Near-Capacity Transceiver Design Using Exit-Curve Fitting: Three-Stage Turbo Detection of Irregular Convolutional Coded Joint Sphere-Packing Modulation and Space-Time Coding

Conventional two-stage turbo-detected schemes typically suffer from a bit error rate (BER) floor, preventing them from achieving infinitesimally low BER values, especially, when the inner coding stage is of non-recursive nature. We circumvent this deficiency by proposing a three-stage turbo-detected sphere packing (SP) aided space-time block coding (STBC) STBC-SP scheme, where a rate-1 recursive inner precoder is employed to avoid having a BER floor. The convergence behaviour of this serially concatenated scheme is investigated with the aid of 3D extrinsic information transfer (EXIT) charts. Furthermore, the capacity of the STBC-SP scheme is shown and an algorithm is proposed for calculating a tighter upper bound on the maximum achievable bandwidth efficiency. The proposed three-stage turbo-detected scheme operates within about 1.0 dB of the capacity and within 0.5 dB of the maximum achievable bandwidth efficiency limit.