Study The Phase Characteristics Of The Communication Channel In Body And Key Technologies Of MAC Layer

WBAN (wireless body area network) have been widely applied to continuously monitor health information and exchange the entertainment information recent years. However, the traditional wireless communication technologies, such as Bluetooth and Zigbee, cannot meet the demand of WBAN. Due to the large range of coverage in ISM bands, signal overlays and, consequently, unwanted interferences between different WBAN may easily occur.Therefore, human body communication (HBC), which uses the human body as a propagation medium, is an alternative wireless communication technology, which has low power, security characteristics.In this work, the characteristic of HBC propagation delay and phase deviation were investigated in the frequency bands:1-200MHz. In order to investigate the propagation delays in different transmit paths and different frequency bands, the1-200MHz frequency band was divided into two sub-bands:1-100MHz and100-200MHz and the four measurement paths were set on every volunteer. The statistical analysis of measurement date showed that the propagation delay is independent on transmit path. However, from1MHz to100MHz the delay is generally longer than that in the frequency band100-200MHz. The normalized phase deviation curve indicated that the phase deviation is larger in frequency band20-40MHz compared with other measured frequency band. Lognormal model is found to be the best fitting distribution for the normalized phase deviation according the maximum likelihood estimation (MLE) and Akaike information criterion (AIC).In order to realize the multipoint communication based on the HBC prototyping devices, this paper has proposed a MAC protocol based on statistical frame-.The frame structure and scheduling mechanism and the frame structure and scheduling mechanism are designed. The; the energy model also is proposed. Compared with the TDMA and CSMA protocol, MAC protocol proposed in the paper has better performance in the efficiency of energy and it is more suitable for the star topology network.