Double Walsh-Hadamard Transform for Improved Efficiency in OFDM-IM

Amidst the rapidly evolving landscape of B5G/6G wireless networks, the emergence of index modulation has marked a significant development, and one key technique gaining ground is orthogonal frequency division multiplexing-index modulation (OFDM-IM), which boosts both communication and signal transmission spectral efficiency. Although OFDM-IM is an innovative multicarrier modulation technique that builds on the conventional OFDM system. It still confronts a significant challenge related to the High Power Amplifier (HPA) cost, which arises from the distortion that OFDM-IM signals cause when passing through nonlinear devices. This distortion is driven by the considerable Peak-to-Average Power Ratio (PAPR) that characterizes the OFDM-IM signal. In this paper, we propose a novel waveform named Double WHT-OFDM-IM, which combines Double Walsh-Hadamard Transform (WHT) with orthogonal frequency division multiplexing-index modulation (OFDM-IM) to improve the system performance and combat the enormous PAPR of WHT-OFDM-IM in the low number of activated subcarriers scenarios. The proposed approach satisfies the demanding criteria of 6th-generation (6G) and beyond communication schemes, specifically with regard to low peak-to-average power ratio (PAPR), and low bit-error rate (BER).