Improved wireless propagation channel estimations: some experimental results

Multipath fading seriously degrades the performances of wireless communications systems operating in the UHF band. The purpose of this paper is to characterize the multipath medium by the identification of the wireless propagation media with the estimation of its complex impulse responses. So, transmitter and receiver can be designed to match the channel and to reduce the effect of these disturbances. Some wideband experimental results are presented, based on 2.2 GHz measurements. Based on the assumption that a linear, time varying filter, is an acceptable model of the propagation channel in the UHF band, the propagation media is completely defined by its varying complex impulse response. Some classical identification techniques are exposed. A measurement tool based on the correlation technique will be presented. In order to improve the quality of estimation regularisation techniques have been introduced. Some experimental results will confirm the expected enhancements of the measurements quality. Lastly, in order to improve the temporal resolution for multipath detection, a parametric model of the impulse response is proposed, and used in recently introduced high resolution techniques.