On the use of Diversity in Transdermal Optical Wireless Links with Nonzero Boresight Pointing Errors for Outage Performance Estimation

Transdermal Optical Wireless Links with Multiple Receivers in the Presence of Skin-Induced Attenuation and Pointing Errors

“…These signals are forwarded to the transmitter, which emits M data copies of the same part of information towards the internal unit that consists, in turn, of the corresponding receiver(s), DSP unit and the stimulation (STM) unit that eventually stimulates the appropriate nerve. Thus, the internal DSP and STM units are responsible for generating the appropriate stimulations [14,[36][37][38][39]. In this context, the statistical channel model for the examined TOW system is given as [39] y…”

“…Thus, the internal DSP and STM units are responsible for generating the appropriate stimulations [14,[36][37][38][39]. In this context, the statistical channel model for the examined TOW system is given as [39] y…”

“…where h l,m stands for the deterministic channel coefficient due to the propagation losses of the m-th channel though the skin and h p,m represents the corresponding stochastic process that models the geometric spread due to the presence of pointing errors. The former deterministic term is expressed as [36][37][38][39]…”

“…Nevertheless, this skin-induced attenuation described above remains a major concern in TOW communication since even for the highest tissue transmittance, i.e., for wavelengths between 800 nm and 1300 nm, only 10% to 30% of incident optical power is transmitted through skin of typical thickness, i.e., 2 mm to 6 mm, when the emitter and the detector are aligned [33][34][35]. Considering also the pointing errors due to unavoidable misalignments between transmitter and receiver terminals that is also an effect of primary concern in TOW communication, as well as in the wider FSO communication, the performance and availability of TOW transmissions is further degraded [2,4,7,[36][37][38][39].…”

“…Nevertheless, NZB pointing errors had never been examined in TOW literature, just as no method had been proposed in order to enhance the TOW outage performance and availability. Only, very recently, authors demonstrated for the first time, in [39], that a diversity method-i.e., in space, in time, or in wavelength-is an effective technique to enhance the outage performance of a typical TOW in terms of outage probability metric, by considering the joint impact of both attenuation-induced fading and misalignment-induced fading with NZB, modeled by the accurate Beckmann distribution [3,[41][42][43][44][45][46]. In basic terms, diversity refers to the consideration of multiple copies of the propagated signals in an attempt to overcome a poor transmission media state so as to reinforce the communication link's availability and robustness.…”