Modulated Retro-Reflector Transdermal Optical Wireless Communication Systems with Wavelength Diversity over Skin-Induced Attenuation and Pointing Errors

Signal Intensity Estimation in Transdermal Optical Wireless Links with Stochastic Pointing Errors Effect

“…With regard to pointing errors, by assuming that the elevation and the horizontal displacement follow independent and identical Gaussian distributions [32,33], the radial displacement at the receiver side should follow a Rayleigh distribution. Consequently, the PDF of the random variable K p can be expressed as [17,22,34]:…”

“…What these papers have in common is the operation with appropriate wavelengths within the optical tissue window, i.e., between 600 and 1300 nm, as an attempt to minimize photon absorption inside skin [6,15], as well as the use of On-Off Keying (OOK) modulation formats, while pointing errors have been considered either as a deterministic effect or as a negligible one. Lately, authors in [16][17][18][19] and more recently authors in [20][21][22] evaluated the stochastic nature of pointing errors which arise from the realistic relative motion between the transmitter and the receiver terminals along with the transdermal path loss. Their results demonstrate that pointing errors can significantly aggravate the already important TOW performance degradation due to skin-induced attenuation, even within the optical tissue window [13,14].…”

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

“…Apart from transdermal pathloss, TOW performance and availability is strongly degraded by the effect of pointing errors due to random misalignments between transmitter and receiver apertures that result, in turn, in significant random misalignment-induced irradiance fading of the propagating information-bearing light signal at the receiver side, [17,18]. Indeed, despite the directional behavior of light sources and photodetectors, the relative motion between the transmitter and receiver in several biomedical applications is unavoidable due to biological functions [19].…”

“…Consequently, since the light signal passes through the skin channel twice, the impact of the skin-induced attenuation effect becomes more significant in the latter case. However, the latter configuration has the distinct advantage of placing both transmitter and receiver terminals on the outside of body, which makes this configuration much more flexible for deployment and redeployment [18,23]. Additionally, it makes possible to conserve the energy of the battery of the implanted device in a more effective and flexible way [3,18].…”

“…Next, the authors in [12,17] extended this concept by modeling the more generalized NZB pointing errors impact on direct TOW typical links with diversity in space, in time or in wavelength. More recently, the authors in [4,18] introduced the presence of stochastic zero-boresight pointing errors for MRR TOW links with diversity. In particular, the total outage probability and the total average bit error rate (ABER) have been evaluated in [18] and in [4], respectively.…”