Back to Single-Carrier for Beyond-5G Communications above 90GHz ? ? Novel Index Modulation techniques for low-power Wireless Terabits system in sub-THz bands ?

Wireless Terabits per second (Tbps) link is needed for the new emerging data-hungry applications in Beyond 5G (B5G) (e.g., high capacity broadband, enhanced hotspot, 3D extended reality, etc.). The sub-GHz bands are scarce and overused, while the considered millimeter Wave bands in 5G are insufficient to reach the desired ultra-high throughput. Thus, the sub-THz/THz bands are envisaged as the next frontier for B5G wireless communication. Even though a wider bandwidth and large-scale MIMO are envisioned at sub-THz bands, but the system and waveform design should consider the channel characteristics, technological limitations, and high RF impairments. Based on these challenges, we proposed to use an energy-efficient low order single carrier modulation accompanied by spectral-efficient Index Modulation (IM) with advanced MIMO techniques In the first part of this thesis, the spectral-efficient MIMO Spatial Multiplexing (SMX) and Generalized Spatial Modulation (GSM that generalizes several spatial IM schemes, are studied in the sub-THz environment. In particular, the high spatial correlation effect on GSM system is tackled by proposing two relevant techniques, and an optimal detector offering a 99% computational complexity reduction is proposed for each scheme. Besides, we proposed dual-polarized (DP)-GSM that provides higher spectral efficiency (SE) via multi-dimensional IM. In the second part, we proposed a novel IM domain, called filter IM domain, that generalizes most existing SISO IM schemes. In this new IM domain, we proposed two novel schemes: Filter Shapes IM (FSIM) and Quadrature FSIM (IQ-FSIM), to enhance system SE and energy efficiency (EE) while providing other critical advantages for sub-THz systems. In addition, their optimal low complexity detectors and their specialized equalization techniques are designed. Striving for further SE and EE improvement, this proposed IM domain is exploited in the MIMO context. Besides, we theoretically characterized the performance of all the three proposed systems in the novel IM domain and DP-GSM scheme of the first part. To conclude, the proposed SMX-FSIM is compared in the sub-THz environment to the previously considered candidates. The results confirm that SMX with FSIM based scheme is the most promising solution for a low-power wireless Tbps B5G system due to its high SE/EE, robustness to RF impairments, low power consumption, and low complexity/cost with a simple linear receiver. Finally, the challenging filter bank design problem imposed by the filter IM domain is tackled by optimization approach to achieve better results.