Abstract
The last few years, the scientific field of optical wireless communications (OWC) has witnessed tremendous progress, as reflected in the continuous emergence of new successful high data rate services and variable sophisticated applications. One such development of vital research importance and interest is the employment of high speed, robust, and energy-effective transdermal optical wireless (TOW) links for telemetry with implantable medical devices (IMDs) that also have made considerable progress lately for a variety of medical applications, mainly including neural recording and prostheses. However, the outage performance of such TOW links is significantly degraded due to the strong attenuation that affects the propagating information-bearing optical signal through the skin, along with random misalignments between transmitter and receiver terminals, commonly known as pointing error effect. In order to anticipate this, in this work we introduce a SIMO TOW reception diversity system that employs either OOK or more power-effective L-PPM schemes. Taking into account the joint impact of skin-induced attenuation and non-zero boresight pointing errors, modeled through the suitable Beckmann distribution, novel closed-form mathematical expressions for the average BER of the total TOW system are derived. Thus, the possibility of enhancing the TOW availability by using reception diversity configurations along with the appropriate modulation format is investigated. Finally, the corresponding numerical results are presented using the new derived theoretical outcomes.
Highlights
Over the last few years, the growing increase in traffic carried by emerging telecommunication network applications, which require higher data rates, higher security levels, along with lower power consumption and cost, has triggered remarkable scientific interest in the transition from the increasingly crowed radio frequency (RF) spectrum to the more bandwidth-effective optical spectrum, where optical wireless communications (OWC), commonly known as Free Space Optical (FSO) communications, have attracted particular attention lately for a variety of applications in both medical and telecommunication fields [1,2]
To the best of our knowledge, transdermal optical wireless (TOW) links have been evaluated only in terms of instantaneous BER, when the reality is that the average bit error rate (ABER) metric is recommended in order to be able to draw meaningful conclusions for their reliability
Note that without loss of generality we focus on spatial diversity, i.e., the examined TOW system may support single input–multiple output (SIMO) configurations where the transmitter simultaneously emits the same part of information to more than one spatially separated receiver apertures
Summary
Over the last few years, the growing increase in traffic carried by emerging telecommunication network applications, which require higher data rates, higher security levels, along with lower power consumption and cost, has triggered remarkable scientific interest in the transition from the increasingly crowed radio frequency (RF) spectrum to the more bandwidth-effective optical spectrum, where OWC, commonly known as Free Space Optical (FSO) communications, have attracted particular attention lately for a variety of applications in both medical and telecommunication fields [1,2]. They demonstrated that pointing errors can degrade the TOW performance by more than 10% In the latter works, the stochastic nature of misalignment due to the relative motion between the transmitter and the receiver terminals is modeled by the commonly used model that has been proposed in [7] for outdoor FSO communication links, which takes into account the jitter but ignores the non-zero boresight displacement. To the best of our knowledge, TOW links have been evaluated only in terms of instantaneous BER, when the reality is that the average bit error rate (ABER) metric is recommended in order to be able to draw meaningful conclusions for their reliability Motivated by these facts, a key novelty in this work is the estimation of the ABER performance of a SIMO TOW system that may employ apart from OOK, L-PPM modulation format alike, under the joint impact of skin-induced attenuation and pointing errors with non-zero boresight.
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