Research On Key Technologies Of Channel Access And Resource Allocation For Wireless Body Area Networks

Wireless body area network(WBAN) is a network comprised of wearable or implanted sensors around or inside human body. In this dissertation, we focus on the key technologies of channel access and resource allocation issues in WBAN. First, IEEE 802.15.6 is a communication standard developed for WBAN. Modeling and analysis of the standard is favorable to performance forecast and system optimization. Second, changes of the body posture or position will incur shade effect between sensor nodes and the coordinator and thus lead to packet transmission failure. It is therefore indispensable to design a transmission strategy that can adapt to the time-varying channel quality. Third, WBANs are generally densely distributed. Interference from coexisting nearby WBANs could cause network performance degradation. It is therefore essential to study how to allocate the power resources among different WBANs so as to ensure QoS of different data priorities. Based on the above-mentioned issues, the major work of this dissertation is as follows:1. To understand the intrinsic nature of IEEE 802.15.6 communication standard designed for WBAN, the CSMA/CA channel access mechanism under saturation condition is modeled by Markov chain to analyze the throughput, successful packet delivery rate, and delay. Simulation results confirm the accuracy of the model analysis. Both analyses and simulation results show that this standard not only provides differentiated service for different priorities but also indicates that under saturation condition the medium is mostly preempted by the highest priority, while starving other priorities.2. To adapt to time-varying characteristic of the channel quality, a burst transmission strategy is proposed which forecasts the number of redundant transmissions based on channel estimation. The energy consumption, successful packet reception rate and the transmission delay under the proposed strategy are analyzed. Simulation results show that the proposed transmission strategy effectively reduces the energy consumption and transmission delay which still maintains the reliability compared with traditional transmission method.3. To solve the inter-WBAN interference problem, a utility-based and QoS-aware power control scheme is proposed. Generally, the QoS objective is viewed as a utility function, which represents the degree of user satisfaction while the power consumption is viewed as a cost function. The power control problem consequently becomes a non-cooperative multiplayer game, in which each user(player) tries to maximize its net utility, i.e., utility minus cost. Optimal power allocation of each WBAN is achieved by find the Nash equilibrium of the game. Simulation results show that the proposed algorithm makes a good tradeoff between the QoS of different data priorities and the energy consumption of body sensors.