RADIO RELAY STATION AND CONTROL METHOD

• US 20130052941A1
• Filed: 01/26/2011
• Published: 02/28/2013
• Est. Priority Date: 01/26/2010
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Kitaji, Mitsuhiro
• Granted Patent: US 9,585,071 B2
• Time in Patent Office: Days
• US Class Current: 455/7
• CPC Class Codes: H04B 7/15592 Adapting at the relay station communication parameters for supporting cooperative relaying, i.e. transmission of the same data via direct - and relayed path cooperative diversity H04B7/024
• CPC Class Codes: H04W 36/0005 Control or signalling for completing the hand-off
• CPC Class Codes: H04W 36/0016 Hand-off preparation specially adapted for end-to-end data sessions
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/22 for handling the traffic
• CPC Class Codes: H04W 84/047 using dedicated repeater stations

Abstract

When a relay station load, which is the load of communications with radio terminals (300E-300G), of a relay node (200) exceeds a load allowable amount, which is determined according to the load of a radio base station (100A), the relay node transmits a handover request, which requests permission for a relay handover, to the radio base station (100A) and performs a relay handover if the relay node receives a handover command which instructs a relay handover.

Claims

1. A radio relay station, comprising:

a first communication unit configured to communicate with a radio base station or a different radio relay station as a connection destination;

a second communication unit configured to communicate with at least one radio terminal;

a relay unit configured to relay data to be exchanged between the connection destination of the first communication unit and the radio terminal; and

a controller configured to control the first communication unit and the second communication unit, wherein

the controller comprises;

a handover request unit configured to control the first communication unit so that the first communication unit transmits a handover request for executing a relay station handover in which the first communication units switches the connection destination, when a relay station load that is a load of a communication performed by the second communication unit with the radio terminal exceeds a load allowable amount determined according to a load of the connection destination of the first communication unit or when it is predicted that the relay station load exceeds the load allowable amount; and

a handover controller configured to control the first communication unit so that the first communication unit executes the relay station handover when the first communication unit receives a response message indicating that the relay station handover is allowed or instructed.

2. The radio relay station according to claim 1, wherein the handover request unit controls the first communication unit so that the first communication unit transmits the handover request containing relay station load information indicating the relay station load.

3. The radio relay station according to claim 1, wherein the handover request unit controls the first communication unit so that the first communication unit transmits the handover request to a relay station handover candidate which is a candidate of anew connection destination of the first communication unit.

4. The radio relay station according to claim 1, wherein

the controller further comprises:

a notification request unit configured to control the first communication unit so that the first communication unit transmits a load notification request for requesting a load notification notifying a load of a relay station handover candidate which is a candidate of a new connection destination of the first communication unit; and

a connection destination determination unit configured to determine a new connection destination of the first communication unit based on the load notification received by the first communication unit, wherein

the handover request unit controls the first communication unit so that the first communication unit transmits the handover request to the new connection destination determined by the destination determination unit.

5. The radio relay station according to claim 4, wherein the connection destination determination unit determines, as the new connection destination, a relay station handover candidate having the smallest load or a smaller load than a predetermined amount among the relay station handover candidates based on the load notification.

6. The radio relay station according to claim 4, wherein

the first communication unit measures a reception quality of a received radio signal, and

the connection destination determination unit determines the new connection destination of the first communication unit based on the load notification and the radio quality.

7. The radio relay station according to claim 1, wherein

the controller further comprises:

a notification request unit configured to control the first communication unit so that the first communication unit transmits a load notification request for requesting a load notification notifying a load of a relay station handover candidate being a candidate of a new connection destination of the first communication unit; and

a handover determination unit configured to determine whether or not to execute the relay station handover based on the load notification received by the first communication unit, wherein

when the relay station load exceeds the load allowable amount or when it is predicted that the relay station load exceeds the load allowable amount, and when it is determined that the relay station handover is to be executed, the handover request unit controls the first communication unit so that the first communication unit transmits the handover request.

8. The radio relay station according to claim 7, wherein

the handover determination unit

calculates a load of the relay station handover candidate that the relay station handover candidate may have if the relay station handover to the relay station handover candidate is executed, based on the load notification and the relay station load, and

determines whether or not to execute the relay station handover based on the calculated load.

9. The radio relay station according to claim 1, wherein when the first communication unit switches the connection destination by the relay station handover, the relay unit relays data to be exchanged between the new connection destination of the first communication unit and the radio terminal.

10. A control method for a radio relay station which comprises a first communication unit configured to communicate with a radio base station or a different radio relay station as a connection destination, a second communication unit configured to communicate with at least one radio terminal, and a relay unit configured to relay data to be exchanged between the connection destination of the first communication unit and the radio terminal, the control method comprising:

controlling the first communication unit so that the first communication unit transmits a handover request for executing a relay station handover in which the first communication units switches the connection destination, when a relay station load that is a load of a communication performed by the second communication unit with the radio terminal exceeds a load allowable amount determined according to a load of the connection destination of the first communication unit or when it is predicted that the relay station load exceeds the load allowable amount, and

controlling the first communication unit so that the first communication unit executes the relay station handover when the first communication unit receives a response message indicating that the relay station handover is allowed or instructed.

