Turn Back the Clock: Time Reversal for Green Radio Communications

In this article, time reversal (TR) signal processing techniques are studied and evaluated over novel realistic green use cases. The principles of TR are first explained and practical use cases for green communications are designed considering long-term evolution-advanced coordinated multipoint (LTE-A CoMP) transmission/reception, fast session transfer (FST) extensions, and multiradio access technology (multi-RAT) architectures foreseen as promising green networks. Related to the FST use case, a propagation analysis of mixed indoor and outdoor channels is carried out, and dedicated TR use cases are defined to identify the limitations and advantages of TR in a green radio context: frequency selectivity and bandwidth size influence, number of antennas, Doppler effect impact, antenna mismatch alignment, and synchronization problems. Such use cases are used to provide guidelines concerning the use of TR techniques. Some performance statistics are then given to stress the advantages of TR in a green radio communications context.