Automatic repeat request (ARQ) protocol for a multihop cooperative relay communication network

• US 7,760,702 B2
• Filed: 08/29/2008
• Issued: 07/20/2010
• Est. Priority Date: 08/29/2008
• Status: Active Grant

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ramachandran, Shyamal, Deng, Shi-Qiang, Sartori, Philippe J.
• Primary Examiner(s): Nguyen, Hanh
• Assistant Examiner(s): LIU, JUNG-JEN
• Application Number:
  US12/202,149
• Publication Number:
  US 20100054137A1
• Time in Patent Office: 690 Days
• Field of Search: 370/315, 370/351, 370/390, 714/746, 714/748, 714/798, 714/799
• US Class Current: 370/351
• 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: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal
• CPC Class Codes: H04L 1/1829 Arrangements specially adapted for the receiver end
• CPC Class Codes: H04L 1/1867 Arrangements specially adapted for the transmitter end
• CPC Class Codes: H04L 2001/0097 Relays

Abstract

A method is provided for confirming whether a data unit transmitted from a base station (BS) was successfully relayed to a subscriber station via one of a plurality of relay stations in a multihop cooperative relay network. Selected ones of the relay stations are designated as: a front-linked relay station designed to only transmit a negative acknowledgement message to the BS upon receiving a data unit from the BS that is unable to be decoded and not to transmit an acknowledgement message upon receiving a data unit from the BS that is able to be decoded, and a back-linked relay station designed to only transmit a acknowledgement message to the BS upon receiving the data unit from the BS that is able to be decoded and not to transmit a negative acknowledgement message to the BS upon receiving a data unit from the BS that is unable to be decoded.

Claims

1. A method for confirming whether a data unit transmitted from a source base station was successfully relayed to a destination subscriber station via one of a plurality of relay stations in a multihop cooperative relay network, the method comprising:

designating selected ones of a plurality of relay stations as;

a front-linked relay station designed to only transmit a negative acknowledgement message (R-NACK) to the base station upon receiving the data unit from the base station that is unable to be decoded and not to transmit an acknowledgement message upon receiving the data unit from the base station that is able to be decoded; and

a back-linked relay station designed to only transmit a acknowledgement message (R-ACK) to the base station upon receiving the data unit from the base station that is able to be decoded and not to transmit a negative acknowledgement (NACK) message to the base station upon receiving the data unit from the base station that is unable to be decoded;

transmitting, from the base station, the data unit to a plurality of relay stations;

determining, at the base station, whether a new negative acknowledgement (R-NACK) message was received from the front-linked relay station;

determining, at the base station, whether the base station has ever received an acknowledgment message (R-ACK) message from the back-linked relay station when the base station receives the new negative acknowledgement (R-NACK) message from the front-linked relay station; and

retransmitting the data unit from the base station to all relays stations in the multicast communication group when the base station determines that it has not ever received an acknowledgment message (R-ACK) message from the back-linked relay station.

2. A method according to claim 1, wherein the step of designating selected ones of a plurality of relay stations further comprises:

designating one of a plurality of relay stations as a mean-linked relay station that is designed to retransmit an acknowledgement message (M-ACK) to the base station upon receiving an acknowledgement message (M-ACK) from the subscriber station and to retransmit a negative acknowledgement (M-NACK) message to the base station upon receiving a negative acknowledgement (M-NACK) message from the subscriber station;

and further comprising;

determining, at the base station, whether the base station has received a new acknowledgment message (R-ACK) message from the back-linked relay station when the base station has not received a new negative acknowledgement (R-NACK) message from the front-linked relay station;

determining, at the base station, whether the base station determines has received a new negative acknowledgment (M-NACK) message from the mean-linked relay station when the base station determines that it has not received a new acknowledgment message (R-ACK) message from the back-linked relay station;

determining, at the base station, whether an acknowledgment message (R-ACK) message was ever received from the back-linked relay station when the base station determines that the base station has received a new negative acknowledgment (M-NACK) message from the mean-linked relay station; and

sending a resend command message from the base station to each of the relay stations in the multicast communication group when the base station determines that an acknowledgment message (R-ACK) message was ever received from the back-linked relay station, wherein the resend command message commands the recipient relay stations to resend the data unit to the subscriber station.

