Off-body UWB channel characterisation within a hospital ward environment

Received signal strength measurements and delay statistics are presented for both a stationary and mobile user equipped with a wearable UWB radio transmitter (TX) within a hospital environment. The measurements were made for both waist and chest mounted antennas using RF-over-fibre technology to eliminate any spurious electromagnetic scattering effects associated with metallic coaxial cables. The results show that received signal strength values were dependent on whether transmit and receive antennas had line of sight (LOS) and were also affected by body-shadowing and antenna-body position. For mobile conditions, received signal strength tended to be log normally distributed with non-LOS (NLOS) links having significantly lower mean values. Excess time delay results for mobile user tests were best described by the Weibull distribution. Overall, the results favoured the chest mounted antenna position, with higher mean signal levels, reduced mean excess delay and less difference between LOS and NLOS channels.