We address the features channel characterization and performance evaluation for wireless body-area networks (WBANs) in medical applications during a walk scenario using optical wireless transmission. More specifically, we focus on optical extra-WBAN uplink communication between a central coordinator node (CN) placed on the patient’s body and an access point (AP) in a typical hospital room. To characterize the optical wireless channel, we use a Monte Carlo ray tracing-based method and take into account the effects of body shadowing and mobility based on realistic models, in contrast to the previous simplistic models considered in the literature. Using this approach, we derive the dynamic behavior of the channel DC gain for different configurations of the CNs and APs. Furthermore, based on the obtained results, we develop a statistical channel model based on kernel density estimation, which we use to investigate the impact of CN and AP placement on the communication link parameters. Also, based on the outage probability criterion, we discuss the link performance and further analyze the improvement in performance achieved through spatial diversity, i.e., by using multiple APs in the room, for different photodetector types, under different background noise conditions. The presented results show that CN placement and user’s local and global mobility significantly impact the performance of extra-WBAN links, which can nevertheless be reduced using spatial diversity. Finally, the presented performance analysis shows that a single AP equipped with an avalanche photodiode photodetector allows an acceptable link performance for low-to-moderate background noise conditions, whereas multiple APs equipped with PIN photodetectors should be used in the case of moderate-to-strong background noise.
KEYWORDS: Monte Carlo methods, Wireless communications, Optical communications, Wireless medical sensors, Non-line-of-sight propagation, Sensor networks
We investigate channel characterization for wireless body-area networks (WBANs) in medical applications using optical signal transmission. More specifically, we focus on uplink communication from a central coordinator node (CN), placed on the patient's body, to an access point (AP) in a typical hospital room, which is usually referred to as extra-WBAN link. Using a ray-tracing based approach, we quantify the main characteristics of the optical channel while considering the effects of body shadowing and mobility (accounting for body movements and user global mobility inside the room). Based on the presented results, we discuss the impact of the positions of the CN and the AP on the link parameters. We also evaluate the link performance based on the outage probability criterion, and further quantify the performance improvement achieved by using multiple APs in the room.
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