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

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.