Generalized Dual-Mode Index Modulation Aided OFDM

Abstract

Abstract-Dual-mode index modulation aided orthogonal frequency division multiplexing (DM-OFDM) is recently proposed, where subcarriers are partitioned into OFDM subblocks, divided into two groups within each subblock, and modulated by two differentiable constellation alphabets. In DM-OFDM, additional bits can be transmitted through indices of subcarriers modulated by the same constellation alphabet. In this letter, generalized DM-OFDM (GDM-OFDM) is proposed, where the number of subcarriers modulated by the same constellation mode in each subblock is alterable. By applying such enhancement, the spectral efficiency can be improved at the cost of marginal performance loss. Moreover, since the BER performance of GDM-OFDM degrades at low signal-to-noise ratios (SNRs), an interleaving technique is employed to address this issue. At the receiver, a maximum-likelihood (ML) detector and a reduced-complexity log-likelihood ratio (LLR) detector are employed for demodulation. Simulation results demonstrate that the proposed GDM-OFDM is capable of enhancing the spectral efficiency compared with DM-OFDM at the cost of negligible performance loss, and the interleaved GDM-OFDM (IGDM-OFDM) can harvest on performance gain over GDM-OFDM.Index Terms-Orthogonal frequency division multiplexing (OFDM), index modulation, maximum likelihood detection, loglikelihood ratio based detection, interleaving technique.

Compressed-Sensing-Aided Space-Time Frequency Index Modulation

“…The most recent study by Wen et al [22] investigated OFDM relying on hybrid in-phase/quadrature-phase index modulation (OFDM-HIQ-IM), which allows transmission of more information bits for indexing in each subcarrier block and achieves better error performance than conventional OFDM-IM. Additionally, Mao et al [23] proposed a dual-mode OFDM technique for enhancing the attainable throughput of the conventional OFDM-IM for achieving an improved error performance. Additionally, OFDM-IM is also combined with MIMO techniques in [24] and [25], which are proposed as promising energy-efficient 5G wireless communications systems.…”

Set Partition Modulation

“…where D(X i → X j ) is the number of bits in error for the corresponding pairwise error event. Note that the upper-bound expression given in (19) is valid for all OFDM-SPM schemes.…”

“…where Γ is the set of nonzero diagonal elements of Z ij . Finally, an asymptotic expression for the BER of the OFDM-SPM variants can be obtained by substituting (21) into (19). As explained in the previous sections, OFDM-SPM codebooks can be designed in a way that the minimum Hamming distance between index symbols for the set partitions is equal to two.…”

Enhanced Subband Index Carrierless Amplitude and Phase Modulation in Visible Light Communications

“…This is in contrast to the conventional m-CAP which modulates its subbands with symbols drawn from a single constellation. The dual constellations, M A and M B , are such that M A ∩ M B = ∅ and M A ∪ M B = M, where M is the union or combination of constellations M A and M B [9,10]. Since M A and M B are non-overlapping constellations, this makes it possible to encode additional data bits on the positions/indices of the subbands on which the constellations are modulated.…”