Near-Optimal Waveform Design for Sum Rate Optimization in Time-Reversal Multiuser Downlink Systems

Abstract

Abstract-Utilizing channel reciprocity, the traditional timereversal technique boosts the signal-to-noise ratio at the receiver with very low transmitter complexity. However, the large delay spread gives rise to severe inter-symbol interference (ISI) when the data rate is high, and the achievable transmission rate is further degraded in the multiuser downlink due to the interuser interference (IUI). In this work, we study the weighted sum rate optimization problem by means of waveform design in the time-reversal multiuser downlink where the receiver processing is based on a single sample. Power allocation has a significant impact on the waveform design problem. We propose a new power allocation algorithm named Iterative SINR Waterfilling, which is able to achieve comparable sum rate performance to that of globally optimal power allocation.

Time-Reversal Wireless Paradigm for Green Internet of Things: An Overview

“…A system-level theoretical investigation and comprehensive performance analysis of a TR-based multiuser communication system was conducted in [25], where the concept of TRDMA was proposed. To improve the performance of the TRDMA systems, interference suppression through waveform design [27], [49] and interference cancelation [50] are proposed. The implementation complexity issue is studied in [26], [51], and [52].…”

“…Therefore, beamforming approaches, such as singular value decomposition (SVD), zero forcing (ZF), and minimal mean square error (MMSE), can be analogously employed in waveform design. In the literature, there have been many studies investigating the problems of designing advanced waveforms to suppress the interference [27], [46], [71]- [76]. If the basic TR waveforms are adopted, i.e., , then the intended signal power for each user is maximized but without considering the interference caused by other symbols.…”

“…Thus, the resulting SNR can be very low and causes severe performance degradation especially when the transmit power is relatively low. In [27], it has been shown that well-designed waveforms can strike a balance between enhancing the intended signal power and suppressing the interference power.…”

“…Fig. 16 shows the BER performance for a single user TR system when using different waveforms, including basic TR waveform, the waveform design in [27], and the joint waveform design and interference pre-cancelation in [49]. It can be seen that when , the ISI is so severe that the BER curve of the basic TR waveform starts to saturate at even middle SNR, which is unacceptable.…”

“…Note that the achievable rate can still be very high when the bandwidth is wide enough as shown in [26]. In addition, the TR system can easily support heterogeneous terminal devices by providing various QoS options through adjusting the waveform and backoff factor [25], [27]. Finally, the unique location-specific signature in TR system can provide additional physical-layer security and thus can enhance the privacy and security of customers in IoT [24].…”