Research On Quality Of Service Guarantee Mechanism In Wireless Sensor Network

With the development of research on wireless technique and other related techniques,wireless sensor networks(WSNs)have been widely used in various applications which involve diverse working environments,monitoring objects and data conditions.Different applications require different QoS for data collection and data transmission.Thus,it is essential to provide QoS guarantee mechanisms in WSNs to achieve good performance in various applications.Accordingly,it is of great significance to study the QoS guarantee mechanisms in WSNs.In general terms,the QoS of WSNs focuses on timeliness and reliability of data transmission,as well as coverage and connectivity of network topology for data collection.The QoS guarantee implementation relies on different mechanisms in WSNs.Although many methods and techniques have been proposed in existing studies,the QoS guarantee mechanism is still faced with the following challenges in complex applications:(1)There exist several types of data traffic which have different QoS requirements.Therefore,a multiple-level QoS guarantee mechanism is in great demand.(2)There could be multiple QoS requirements for one data traffic.Thus it is necessary to provide multiple-QoS guarantee mechanism for theses traffics.(3)Since the traffic distributes non-uniformly in space and time,a method for the efficient transmission in a dynamic traffic is required.(4)There exists non-uniform replacement of the nodes as well as dynamic and changeful topology in many applications of WSN.It is necessary to provide an efficient deployment method to satisfy the requirement of effectively covering.Therefore,this dissertation focuses on four QoS issues in WSNs and presents the corresponding solutions respectively.These issues are(1)multi-level guarantee in different types of data traffic transmission,(2)multiple QoS guarantee for the end-to-end transmission,(3)scheduling method of nodes in dynamic traffic scenario,(4)deployment method for maintaining coverage.The main contributions of this dissertation are as follows:(1)A localized and multi-level QoS routing protocol TDMQR is proposed for multi-level guarantee in different types of data traffic transmission.Data traffic is divided into four types:Regular Traffic(RT),Reliability-Required Traffic(RRT),Timeliness-Required Traffic(TRT)and Timeliness-and-Reliability RequiredTraffic(TRRT).Each type is prioritized based on its' QoS requirement.TDMQR schedules the packet according to the priority of a multi-queue where the packets are cached in categorization.The proposed TDMQR attempts to select the optimal forwarder to fulfill the required timeliness and reliability QoS metric while considering power efficiency.For good timeliness,TDMQR estimates dwell time of neighbor nodes and two-hop advance velocity to seek a better routing.For good reliability,TDMQR employs WMEWMA to estimate link quality.In addition to guaranteeing of timeliness and reliability,TDMQR takes energy-balancing into consideration and selects the node with optimal energy efficiency.Extensive simulations show that the proposed TDMQR outperforms the typical traffic differentiated QoS routings.TDMQR can ensure good QoS with higher energy efficiency and a longer lifetime.(2)For multiple QoS guarantee of end-to-end transmission,a directional transmission based QoS-aware opportunistic routing DTQOR is proposed to achieve a timely and reliable delivery.Based on the analysis of the impact of directional transmission on the connectivity and constraint relationship of forwarding candidates,an approach is designed to reduce the selecting scope of next hop candidate nodes.At first,by partitioning the end-to-end delay and reliability into each hop on a path,the QoS routing metric subjected to reliability and delay is formulated as a multi-objective multi-constraint optimization problem.A heuristic algorithm to construct prioritized permutation of forwarding candidates is further proposed to achieve sufficient sub-optimal aim and finally the whole routing mechanism is provided.Compared with the multi-constrained QoS multipath routing,the simulations results have demonstrated that DTQOR reduces the end-to-end delay significantly and improves the energy efficiency.(3)For the scheduling method of nodes in dynamic traffic scenario,WAT,a receiver-initiated duty cycle mechanism of MAC is proposed to improve the energy efficiency,delivery ratio and delay.In this design,the WAT reduces sensor nodes' duty cycle by enabling a receiver to choose a wakeup interval according to traffic,and then produces the next wakeup time randomly.The neighboring nodes get next wakeup time of each by piggybacking of beacon broadcasting.At the same time,WAT enables a node to wake up at the predictive wakeup time of the intended receiver to make a transmission or retransmission in successive cycles.This duty cycle schedule can reduce collisions and idle listening.By evaluating and comparing with other similar duty cycle protocols in simulation,WAT significantly outperforms other receiver-initiated duty cycle protocols under different scenarios.It achieves lower average duty cycle in a wide range of traffic,and maintains a high packet delivery ratio with a low packet delivery delay.(4)For deployment method for maintaining coverage,a mobile self-adjusting deployment algorithm for mobile sensor node(MSN)LLSAD is proposed.Based on the analysis of the theory on optimal nodes distribution with full coverage,a rule of node adjusting and location update is proposed.LLSAD algorithm adjusts sensor nodes'position according to relative local position to fully cover the monitoring area,which updates nodes' distribution and achieves more optimal global coverage.The simulation results have demonstrated that LLSAD can rapidly improve the coverage and achieve convergence under several different initial deployment distributions to provide reliant QoS guarantee for coverage.Moreover,sensor node does not need to maintain global network topology.Thus,it is highly applicable for sensor network with limited resource.