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.
Highlights
In recent years, an exponential growth in demand for high data-rate transmission has shifted the focus in the orthogonal frequency division multiplexing (OFDM) scheme and its variants in the wireless communication system
The closed-form expressions for pairwise error probability (PEP) and average bit error probability (ABEP) have been derived over the proposed channel and validated using Monte Carlo simulation
The closed-form boundaries of spectral efficiency (SE) and EE for OFDM with index modulation (OFDM-index modulation (IM)) with the M-QAM modulation scheme have been examined in regards to active subcarriers (k), c and m channel parameters, and Signal to Noise Ratio (SNR)
Summary
An exponential growth in demand for high data-rate transmission has shifted the focus in the orthogonal frequency division multiplexing (OFDM) scheme and its variants in the wireless communication system. The BER of M-ary QAM and PSK modulations in OFDM-IM scheme has been derived with different power allocation policies over Nakagami-m fading channel, [9]. Several techniques have been introduced to improve the performance of an OFDM-IM based wireless communication systems over these fading channel conditions One of these techniques is adaptive modulation, which is employed to enhance spectral efficiency (SE) over wireless channels based on fading and shadowing [10]. The rest of this paper is arranged as follows: In Section 2, the system model of OFDM-IM, the performance analysis of OFDM-IM including pairwise error probability (PEP) and average bit error probability (ABEP) are presented over the composite fading and shadowing channel model.
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