3. A method according to claim 2, further comprising:

determining, at the base station, whether the base station received an acknowledgment message (M-ACK) from the mean-linked relay station when the base station determines that the base station has not received a new negative acknowledgment (M-NACK) message from the mean-linked relay station; and

sending a success message from the base station to all relay stations in the multicast communication group when the base station determines that the base station has received an acknowledgment message (M-ACK) from the mean-linked relay station, wherein the success message indicates to the relay stations in the multicast communication group that the data unit was successfully transmitted to the subscriber station.

4. A method according to claim 2, further comprising:

resending the data unit from the base station to all relay stations in the multicast communication group when the base station determines that an acknowledgment message (R-ACK) message was never received from the back-linked relay station.

5. A method according to claim 2, further comprising:

setting, at the base station, an indicator which indicates that the new acknowledgment message (R-ACK) message from the back-linked relay station was received when the base station has received the new acknowledgment message (R-ACK) message from the back-linked relay station.

6. A method according to claim 2, further comprising:

determining, at the front-linked relay station, whether a resend command message was received from the base station that indicates that the data unit is to be resent by the front-linked relay station when the data unit was not received at the front-linked relay station; and

determining, at the front-linked relay station, whether an indicator is set at the front-linked relay station that indicates that the front-linked relay station has successfully decoded the data unit;

resending the data unit from the front-linked relay station to the subscriber station when the resend command message was received from at the front-linked relay station and the indicator that indicates that the front-linked relay station has successfully decoded the data unit.

7. A method according to claim 6, further comprising:

determining, at the front-linked relay station, whether the success message was received from the base station, wherein the success message indicates that the data unit was successfully transmitted to the subscriber station.

8. A method according to claim 6, further comprising:

determining, at the front-linked relay station, whether a data unit was received from the base station;

determining, at the front-linked relay station, whether the front-linked relay station was able to decode the data unit;

setting, at the front-linked relay station, an indicator that indicates that the front-linked relay station has successfully decoded the data unit;

sending a negative acknowledgment (R-NACK) message from the front-linked relay station to the base station to indicate that the front-linked relay station could not decode the data unit; and

relaying the data unit from the front-linked relay station to the subscriber station when the front-linked relay station was able to decode the data unit received at the front-linked relay station.

9. A method according to claim 2, further comprising:

determining, at the back-linked relay station, whether a resend command message was received from the base station that indicates that the data unit is to be resent by the back-linked relay station when the data unit was not received at the back-linked relay station;

determining, at the back-linked relay station, whether an indicator is set at the back-linked relay station that indicates that the back-linked relay station has successfully decoded the data unit; and

resending the data unit from the back-linked relay station to the subscriber station when the resend command message was received at the back-linked relay station and the indicator that indicates that the back-linked relay station has successfully decoded the data unit.

10. A method according to claim 9, further comprising:

determining, at the back-linked relay station, whether the success message was received from the base station when the resend command message was not received at the back-linked relay station, wherein the success message indicates that the data unit was successfully transmitted to the subscriber station.

11. A method according to claim 9, further comprising:

determining, at the back-linked relay station, whether a data unit was received from the base station;

determining, at the back-linked relay station, whether the back-linked relay station was able to decode the data unit;

sending an acknowledgment (R-ACK) message from the back-linked relay station to the base station to indicate that the back-linked relay station was able to decode the data unit;

setting, at the back-linked relay station, an indicator that indicates that the back-linked relay station has successfully decoded the data unit; and

relaying the data unit from the back-linked relay station to the subscriber station when the back-linked relay station was able to decode the data unit received at the back-linked relay station.