11. A radio relay station, comprising:

a first communication unit configured to communicate with a radio base station or a different radio relay station as a connection destination;

a second communication unit configured to communicate with at least one radio terminal;

a relay unit configured to relay data to be exchanged between a connection destination of the first communication unit and the radio terminal; and

a controller configured to control the first communication unit and the second communication unit, wherein

the controller comprises;

a handover request unit configured to control the first communication unit so that the first communication unit transmits a handover request for executing a terminal handover for switching a connection destination, when a relay station load that is a load of a communication performed by the second communication unit with the radio terminal exceeds a load allowable amount determined according to a load of a connection destination of the first communication unit or when it is predicted that the relay station load exceeds the load allowable amount; and

a handover instruction unit configured to control the second communication unit, when the first communication unit receives a response message indicating that the terminal handover is allowed or instructed, so that the second communication unit transmits a terminal handover instruction corresponding to the received response message to the radio terminal.

12. The radio relay station according to claim 11, wherein the handover request unit controls the first communication unit so that the first communication unit transmits the handover request containing terminal load information indicating a terminal load that is a load of each radio terminal.

13. The radio relay station according to claim 11, wherein the handover request unit controls the first communication unit so that the first communication unit transmits the handover request to a terminal handover candidate which is a candidate of a new connection destination of the radio terminal.

14. The radio relay station according to claim 11, wherein

the controller further comprises:

a notification request unit configured to control the first communication unit so that the first communication unit transmits a load notification request for requesting a load notification notifying a load of a relay station handover candidate which is a candidate of a new connection destination of the first communication unit; and

a connection destination determination unit configured to determine a new connection destination of the first communication unit based on the load notification received by the first communication unit, wherein

the handover request unit controls the first communication unit so that the first communication unit transmits the handover request to the new connection destination determined by the destination determination unit.

15. The radio relay station according to claim 14, wherein the connection destination determination unit determines, as the new connection destination, a terminal handover candidate having the smallest load or a smaller load than a predetermined amount among the terminal handover candidates based on the load notification.

16. The radio relay station according to claim 14, wherein

the first communication unit measures a reception quality of a received radio signal, and

the connection destination determination unit determines a new connection destination of the radio terminal based on the load notification and the radio quality.

17. The radio relay station according to claim 11, wherein

the controller further comprises:

a notification request unit configured to control the first communication unit so that the first communication unit transmits a load notification request for requesting a load notification notifying a load of a relay station handover candidate being a candidate of a new connection destination of the first communication unit; and

a handover determination unit configured to determine whether or not to execute the relay station handover based on the load notification received by the first communication unit, wherein

when the relay station load exceeds the load allowable amount or when it is predicted that the relay station load exceeds the load allowable amount, and when it is determined that the relay station handover is to be executed, the handover request unit controls the first communication unit so that the first communication unit transmits the handover request.

18. The radio relay station according to claim 17, wherein the handover determination unit calculates a load of the terminal handover candidate that the relay station handover candidate may have if the terminal handover to the terminal handover candidate is executed based on the load notification and the relay station load, and determines whether or not to execute the terminal handover based on the calculated load.

19. The radio relay station according to claim 11, wherein the controller further comprises a terminal determination unit configured to determine at least one radio terminal to be caused to execute the terminal handover based on the relay station load and a terminal load that a load of each radio terminal so as to keep the relay station load equal to or smaller than the load allowable amount.

20. The radio relay station according to claim 19, wherein

for each radio terminal, the second communication unit receives a battery notification indicating a remaining battery level of the radio terminal, and

the terminal determination unit determines a radio terminal with a higher remaining battery level as a radio terminal to be preferentially caused to execute the terminal handover based on the battery notification received by the second communication unit.

21. A control method for a radio relay station which comprises a first communication unit configured to communicate with a radio base station or a different radio relay station as a connection destination, a second communication unit configured to communicate with at least one radio terminal, and a relay unit configured to relay data to be exchanged between a connection destination of the first communication unit and the radio terminal, the control method comprising:

controlling the first communication unit so that the first communication unit transmits a handover request for executing a terminal handover for switching the connection destination, when a relay station load that is a load of a communication performed by the second communication unit with the radio terminal exceeds a load allowable amount determined according to a load of the connection destination of the first communication unit or when it is predicted that the relay station load exceeds the load allowable amount, and

controlling the second communication unit, when the first communication unit received a response message indicating that the terminal handover is allowed or instructed, so that the second communication unit transmits a terminal handover instruction corresponding to the received response message.