Wide-Sense-Stationarity of Everyday Wireless Channels for Body-to-Body Networks

TL;DR

This study investigates the wide-sense-stationarity of body-to-body wireless channels in everyday scenarios, finding that such channels are often stationary over short periods and more stable than on-body channels, which impacts network design.

Contribution

The paper provides empirical evidence on the WSS properties of body-to-body channels, demonstrating their stationarity over longer durations than on-body channels in real-world conditions.

Findings

WSS is met in up to 90% of cases for 5-second windows between BAN hubs.

Hub-to-hub channels remain stationary for over 10 seconds with high probability.

Body-to-body channels are more stationary over longer periods than on-body channels.

Abstract

The existence of wide-sense-stationarity (WSS) in narrowband wireless body-to-body networks is investigated for "everyday" scenarios using many hours of contiguous experimental data. We employ different parametric and non-parametric hypothesis tests for evaluating mean and variance stationarity, along with distribution consistency, of several body-to-body channels found from different on-body sensor locations. We also estimate the variation of power spectrum to evaluate the time independence of the auto-covariance function. Our results show that, with 95% confidence, the assumption of WSS is met for at most 90% of the cases with window lengths of 5 seconds for the channels between the hubs of different BANs. Additionally, in the best-case scenario, the hub-to-hub channel remains reasonably stationary (with more than 80% probability of satisfying the null hypothesis) for longer window lengths of more than 10 seconds. The short time power spectral variation for body-to-body channels is also shown to be negligible. Moreover, we show that body-to-body channels can be considered wide-sense-stationary over significantly longer periods than on-body channels.