1 research outputs found
Equalized Time Reversal Beamforming for Indoor Wireless Communications
Time-reversal (TR) is a beamforming technique for frequency-selective
channels, which has received increasing attention due to its high energy
efficiency and low computational complexity for wireless communications. In
this paper, we present two contributions on time-reversal (TR) wireless
beamforming for single-user indoor wideband MISO systems. First, we provide
novel analyses of a baseband TR system using two commonly used indoor
propagation channel models. We derive closed-form approximations for the
inter-symbol interference (ISI) with these channel models in order to
characterize the influence of propagation conditions (such as the power-delay
profile, delay spread, and bandwidth) on TR performance metrics. In particular,
we analyze spatial focusing and time compression performance of TR beamforming,
and their impact on the bit error rate (BER). As a second contribution, we
introduce an equalized TR (ETR) technique that mitigates the ISI of
conventional TR. The proposed ETR utilizes a zero-forcing pre-equalizer at the
transmitter in a cascade configuration with the TR pre-filter. Unlike previous
approaches to ISI mitigation in TR systems, we derive theoretical performance
bounds for ETR and show that it greatly enhances the BER performance of
conventional TR with minimal impact to its beamforming capabilities. By means
of numerical simulations, we verify our closed-form approximations and show
that the proposed ETR technique outperforms conventional TR with respect to the
BER under any SNR.Comment: 30 pages, 8 figure