UWB time reversal: From theory to practice

This paper discusses the theory behind ultrawideband (UWB) transmit waveform design, and reports a proof-of-concept UWB radio testbed with waveform level precoding. Unlike a narrow-band channel, a UWB channel contains a large number of resolved multipath components, which opens a door for exploring new features offered by UWB. Waveform level optimization is meaningful, but it is a great challenge to generate an arbitrary waveform adapting to the channel condition at Giga Hertz sampling frequency. Based on the channel impulse response (CIR) estimation available in the transmitter, a desired waveform is synthesized, aiming at performance maximization. Unique design issues, implementation solutions and results are reported. Using time reversal as an example, our demonstration has shown 3 to 4 dB gain over an ordinary single-carrier UWB system in indoor non-line-of-sight (NLOS) propagation environments.