signal for harm at the predetermined timing, the.

  ADVANTAGE OF THE INVENTION According to this invention, the radio relay apparatus and control method which can raise the probability that the radio | wireless terminal close | similar to a radio relay apparatus will connect to a radio relay apparatus can be provided.

1 is a schematic configuration diagram of a radio communication system according to an embodiment of the present invention. It is a time chart which shows the state of the radio signal which a radio | wireless terminal receives when the service side transmission / reception shift system is used. It is a communication frame block diagram which shows the structure of the communication frame used with the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the structure of the communication frequency band which can be utilized with the radio | wireless communications system which concerns on embodiment of this invention. It is a block diagram which shows the functional block structure of the radio relay apparatus which concerns on embodiment of this invention. It is a schematic perspective view which shows the example of mounting of the radio relay apparatus concerning embodiment of this invention. It is a time chart for demonstrating schematic operation | movement of the radio relay apparatus which concerns on embodiment of this invention. It is a time chart for demonstrating detailed operation | movement of the radio relay apparatus which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement flow of the radio relay apparatus which concerns on embodiment of this invention. It is a figure which shows the structural example of the transmission power table which concerns on embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. Specifically, (1) the outline of the radio communication system, (2) the configuration of the radio relay apparatus, (3) the operation of the radio relay apparatus, (4) the operation and effect, and (5) other embodiments will be described. In the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Overview of Radio Communication System First, regarding the overview of the radio communication system according to the present embodiment, (1.1) overall schematic configuration, (1.2) configuration of communication frame, (1.3) communication frequency band It demonstrates in order of a structure.

(1.1) Overall Schematic Configuration FIG. 1 is a schematic configuration diagram of a wireless communication system 1 according to the present embodiment. The wireless communication system 1 has a configuration based on WiMAX (IEEE802.16). That is, the radio communication system 1 employs an orthogonal frequency division multiple access (OFDMA) system and a time division duplex (TDD) system.

  The OFDMA scheme realizes multiple connections using a number of subcarriers orthogonal to each other. The TDD scheme realizes bidirectional communication by executing uplink communication and downlink communication in a time division within one communication frame. The uplink means the communication direction from the radio terminal to the radio base station, and the downlink means the communication direction from the radio base station to the radio terminal.

  In the wireless communication system 1, in one communication frame, downlink communication is first executed, and then uplink communication is executed. Hereinafter, a period in which downlink communication is performed in one communication frame is referred to as a downlink period, and a period in which uplink communication is performed in one communication frame is referred to as an uplink period.

  As illustrated in FIG. 1, the wireless communication system 1 includes a wireless relay device 100, a wireless base station 200 (wireless base stations 200A and 200B), and a wireless terminal 300.

  Each of the radio base stations 200A and 200B is a macro cell base station that forms a large cell. Radio base stations 200A and 200B operate in synchronization with each other. The radio relay apparatus 100 is connected to the radio base station 200A.

  The wireless terminal 300 is not connected to the wireless base stations 200A and 200B or the wireless relay device 100. In the present embodiment, it is assumed that the wireless terminal 300 is in a position close to the wireless relay device 100.

  When connected to the radio relay apparatus 100, the radio terminal 300 communicates with the radio base station 200A via the radio relay apparatus 100. When the radio terminal 300 is connected to the radio base station 200A or 200B, the radio terminal 300 directly communicates with the radio base station 200A or 200B.

  Radio relay apparatus 100 uses communication frequency band fA for radio communication with radio base station 200 </ b> A, and uses communication frequency band fB for radio communication with radio terminal 300. Radio base station 200 </ b> B uses communication frequency band fB for radio communication with radio terminal 300.

  Radio base stations 200A and 200B and radio relay apparatus 100 periodically transmit a preamble signal (synchronization signal) that is a radio signal used by radio terminal 300 to establish synchronization. The preamble signal is composed of the first 1 OFDM symbol in the downlink period. Hereinafter, the preamble signal transmitted by the radio base stations 200A and 200B is referred to as a “base station preamble signal (first synchronization signal)”, and the preamble signal transmitted by the radio relay apparatus 100 is referred to as a “relay station preamble signal (second synchronization signal). Signal) ”.

  The wireless terminal 300 searches for a preamble signal when starting wireless communication, and establishes synchronization with the transmission source of the preamble signal when it successfully receives the preamble signal. Connecting.

