Sixty Years of Coherent Versus Non-Coherent Tradeoffs and the Road From 5G to Wireless Futures

Abstract

Sixty years of coherent versus non-coherent tradeoff as well as the twenty years of coherent versus non-coherent tradeoff in Multiple-Input Multiple-Output (MIMO) systems are surveyed. Furthermore, the advantages of adaptivity are discussed. More explicitly, in order to support the diverse communication requirements of different applications in a unified platform, the 5G New Radio (NR) offers unprecendented adaptivity, abeit at the cost of a substantial amount of signalling overhead that consumes both power and the valuable spectral resources. Striking a beneficial coherent versus non-coherent tradeoff is capable of reducing the pilot overheads of channel estimation, whilst relying on low-complexity detectors, especially in high-mobility scenarios. Furthermore, since energy-efficiency is of salient importance both in the operational and future networks, following the powerful Index Modulation (IM) pholosophy, we conceive a holistic adaptive pholosophy striking the most appropriate coherent/non-coherent, single-/multiple-antenna and diversity/multiplexing tradeoffs, where the number of RF chains, the Peak-to-Average Power Ratio (PAPR) of signal transmission and the maximum amount of interference tolerated by signal detection are all taken into account. We demonstrate that this intelligent tripple-fold adaptivity offers significant benefits in next-generation applications of mmWave and Terahertz solutions, in space-air-ground integrated networks, in full-duplex techniques and in other sophisticated channel coding assisted system designs, where powerful machine learning algorithms are expected to make autonomous decisions concerning the best mode of operation with minimal human intervention.

NC-OFDM-SPM: A Two-Dimensional Non-Coherent Modulation Scheme for Achieving the Coherent Performance of OFDM along with Sending an Additional Data-stream

“…From another side, regarding complexity reduction in current communication systems, one of the promising design solutions is the use of non-coherent structures; which unlike coherent systems do not require expensive and complex carrier recovery circuit [5]. In the literature, numerous OFDM-based non-coherent techniques have been developed.…”

Space-, Time- and Frequency-Domain Index Modulation for Next-Generation Wireless: A Unified Single-/Multi-Carrier and Single-/Multi-RF MIMO Framework

“…However, as the result of compromising the OFDM orthogonality, the receiver's signal detection complexity is increased and nonlinear distortion is inflicted. Moreover, the discrete Fourier transform spread-OFDM (DFT-S-OFDM), which is standardized in the 4G LTE and 5G NR uplink [6], [7], emulates single-carrier transmission that exhibits low PAPR. However, DFT-S-OFDM's rectangular TD pulse leads to a frequencydomain (FD) sinc function that has high side lobes.…”

Deep-Learning-Aided Joint Channel Estimation and Data Detection for Spatial Modulation

“…For coping with the dramatically increasing data traffic, novel transmission schemes are in urgent demand for improving the throughput while minimizing the deployment complexity. Among numerous cutting-edge techniques, spatial modulation (SM) [1][2][3][4][5][6][7] has constitute a promising next generation scheme for massive machine type communications (mMTC) [8][9][10], for TeraHertz communications [11] and for intelligent reconfigurable surfaces (IRS) [12][13][14].…”