SR-ARQ for MIMO OFDM Systems with Channel State Information Only at the Receiver

In this paper, we compare two selective-repeat automatic-repeat-request (SR-ARQ) protocols for spatial multiplexintiplexingg multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexed (OFDM) systems assuming perfect channel state information (CSI) only at the receiver. These two SR-ARQ protocols differ in the number of packets transmitted simultaneously. In one protocol, a single packet is transmitted on all subcarriers from all antennae at the same time. In the other protocol, multiple packets are simultaneously transmitted. For the latter protocol, we also consider schemes that differ in the way that the subcarriers transmitted from different antennae are grouped to support the transmission of multiple packets in parallel. We compare the throughput and the resequencing delay of these SR-ARQ protocols in a frequency selective fading channel. Simulation results suggest that in such a system, the single ARQ protocol is the best choice. If we have to transmit multiple packets in parallel, each packet should be transmitted over a subband of adjacent subcarriers emitted from all transmit antennae.