Effect of channel estimation error on performance of time reversal-UWB communication system and its compensation by pre-filter

Abstract

Time reversal (TR) technique is an effective and simple method for data transmission in extremely multipath indoor ultra-wideband (UWB) channels. Temporal focusing property supported by TR, mitigates the complexity of receiver by reducing the effective channel taps. In spite of its good performance in perfect channel state information (CSI), TR method is very sensitive to the channel estimation error. The effect of channel imperfection on TR technique is considered the study. At first, the bit error rate (BER) of the TR-UWB communication system under the assumptions of the simple matched filter (MF) receiver under the channel estimation errors is derived in closed-form. Then, based on optimal minimum mean square error (MMSE) estimator receiver, a pre-filter is calculated in closed-form to improve the performance of the TR-UWB system in an imperfect CSI scenario. Furthermore, in order to compare the results, similar calculation for pre-filter is carried out based on a simple MF receiver. Unfortunately, it was not possible for us to drive a closed-form solution for pre-filter in this case. To overcome this shortcoming, a two stage iteration-based algorithm is developed at transmitter to calculate a pre-filter in MF receiver. This improved algorithm causes the channel estimation error tends to zero in some steps for the TR-UWB system with MF. The initial value for this iteration-based improved algorithm is considered to be closed-form pre-filter where is calculated based on TR-UWB system with an optimal MMSE estimator. Finally, exhaustive simulations are done to demonstrate the performance advantage attained by the proposed algorithms.

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

“…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.…”

“…Due to the focalization property of TR, much research efforts have been put recently on the analysis of TR-based transmission [5][6][7][8][9][10][11]. Popovski et al [6] give approximate derivations of ISI and IUI for TR-UWB system.…”

“…Furthermore, in practice, the accuracy of the estimated channel plays an importance role in determining the performance of TR systems. Although the effects of CEE on TR have been studied in [8][9][10], there have been no works conducting the analysis for multi-user systems assuming imperfect CIR condition.…”

Robustness of Time Reversal versus All‐Rake Transceivers in Multiple Access Channels

“…Only recently, the impact of imperfect channel state information (CSI) on the performance of TR was experimentally investigated in the case of UWB signals in [34], and analytic expressions for BER evaluation in a TR-UWB system in presence of channel estimation errors were provided in [35], where an iterative algorithm to compensate for estimation errors was also proposed. The impact of a channel estimation error in a TR-UWB system was analyzed in terms of Bit Error Probability also in [36], focusing however only on BPSK modulation, and in [37], where an uncoordinated network of IR-UWB devices was considered.…”

Performance of ultra‐wideband time‐reversal systems under imperfect channel side information at the transmitter

“…However, the requirement of accurate channel state information at the transmitter (CSIT) impedes its adoption in practical systems. Although most of the research on TR-UWB systems assumes perfect knowledge of CSIT, some researchers have recently focused on TR-UWB under imperfections in channel estimation [1,2], and under time-varying environments [3].In this Letter, we study the effect of imperfect CSIT in TR-UWB systems that exploit channel reciprocity along with pilot transmissions from the receiver to estimate the channel response at the transmitter. Among multiple sources contributing to imperfections in CSIT, we consider two sources.…”