Iterative trellis search detection for asynchronous MIMO systems

The paper presents a reduced-complexity soft-input soft-output detection scheme for asynchronous space-time bit-interleaved coded modulation (ST-BICM) MIMO systems. This scheme is referred to as asynchronous iterative trellis search (A-ITS) detection. The A-ITS detector is based in part on a reduced-state approximation of the BCJR algorithm, and also uses a special type of bit mapping called multilevel mapping to reduce complexity for high-order QAM modulation schemes. The complexity per bit of the detector is linear in the number of transmit antennas and roughly independent of the signal constellation size. The paper presents error performance results generated from computer simulations of an asynchronous iterative ("turbo") MIMO receiver employing the A-ITS detector. It is demonstrated that allowing transmissions from different antennas to be asynchronous can result in considerable performance improvement compared to synchronous MIMO systems.