Time reversal beamforming in MISO-UWB channels

Multiple-Input Single-Output (MISO) Ultra Wide Band (UWB) communications over a multipath channel is investigated. After introducing a tractable discrete-time multipath MISO channel model accounting for correlation between multiple channels, analytical results for single-user transmissions are drawn in the following two cases: no precoding at transmitter with All-Rake receiver vs. time reversal (TR) at transmitter with One-finger Rake receiver. Channel state information at both transmitter (CSIT) and receiver (CSIR) is assumed. Optimality of TR conditioned on One-finger Rake receiver structure is proved. Robustness brought by TR combined with One-finger Rake with respect to lack of correlation between channels vs. no precoding is shown. Simulations with realistic reference channels show that combining time reversal with multiple transmit antennas amplifies the performance improvement due to each technique when used alone.