Transmit only UWB body area network for medical applications

This paper investigates methods to enhance the reliability of an ultra-wideband transmit-only (UWB Tx-only) sensor system. UWB Tx-only system uses asynchronous burst transmission, where each individual sensor transmits periodically without prior knowledge of other users and the channel condition. The application of UWB Tx-only sensor system for wireless body area network (WBAN) in a single user and multiple user environments is presented. In a single user environment, the main source of interference is from the collision of transmitted signals from individual sensors on the body. In a multiple user scenario, apart from the interference due to collision, there is also another source of interference from transmitting sensors of nearby users. The two major factors affecting the system reliability are the signal to noise ratio and the probability of collisions. The signal to noise ratio can be enhanced with a higher transmission power, which can be achieved through the use of gated systems and by carefully optimizing the pulse repetitive frequency and the gating duty cycle when generating an UWB transmission signal. Meanwhile the collision probability in a Tx-only UWB WBAN system can be reduced by arranging unique transmission intervals. It is shown in this paper that the collision probability for the case of burst transmission can be reduced to less than twice that of a pulse transmission through careful selection of the transmission interval.