(Received: 3-Feb.-2020, Revised: 22-Apr.-2020 , Accepted: 7-May-2020)
This paper proposes a new full-rate space-time block code for MIMO systems at four transmit antennas, which aims at minimizing the bit error rate with low-complexity decoding using ZF and MMSE linear detection techniques in Rayleigh fading channels. The purpose of this code is to optimize the space-time resources offered by MIMO systems and to ensure optimal exploitation of spectral resources. The idea is to take advantage of the direct sequence spread spectrum (DSSS) technique using the orthogonal codes of Walsh-Hadamard in order to ensure the orthogonality between all the symbol vectors to be transmitted and to construct an orthogonal and full-rate STBC code. BER performance versus Eb/No of the proposed STBC code is evaluated for MIMO 4×2, 4×4 and MISO 4×1 configurations in single-user detection mode, using 16QAM modulation, on Rayleigh's MIMO channels assumed to be quasi-static and not frequency selective, compared with those of the orthogonal STBC of Tarokh of 1/2 rate and the full-rate quasi-orthogonal STBC of Jafarkhani. The results of the simulations show that the proposed STBC code significantly improves BER performance while allowing a higher transmission rate with spectral efficiency of 4 bits/s/Hz and simple linear decoding using ZF or MMSE techniques.

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