  The radio relay apparatus 100 shifts a period for transmitting a radio signal to the radio terminal 300 from the downlink period to the uplink period, and shifts a period for receiving the radio signal from the radio terminal 300 from the uplink period to the downlink period. (Refer patent document 1). Hereinafter, such a method is referred to as a “service side transmission / reception shift method”.

  The radio base station 200A transmits a base station preamble signal using the communication frequency band fA within the downlink period. The radio base station 200B transmits a base station preamble signal using the communication frequency band fB within the downlink period. The radio relay apparatus 100 transmits the relay apparatus preamble signal using the communication frequency band fB within the uplink period.

  FIG. 2 is a time chart showing a state of a radio signal received by the radio terminal 300 when the service side transmission / reception shift method is used.

  As illustrated in FIG. 2, the radio terminal 300 receives a base station preamble signal and a relay apparatus preamble signal using the same communication frequency band fB in the downlink period and the uplink period. A wireless terminal 300 in proximity to the wireless relay device 100 can perform wireless communication in a good communication state by connecting to the wireless relay device 100, but a base using the same communication frequency band fB as the relay device preamble signal. By receiving the station preamble signal at different timings, it may be connected to the radio base station 200B, or the synchronization destination may be uncertain and synchronization may not be established.

  Therefore, the radio relay apparatus 100 is a radio signal for interfering with the base station preamble signal at the timing when the radio base station 200B transmits the base station preamble signal (that is, the timing corresponding to the first OFDM symbol in the downlink period). A preamble mask signal (jamming signal) is transmitted to cause interference with the base station preamble signal. As the preamble mask signal, for example, a pilot signal composed of a known signal sequence can be used. The communication frequency band fB is used for transmitting the preamble mask signal.

  The radio terminal 300 becomes unable to detect the base station preamble signal from the radio base station 200B by simultaneously receiving the base station preamble signal and the preamble mask signal. As a result, it is possible to solve the problem that the wireless terminal 300 close to the wireless relay device 100 connects to the wireless base station 200B or the synchronization destination becomes indeterminate and synchronization cannot be established.

(1.2) Configuration of Communication Frame FIG. 3 is a communication frame configuration diagram showing a configuration of a communication frame used in the wireless communication system 1.

  As shown in FIG. 3, the communication frame has a downlink subframe SFR1 corresponding to the downlink period and an uplink subframe SFR2 corresponding to the uplink period. Since a larger communication capacity is required in the downlink than in the uplink, the downlink subframe SFR1 has an uplink / downlink asymmetric frame configuration that is longer than the uplink subframe SFR2. The downlink subframe SFR1 and the uplink subframe SFR2 are each composed of a plurality of symbols.

  The head of the downlink subframe SFR1 is a control data area in which various control data are arranged, and thereafter a burst area in which user data is arranged.

  The control data includes the above-described preamble, FCH (header information transmitted from the radio base station), and MAP that is resource allocation information related to uplink and downlink user data.

  A guard time (TTG) is provided between the downlink subframe SFR1 and the uplink subframe SFR2.

(1.3) Configuration of Communication Frequency Band FIG. 4 is a diagram illustrating a configuration of a communication frequency band that can be used in the wireless communication system 1.

  As shown in FIG. 4, in the radio communication system 1, for example, a system communication frequency band of 30 MHz can be used, and the system communication frequency band is equally divided into three communication frequency bands F1 to F3.

  Any one of the communication frequency bands F1 to F3 corresponds to the communication frequency band fA described above. Any of the remaining communication frequency bands corresponds to the communication frequency band fB described above.

  When connecting to the radio base station 200A, the radio relay device 100 sets one of the communication frequency bands F1 to F3 as a communication frequency band used for radio communication with the radio base station 200A. Further, the wireless relay device 100 sets any of the remaining communication frequency bands as a communication frequency band used for wireless communication with the wireless terminal.

(2) Configuration of Radio Relay Device Next, the configuration of the radio relay device 100 will be described in the order of (2.1) functional block configuration and (2.2) implementation example.

(2.1) Functional Block Configuration FIG. 5 is a block diagram showing a functional block configuration of the wireless relay device 100.

  As illustrated in FIG. 5, the radio relay apparatus 100 includes a donor-side communication unit 110D for communicating with the radio base station 200 and a service-side communication unit 110S for communicating with the radio terminal 300.

