JP2014187566A - Relay station and synchronization target determination method for relay station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relay station and a synchronization target determination method therefor, capable of proper synchronization according to installation condition, and capable of obtaining high synchronization accuracy and stability.SOLUTION: A relay station 120 includes: a radio communication unit 132; a GPS signal receiver 134; a base station selection unit 124 for selecting a candidate base station for synchronization, by referring to a control signal obtained from a base station 130 surrounding the relay station; a timing calculation unit 126 for calculating a timing difference, which is a difference between a reception timing of a clock signal and a reception timing of a control signal from a candidate base station for synchronization; and a synchronization determination unit 128 for determining a synchronization target of the base station to a GPS satellite if the timing difference is a threshold value or more by referring to the timing difference, and determining the synchronization target of the base station to a selected base station as a synchronization target candidate if the timing difference is less than the threshold value.

Description

  The present invention relates to a relay station that relays communication between a radio terminal and a base station, and a relay station synchronization destination determination method that determines a synchronization destination in the relay station.

  In wireless communication systems typified by PHS (Personal Handy phone System), TDD (Time Division Duplex) which performs transmission and reception alternately by dividing a communication path on a time axis in order to realize simultaneous bidirectional communication. A TDMA / TDD system is used, which combines a duplicate signal) and a TDMA (Time Division Multiple Access) in which transmission / reception times (frames) are time-divided into a plurality of time slots. Currently, in this TDMA / TDD system, a radio entrance system (hereinafter referred to as RBS) has been introduced.

  In RBS, a radio repeater (hereinafter referred to as a relay station), generally called a repeater, is installed in a mountainous area, an area where a line does not reach, such as a main road, and a communication network is built via radio with other base stations. (For example, Patent Document 1). This makes it possible to expand the service area at a lower cost than when installing a base station.

  Here, in general, for synchronization between base stations, a GPS synchronization system is built around a specific base station to which a GPS unit is connected (for example, Patent Document 1). In the GPS synchronization system, a GPS connection station to which a GPS unit is connected performs transmission by matching the transmission timing of the base station with the clock from a GPS satellite. The neighboring base stations to which the GPS unit is not connected perform synchronization based on the timing transmitted from the GPS connection station.

  On the other hand, in RBS, a relay station equipped with GPS performs synchronization with GPS, but other base stations do not synchronize with the synchronized relay station. This is because the relay station is generally installed in a remote area away from other base stations, and there is a high possibility that synchronization loss will increase due to propagation delay.

JP 2008-182657 A

  By the way, RBS has been used in areas such as mountainous areas where the line does not reach, but in recent years, the use of RBS in urban areas is also being studied in order to reduce the line cost. As described above, a base station or relay station equipped with a GPS unit is configured to synchronize with a GPS satellite. However, in areas such as urban areas where buildings are dense, the outlook is often poor. In that case, it is difficult to communicate with the GPS satellite, the synchronization becomes unstable, and there is a possibility that synchronization with the neighboring base stations may occur and interfere with each other. Although it is conceivable that the relay station is configured to synchronize with the surrounding base station, the synchronization shift due to the propagation delay occurs depending on the distance to the synchronization destination base station. There is a risk.

  In view of such problems, the present invention provides a relay station and a relay station synchronization destination determination method that can perform synchronization suitable for installation conditions and can obtain high synchronization accuracy and synchronization stability. The purpose is to do.

  In order to solve the above problems, a typical configuration of a relay station according to the present invention is a relay station that relays communication between a wireless terminal and a base station, and performs wireless communication between the wireless terminal and the base station. A radio communication unit to perform, a GPS signal reception unit that receives a GPS signal including a clock signal from a GPS satellite, and a base station selection unit that selects a base station that is a synchronization candidate among the base stations present around the relay station A timing calculation unit that calculates a timing difference that is a difference between the reception timing of the clock signal and the reception timing of the control signal of the base station selected as the synchronization candidate, and the relay station according to the timing difference A synchronization determination unit that determines whether the synchronization destination is the GPS satellite or the base station selected as the synchronization candidate.

  In order to solve the above-described problem, a typical configuration of a relay station synchronization destination determination method according to the present invention is a relay station synchronization destination that determines a synchronization destination in a relay station that relays communication between a wireless terminal and a base station. A determination method that receives a GPS signal including a clock signal from a GPS satellite, acquires a control signal of a base station existing around the relay station, and refers to the acquired control signal to determine a base station that is a synchronization candidate. Select and calculate the timing difference that is the difference between the reception timing of the clock signal and the reception timing of the control signal of the base station selected as the synchronization candidate, refer to the timing difference, and the timing difference is greater than or equal to the threshold Determines the synchronization destination of the relay station as a GPS satellite, and if the timing difference is less than a threshold, determines the synchronization destination of the relay station as a base station selected as a synchronization candidate.

