Abstract:

This paper, aiming at retransmission problem in cooperative communication, proposes a new hybrid ARQ scheme when two users cooperatively communicate with the base station (BS). By sending packets in time-sharing slots, each user stores packets transmitted by its partner last time. After receiving ACK/NACK, each user searches for packets needed to be retransmitted according to indications of the BS. These packets mixed with newly generated ones are then forwarded in the next time slot. This scheme, utilizing space diversity gain introduced by the cooperative communication system, greatly improves the performance of hybrid ARQ. We compared our cooperative system with another system where each user communicates with the BS independently. Through comparisons of throughput, PER, and average delay varying with SNR, we proved that our system could achieve higher throughput and lower PER in the same channel state while increasing the average delay during theoretical analysis and simulation.

Key words: cooperative communication, hybrid ARQ, throughput, maximal ratio combining(MRC)