JP6386724B2 - Base station, relay station and radio communication system - Google Patents

Description

  The present invention relates to a base station, a wireless terminal, and a wireless communication system for wireless connection to these.

  In a wireless communication system typified by PHS (Personal Handy phone System), TDD (Time Division Duplex) that 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, RBS (Radio Bypass System) is introduced to expand the service area.

  The RBS is a type of radio repeater also called a repeater, and communicates with other neighboring base stations via radio to construct a communication area. That is, the RBS is a system that can perform relaying wirelessly instead of a line in an area where a line cannot be laid or an area where a line is not drawn for reasons such as suppressing line cost.

  However, in the RBS, since the connection destination base station and the connection source relay station are connected by radio, the radio resources of the connection destination base station are reduced. The relay station preferentially selects a base station with a high reception level when selecting a connection destination base station. Therefore, when the traffic of the connected base station is high, the radio resource for the wireless terminal to connect to There may be a shortage. When the radio resources are insufficient, there is a possibility that communication quality may be deteriorated when a general user cannot be used in the connected base station or the relay station cannot connect to the optimal base station.

  To deal with this problem, Patent Document 1 describes a repeater device that can increase the number of call channel relays when traffic increases. According to Patent Document 1, an increase in the number of relay call channels can be dealt with by switching from diversity relay to non-diversity relay based on the number of call channels.

JP 2010-062988 A

  However, with the technique described in Patent Document 1, communication quality may be reduced because some or all of the repeater units are switched to non-diversity relay as the number of call channels increases.

  In the present invention, in view of such problems, a base station, a relay station, and a communication system capable of avoiding resource shortage while suppressing deterioration in communication quality when the relay station selects a connection destination base station. It is intended to provide.

  A typical configuration of a radio communication system according to the present invention is a radio communication system including a base station, a radio terminal, and a relay station wirelessly connected to the base station. The base station transmits resource information including at least traffic information to the relay station. The relay station includes a connection destination determination unit that acquires resource information from a plurality of base stations and determines a base station having traffic of a predetermined value or less as a connection destination. To do.

  The connection destination determination unit of the relay station may determine the connection destination when the delay of the signal received from the base station is within a predetermined value.

  The connection destination determination unit of the relay station further determines the type of the base station from the control signal transmitted by the base station, and the base station is an advanced base station having a plurality of radio communication units, or is connected to the micro cell. On the other hand, when the base station is not a macro cell having a wide cover area, it may be determined as a connection destination.

  A representative configuration of a relay station according to the present invention is that a relay station wirelessly connected to a base station and a wireless terminal acquires at least traffic information from a plurality of base stations, and connects a base station whose traffic is a predetermined value or less to a connection destination It is characterized by including a connection destination determination unit for determining as follows.

  A typical configuration of a base station according to the present invention includes a resource information transmission unit that transmits resource information including at least traffic information to a relay station in a base station that is wirelessly connected to a wireless terminal via the relay station. And

  Advantageous Effects of Invention According to the present invention, it is possible to provide a base station, a relay station, and a communication system that can avoid a resource shortage while suppressing deterioration in communication quality when a relay station selects a connection destination base station. .

It is a figure explaining the radio | wireless communications system containing a base station and a relay station. It is a functional block diagram which illustrates the composition of a base station and a relay station. It is a figure which shows the method of accommodating the traffic information of a base station. It is a figure which shows the other method of accommodating the traffic information of a base station. It is a flowchart of the base station selection method of the connection destination by a relay station.

  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 for explaining a radio communication system including a base station and a relay station. As shown in FIG. 1, the wireless communication system 100 includes a base station 110, a wireless terminal 102, and a relay station 120 that is wirelessly connected to these.

  The wireless terminal 102 is a terminal that employs a TDMA / TDD system capable of simultaneous bidirectional communication represented by PHS. The base station 110 communicates with the relay station 120 wirelessly and is connected to the network 104 via a wired line.

  The relay station 120 is a relay station 120 installed in an area where a base station exists in the vicinity of an urban area, and communicates with the wireless terminal 102 and the base station 110 by radio. The wireless terminal 102 is connected to the base station 110 via the relay station 120. That is, the relay station 120 constructs a communication area by relaying communication wirelessly.

