  To remotely monitor the physiological status of the human body, long range
(LoRa) communication has been considered as an eminently suitable candidate for
wireless body area networks (WBANs). Typically, a Rayleigh-lognormal fading
channel is encountered by the LoRa links of the WBAN. In this context, we
characterize the performance of the LoRa system in WBAN scenarios with an
emphasis on the physical (PHY) layer and medium access control (MAC) layer in
the face of Rayleigh-lognormal fading channels and the same spreading factor
interference. Specifically, closed-form approximate bit error probability (BEP)
expressions are derived for the LoRa system. The results show that increasing
the SF and reducing the interference efficiently mitigate the shadowing
effects. Moreover, in the quest for the most suitable MAC protocol for LoRa
based WBANs, three MAC protocols are critically appraised, namely the pure
ALOHA, slotted ALOHA, and carrier-sense multiple access. The coverage
probability, energy efficiency, throughput, and system delay of the three MAC
protocols are analyzed in Rayleigh-lognormal fading channel. Furthermore, the
performance of the equal-interval-based and equal-area-based schemes is
analyzed to guide the choice of the SF. Our simulation results confirm the
accuracy of the mathematical analysis and provide some useful insights for the
future design of LoRa based WBANs.