  ADVANTAGE OF THE INVENTION According to this invention, the suitable synchronization according to an installation condition can be performed, and the synchronization destination determination method of the relay station and relay station which can acquire a high synchronization precision and synchronous stability can be provided.

It is a figure explaining the radio | wireless communications system containing the relay station concerning this embodiment. It is a functional block diagram which illustrates the structure of the relay station of this embodiment. It is a flowchart of the synchronization destination determination method of the relay station of this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a diagram illustrating a radio communication system 100 including a relay station 120 according to the present embodiment. Hereinafter, the relay station 120 and the synchronization destination determination method according to the present embodiment will be described with reference to the radio communication system 100 illustrated in FIG. For ease of understanding, in the embodiment described below, a PHS terminal (hereinafter referred to as a PHS terminal 110) is illustrated as a wireless terminal, but the present invention is not limited to this, and wireless communication is possible. A wireless terminal such as a mobile phone or a smartphone may be used.

  In the following description, the PHS terminal 110 refers to both the PHS terminals 110a and 110b unless otherwise specified. Similarly, when referring to the relay station 120, both of the relay stations 120a and 120b refer to all of the base stations 130a, 130b, 130c, 130d, 130e, and 130f when referred to as the base station 130. To do.

  As illustrated in FIG. 1, the wireless communication system 100 includes a PHS terminal 110, a base station 130, and a relay station 120 that relays the communication. In the present embodiment, the relay station 120a is a relay station installed in an area where a line such as a mountainous area does not reach as in the prior art, and the relay station 120b is an area where the base station 130 exists in the vicinity of an urban area or the like. Is a relay station. The PHS terminal 110a is connected (relayed) to the base station 130a via the relay station 120a, and the PHS terminal 110b is connected to the base station 130a via the relay station 120b. This enables wireless communication between the PHS terminal 110a and the PHS terminal 110b.

  FIG. 2 is a functional block diagram illustrating the configuration of the relay station 120 of this embodiment. As shown in FIG. 2, the relay station 120 of this embodiment includes a control unit 122, a wireless communication unit 132, and a GPS signal receiving unit 134. The control unit 122 manages and controls the entire relay station 120 by a semiconductor integrated circuit including a central processing unit (CPU). The wireless communication unit 132 performs wireless communication with the PHS terminal 110 and the base station 130 via the communication antenna 132a. The GPS signal receiving unit 134 receives a GPS signal from the GPS satellite 102 (see FIG. 1) via the GPS antenna 134a. The GPS signal received by the GPS signal receiving unit 134 includes a clock signal.

  As a feature of the present embodiment, the control unit 122 also functions as a base station selection unit 124, a timing calculation unit 126, and a synchronization determination unit 128. Specifically, the base station selection unit 124 acquires a control signal of the base stations 130 existing around the relay station 120, and refers to the acquired control signal to select a base station 130 that is a synchronization candidate. The timing calculation unit 126 calculates a timing difference that is a difference between the reception timing of the clock signal and the reception timing of the control signal of the base station 130 selected as the synchronization candidate. The synchronization determination unit determines the synchronization destination of the relay station 120 with reference to the timing difference.

  FIG. 3 is a flowchart of the synchronization destination determination method of the relay station 120 of this embodiment. As shown in FIG. 3, in the synchronization destination determination method of the relay station 120 of this embodiment, first, the control unit 122 receives a GPS signal from a GPS satellite by the GPS signal receiving unit 134 (step S202), and the GPS The clock signal included in the signal is acquired (YES in step S204). Then, the control unit 122 performs a base station search by the wireless communication unit 132 (step S206), and the base station selection unit 124 acquires a control signal of the base station 130 existing around the relay station 120 (step S208). YES)

  In the present embodiment, the configuration in which the control signal is acquired in step S206 and step S208 after the clock signal is acquired in step S202 and step S204 is illustrated, but the present invention is not limited to this. They may be performed simultaneously, or the clock signal may be obtained after obtaining the control signal.

  Next, the base station selection unit 124 refers to the acquired control signal, and selects the base station 130 determined to have high communication quality as a synchronization candidate (step S210). Then, the timing calculation unit 126 calculates a timing difference that is a difference between the reception timing of the GPS signal (clock signal) received in step S202 and the reception timing of the control signal of the synchronization candidate base station 130 selected in step S210. Calculate (step S212).

