Scale-Lag Diversity Reception in Mobile Wideband Channels

Abstract

We consider the effect of mobility on a wideband direct sequence spread spectrum (DSSS) communication system, and study a scalelag Rake receiver capable of leveraging the diversity that results from mobility. A wideband signal has a large bandwidth-to-center frequency ratio, such that the typical narrowband Doppler spread assumptions do not apply to mobile channels. Instead, we assume a more general temporal scaling phenomenon, i.e., a dilation of the transmitted signal's time support. Such analysis applies, for example, to ultra-wideband (UWB) radio frequency channels and underwater wideband acoustic channels.

Joint scale-lag diversity in mobile ultra-wideband systems

“…The expected value of the inner product (7) evaluated at a = a o vanishes if and only if the pulse-shape has zero DC component [6]. Hence, we define a o as the minimum resolvable dilation.…”

“…Hence, the noise coefficients are approximately uncorrelated. In [6], we showed that the scale-lag Rake receiver outperforms the conventional lag-only Raker receiver, which ignores dilation components in the channel. The coefficients {r m,n } are effectively a sampling of the scale-lag plane, as shown in Fig.…”