Fast Differential Unitary Space-Time Modulation Decoding for a MIMO Radio Channel

Improved decoding efficiency is achieved for differential unitaryspace-time modulation across a multiple-input multiple-output(MIMO) channel. The group nature of constellations used for signaltransmission, and hence a minimised search space for maximumlikelihood (ML) decoding are utilised to give this improvement. Aprocedure using lattice reduction for fast decoding across amultiple-input single-output (MISO) channel is generalised to aMIMO channel effectively, as a modification to a previousproposal, and used to generate the ML decoder search space.Further insight into the application of this algorithm is given.The decoding technique developed is shown to have very good errorperformance for reasonably sized MIMO channels.