  The donor-side communication unit 110D has a communication function equivalent to that of a radio terminal, and the service-side communication unit 110S has a communication function equivalent to that of a radio base station. The donor-side communication unit 110D and the service-side communication unit 110S are connected by wire using Ethernet (registered trademark) or the like.

  The donor-side communication unit 110D includes a donor-side radio communication unit 120D, a donor-side control unit 130D, a storage unit 172, an interface (I / F) unit 173, and an indicator 174. In the present embodiment, the donor-side radio communication unit 120D corresponds to the first radio communication unit.

  The donor-side radio communication unit 120D is configured to perform radio communication with the radio base station 200 using OFDMA and TDD. The donor-side radio communication unit 120D receives a radio signal from the radio base station 200 in the downlink period.

  The donor-side radio communication unit 120D includes donor antennas 161a and 161b, transmission / reception changeover switches 162a and 162b, power amplifiers (PA) 163a and 163b, low noise amplifiers (LNA) 164a and 164b, and a high frequency / baseband (RF / BB) unit. 165a and 165b. Thus, in this embodiment, the diversity effect is obtained by providing two transmission / reception systems in the donor-side radio communication unit 120D.

  The donor-side control unit 130D is configured by a CPU, for example, and controls various functions provided in the donor-side communication unit 110D. The donor-side control unit 130D includes an RSSI (Received Signal Strength Indicator) indicating a reception power level of a radio signal received by the donor-side radio communication unit 120D, and an SNR indicating the radio quality of the radio signal received by the donor-side radio communication unit 120D. (Signal to Noise ratio) is measured.

  The storage unit 172 includes, for example, a memory, and stores various types of information used for control in the donor-side communication unit 110D. The I / F unit 173 is connected to the service communication unit 110S. The indicator 174 is controlled by the donor-side control unit 130D and displays information indicating the received power level from the radio base station 200.

  The service side communication unit 110S includes a service side wireless communication unit 120S, a service side control unit 130S, a storage unit 132, and an I / F unit 133. In the present embodiment, the service-side wireless communication unit 120S corresponds to a second wireless communication unit.

  The service-side wireless communication unit 120S is configured to perform wireless communication with the wireless terminal 300 using OFDMA and TDD. The service-side radio communication unit 120S transmits the relay device preamble signal described above.

  The service-side wireless communication unit 120S includes service antennas 121a and 121b, transmission / reception changeover switches 122a and 122b, PAs 123a and 123b, LNAs 124a and 124b, and RF / BB units 125a and 125b. Thus, in the present embodiment, the diversity effect is obtained by providing two transmission / reception systems in the service-side wireless communication unit 120S.

  The service-side control unit 130S is constituted by, for example, a CPU and controls various functions provided in the service-side communication unit 110S. The storage unit 132 is configured by a memory, for example, and stores various types of information used for control and the like in the service side communication unit 110S. The I / F unit 133 is connected to the donor-side communication unit 110D.

  In this embodiment, the donor-side control unit 130D, the service-side control unit 130S, the storage units 172 and 132, the I / F units 173 and 133, and the indicator 174 are connected to the donor-side radio communication unit 120D and the service-side radio communication unit 120S. A control unit to be controlled is configured.

  The control unit 130 sets the communication frequency band having the highest SNR (radio quality) measured for the donor-side radio communication unit 120D among the plurality of communication frequency bands that can be used by the radio relay apparatus 100 to the donor-side radio communication unit 120D. The communication frequency band having the lowest SNR measured for the donor-side radio communication unit 120D is set for the service-side radio communication unit 120S.

  The control unit 130 controls the service-side radio communication unit 120S to transmit the preamble mask signal at the transmission timing of the base station preamble signal (that is, the leading timing in the downlink period).

  The control unit 130 controls the service-side radio communication unit 120S to transmit a preamble mask signal with limited transmission power in consideration of interference with the donor-side radio communication unit 120D. For example, the transmission power of the preamble mask signal is controlled to be smaller than the transmission power when the service-side wireless communication unit 120S transmits user data (see FIG. 8C).

  The control unit 130 also determines a preamble mask according to the frequency interval between the communication frequency band set for the service-side radio communication unit 120S and the communication frequency band set for the donor-side radio communication unit 120D. Controls signal transmission power.

