Turn Back the Clock: Time Reversal for Green Radio Communications

Abstract

International audienceIn 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

Generalized analysis of MU-MISO time reversal-based systems over correlated multipath channels with estimation error

“…Moreover, we can evaluate that (12) well approximates (10) even in the presence of correlation and CEE. These observations have validated the expression in (12).…”

“…We remark that the simulation results are obtained with the original expression (10), whereas the analytical results are achieved with the approximation (12).…”

“…The time reversal (TR) technique is one of the most popular forms of linear precoding, especially for ultra-wideband (UWB) systems over multipath channels. It is considered as a beamforming technique [2][3][4][5][6][7][8][9][10][11][12][13][14]. TR tightly focuses the energy of all the taps of the propagation channel, in the time and space domains at the intended terminals by utilizing the time-reversed of channel impulse response (CIR) to prefilter transmit signals.…”

“…The analysis conducted in [2,5,11] considers specific wideband channels where the average power of each tap decays exponentially. However, the applications of TR techniques can be completely extended to conventional broadband systems as shown in [11][12][13]. In fact, a channel with a narrower bandwidth has a smaller multipath delay spread [14].…”

On the use of time-reversal for packet switching in green communications

“…Thereby, TR has been identified as a promising technique for low-complexity and energy-efficient wireless communications [9]. TR benefits and limits have been evaluated over realistic multi-Radio Access Technologies (RAT) green scenarios in [10]. Results show that TR improves the energy-efficiency of the physical (PHY) layer owing to a reduction of the receive power required to ensure a given Bit Error Rate (BER).…”