Non-orthogonal space-frequency block codes from cyclic codes for wireless systems employing MIMO-OFDM with index modulation

摘要

Space-frequency codes (SFC) having error correcting structure can be used to enhance the bit error rate (BER) performance of modern wireless systems (5G and beyond) employing multiple-input multiple-output (MIMO) and multi-carrier communication. In this work, the construction of non-orthogonal space-frequency block codes (NSFBC) from (n, k) cyclic codes has been proposed. In which, n represents the number of symbols in the codeword and k represents the number of symbols in the information sequence. The performance of proposed codes has been evaluated in MIMO systems employing orthogonal frequency division multiplexing and index modulation (MIMO-OFDM-IM). We initially obtained (n, k) full rank cyclic codes for any 1 k left perpendicular n/m right perpendicular using Galois field Fourier transform (GFFT) description of (n, k) cyclic codes over F-qm. Further, NSFBCs are obtained from full rank codes using Rank preserving maps. In a 2 x 2 system and a 10-path MIMO channel, the proposed full rank NSFBC with rank-preserving IM mapping (FR-NSFBC-IM), over F-52, provides he similar BER performance when compared to MIMO-OFDM-IM system with Rate-1 Alamouti code and QPSK. Moreover, it provides an improvement in spectral efficiency of about 0.9 b/s/Hz. When compared to the MIMO-OFDM-IM with BPSK, FR-NSFBC-IM codes over F-52 provide an asymptotic SNR gain of about 1 dB and also the spectral efficiency has been improved by about 0.6 b/s/Hz. In the 4 x 4 scenario, full rank NSFBCs over F-54 with rank deficient IM mapping (RD-NSFBC-IM) provide an improvement in spectral efficiency of about 1.3 b/s/Hz. However, BER performance is similar to that of MIMO-OFDM-IM with BPSK. (C) 2019 Elsevier B.V. All rights reserved.