Joint Hybrid ARQ and Iterative Space-Time Equalization for Coded Transmission over the MIMO-ISI Channel

This paper focuses on the problem of efficient packet combining techniques for coded systems with hybrid automatic repeat request (ARQ) protocols operating over the frequency selective fading multiple input multiple output (MIMO) channel. We introduce a receiver scheme where space-time soft equalization is integrated into the packet combiner. This allows to create at each transmission an additional set of virtual receive antennas, thereby increasing the diversity order of the system. We also propose a second packet combining scheme where equalization is performed separately for each transmission. Iterative channel estimation is also investigated, and a training scheme where the pilot symbols are not retransmitted is introduced. Block error rate (BLER) performance is investigated via computer simulations for both perfect and imprecise channel state information (CSI) at the receiver side for demonstrating the potential of integrated soft equalization-based packet combining for transmission over multipath MIMO channels.