System and method for relaying in multi-hop cellular networks

• US 8,175,064 B2
• Filed: 10/21/2004
• Issued: 05/08/2012
• Est. Priority Date: 10/21/2004
• Status: Expired due to Fees

• Current Assignee: Sovereign Peak Ventures, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Tan, Poy Boon, Shivanajay, Marwaha
• Primary Examiner(s): Chang, Kent
• Assistant Examiner(s): Siddiqui, Kashif
• Application Number:
  US11/577,643
• Publication Number:
  US 20070280172A1
• Time in Patent Office: 2,756 Days
• Field of Search: 370315-350, 455 7- 25
• US Class Current: 370/335
• CPC Class Codes: H04B 7/026 Co-operative diversity, e.g. using fixed or mobile stations as relays
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04W 16/26 Cell enhancers or enhancement, e.g. for tunnels, building shadow
• CPC Class Codes: H04W 88/04 adapted for relaying to or from another terminal or user
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

A radio communication system using TDD-CDMA multiple access system includes a base station and a plurality of mobile stations. Each mobile station includes a mechanism for measuring signal strength of coded signals from neighboring mobile stations; a mechanism for signalling the base station to switch from single-hop to multi-hop communication; and a mechanism for reporting to the base station candidate mobile stations for acting as a relay mobile station for multi-hop communication between the mobile station and the base station. The base station includes a mechanism for selecting a relay mobile station from a list of candidate mobile stations received from the mobile station.

Claims

1. A radio communication system using a TDD-CDMA multiple access system comprising:

a mobile station;

a base station;

wherein the mobile station is configured to measure signal strength values of coded signals transmitted from neighboring mobile stations and a received signal strength of a signal from the base station, and is configured to send candidate relay station information based on the measured signal strength values directly to the base station;

wherein if the received signal strength is below a threshold value, the mobile station is configured to send a request message directly to the base station requesting for a switch from single hop to multi-hop communication between itself and the base station; and

wherein the base station decides whether or not to establish multi-hop communication with the mobile station upon receipt of said request and based on the candidate relay station information.

2. The system as claimed in claim 1, wherein each mobile station uses the same respective up-link and downlink communication timeslots in both single-hop and multi-hop communications.

3. The system as claimed in claim 1, wherein a relay mobile station utilizes the same respective up-link and down-link communication timeslots for both communications with the base station and communications with a relayed mobile station (MST), wherein different codes are used in the uplink and downlink directions for communicating with the base station and the relayed mobile station MST.

4. The system as claimed in claim 1, wherein the measurement of the signal strength values of coded signals transmitted from neighboring mobile stations comprises measuring the signal strength of coded signals from neighboring mobile stations received in the same time slot as communications received from the base station.

5. The system as claimed in claim 4, wherein the measurement at the mobile station further comprises scanning an entire frequency channel for one complete frame and measuring the signal strength of coded signals from neighboring mobile stations.

6. The system as claimed in claim 5, wherein the entire frequency channel is scanned if there exists no mobile station that can act as a relay mobile station whose up-link timeslot is the same as the assigned down-link timeslot of the measuring mobile station.

7. The system as claimed in claim 1, wherein a relay mobile station comprises a storage means for maintaining a forwarding table to store values of logical addresses of the base station and neighboring mobile stations.

8. The system as claimed in claim 1, wherein the base station is capable of sending a signal to a relay mobile station using a first control message, wherein the first control message comprises downlink code usable by the mobile station to communicate with the relay mobile station.

9. The system as claimed in claim 1, wherein a relay mobile station is capable of sending a signal to the mobile station using a second control message, wherein the second control message comprises an uplink code and a time slot to be used by the mobile station in communication with the relay mobile station.

10. The system as claimed in claim 8, further comprising:

the relay mobile station de-multiplexing a received data stream comprising one or more of three coded signals, wherein;

a first coded signal is associated with data streaming from the base station and destined for the relay mobile station;

a second coded signal is associated with data streaming from the base station and destined for the mobile station; and

a third coded signal is associated with data streaming from the mobile station to the relay mobile station;

the relay mobile station re-transmitting the second coded, de-multiplexed signal on the next available up-link timeslot using the up-link code specified in the received first control message; and

the relay mobile station multiplexing the third coded, de-multiplexed signal with an up-link data stream originating from the relay mobile station itself, on the next available up-link time-slot using the up-link code of the relay mobile station.

11. The system as claimed in claim 1, wherein a relay mobile station maintains a forwarding table to store values of a logical address of the mobile station that it is serving.