  Further, the control unit 130 controls the transmission power of the preamble mask signal according to the RSSI (reception power level) of the radio signal received by the donor-side radio communication unit 120D from the radio base station 200. Note that the transmission power control of the preamble mask signal in accordance with the RSSI of the radio signal may be performed while the radio relay apparatus 100 is performing a relay operation in consideration of changes in the radio environment.

(2.2) Mounting Example FIG. 6 is a schematic perspective view illustrating a mounting example of the wireless relay device 100.

  As shown in FIGS. 6A and 6B, in the casing 105 of the wireless relay device 100, the substrate 101 on which the donor-side communication unit 110D is mounted and the substrate 103 on which the service-side communication unit 110S is mounted. And a substrate 102 on which a relay mechanism between the donor-side communication unit 110D and the service-side communication unit 110S is mounted.

  Donor antennas 161 a and 161 b extend from the substrate 101 to the outside of the housing 105. Service antennas 121 a and 121 b are disposed on substrate 103. As described above, in the wireless relay device 100, the donor antennas 161a and 161b and the service antennas 121a and 121b are arranged close to each other without providing a radio wave shielding plate. The donor antennas 161a and 161b may be disposed on the substrate 101 in the same manner as the service antennas 121a and 121b.

(3) Operation of Radio Relay Device Next, the operation of the radio relay device 100 will be described in the order of (3.1) general operation, (3.2) detailed operation, and (3.3) operation flow.

(3.1) Schematic Operation FIG. 7 is a time chart for explaining the schematic operation of the radio relay apparatus 100.

  FIGS. 7A to 7D show a state in which the radio base station 200, the radio relay device 100, and the radio terminal 300 communicate without following the service side transmission / reception shift method. FIG. 7 (a ′) to FIG. 7 (d ′) illustrate how the radio base station 200, the radio relay device 100, and the radio terminal 300 communicate according to the service-side transmission / reception shift method.

  7 (a) and 7 (a ′) show operations in the radio base station 200, and FIGS. 7 (b) and 7 (b ′) show operations in the donor-side radio communication unit 120D of the radio relay device 100. 7 (c) and 7 (c ′) show the operation in the service-side wireless communication unit 120S of the wireless relay device 100, and FIGS. 7 (d) and 7 (d ′) show the operation in the wireless terminal 300. Is shown.

  As shown in FIGS. 7A to 7D, in each communication frame period Tn, a downlink period t1 and an uplink period t2 are provided in a time division manner. As illustrated in FIG. 7B, the donor-side radio communication unit 120D of the radio relay apparatus 100 receives a radio signal from the radio base station 200 in the downlink period t1, and wirelessly transmits to the radio base station 200 in the uplink period t2. Send a signal.

  In the method not complying with the service side transmission / reception shift method, as shown in FIG. 7C, the service side wireless communication unit 120S of the wireless relay device 100 transmits a wireless signal to the wireless terminal 300 in the downlink period t1, and the uplink A radio signal is received from the radio terminal 300 in the period t2. For this reason, the service-side radio communication unit 120S interferes with the donor-side radio communication unit 120D in the downlink period t1, and the donor-side radio communication unit 120D interferes with the service-side radio communication unit 120S in the uplink period t2.

  On the other hand, in the service-side transmission / reception shift method, as shown in FIG. 7C ′, the service-side control unit 130S of the service-side communication unit 110S is the service side where the service-side radio communication unit 120S transmits a radio signal to the radio terminal 300. The transmission period P1 is set by shifting to the uplink period t2. Further, the service side control unit 130S shifts and sets the service side reception period P2 in which the service side radio communication unit 120S receives a radio signal from the radio terminal 300 to the downlink period t1.

  For example, as shown in FIGS. 7 (a ′) to 7 (d ′), the radio relay device 100 transmits a radio signal received from the radio terminal 300 in the downlink period t1 of the communication frame period T1 to the communication frame period T1. Is transmitted to the radio base station 200 in the uplink period t2. Also, the radio relay apparatus 100 transmits a radio signal received from the radio base station 200 in the downlink period t1 of the communication frame period T1 to the radio terminal 300 in the uplink period t2 of the communication frame period T1. This avoids the interference described above.

  The time length of the downlink period t1 is longer than the time length of the uplink period t2. Therefore, since the service-side control unit 130S sets the service-side transmission period P1 to the uplink period t2, a part of the service-side transmission period P1 overlaps with a part of the downlink period t1 beyond the uplink period t2. Hereinafter, a part of the service-side transmission period P1 that overlaps the downlink period t1 is referred to as an overlapping part Δt.