12. A method according to claim 2, further comprising:

determining, at the mean-linked relay station, whether a resend command message was received from the base station that indicates that the data unit is to be resent by the mean-linked relay station when the data unit was not received at the mean-linked relay station;

determining, at the mean-linked relay station, whether an indicator is set at the mean-linked relay station that indicates that the mean-linked relay station has successfully decoded the data unit; and

resending the data unit from the mean-linked relay station to the subscriber station when the resend command message was received from at the mean-linked relay station and the indicator that indicates that the mean-linked relay station has successfully decoded the data unit.

13. A method according to claim 12, further comprising:

determining, at the mean-linked relay station, whether the success message was received from the base station when the mean-linked relay station determines that at least one of an acknowledgement (ACK) message and a negative acknowledgment (NACK) message was not received from the subscriber station at the mean-linked relay station, wherein the success message indicates that the data unit was successfully transmitted to the subscriber station.

14. A method according to claim 12, further comprising:

determining, at the mean-linked relay station, whether one of an acknowledgement (ACK) message and a negative acknowledgment (NACK) message was received from the subscriber station when the resend command message was not received at the mean-linked relay station; and

forwarding, from the mean-linked relay station to the base station, the one of an acknowledgement (ACK) message and a negative acknowledgment (NACK) message that was received from the subscriber station.

15. A method according to claim 12, further comprising:

determining, at the mean-linked relay station, whether a data unit was received from the base station;

determining, at the mean-linked relay station, whether the mean-linked relay station was able to decode the data unit;

setting, at the mean-linked relay station, an indicator that indicates that the mean-linked relay station has successfully decoded the data unit; and

relaying the data unit from the mean-linked relay station to the subscriber station when the mean-linked relay station was able to decode the data unit.

16. A method according to claim 2, wherein any relay station that is not designated as being one of the front-linked relay station, the back-linked relay station, and the mean-linked relay station is a non-designated relay station, and further comprising:

determining, at the non-designated relay station, whether a data unit was received from the base station;

determining, at the non-designated relay station, whether the non-designated relay station was able to decode the data unit;

setting, at the non-designated relay station, an indicator that indicates that the non-designated relay station has successfully decoded the data unit;

relaying the data unit from the non-designated relay station to the subscriber station when the non-designated relay station was able to decode the data unit;

determining, at the non-designated relay station, whether a resend command message was received from the base station that indicates that the data unit is to be resent by the non-designated relay station when the data unit was not received at the non-designated relay station;

determining, at the non-designated relay station, whether an indicator is set in at the non-designated relay station that indicates that the non-designated relay station has successfully decoded the data unit;

resending the data unit from the non-designated relay station to the subscriber station when the resend command message was received from the non-designated relay station and the indicator that indicates that the non-designated relay station has successfully decoded the data unit; and

determining, at the non-designated relay station, whether the success message was received from the base station when the non-designated relay station determines that the resend command message was not received at the non-designated relay station, wherein the success message indicates that the data unit was successfully transmitted to the subscriber station.

17. A method according to claim 1, wherein each relay station communicates with the base station over a front link between that relay station and the base station, and wherein each relay station communicates with the subscriber station over a back link between that relay station and the subscriber station, and wherein the step of designating selected ones of a plurality of relay stations, comprises:

measuring, at each of the plurality of relay stations, a back link metric of a back link to the subscriber station, determining whether the measured back link metric is above a first threshold (T1), and reporting the measured back link metric to the base station when the measured back link metric is above the first threshold (T1);

receiving, at the base station, the measured back link metrics from each of the relay station for which the measured back link metric exceeds the first threshold (T1) and adding those relay stations to a multicast candidate group (MCG);

measuring, at the base station, a front link metric of a front link to each relay station in the multicast candidate group (MCG), determining which of the measured front link metrics are below a second threshold (T2), and removing any relay stations having measured front link metrics below the second threshold (T2) from the MCG; and

determining, at the base station based on the measured back link metrics and the measured front link metrics for each relay station that remains in the MCG, selected ones of the relay stations that remain in the MCG that are to be designated as the front-linked relay station, the back-linked relay station.

