Patent ID: 7760702

Claim:
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.