Index and mode modulated orthogonal frequency division multiplexing with enhanced spectral efficiency

Abstract

Index modulation aided orthogonal frequency division multiplexing (OFDM-IM) is a potential multicarrier transmission technique for wireless data transmission systems due to its attractive error performance and energy efficiency. However, it fails to cope with increasing demand of high data rate in upcoming mobile data services, mainly, due to the lower spectral efficiency.In this communication, an efficient transmission technique, called index and mode modulation OFDM, is proposed that delivers additional information through permutations of multiple modes and indexed bits patterns resulting in higher spectral efficiency. For the proposed technique, a low complexity log-likelihood ratio detector with suitable algorithm is designed and its computational complexity has been analysed. The simulation results indicate improved performance of this newly proposed scheme in terms of spectral efficiency, bit error rate, as well as energy efficiency over other existing index modulated and multiple mode based OFDM schemes, while maintaining considerably low computational complexity in detection. That proclaims the scheme as a potential transmission technique to meet the data transmission challenges in 5G and beyond.

Generalized index and mode modulated OFDM with improved spectral and energy efficiency

“…4. Another noteworthy feature of GIMM-OFDM is its capability to outperform all of its five descendent schemes, classic OFDM, OFDM-IM, 8 Gen-OFDM-IM, 18 MM-OFDM-IM, 11 and IMM-OFDM 16 in terms of improved SE and EE, which has been established qualitatively and quantitatively in this article. 5.…”

“…16 This generalized scheme has come out as the unified model for classic OFDM, 17 OFDM-IM, 8 Generalized-OFDM-IM, 18 MM-OFDM-IM 11 and IMM-OFDM. 16 It signifies that simulation of this single generalized scheme with different design parameters (n, k, Q) is capable of providing characteristics of all those five schemes, which is a novel feature of this proposed model. Consequently, this parent scheme is capable enough of replacing individual models of those five descendent schemes.…”

“…7 However, in spite of the advantage of better EE, OFDM-IM suffers from lower SE than classic OFDM for higher order of modulation 10 because of partial subcarrier activation. In our previous work, we have proposed IMM-OFDM 16 scheme, in which the problem of poor SE due to partial subcarrier activation has been successfully resolved by combining mode modulation to index modulation in each OFDM symbol. Here mode modulation implies use of permutation and combinations of multiple non-overlapping customized constellations of same size and type, called modes, which constitute various unique mode patterns decided by incoming bits pattern.…”

“…Purely maximum likelihood (ML) detection process is avoided as it incurs excessively high metric computation complexity. 30,31 In our former scheme, IMM-OFDM, we had designed low complexity log-likelihood ratio (LLR) detector combined with maximum likelihood (ML) algorithm, 16 which was shown to provide same accuracy as that obtained from pure ML detector. Here, we have adopted the similar design with suitable upgradation for the extra task of detection of active subcarrier number in each subblock.…”

“…Novelty of this scheme is that this single scheme actually comes out to be a unified model of four benchmark OFDM schemes, classic OFDM, OFDM-IM, 8 Gen-OFDM-IM, 18 MM-OFDM-IM, 11 along with IMM-OFDM. 16 All of these five schemes can be derived from GIMM-OFDM as special cases with suitable choice of design parameters. Consequently, GIMM-OFDM can replace individual models of these five schemes.…”