(3.2) Detailed Operation FIG. 8 is a time chart for explaining the detailed operation of the wireless relay device 100.

  As shown in FIGS. 8A and 8B, the service-side control unit 130S transmits from the service-side radio communication unit 120S to the radio terminal during the period excluding the preamble signal transmission timing in the downlink period t1 in the overlapping portion Δt. The transmission to 300 is stopped. This prevents the service-side wireless communication unit 120S from interfering with the donor-side wireless communication unit 120D in the overlapping portion Δt.

  In the transmission stop period, data is not transmitted, but the data can be transmitted to the wireless terminal 300 by using a mechanism such as retransmission control. It is preferable to arrange data in which communication delay is allowed in the overlapping portion Δt, and it is preferable not to arrange data having high real-time characteristics and required service quality (QoS) such as voice data in the overlapping portion Δt.

  As illustrated in FIG. 8C, the service-side control unit 130S transmits the preamble mask signal (pilot signal) at the preamble signal transmission timing in the downlink period t1 in the overlapping portion Δt. 120S is controlled. Specifically, the service-side control unit 130S continues the transmission of the pilot signal while stopping the user data transmission from the service-side wireless communication unit 120S.

  Since the preamble mask signal also leads to interference with the donor-side radio communication unit 120D, the donor-side control unit 130D and the service-side control unit 130S have an acceptable degree of interference with the donor-side radio communication unit 120D. In this manner, the transmission power of the preamble mask signal is set. Thereby, it is not necessary to provide an interference countermeasure mechanism (such as a shielding plate) in the housing, and the donor-side communication unit 110D and the service-side communication unit 110S can be housed in a more compact housing.

  When considering the influence of interference from the service-side radio communication unit 120S to the donor-side radio communication unit 120D, the degree of interference changes depending on the relationship (interval) between the service transmission frequency and the donor reception frequency. Specifically, it differs between the case where the service transmission frequency and the donor reception frequency are adjacent and the case where the frequency interval is equal to or greater than the next adjacent frequency. Therefore, the donor-side control unit 130D and the service-side control unit 130S control the transmission power of the preamble mask signal according to such frequency relationship.

  Further, the degree (ratio) of interference received by the donor-side control unit 130D from the service-side radio communication unit 120S varies depending on the state of the radio signal received by the donor-side radio communication unit 120D from the radio base station 200. Therefore, the donor-side control unit 130D and the service-side control unit 130S control the transmission power of the preamble mask signal according to the RSSI in the donor-side radio communication unit 120D.

(3.3) Operation Flow FIG. 9 is a flowchart showing an operation flow of the wireless relay device 100. This operation flow is executed when the radio relay apparatus 100 connects to the radio base station 200A, but can be periodically executed even after the radio relay apparatus 100 connects to the radio base station 200A.

  In step S11, the donor-side control unit 130D measures the SNR of the radio signal received by the donor-side radio communication unit 120D for each of the communication frequency bands F1 to F3 (see FIG. 3).

  In step S12, the donor-side control unit 130D sets a communication frequency band having the highest SNR among the communication frequency bands F1 to F3 for the donor-side radio communication unit 120D. Also, the donor-side control unit 130D notifies the service-side control unit 130S of the communication frequency band having the lowest SNR among the communication frequency bands F1 to F3. The service-side control unit 130S sets a communication frequency band having the lowest SNR among the communication frequency bands F1 to F3 for the service-side wireless communication unit 120S.

  In step S13, the donor-side control unit 130D measures the RSSI of the radio signal received from the radio base station 200A in the communication frequency band set for the donor-side radio communication unit 120D.

  In step S14, the donor-side control unit 130D determines the transmission power of the preamble mask signal according to the frequency interval of the communication frequency band set in step S12 and the RSSI measured in step S13.

  In the present embodiment, the storage unit 172 stores a transmission power table as shown in FIG. 10 in advance. The donor-side control unit 130D acquires the transmission power corresponding to the frequency interval and the RSSI from the transmission power table stored in the storage unit 172.

  As shown in FIG. 10, the transmission power table has a relationship of “adjacent” in which the frequency interval is substantially zero (for example, the relationship between F1 and F2 shown in FIG. 4) and a frequency interval of one communication frequency band or more. It is classified into a certain “next or higher” (for example, the relationship between F1 and F3 shown in FIG. 4). Each of “adjacent” and “next adjacent or higher” is classified for each RSSI range.

