Diversity Measurements Aid Body-Worn Systems At 868 MHz

Mobile body-worn communications systems suffer from problems like near-field coupling, radiation-pattern fragmentation, and shifts in antenna impedance. Aside from degrading system efficiency, these issues can reduce signal reliability. To mitigate these effects, Simon L. Cotton and William G. Scanlon from the Queen's University of Belfast have presented a systematic measurement campaign of diversity-measurement techniques for use in wearable multiple-antenna systems at 868 MHz.

The researchers performed experiments using six time-synchronized body-worn receivers. They considered mobile off-body communications in an anechoic chamber, open office area, and a hallway. The cross-correlation coefficient between the signal fading measured by the body-worn receivers was typically below 0.7. In an open office area, the 5.7-dB diversity gain obtained with a dual-branch, body-worn maximal-ratio diversity system was improved to 11.1 dB by using a six-branch system. See "Measurements, Modeling and Simulation of the Off-Body Radio Channel for the Implementation of Bodyworn Antenna Diversity at 868 MHz," IEEE Transactions On Antennas And Propagation, December 2009, p. 3951.