Differential Space-Time Spreading Using Four Transmit Antennas and Iteratively Detected Sphere Packing Modulation

This paper presents a novel differentially encoded space-time spreading (DSTS) scheme using four transmit antennas that can be readily combined with PSK, QAM, as well as sphere packing (SP) modulation schemes. The advocated SP-aided system has simple encoding and decoding algorithms that requires no channel knowledge and outperforms the DSTS dispensing with SP. Further improvement to the system performance can be obtained by serially concatenated convolutional coding and then performing SP-symbol-to-bit demapping as well as channel decoding iteratively. Explicitly, the proposed turbo-detected DSTS-SP scheme exhibits an E_b/N₀ gain of 18 dB at a bit error rate (BER) of 10^-5 over an uncoded identical-throughput system and an E_b/N₀ gain of 2 dB over an equivalent 1 bits/symbol effective throughput QPSK-modulated turbo-detected DSTS scheme dispensing with SP