On the Utilization of L-PAM Technique in Transdermal Optical Wireless Links with Stochastic Pointing Errors for ABER Performance Estimation

Ongoing research into implantable medical devices (IMDs) and optical wireless communication (OWC) links has recently revealed the feasibility of establishing high speed transdermal optical wireless (TOW) communication links between an in-body device and an external one with a reasonable low power consumption. Still, numerous emerging biomedical applications including mainly cortical recording and neural prosthesis require an increasingly higher modulation bandwidth and need to harvest the full benefits of this optical wireless communication modality. Thus, in the present contribution the potential of the enhancement of TOW spectral efficiency is investigated by utilizing the bandwidth efficient L symbol pulse amplitude modulation (L-PAM) scheme. In more detail, by taking varying and realistic parameter values for a typical direct TOW link into account and by considering also transdermal pathloss and the stochastic nature of weak to strong pointing errors, the average bit error rate (ABER) performance metric is evaluated for various PAM configurations. In this context, novel ABER analytical expressions are derived. Corresponding results which are further validated by Monte Carlo simulations over a wide signal to noise ratio (SNR) regime demonstrate the feasibility of our suggestions.