  In “adjacent”, when the RSSI is greater than −90 and −80 or less, the transmission power of the preamble mask signal is −14 [dB], and when RSSI is greater than −80 and −70 or less, the preamble When the transmission power of the mask signal is −11 [dB] and the RSSI is greater than −70 and −60 or less, the transmission power of the preamble mask signal is −8 [dB] and the RSSI is greater than −60. In this case, the transmission power of the preamble mask signal is -5 [dB].

  In “next adjacent or higher”, when the RSSI is greater than −90 and −80 or less, the transmission power of the preamble mask signal is −9 [dB], and the RSSI is greater than −80 but −70 or less. When the transmission power of the preamble mask signal is -6 [dB] and the RSSI is greater than -70 and equal to or less than -60, the transmission power of the preamble mask signal is -3 [dB] and the RSSI is from -60. Is larger, the transmission power of the preamble mask signal is 0 [dB].

  In this way, in the transmission power table, “next or higher” is set to have a higher transmission power of the preamble mask signal than “adjacent”. Further, the higher the RSSI is, the larger the transmission power of the preamble mask signal is set.

  The donor-side control unit 130D notifies the service-side control unit 130S of the determined transmission power of the preamble mask signal. The service-side control unit 130S sets the notified transmission power of the preamble mask signal for the service-side wireless communication unit 120S.

(4) Operation / Effects As described above, the radio relay apparatus 100 transmits a preamble mask signal at a timing when the radio base station 200 transmits a base station preamble signal, so that the radio terminal close to the radio relay apparatus 100 The reception of the base station preamble signal by 300 is obstructed. As a result, it is possible to solve the problem that the wireless terminal 300 close to the wireless relay device 100 connects to the wireless base station 200 or the synchronization destination becomes indeterminate and synchronization cannot be established.

  Since the radio relay apparatus 100 transmits the relay apparatus preamble signal at a timing different from the timing at which the radio base station 200 transmits the base station preamble signal, the radio terminal 300 in the vicinity of the radio relay apparatus 100 transmits the relay apparatus preamble signal. Can be received well, and synchronization with the radio relay apparatus 100 is established and the radio relay apparatus 100 is connected. Therefore, it is possible to increase the probability that the wireless terminal 300 in proximity to the wireless relay device 100 connects to the wireless relay device 100.

  In the present embodiment, the control unit 130 controls the service-side radio communication unit 120S to transmit a preamble mask signal with limited transmission power in consideration of interference with the donor-side radio communication unit 120D. Thereby, the influence of the interference which a preamble mask signal gives to the donor side radio | wireless communication part 120D can be reduced.

  In the present embodiment, the control unit 130 responds to the frequency interval between the communication frequency band set for the service-side radio communication unit 120S and the communication frequency band set for the donor-side radio communication unit 120D. The transmission power of the preamble mask signal is controlled.

  When the frequency interval is wide, the influence of the interference of the preamble mask signal on the donor-side radio communication unit 120D is small. Therefore, by increasing the transmission power of the preamble mask signal, the base station preamble signal is more reliably disturbed. be able to.

  On the other hand, when the frequency interval is narrow, the influence of the interference that the preamble mask signal has on the donor-side radio communication unit 120D is large. Therefore, by reducing the transmission power of the preamble mask signal, the preamble mask signal is transmitted to the donor-side radio communication. The influence of interference on the unit 120D can be reduced.

  In the present embodiment, the control unit 130 controls the transmission power of the preamble mask signal according to the RSSI of the radio signal received from the radio base station 200 by the donor-side radio communication unit 120D.

  When the RSSI is large, the influence of the interference of the preamble mask signal on the donor-side radio communication unit 120D becomes relatively small. Therefore, by increasing the transmission power of the preamble mask signal, it is possible to make the base station preamble signal more reliable. Can be disturbed.

  On the other hand, when the RSSI is small, the influence of the interference of the preamble mask signal on the donor-side radio communication unit 120D becomes relatively large. Therefore, by reducing the transmission power of the preamble mask signal, the preamble mask signal is The influence of interference on the side wireless communication unit 120D can be reduced.

  In the present embodiment, the control unit 130 selects the communication frequency band having the highest SNR measured for the donor-side radio communication unit 120D among the plurality of communication frequency bands that can be used by the radio relay apparatus 100 as the donor-side radio communication unit 120D. Set for. Thereby, the influence of the interference which the preamble mask signal has on the donor-side radio communication unit 120D can be relatively reduced.

