WIRELESS COMMUNICATION SYSTEM

• US 20110256826A1
• Filed: 06/27/2011
• Published: 10/20/2011
• Est. Priority Date: 01/29/2009
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: OBUCHI, Kazuhisa, ODE, Takayoshi
• Granted Patent: US 9,083,433 B2
• Time in Patent Office: Days
• US Class Current: 455/7
• CPC Class Codes: H04B 7/15507 Relay station based processing for cell extension or control of coverage area, network planning with network coordinated processing with regard to cell extension H04W16/26; network topologies using dedicated repeater stations H04W84/047; terminal devices adapted for relaying to or from an other terminal H04W88/04
• CPC Class Codes: H04B 7/15535 Control of relay amplifier gain amplifier gain control in general H03G3/00; gain control reducing self - or loop interference H04B7/15578
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0232 according to average transmission signal activity
• CPC Class Codes: H04W 52/0235 where the received signal is a power saving command
• CPC Class Codes: H04W 84/047 using dedicated repeater stations
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A wireless communication system includes a wireless base station, a mobile station configured to communicate with the wireless base station, and a relay station configured to relay the communication between the wireless base station and the mobile station. When the number of the mobile stations communicating with the wireless base station is judged to have become smaller than or equal to a given number, a power controller in the relay station executes at least one of power control to cut off the power for relaying the communication, power control to perform intermittent operation, and power control to perform power-saving operation.

Claims

1. A wireless communication system comprising:

a wireless base station;

mobile stations each configured to communicate with the wireless base station; and

a relay station configured to relay communication between the wireless base station and the mobile stations,

wherein the relay station includes a power controller which is configured to execute at least one of power control to cut off power for relaying the communication, power control to perform intermittent operation, and power control to perform power-saving operation if it is judged that a number of the mobile stations communicating with the wireless base station has become smaller than or equal to a given number.

2. The wireless communication system according to claim 1, wherein the power controller recognizes the number of the relayed mobile stations by measuring received powers from the respective mobile stations, comparing the measured received powers with a received power threshold, regarding the mobile stations of which the received power is greater than the received power threshold, as mobile stations being relayed by the relay station, and regarding the mobile stations of which the received power is smaller than the received power threshold, as mobile stations not relayed by the relay station.

3. The wireless communication system according to claim 1, wherein:

the relay station includes a signal extractor configured to receive and extract connection request signals or control signals transmitted from the respective mobile stations, and

where the connection request signal or the control signal is extracted, the power controller regards the mobile station which is transmitting the connection request signal or the control signal, as the mobile station being relayed by the relay station, and regards the mobile station which is not transmitting the connection request signal or the control signal, as the mobile station not relayed by the relay station, to recognize the number of the relayed mobile stations.

4. The wireless communication system according to claim 1, wherein:

the relay station includes a signal extractor configured to receive and extract connection request signals or control signals transmitted from the respective mobile stations,

the signal extractor determines whether the connection request signal or the control signal extracted thereby is directed to the own relay station or other relay station, and

where the connection request signal or the control signal is judged to be directed to the own relay station, the power controller regards the mobile station which is transmitting the connection request signal or the control signal directed to the own relay station, as the mobile station being relayed by the relay station, and where the connection request signal or the control signal is judged to be directed to other relay station, the power controller regards the mobile station which is transmitting the connection request signal or the control signal directed to the other relay station, as the mobile station not relayed by the relay station, thereby recognizing the number of the relayed mobile stations.

5. The wireless communication system according to claim 1, wherein:

the wireless base station includes a timing signal notifier configured to notify a timing signal indicating timing for transition from normally powered operation to the power control, and

where the power control is to be executed, the power controller notifies the wireless base station or the mobile stations that the power control will be executed, the timing signal notifier of the wireless base station transmits the timing signal to the relay station when notified of execution of the power control, and the power controller executes the power control in accordance with the timing signal.

6. The wireless communication system according to claim 1, wherein, when the power control is executed at the relay station, the wireless base station reallocates radio resources of uplink from the mobile stations to the relay station and radio resources of downlink from the relay station to the mobile stations.

7. The wireless communication system according to claim 1, wherein:

the relay station includes a handover request unit, and

when the power control is to be executed by the power controller, the handover request unit causes the mobile stations being relayed or the wireless base station to execute handover to other relay station or other wireless base station, and after the handover is executed, the power controller executes the power control.

8. The wireless communication system according to claim 1, wherein:

the relay station includes a handover request unit, and

the power controller determines timing for executing the power control, the handover request unit transmits information about the timing to the mobile stations or the wireless base station to cause the mobile stations being relayed or the wireless base station to execute handover to other relay station or other wireless base station, and after the handover is executed, the power controller executes the power control.

9. The wireless communication system according to claim 1, wherein the power controller executes the power control by powering off a transmitter and a receiver which relay the communication with the wireless base station, and intermittently operating a transmitter and a receiver which relay the communication with the mobile stations.

10. The wireless communication system according to claim 1, wherein the power controller executes the power control by powering off a transmitter and a receiver which relay the communication with the wireless bases station, operating, with reduced power, a transmitter which relays the communication with the mobile stations, and intermittently operating a receiver which relays the communication with the mobile stations.

11. The wireless communication system according to claim 1, wherein, if the number of the mobile stations has become larger than the given number or if a connection request is received from the wireless base station or the mobile stations, the power controller terminates the power control and performs normally powered operation.

12. The wireless communication system according to claim 1, wherein:

the relay station includes a handover request unit, and

when the power control is to be executed by the power controller, the handover request unit transmits a handover request to the mobile stations being relayed or the wireless base station, the mobile stations and the wireless base station execute handover to other relay station or other wireless base station upon receiving the handover request, and after the handover is executed, the power controller executes the power control.

13. A wireless communication method, comprising:

causing a relay station to recognize a number of mobile stations communicating with a wireless base station; and

causing the relay station to execute at least one of power control to cut off power for relaying the communication, power control to perform intermittent operation, and power control to perform power-saving operation if it is judged that the number of the mobile stations has become smaller than or equal to a given number.

14. A relay device comprising:

a relay communicator configured to control transmission and reception of communication relayed between a wireless base station and mobile stations; and

a power controller configured to recognize a number of the mobile stations communicating with the wireless base station and execute, if it is judged that the number of the mobile stations has become smaller than or equal to a given number, at least one of power control to cut off power for relaying the communication, power control to perform intermittent operation, and power control to perform power-saving operation.