18. A method according to claim 17, wherein the step of determining, at the base station based on the measured back link metrics and the measured front link metrics for each relay station that remains in the MCG, selected ones of the relay stations that remain in the MCG that are to be designated as the front-linked relay station, the back-linked relay station, comprises:

determining, at the base station, which one of the relay stations remaining in the multicast communication group has the highest measured front link metric, which one of the relay stations remaining in the multicast communication group has the highest measured back link metric, and which one of the relay stations remaining in the multicast communication group has the highest average of the measured front link metric and the measured back link metric; and

designating, at the base station, the one of the relay stations having the highest measured front link metric as the front-linked relay station, the one of the relay stations having the highest measured back link metric as the back-linked relay station, and the one of the relay stations having the highest average of the measured front link metric and the measured back link metric as the mean-linked relay station.

19. A method according to claim 17, wherein the each of the front link metrics comprise a front link capacity metric.

20. A method according to claim 17, wherein the each of the front link metrics comprise a front link quality metric.

21. A method according to claim 17, wherein the each of the front link metrics comprise a combination of a front link capacity metric and a front link quality metric.

22. A method according to claim 17, wherein the each of the back link metrics comprise a back link capacity metric.

23. A method according to claim 17, wherein the each of the back link metrics comprise a back link quality metric.

24. A method according to claim 17, wherein the each of the back link metrics comprise a combination of a back link capacity metric and a back link quality metric.

25. A method according to claim 1, wherein each relay station communicates with the base station over a front link between that relay station and the base station, and wherein each relay station communicates with the subscriber station over a back link between that relay station and the subscriber station, and wherein the step of designating selected ones of a plurality of relay stations, comprises:

determining a first group of relay stations having front link metrics that exceed a first threshold, and pseudo-randomly designating a selected one of the first group of relay stations as the front-linked relay station; and

determining a second group of relay stations having back link metrics that exceed a second threshold, and pseudo-randomly designating a selected one of the second group of relay stations as the back-linked relay station.

26. A method according to claim 25, further comprising:

pseudo-randomly designating a selected one of the first group of relay stations and the second group of relay stations as a mean-linked relay station.

27. A method according to claim 25, wherein the each of the front link metrics comprise a front link capacity metric.

28. A method according to claim 25, wherein the each of the front link metrics comprise a front link quality metric.

29. A method according to claim 25, wherein the each of the front link metrics comprise a combination of a front link capacity metric and a front link quality metric.

30. A method according to claim 25, wherein the each of the back link metrics comprise a back link capacity metric.

31. A method according to claim 25, wherein the each of the back link metrics comprise a back link quality metric.

32. A method according to claim 25, wherein the each of the back link metrics comprise a combination of a back link capacity metric and a back link quality metric.

33. A method according to claim 1, wherein each relay station communicates with the base station over a front link between that relay station and the base station, and wherein each relay station communicates with the subscriber station over a back link between that relay station and the subscriber station, and wherein the step of designating selected ones of a plurality of relay stations, comprises:

providing the base station with a front link metric associated with each of the relay stations;

determining, at the base station based on the front link metrics associated with each of the relay stations, which relay station has a highest front link metric with the base station;

designating the one of the relay stations that has the highest front link metric with the base station as the front-linked relay station; and

providing the base station with a back link metric associated with each of the relay stations;

determining, at the base station based on the back link metrics associated with each of the relay stations, which relay station has a highest back link metric with the subscriber station; and

designating the one of the relay stations that has the highest back link metric as the back-linked relay station.

34. A method according to claim 33, further comprising:

determining, at the base station, a mean link metric for each of the relay stations, wherein the mean link metric for each relay station is determined based on a front link metric associated with that relay station and a back link metric associated with that relay station; and

determining, at the base station, which relay station has a highest mean link metric; and

designating the one of the relay stations that has the highest mean link metric as a mean-linked relay station.