Study On Traffic Adaptive Mechanism Based MAC Protocols In Wireless Sensor Networks

Wireless sensor networks(WSNs)consist of sensor nodes which have the function of sensing,computing,and communicating.After collecting environmental information via sensors,these nodes process and then deliver the information to sink node for comprehensive and efficient environmental monitoring.The technology of WSN has been widely used in the area of national defense and military,environmental monitoring,space exploration,disaster prevention,and smart home,and this emerging technology will have a wide application prospect in the future.In wireless sensor network architecture,media access control(MAC)protocol plays an important role in the deployment of wireless channel for network nodes and has been at the core of ensuring effective communication.Based on different media access mechanism,MAC protocol in WSN can be divided into contention-based protocol,schedule-based protocol,and hybrid protocol.Hybrid MAC protocol is a combination of contention-based and schedule-based MAC protocols and this hybrid mechanism can benefit from the merits of both schemes while mitigating their drawbacks.The main tasks of this thesis are listed as follows.Firstly,this thesis introduces fundamental characteristics of wireless sensor networks.Besides,some existing MAC protocols,especially hybrid MAC protocols,are introduced and analyzed in detail.Secondly,contention mechanism is an important component in hybrid MAC protocols.In this thesis,back-off algorithm is optimized,which is at the core of contention mechanism.Performance comparison is then implemented with contention-based MAC protocol which adopts traditional back-off algorithm.Results show that improved algorithm has good performance in throughput,delay,and energy consumption.Thirdly,this thesis makes improvement on I-MAC,which is a traditional schedule-based MAC protocol.The detailed mechanism of network construction,time synchronization,and slot scheduling is provided.And then,performance tests are implemented with I-MAC.Finally,a hybrid MAC protocol is proposed based on the former research results.It combines contention-based and schedule-based protocols.Test results show that it outperforms some other MAC protocols in aspect of throughput and time delay.