An experimental justification for the proportionality between the coherence bandwidth and the root mean square time delay spread using deterministic time of arrivals

Abstract

In this paper, a novel approach of using deterministic multipath arrivals is presented to highlight the relationship between the coherence bandwidth and the root mean square time delay spread. This is done via a measurement campaign that sounds the wireless channel using frequency sweep measurements, where the wireless link is purposefully disturbed by the motion of a reflecting surface mounted to a robot arm. That motion is designed to induce deterministic components into the set of multipath arrivals, allowing those components to be isolated from those multipaths that are random. Those isolated deterministic arrivals are then manipulated using signal processing methods to confirm the well known inverse proportionality between the coherence bandwidth and the time delay spread to highlight the efficacy of this novel deterministic multipath approach. As such, it will be shown that the inverse proportionality constant determined in our controlled environment is nearly identical to a theoretical lower bound proposed in the literature. Finally, the use of deterministic paths for improved medium access control level performance is discussed relative to traditional physical layer statistical methods. We argue that the ability to extract deterministic paths in a multipath environment may reduce the amount of signal processing required to study the statistical nature of wireless channels for some applications of interest.