Distributed Space Time Coding for Bit-Interleaved Coded Modulation in Two-Way Relaying Communications

This paper proposes a design of distributed spacetime coding (DSTC) for the multiple access (MA) phase of a two-way relaying communication system. Bit-interleaved coded modulation (BICM) is used by the two terminal nodes and decoding based on the quaternary code representation is adopted at the relay. Based on an upper bound of the error probability, the impact of DSTC on the error performance is analyzed by considering three error types in the MA phase. Specifically, it is shown that type-3 errors need to be carefully taken into account in the design of a DSTC scheme. By developing a performance metric related to type-3 errors, a single parameter can be searched and its optimal value is obtained. To corroborate the analysis and optimization, simulation results are provided to show the advantage of the proposed DSTC scheme over other schemes under both Rayleigh and Rician fading channels.