  In the present embodiment, the control unit 130 selects a communication frequency band having the lowest SNR measured for the donor-side radio communication unit 120D among a plurality of communication frequency bands that can be used by the radio relay apparatus 100, as a service-side radio communication unit 120S. Set to. Thereby, in preparation for the case where the communication frequency band set with respect to the donor side radio | wireless communication part 120D is switched, the communication frequency band of a favorable SNR can be ensured. As a result, even after the communication frequency band set for the donor-side radio communication unit 120D is switched, the influence of the interference that the preamble mask signal has on the donor-side radio communication unit 120D can be relatively reduced.

(5) 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 embodiment described above, the frequency interval between the communication frequency band set for the service-side radio communication unit 120S and the communication frequency band set for the donor-side radio communication unit 120D, and the donor-side radio communication unit Although 120D explained the example which controls the transmission power of a preamble mask signal based on both the RSSI of the radio signal received from the radio base station 200, the transmission power of the preamble mask signal is controlled based on only one of them. May be. In addition, the transmission power of the preamble mask signal is not limited to being changed as appropriate, and the transmission power of the preamble mask signal may be controlled to a preset fixed value. Further, the transmission power of the preamble mask signal may be controlled using the SNR of the radio signal instead of RSSI.

  In the above-described embodiment, the wireless communication system 1 based on WiMAX (IEEE802.16) has been described. The present invention can also be applied to the LTE (Long Term Evolution) TDD mode (TDD-LTE), etc.

  Furthermore, the wireless relay device 100 is not limited to a fixed type, and may be a mobile type mounted on a vehicle, for example.

  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.

  DESCRIPTION OF SYMBOLS 1 ... Wireless communication system, 100 ... Wireless relay apparatus, 101-103 ... Board | substrate, 105 ... Housing | casing, 110D ... Donor side communication unit, 110S ... Service side communication unit, 120D ... Donor side wireless communication part, 120S ... Service side radio | wireless Communication unit, 121a, 121b ... service antenna, 122a, 122b ... switch, 123a, 123b ... PA, 124a, 124b ... LNA, 125a, 125b ... RF / BB unit, 130 ... control unit, 130D ... donor side control unit, 130S ... Service-side control unit, 132 ... Storage unit, 133 ... I / F unit, 161a, 161b ... Donor antenna, 162a, 162b ... Switch, 165a, 165b ... RF / BB unit, 172 ... Storage unit, 172, 132 ... Storage Part, 173, 133 ... I / F part, 174 ... indicator, 200 ... none Base station, 300 ... wireless terminal

Claims (2)

A wireless relay device used in a wireless communication system in which a wireless base station transmits a synchronization signal, which is a wireless signal used for establishing synchronization by a wireless terminal, at a predetermined timing,
A first wireless communication unit that performs wireless communication with the wireless base station;
A second wireless communication unit that performs wireless communication with the wireless terminal;
A control unit for controlling the first wireless communication unit and the second wireless communication unit;
Comprising
The controller is
Of the plurality of communication frequency bands that can be used by the wireless relay device, a communication frequency band having the highest wireless quality level measured for the first wireless communication unit is set for the first wireless communication unit, and the plurality Among the communication frequency bands, the communication frequency band having the lowest radio quality level measured for the first radio communication unit is set for the second radio communication unit,
A radio relay apparatus that controls the second radio communication unit to transmit an interference signal, which is a radio signal for interfering with the synchronization signal, at the predetermined timing. Used in a wireless communication system in which a wireless base station transmits a synchronization signal, which is a wireless signal used for establishing synchronization by a wireless terminal, at a predetermined timing,
A first wireless communication unit that performs wireless communication with the wireless base station;
A second wireless communication unit that performs wireless communication with the wireless terminal;
A method for controlling a wireless relay device comprising:
Among the plurality of communication frequency bands that can be used by the wireless relay device, a communication frequency band having the highest wireless quality level measured for the first wireless communication unit is set for the first wireless communication unit, and the plurality A communication frequency band having the lowest radio quality level measured for the first radio communication unit among the communication frequency bands of the second radio communication unit;
Controlling the second wireless communication unit to transmit an interference signal, which is a wireless signal for interfering with the synchronization signal, at the predetermined timing;
Control method.

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