A New Design Of Unitary Space-Time Constellation

Space-time coding is a burgeoning techonology on channel coding in wireless communication.Unitary Space-Time Modulation(USTM) is a branch of Space-Time coding.It aims at the situation which is receiver noncoherent. One method for communication with multiple antennas is to encode the transmitted data differentially using unitary matrices at the transmitter, and to decode differentially without knowing the channel coefficients at the receiver.That is what we called Differential Unitary Space-Time Modulation (DUSTM).Considering the design of Unitary space-time constellation has some restriction in number of transmitted antennas and performa less well in low and moderate SNR,We study a lot of previous work on design of Unitary space-time constelltion ,and introduce a a new design criterion and a new class of unitary signal constellations for differential space-time modulation for MIMO Systems over Rayleigh flat fading .The design of the new codes is accomplished in a systematic way through the optimization of a performance index that closely describes the bit-error rate as a function of SNR.The new performance index is computationally simple and we can use analytical expressions for its gradient with respect to constellation parameters.We continue there research ,and get a constellation. It is shown in simulation results that our code outperforms approximate 2dB better than previous work at bit error rate 10?4 .Further more, we combine the Unitary Space-time Constellation we obtained with turbo code,and amend the metric quation in [41] to adapt to our scheme.Simulation shows that our scheme just requires 9.4dB at bit error rate 10^-5 .We also propose a new coded modulation scheme which combined CT-TCM with DUST.Theoretical analysis shows that this scheme can perform well with higher spectral efficiency than Turbo-DUST and lower complexity than both Turbo-DUST and TTCM-DUST.