  FIG. 2 is a functional block diagram illustrating the configuration of the base station and the relay station. As illustrated in FIG. 2, the base station 110 includes a base station control unit 112, a resource information transmission unit 114, a communication unit 116, and transmission / reception units 118 and 122. The base station control unit 112 manages and controls the entire base station 110 by a semiconductor integrated circuit including a central processing unit (CPU). The communication unit 116 is connected to the network 104 (see FIG. 1) via a wired line. The transmission / reception units 118 and 122 perform wireless communication with the wireless terminal 102 or the relay station 120 via the communication antennas 118a and 122a, respectively.

  The base station 110 is an advanced base station that includes two or more transmission / reception units. The advanced base station has the same number of radio communication units (high frequency circuits) as the number of transmission / reception units, has a large number of radio terminals, and high-speed adaptive modulation enables high-speed packet communication and a wide communication area. The base station has higher performance than the conventional one. The resource information transmission unit 114 transmits resource information including at least traffic information of the local station to the relay station. The traffic information is information in which traffic for a predetermined number of days is calculated based on the number of terminals accommodated by the base station 110 and the call duration. Further, the resource information includes location information of the base station 110 and the like.

  The relay station 120 includes a relay station control unit 124, a neighboring base station search processing unit 126, a connection destination determination unit 128, a terminal unit 132, and a base station unit 134. The relay station control unit 124 manages and controls the entire relay station 120 by a semiconductor integrated circuit including a central processing unit (CPU). The terminal unit 132 communicates with the base station 110 via the communication antenna 132a. In addition, the above-described resource information is received from the base station 110. The base station unit 134 communicates with the wireless terminal 102 via the communication antenna 134a. The peripheral base station search processing unit 126 acquires the ID and reception level of the peripheral base station 110.

  The connection destination determination unit 128 acquires resource information from a plurality of base stations including the base station 110 and determines the base station 110 to be connected from the traffic value. The connection destination determination unit 128 determines the base station 110 to be connected based on the delay value of the received signal and the control signal transmitted by the base station 110.

  FIG. 3 is a diagram illustrating a method for accommodating traffic information of a base station. In FIG. 3, traffic information is transmitted using a case where the PCH transmitted eight times during one superframe (1.2 seconds) transmits an idle message (idle PCH). A PCH (Paging Channel) is a type of CCH (Control Channel) and is a channel used when the base station 110 notifies an incoming call to a wireless terminal in the cover area. The PCH is not always used, and when there is no incoming call, an idle PCH in which the data area is filled with 0 (zero) is transmitted. In the example shown in FIG. 3, the traffic information of the base station 110 is accommodated and transmitted in the idle PCH. Therefore, idle PCH that has not been substantially used can be effectively utilized.

  In FIG. 3, traffic information of 3 octets (3 bytes) is accommodated. However, this is only an example, and the data amount of the traffic information to be accommodated may be changed according to the free space. Further, another CCH having an idle message capable of accommodating traffic information may be used. For example, an idle message of SCCH (Signaling Control Channel: channel for dedicated cell) that is connected to a terminal by telephone call may be used.

  FIG. 4 is a diagram illustrating another method for accommodating traffic information of a base station. In the example shown in FIG. 4, traffic information is accommodated and transmitted in a CCH of a new data type in a CCH time slot in which nothing is transmitted in one superframe (1.2 seconds). In this case, the data amount of the traffic information can be freely changed, and resource information such as location information can be accommodated at the same time. In this case, as shown in FIG. 4, the relay station 120 can determine what information is included according to the data type. Note that the format shown in FIG. 4 is merely an example, and the number of traffic information accommodated, the data structure, and the like may be changed as appropriate.

  FIG. 5 is a flowchart of a connection destination base station selection method by the relay station. As shown in FIG. 5, the relay station 120 controls the base station whose connection destination determination unit 128 is an advanced base station from the neighboring base stations 110 or is not a macro cell having a wide coverage area with respect to the micro cell. Extraction is performed based on the signal (step S202). Then, the neighboring base station search processing unit 126 ranks the neighboring base stations 110 determined as connection destination candidates by the above-described method in descending order of reception level (step S204).

  Next, the connection destination determination unit 128 acquires traffic information of the base station 110 having a higher rank (step S206). When there is no traffic information notification from the target base station 110 (NO in step S208), the connection destination determination unit 128 checks whether there is a next connection target base station (step S216).

  Proceeding to the process of step S216, if there is a connection target base station corresponding to the next order (YES in step S216), the connection destination determination unit 128 performs a process of acquiring traffic information from the next connection target base station (step S206). When there is no next connection target base station (NO in step S216), that is, when there is no notification of traffic information in all connection target base stations, the base station with the highest priority is selected as the connection destination (step S218). ).

