Layered steered space-time codes using multi-dimensional sphere packing modulation

Abstract

We present a novel multi-functional multiple-input multiple-output (MIMO) scheme, that combines the benefits of space-time codes (STC), of vertical Bell Labs layered space-time (V-BLAST) scheme as well as of beamforming. To further enhance the attainable system performance and to maximise the coding advantage of the proposed transmission scheme, the system is also combined with multi-dimensional sphere packing (SP) modulation. Additionally, we quantify the capacity of the proposed multi-functional MIMO aided multi-dimensional SP arrangement and propose a novel technique of computing an upper limit on the achievable bandwidth efficiency of the system based on extrinsic information transfer (EXIT) charts. Further system performance improvements can be attained by serially concatenating our proposed scheme with an outer code together with a unity-rate code (URC), where three different receiver structures are created by varying the iterative detection configuration of the constituent decoders/demappers. Moreover, the convergence behaviour of the proposed schemes is evaluated with the aid of EXIT charts. Explicitly, the three proposed systems are capable of operating within 0.9 dB, 0.6 dB and 0.4 dB of the maximum achievable rate limit. Additionally, the three stage assisted SP aided scheme is capable of outperforming its counterpart employing QPSK by 1 dB at a BER of 10-6.