Spatiotemporal Focusing of Phase Compensation and Time Reversal in Ultrawideband Systems With Limited Rate Feedback

We investigate the performance of phase compensation (PC) and time reversal pre-equalizers in multipath indoor channels when a quantized version of the channel state information (CSI) is available at the transmitter side. We conduct a comprehensive experimental study to assess their spatial and temporal focusing as a function of the number of quantization levels over the frequency band of 2-12 GHz. To characterize multipath compression performance, root-mean-square (RMS) delay spread and peak-to-average power ratio (PAPR) are calculated for different numbers of quantization levels. Bit error rate (BER) curves have been simulated for data rates in the range of 125-4000 Mb/s based on the measured channel responses. To assess spatial focusing, we investigate the decay of the received response peak power as we move away from the intended receiver. Our study suggests that for the same feedback rate, PC has considerably superior performance in suppressing multipath dispersions and focusing the transmitted energy at the intended receiver.