  Subsequently, the synchronization determination unit 128 refers to the timing difference calculated in step S212, and determines whether or not the timing difference is greater than or equal to a threshold value (step S214). If the timing difference is equal to or greater than the threshold (YES in step S214), the synchronization determination unit 128 determines the synchronization destination of the relay station 120 as a GPS satellite (step S216), and synchronizes with GPS (GPS synchronization). This is performed (step S218). On the other hand, if the timing difference is less than the threshold (NO in step S214), the synchronization determination unit 128 determines the synchronization destination of the relay station 120 as the base station 130 selected as the synchronization candidate (step S220), and the base Synchronization (frame synchronization) with the station 130 is performed (step S222).

  When the GPS signal cannot be received and the clock signal cannot be acquired (NO in step S204), the synchronization determination unit 128 determines the synchronization destination of the relay station 120 as the base station 130 selected as the synchronization candidate. (Step S220). On the other hand, when the control signal of the base station 130 existing around the relay station 120 cannot be acquired in the base station search (NO in step S208), the synchronization determination unit 128 determines the synchronization destination of the relay station 120 as a GPS satellite. 102 (see FIG. 1) is determined (step S216).

  According to the above configuration, if the timing difference is greater than or equal to the threshold value, that is, if the distance from the surrounding base station 130 is far away and there is a high possibility that synchronization loss will increase due to propagation delay, GPS synchronization is performed. Is called. As a result, the synchronization accuracy of the relay station 120 installed at a location distant from the base station 130, such as the relay station 120a, can be improved, and it is possible to prevent the occurrence of synchronization loss due to a propagation delay, and thus interference caused by the synchronization. It becomes. On the other hand, if the timing difference is less than the threshold, it is assumed that the distance from the surrounding base station 130 is short, and frame synchronization with the base station 130 is performed. As a result, high synchronization stability can be ensured in a relay station installed in an area where there are many buildings such as urban areas, such as the relay station 120b, where synchronization with the GPS satellite 102 is difficult. Therefore, according to the relay station 120 and the synchronization method according to the present embodiment, it is possible to perform synchronization suitable for the installation status of the relay station 120.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  INDUSTRIAL APPLICABILITY The present invention can be used as a relay station that relays communication between a wireless terminal and a base station, and a synchronization destination determination method for a relay station that determines a synchronization destination in the relay station.

DESCRIPTION OF SYMBOLS 100 ... Wireless communication system, 102 ... GPS satellite, 110 ... PHS terminal, 110a ... PHS terminal, 110b ... PHS terminal, 120 ... Relay station, 120a ... Relay station, 120b ... Relay station, 122 ... Control part, 124 ... Base station Selection unit 126 ... Timing calculation unit 128 ... Synchronization determination unit 130 ... Base station 130a ... Base station 130b ... Base station 130c ... Base station 130d ... Base station 130e ... Base station 130f ... Base station 132 ... Wireless communication unit, 132a ... Communication antenna, 134 ... GPS signal receiver, 134a ... GPS antenna

Claims (2)

A relay station that relays communication between a wireless terminal and a base station,
A wireless communication unit for performing wireless communication with the wireless terminal and the base station;
A GPS signal receiver that receives a GPS signal including a clock signal from a GPS satellite;
A base station selection unit that selects a base station that is a synchronization candidate among the base stations existing around the relay station;
A timing calculation unit that calculates a timing difference that is a difference between the reception timing of the clock signal and the reception timing of the control signal of the base station selected as the synchronization candidate;
A synchronization determination unit that determines the synchronization destination of the relay station as either the GPS satellite or the base station selected as the synchronization candidate according to the timing difference;
A relay station comprising: A relay station synchronization destination determination method for determining a synchronization destination in a relay station that relays communication between a wireless terminal and a base station,
Receive GPS signals including clock signals from GPS satellites,
Obtaining a control signal of the base station existing around the relay station;
Select the base station to be a synchronization candidate with reference to the acquired control signal,
Calculating a timing difference that is a difference between the reception timing of the clock signal and the reception timing of the control signal of the base station selected as the synchronization candidate;
Referring to the timing difference, if the timing difference is greater than or equal to a threshold value, the synchronization destination of the relay station is determined to be a GPS satellite, and if the timing difference is less than the threshold value, the synchronization destination of the relay station is A method for determining a synchronization destination of a relay station, wherein a base station selected as a synchronization candidate is determined.