Doppler spread analysis of human motions for Body Area Network applications

Many current and future medical devices are wearable and the human body is used as a carrier for wireless communication, which implies that the human body is a crucial part of the transmission medium in Body Area Networks (BANs). In order to understand the propagation characteristics of the human body, it is imperative to analyze the Doppler spread spectrum, which is caused by human body motions. Using a network analyzer, Doppler spreads and coherence time of temporal variations caused by human body motions can be measured and analyzed using a single tone waveform for different scenarios in a shielded room. From the narrowband measurement results, the Doppler spread varies approximately from 0.6Hz to 12Hz for different scenarios, the RMS Doppler bandwidth is in the range from 0.6Hz to 4Hz, and the coherence time differs from 20ms to 1s, all of which are measured at the Medical Implant Communication Service (MICS) band, the Industrial Scientific Medical (ISM) band and the Ultra-Wideband (UWB) band. Root mean square fittings of three different functions to received signal strength measurements were performed for different scenarios. Results show that the Gaussian function generally provides a good fitting model, which is independent of center frequencies.