Research And Design On MAC Protocol For Wireless Sensor Networks

Wireless sensor networks(WSN),which is made by the convergence of sensor, embedded computation,networks and wireless communication technologies,is a novel technology for acquiring and processing information.WSN can be widely used in industrial control,biological and medical treatment,environmental testing and so on.In WSN,medium access control(MAC) protocols determine the usage mode of wireless channel,allocate limited radio resource among sensor nodes.It is the quarantee of WSN efficient communication limitless key supporting protocol and have a great influence on the performance of WSN.Therefore,researching on the MAC layer protocol is quite common and having important meaning.WSN is formed by lots of cheap sensor nodes,each one of them energy extremely limited.In the design of MAC protocol,saving energy and prolonging life cycle are the primary goal.This thesis analyzes WSN MAC protocol form the prespective of low energy consumption,high throughput rate and low-delay.This thesis firstly analyzes the development status of wireless sensor network,system structure,protocol stack and its unique features.Then analysis the main causes of the energy consumption and performance index in MAC protocols.Then analysis and comparison of several foreign wireless sensor network MAC protocols.Finally, according to the application of high emergencies load flow,proposes the Path Reservation-MAC(PR-MAC) protocol from the finest thoughts of other MAC protocols.PR-MAC is a low-delay,energy-efficient and extensible protocol that based on competition and Time Division Multiple Access MAC protocol.PR-MAC proposes asynchronous frame structure,cmposed of the basic length and multiply length frame.All nodes adjust their own working frame structure (integer multiples of basic length frame) based on local node density.The frame structure is divided into reservation section and data transmission section.A slot selection mode is proposed in the slot reservation section based on the priority of slots.Each node is competion for data transmission slot.This approach provides excellent expansibility.In data transmission phase,nodes can no conflict for data transimission,effectively reduce the idle monitor and state transition.Through using asynchronous frame structure,it effectively reduces the probability of transmission collision in high throughput,raising channel utilization rate,reduce unnecessary energy consumption.According to PR-MAC protocol,this thesis proposes a energy analysis model,theoretically analyses the energy consumption.In order to avoid intermittent transmission delay for single packet data in forwarding paths,PR-MAC protocol proposes a multiple hops path reservation scheme,uses the carry mechanism continuous reserving multiple slots.Then in the data transmission phase, the data can be transmitted multiple hops in the routing.The network simulation results showed that in high throughput,compared with S-MAC and T-MAC, PR-MAC had higher throughput,lower energy consumption and delay.