Low-Complexity Detection for Multiple-Mode OFDM with Index Modulation

Abstract

Multiple-mode orthogonal frequency division multiplexing with index modulation (MM-OFDM-IM) is a recently proposed multicarrier transmission technique, which transmits distinguishable constellations (modes) according to their full permutations. For an uncoded system, the maximum-likelihood (ML) detector achieves the optimal performance, but its computational complexity is extremely high due to a large number of symbol modes. Existing low-complexity detectors may output an illegal mode permutation, which leads to catastrophic errors in the demodulation. redIt is well known that sphere decoding algorithms can reduce the computational complexity effectively and achieve near-ML bit error rate (BER) performance. In this paper, employing a sphere-decoding-like algorithm, we propose a novel detector, which can achieve near-ML performance with considerably low computational complexity. For coded MM-OFDM-IM systems, we propose a simplified log-likelihood ratio (LLR) calculation algorithm to achieve near-optimal coded BER performance with considerably low computational complexity. Computer simulation and numerical results demonstrate that the proposed detectors can achieve outstanding performance at the cost of low computational complexity.