Switched Diversity Techniques for Indoor Off-Body Communication Channels: An Experimental Analysis and Modeling

Abstract

This communication investigates the potential improvement in signal reliability for indoor off-body communications channels operating at 5.8 GHz using switched diversity techniques. In particular, we investi-gate the performance of switch-and-stay combining (SSC), switch-and-examine combining (SEC), and (SECps) schemes, which utilize multiple spatially separated antennas at the base station. During the measurements, a test subject, wearing an antenna on his chest, performed a number of walking movements toward and then away from a uniform linear array. It was found that all the considered diversity schemes provided a worthwhile signal improvement. However, the performance of the diversity systems varied according to the switching threshold that was adopted. To model the fading envelope observed at the output of each of the combiners, we have applied diversity specific equations developed under the assumption of Nakagami- $m$ fading. As a measure of the goodness-of-fit, the Kullback–Leibler divergence between the empirical and theoretical probability density functions (pdfs) was calculated and found to be close to 0. To assist with the interpretation of the goodness-of-fit achieved in this communication, the standard deviation $\sigma $ of a zero-mean, $\sigma ^{2}$ variance Gaussian pdf used to approximate a zero-mean, unit variance Gaussian pdf is also presented. These were generally quite close to 1 indicating that the theoretical models provided an adequate fit to the measured data.