Toward Ultra-Power-Efficient, Tbps Wireless Systems via Analogue Processing: Existing Approaches, Challenges and Way Forward

Exploiting ultra-wide bandwidths is a promising approach to achieve the terabits per second (Tbps) data rates required to unlock emerging mobile applications like mobile extended reality and holographic telepresence. However, conventional digital systems are unable to exploit such bandwidths efficiently. In particular, the power consumption of ultra-fast, high-precision digital-to-analogue and analogue-to-digital converters (DACs/ADCs) for ultra-wide bandwidths becomes impractical. At the same time, achieving ultra-fast digital signal processing becomes extremely challenging in terms of power consumption and processing latency due to the complexity of state-of-the-art processing algorithms (e.g., "soft" detection/decoding) and the fact that the increased sampling rates challenge the speed capabilities of modern digital processors. To overcome these bottlenecks, there is a need for signal processing solutions that can, ideally, avoid DACs/ADCs while minimizing both the power consumption and processing latency. One potential approach in this direction is to design digital systems that do not require DACs/ADCs and perform all the corresponding processing directly in the analogue domain. Despite existing attempts to develop individual components of the transceiver chain in the analogue domain, as we discuss in detail in this work, the feasibility of complete analogue processing in ultra-fast wireless systems is still an open research topic. In addition, existing analogue-based approaches have inferior spectrum utilization than digital approaches, partly due to their inability to exploit the recent advances in digital systems such as "soft" detection/decoding. In this context, we also discuss the challenges related to performing "soft" detection/decoding directly in the analogue domain, as has been recently proposed by the DigiLogue processing concept, and we show with a simple example that analogue-based "soft" detection/decoding is feasible and can achieve the same error performance as digital approaches with more than 37x power savings. In addition, we discuss several challenges related to the design of ultra-fast, fully analogue wireless receivers that can perform "soft" processing directly in the analogue domain and we suggest research directions to overcome these challenges.