A closed-form derivation of self and multi-user interference for time-reversed UWB communications

Multipath degradation is a significant consideration for all wireless communication systems. A time-reversed UWB system harnesses the multipath channel to achieve temporal and spatial focusing through signal pre-filtering at the transmitter side. In cases where the RMS delay spread of a channel is larger than a user’s transmitted pulse separation, inter-pulse, -frame, and -symbol interference may occur. Of even more concern is multi-user interference, which significantly reduces system performance. This paper presents closed-form expressions for self and multi-user interference for a UWB system utilizing a time-reversed approach. The influence of user multiplexing codes is taken to account through incorporation of a ‘separation probability’, which characterizes a family of hopping sequences. The standardized IEEE 802.15.3a channel model is applied, and the derived performances are compared with that of a simulated time hopped time-reversed UWB system.