Abstract
Index modulation (IM) is an attractive concept for next generation communication systems. However, as an emerging technique, there are still some challenges need to be tackled in this frontier. In this paper, we consider two aspects of IM, which are diversity and detection complexity. Specifically, we propose a linear precoding assisted index modulation (LPIM) scheme for orthogonal frequency division multiplexing (OFDM) systems. We commence by analyzing the diversity and coding gains of the proposed scheme. Moreover, a detailed codebook design criterion is proposed. Then, our LPIM codebook is designed based on the maximum diversity and coding gain criteria. In contrast to the signaling model of the existing full diversity precoder designed for OFDM, we introduce a modeling method to link the zero-valued IM symbols to the origin of a Lattice for implementing our full diversity precoder designed for OFDM-IM. Both analytical and computer simulation results are provided for characterizing the attainable performance of OFDM-LPIM, demonstrating that it is capable of achieving full diversity as well as an attractive coding gain. However, the maximum-likelihood (ML) detection complexity of OFDM-LPIM is excessive, hence a low-complexity generalized iterative residual check detector (GIRCD) is proposed, which is inspired by the existing sparse recovery algorithms. Finally, computer simulation results are provided for demonstrating that GIRCD can provide a beneficial trade-off between bit error ratio performance and complexity.
Highlights
I NDEX modulation (IM) is a compelling candidate for 5G wireless networks [1]–[3]
The bit error ratio (BER) performance of classical orthogonal frequency-division multiplexing (OFDM), conventional OFDM-IM, OFDM with dual-mode index modulation (OFDM-DM-IM), OFDM with coordinate interleaving aided index modulation (OFDM-CI-IM), OFDM with linear precoding (OFDM-LP), as well as our OFDM-linear precoding assisted index modulation (LPIM) system is compared in Fig. 3 (a) and Fig. 3 (b)
A generalized system model and an unified performance analysis of OFDM-IM systems have been offered, where the bit-to-symbol mapping rule has been modeled as a codebook
Summary
I NDEX modulation (IM) is a compelling candidate for 5G wireless networks [1]–[3]. Recently, orthogonal frequency-division multiplexing (OFDM) has been combined with IM (OFDM-IM) [4]–[6], where information is implicitly conveyed by the indices of the activated subcarriers and by the conventional amplitude-phase modulated (APM) symbols. Later in [15], a transmit diversity scheme, namely the coordinate interleaved orthogonal design [18], has been integrated to OFDM-IM systems to improve the BER performance. In [30], an optimal symbol interleaver, which relies on FD subcarrier grouping, was designed as a means of further increasing the coding gain of a precoded OFDM system. As a further advance in the field, Xia et al proposed cyclotomic lattices for modeling the full diversity codes in [24], yielding a generalized optimal design for the existing classical modulation constellations, such as QAM and phase-shift keying (PSK). It is demonstrated that the proposed OFDM-LPIM system is capable of achieving the maximum attainable diversity gain as well as coding gain, yielding a significant BER performance improvement. Based on (1), a designed precoding matrix U ∈ Cm×m is applied to xg, yielding
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