  When there is a traffic information notification from the base station 110 (YES in step S208), the connection destination determination unit 128 checks whether the traffic is equal to or greater than a predetermined value (step S210). If the traffic is equal to or greater than the predetermined value (YES in step 210), the connection destination determination unit 128 proceeds to step S216 and performs the above-described processing. That is, the base station 110 with low traffic is not connected, and the base station 110 with low traffic is set as a connection destination candidate.

  On the other hand, when the traffic of the connection destination candidate base station 110 is less than or equal to the predetermined value (NO in step S210), the connection destination determination unit 128 checks the value of the delay in the reception timing of the signal received from the base station 110 (step S212). ). If the delay of the reception timing is equal to or greater than the predetermined value (YES in step S212), the connection destination determination unit 128 proceeds to step S216 and performs the above-described processing. A large delay means a long distance. When the delay between the base station 110 and the relay station 120 is large, the delay between the base station 110 and the wireless terminal 102 results in an allowable amount when the distance between the relay station 120 and the wireless terminal 102 increases. Will be exceeded. Therefore, the base station 110 with a large delay is not connected, and the base station 110 with a small delay is set as a connection destination candidate.

  Therefore, when the delay of the reception timing of the signal received from the base station 110 is equal to or less than a predetermined value (within a predetermined value) (NO in step S212), the connection destination determination unit 128 selects the base station 110 as a connection destination. (Step S214), the process ends.

  According to the above configuration, the relay station 120 is not connected to the macro cell base station. A macro cell base station with a wide cover area may cause a problem in communication due to concentration of communication. Therefore, by excluding the macro cell base station from the connection destination, it is possible to prevent the communication quality from being deteriorated. Further, by selecting an advanced base station such as the base station 110 as a connection destination, communication quality can be stabilized.

  Also, the relay station 120 selects the base station 110 with low traffic as a connection destination based on the traffic information of the base station 110. For this reason, it is possible to prevent a bias in traffic at the base station 110 and to prevent a shortage of radio resources of the base station 110, thereby preventing a reduction in communication quality.

  Furthermore, since the relay station 120 selects the base station 110 with a small delay of the received signal as the connection destination, the relay station 120 can be connected to the base station 110 capable of further stable communication among the base stations 110 with low traffic. Therefore, it is possible to prevent the communication quality from deteriorating.

  In addition, when there is no base station 110 that satisfies all the conditions, the relay station 120 connects to the base station with the highest priority among the neighboring base stations. Therefore, the relay station 120 can select the most suitable base station 110 at that time as the connection destination.

  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 the example which concerns. 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 for a base station, a wireless terminal, and a wireless communication system that is wirelessly connected to these.

DESCRIPTION OF SYMBOLS 100 ... Wireless communication system, 102 ... Wireless terminal, 104 ... Network, 110 ... Base station, 112 ... Base station control part, 114 ... Resource information transmission part, 116 ... Communication part, 118 ... Transmission / reception part, 118a, 122a, 132a, 134a ... communication antenna 120 ... relay station 122 ... transmission / reception unit 124 ... relay station control unit 126 ... neighboring base station search processing unit 128 ... connection destination determination unit 132 ... terminal unit 134 ... base station unit

Claims (3)

In a wireless communication system comprising a plurality of base stations, wireless terminals, and relay stations wirelessly connected to them,
The plurality of base stations includes a resource information transmitting unit that transmits resource information including at least traffic information to the relay station,
The relay station extracts an advanced base station including a plurality of radio communication units from the plurality of base stations, acquires the resource information, and is the advanced base station whose traffic is a predetermined value or less, A wireless communication system, comprising: a connection destination determination unit that determines, as a connection destination, the advanced base station in which a delay of a signal received from a base station is a predetermined value or less . The relay station has a processing unit that ranks in order of the base station with the highest reception level among the advanced base stations,
The connection destination determination unit connects the advanced base stations whose traffic is less than or equal to a predetermined value and whose delay of a signal received from the advanced base station is less than or equal to a predetermined value in the order of ranking. The wireless communication system according to claim 1, wherein the wireless communication system is determined as a destination. In a relay station wirelessly connected to a plurality of base stations that transmit resource information including traffic information and a wireless terminal,
An advanced base station having a plurality of wireless communication units is extracted from the plurality of base stations, the resource information is acquired, and the traffic is the advanced base station having a predetermined value or less and received from the advanced base station A relay station, wherein the advanced base station whose signal delay is equal to or less than a predetermined value is determined as a connection destination.

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