Error Performance Estimation of Modulated Retroreflective Transdermal Optical Wireless Links with Diversity under Generalized Pointing Errors

George K Varotsos,Kanhira Kadavath Mujeeb Rahman,Fadi Jaber,Konstantinos Aidinis,Hector E Nistazakis,Mohd Nasor

doi:10.3390/telecom2020011

George K Varotsos, Kanhira Kadavath Mujeeb Rahman + Show 4 more

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https://doi.org/10.3390/telecom2020011

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Abstract

Recent developments in both optical wireless communication (OWC) systems and implanted medical devices (IMDs) have introduced transdermal optical wireless (TOW) technology as a viable candidate for extremely high-speed in-body to out-of-body wireless data transmissions, which are growing in demand for many vital biomedical applications, including telemetry with medical implants, health monitoring, neural recording and prostheses. Nevertheless, this emerging communication modality is primarily hindered by skin-induced attenuation of the propagating signal bit carrier along with its stochastic misalignment-induced fading. Thus, by considering a typical modulated retroreflective (MRR) TOW system with spatial diversity and optimal combining (OC) for signal reception in this work, we focus, for the first time in the MRR TOW literature, on the stochastic nature of generalized pointing errors with non-zero boresight (NZB). Specifically, under these circumstances, novel analytical mathematical expressions were derived for the total average bit error rate (BER) of various system configurations. Their results revealed significant outage performance enhancements when spatial diversity was utilized. Moreover, taking into consideration the total transdermal pathloss along with the effects of stochastic NZB pointing errors, the critical average signal-to-noise ratio (SNR) metric was evaluated for typical power spectral-density values.

Highlights

Introduction published maps and institutional affilTransdermal optical wireless links that transmit information data via light waves through the skin have lately attracted particular research and commercial interest, mainly due to their effective high-speed operation within a very large unlicensed available bandwidth with low probability of intercept, low power consumption, ease of modulation and demodulation, compact and light equipment, flexibility for deployment and redeployment, and electromagnetic interference (EMI) immunity, [1,2,3,4,5,6]
In this work, we introduce the presence of stochastic non-zero boresight (NZB) pointing errors for modulated retroreflective (MRR) transdermal optical wireless (TOW) links with spatial diversity, along with the optimal combining (OC) technique for signal reception
The power efficiency of the proposed MRR TOW system was evaluated in terms of its attainable average electrical signal-to-noise ratio (SNR) within a specific and desirable powerdensity-spectrum regime, considering once again transdermal pathloss and stochastic NZB

Summary

Introduction

Transdermal optical wireless links that transmit information data via light waves through the skin have lately attracted particular research and commercial interest, mainly due to their effective high-speed operation within a very large unlicensed available bandwidth with low probability of intercept, low power consumption, ease of modulation and demodulation, compact and light equipment, flexibility for deployment and redeployment, and electromagnetic interference (EMI) immunity, [1,2,3,4,5,6] In view of these concrete advantages over their radio frequency (RF) and inductive-coupling counterparts, which are widely used in most transcutaneous communication systems with medical implants nowadays, TOW (transdermal optical wireless) technology affords a prime alternative, if not the only viable choice for establishing robust transdermal wireless communication links that can simultaneously reach the growing high capacity and low power requirements of different but important medical applications such as natural-feeling prosthetic iations. Even within the medical optical window; i.e., the desirable wavelength regime between 0.6μm and 1.3μm where photon absorption by tissue is minimized, skin highly attenuates the information-bearing light signal and limits its maximum depth of penetration into tissue by as much as several centimeters, [1,7,8,14,15,16]

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