Terahertz Channel Characterization Inside the Human Skin for Nano-Scale Body-Centric Networks

This paper focuses on the development of a novel radio channel model inside the human skin at the terahertz range, which will enable the interaction among potential nano-machines operating in the inter cellular areas of the human skin. Thorough studies are performed on the attenuation of electromagnetic waves inside the human skin, while taking into account the frequency of operation, distance between the nano-machines and number of sweat ducts. A novel channel model is presented for communication of nano-machines inside the human skin and its validation is performed by varying the aforementioned parameters with a reasonable accuracy. The statistics of error prediction between simulated and modeled data are: mean (μ)= 0.6 dB and standard deviation (σ)= 0.4 dB, which indicates the high accuracy of the prediction model as compared with measurement data from simulation. In addition, the results of proposed channel model are compared with terhaertz time-domain spectroscopy based measurement of skin sample and the statistics of error prediction in this case are: μ = 2.10 dB and σ = 6.23 dB, which also validates the accuracy of proposed model. Results in this paper highlight the issues and related challenges while characterizing the communication in such a medium, thus paving the way towards novel research activities devoted to the design and the optimization of advanced applications in the healthcare domain

Ellipticity Statistics of Ultra Wideband MIMO Channels for Body Centric Wireless Communication

In this paper, ellipticity statistics of 2 × 2 ultra wideband multiple-input-multiple-output (MIMO) channel for body-centric wireless communication is evaluated by quantifying four different on body links namely; waist-back, waist-chest, waist-ankle and waist-wrist. Results show that at lower values of signal to noise (SNR), spatial multiplexing dependent capacity degrades as the eigen value dispersion decreases (i.e., lower ellipticity statistic), whereas it increases at higher values of SNR

Experimental Investigation on Time Reversal Precoding for Space-Time Focusing in Wireless Communications

This work presents the results of indoor wideband measurements investigating the spacetime properties of wireless signal transmission with online time reversal precoding. The measurements were conducted using a new time-reversal wideband MIMO channel sounder operating at 2.45 GHz with a bandwidth of 240 MHz. Both line of sight and non line of sight propagation conditions were investigated. Spatial focusing and temporal compression can be seen clearly with time reversal precoding, which may be useful for future wireless systems applications. Channel hardening due to time reversal is also observed under both line and non line of sight conditions

Modeling of Fading Figure for Non-stationary Indoor Radio Channels

Fading models of practical mobile radio channel may change over time and/or due to mobility being Rice, Rayleigh, double-Rayleigh, etc, depending on the nature of radio wave propagation, which results in a non-stationary channel. This work is based on investigation of fading figure (FF) that addresses non-stationarity nature of radio channels. The FF is represented by the parameter m of Nakagami-m distribution. For an indoor environment system, our results show the parameter m, which can be modeled as a generalized extreme value distribution. The statistical distribution model of parameter m can be used to study performance of wireless communication system under non-stationary radio channels

Condition Number Variability of Ultra Wideband MIMO on Body Channels

This paper presents, condition number (CN) variability of ultra wideband 2 × 2 multiple-input-multiple-output (MIMO) on-body channels for four different links namely; waist-to-wrist, waist-to-back, waist-to-chest and waist-to-ankle. The relationship between condition number, capacity and signal to noise ratio is studied and results indicate that for fixed value of signal to noise ratio (SNR), the capacity decreases with increasing CN, whereas for fixed values of capacity, SNR increases with CN. For high SNR (> 8 dB), the correlation becomes negative, which means that for the fixed CN, the capacity increases with increasing SNR

On the characteristics of MIMO

We consider a Multiple-Input Multiple-Output (MIMO) communication system where the transmitted vector has a Gaussian distribution with (scaled) identity correlation matrix; this is the capacity-achieving channel input distribution for a block fading Rayleigh iid MIMO channel when the transmitter has no channel knowledge and the receiver knows the channel perfectly. We decompose a high-SNR approximation of the mutual information as a sum of three terms involving: i) a supremum capacity; ii) the effect of fluctuation of SNR about its mean; iii) the effect of eigenvalue dispersion of the channel. The decomposition provides some insight on the mechanisms that affect the MIMO mutual information at high SNR. Further, we analyze the first and second order statistics of the terms in the decomposition under the assumption of frequency-flat Rayleigh iid fading