  Coexistence, and hence interference mitigation, across multiple wireless body
area networks (WBANs) is an important problem as WBANs become more pervasive.
Here, two-hop relay-assisted cooperative communications using opportunistic
relaying (OR) is proposed for enhancement of coexistence for WBANs. Suitable
time division multiple access (TDMA) schemes are employed for both intra-WBAN
and inter-WBANs access protocols. To emulate actual conditions of WBAN use,
extensive on-body and inter-body "everyday" channel measurements are employed.
In addition, a realistic inter-WBAN channel model is simulated to investigate
the effect of body shadowing and hub location on WBAN performance in enabling
coexistence. When compared with single-link communications, it is found that
opportunistic relaying can provide significant improvement, in terms of
signal-to-interference+noise ratio (SINR), to outage probability and level
crossing rate (LCR) into outages. However, average outage duration (AOD) is not
affected. In addition a lognormal distribution shows a better fit to received
SINR when the channel coherence time is small, and a Nakagami-m distribution is
a more common fit when the channel is more stable. According to the estimated
SINR distributions, theoretical outage probability, LCR and AOD are shown to
match the empirical results well.