12. The system as claimed in claim 1, wherein the mobile station is capable of distinguishing neighboring mobile stations of the same cell and neighboring mobile stations of adjacent cells by utilizing a variation in a scrambling code used in adjacent cells.

13. The system as claimed in claim 1, wherein the mobile station is capable of sending a signal from the mobile station to a relay mobile station for stopping multi-hop communication by sending a control message when the mobile station detects that the received signal strength (RSS) of the base station is greater than the threshold value.

14. The system as claimed in claim 1, wherein the mobile station is capable of monitoring, by using a timer, receipt of a control message from the base station within a specified amount of time.

15. The system as claimed in claim 1, wherein the candidate relay station information comprises a list of the neighboring mobile stations;

and the base station selects a relay mobile station from the list of neighboring mobile stations.

16. A method of radio communication using a TDD-CDMA multiple access system comprising:

measuring, at a mobile station, signal strength values of coded signals transmitted from neighboring mobile stations and a received signal strength of a signal from the base station;

sending candidate relay station information based on the measured signal strength values from the mobile station directly to the base station;

sending, if the received signal strength is below a threshold value, a request message from the mobile station directly to the base station in single hop communication for a switch from single hop to multi-hop communication between the mobile station and the base station; and

deciding, at the base station, whether or not to establish multi-hop communication with the mobile station upon receipt of said request and based on the candidate relay station information.

17. The method as claimed in claim 16, wherein each mobile station uses the same respective up-link and downlink communication timeslots in both single-hop and multi-hop communications.

18. The method as claimed in claim 16, wherein a relay mobile station utilizes the same respective up-link and down-link communication timeslots for both communications with the base station and communications with a relayed mobile station (MST), wherein different codes are used in the uplink and downlink directions for communicating with the base station and the relayed mobile station (MST).

19. The method as claimed in claim 16, wherein the measuring at the mobile station the signal strength values of coded signals transmitted from neighboring mobile stations comprises measuring the signal strength of coded signals from neighboring mobile stations received in the same time slot as communications received from the base station.

20. The method as claimed in claim 19, wherein the measuring at the mobile station further comprises scanning an entire frequency channel for one complete frame and measuring the signal strength of coded signals from neighboring mobile stations.

21. The method as claimed in claim 20, wherein the entire frequency channel is scanned if there exists no mobile station that can act as a relay mobile station whose up-link timeslot is the same as the assigned down-link timeslot of the measuring mobile station.

22. The method as claimed in claim 16, further comprising maintaining in a storage means of a relay mobile station a forwarding table to store values of logical addresses of the base station and neighboring mobile stations.

23. The method as claimed in claim 16, further comprising sending a signal from the base station to a relay mobile station using a first control message, wherein the first control message comprises downlink code usable by the mobile station to communicate with the relay mobile station.

24. The method as claimed in claim 16, further comprising sending a signal from a relay mobile station to the mobile station using a second control message, wherein the second control message comprises an uplink code and a time slot to be used by the mobile station in communication with the relay mobile station.

25. The method as claimed in claim 23, further comprising:

de-multiplexing at the relay mobile station a received data stream comprising one or more of three coded signals, wherein;

a first coded signal is associated with data streaming from the base station and destined for the relay mobile station;

a second coded signal is associated with data streaming from the base station and destined for the mobile station; and

a third coded signal is associated with data streaming from the mobile station to the relay mobile station;

re-transmitting at the relay mobile station the second coded, de-multiplexed signal on the next available up-link timeslot using the up-link code specified in the received first control message; and

multiplexing at the relay mobile station the third coded, de-multiplexed signal with an up-link data stream originating from the relay mobile station itself, on the next available up-link time-slot using the up-link code of the relay mobile station.

26. The method as claimed in claim 16, further comprising maintaining at a relay mobile station a forwarding table to store values of a logical address of the mobile station that it is serving.

27. The method as claimed in claim 16, further comprising distinguishing at the mobile station neighboring mobile stations of the same cell and neighboring mobile stations of adjacent cells by utilizing a variation in a scrambling code used in adjacent cells.

28. The method as claimed in claim 16, further comprising sending a signal from the mobile station to a relay mobile station for stopping multi-hop communication by sending a control message when the mobile station detects that the received signal strength (RSS) of the base station is greater than the threshold value.

29. The method as claimed in claim 16, further comprising monitoring at the mobile station, by using a timer, receipt of a control message from the base station within a specified amount of time.

30. The method as claimed in claim 16, wherein the candidate relay station information comprises a list of the neighboring mobile stations;

and the method further comprises selecting at the base station a relay mobile station from the list of neighboring mobile stations.