Adaptive OFDM-IM System Over Faded Shadowing Channel

Abstract

Spectral efficiency (SE) and energy efficiency (EE) play major roles in evaluating the quality of service (QoS) of a wireless communication system. Designing an efficient wireless communication system requires trade-off between these two parameters. Orthogonal frequency division multiplexing technique with Index Modulation (OFDM-IM) has been introduced in the literature to increase the SE compared to traditional OFDM. In this paper, an adaptive technique with OFDM-IM is introduced in an M-QAM based scheme to maintain a guaranteed level of average bit error probability (ABEP) with enhanced SE. It has been demonstrated that by adaptively varying the number of active subcarriers and modulation levels in M-QAM scheme, maximum EE can also be achieved for an acceptable ABEP. The closed-form expressions of ABEP and pairwise error probability (PEP) for OFDM-IM with M-ary QAM modulation are derived and examined over the composite Nakagami-m Gamma (NG) fading channel model using greedy detection (GD). In addition, the performance of adaptive OFDM-IM with M-QAM Modulation scheme is evaluated in terms of efficiency metrics, outage probability, and ABEP. The obtained results show that the adaptive scheme offers high potential for accomplishing significant improvement in SE and EE while maintaining acceptable ABEP even under severe channel impairment.