Quality Of Service Support For Event Detection In Wireless Sensor Networks

In its broadest form,quality of service(QoS) refers to the contract between the service provider and customers.In term of networks,guaranteeing certain level of QoS is the most important design criterion.The purpose of a wireless sensor network(WSN) is to extract model parameters of the physical world according to the fidelity requirement set by the end users,for applications such as surveillance,tracking and control.Thus QoS provisioning in WSN is without exception a requirement.The fundamental theories and key technologies of QoS support for event detection in WSN are studied in this dissertation,in term of connectivity guarantee,node deployment for achieving differentiated coverage and probabilistic connectivity,real-time routing ensuring in-time transmission and quality of information under fading channel.First of all,in order to develop algorithms and protocols for WSN and give mathematical correctness and performance evaluation,models for various aspects of WSN are needed. Several essential models,such as sensing model,communication model,network model and energy model are presented,analyzed and improved.To ensure connectivity of a random network,we analyze the connectivity scaling law of WSN in a non-isotropic log-normal shadowing environment.An explicit closed-form expression of node non-isolation probability is derived as the upper bound of one-connectivity, based on an analytical link model which incorporates important parameters such as path loss exponent,shadowing variance of channel,modulation,encoding method etc.A tight lower bound for the minimum node density that is necessary to obtain an almost surely connected network is also obtained.To meet user's requirement of differentiated coverage and probabilistic connectivity, novel deployment strategies based on heuristic algorithms are proposed.The deployment problem is formulated as a multi-objective optimization problem,tabu search(TS) and generic algorithm(GA) are proposed to provide solutions.Simulation results show that GA and TS based deployment outperforms random and regular lattice deployment.Furthermore. GA provides diverse solutions with better tradeoffs between multiple objectives. To satisfy real-time and reliable delivery requirement,a two-hop neighborhood information based real-time routing protocol is proposed.The packet deadline is mapped to a network-wide velocity while routing decision is made based on the novel two-hop velocity integrated with energy balancing mechanism.Initiative drop control is embedded to enhance energy utilization efficiency while reducing packet deadline miss ratio.The proposed routing has one-hop more prediction capability as using a "telescope" in finding the way. Simulation and comparison show that the new protocol has led to lower deadline miss ratio, higher energy efficiency and load balance than two existing popular schemes.Finally decision fusion rules under fading channel in WSN are investigated to ensure high quality of detection.We propose three sub-optimal fusion rules based on optimal like-lihood ratio rule.Compared with the optimal rule,our proposed su-optimal solutions is with lower computation complexity and requires less a priori information.They perform well in their respective SNR ranges.We draw the conclusion that in resource-constrained WSN,a tradeoff should be considered among performance,resource cost and computation complexity while choosing the fusion rules.