Beacon Mode 802.15.4 Mac Protocol Research

IEEE802.15.4provides the physical layer and the medium access control layerstandard for low-rate wireless personal network,which has a low complexity, low costand low power consumption,and becomes the most popular standard for WSN. Thereare two modes in IEEE802.15.4,beacon-enabled and nonbeacon-enabled mode. Thethesis mainly improves IEEE802.15.4MAC protocol on beacon-enabled mode, anddesigns a MAC protocol which is suitable for real-time application.In IEEE802.15.4MAC protocol, frames can be transmitted in CAP or CFP. InCAP,device must competes the channel to transmit while accesses the channel directlyin CFP which can gurantee the time for time-bound application. While in IEEE802.15.4standard,nodes must request coordinator for GTS before use,and compete to accesschannel to send GTS request, the way of which is the same as common data, which can’tguarantee sending out GTS request in time, and influent the performance of real-timedata. To solve the problem, the thesis puts forward a polling mechanism for GTSrequest commands, coordinator polls the node in poll list to ask whether it has thereal-time data or not, which completely avoid conflict in GTS request between devices.While the polling procedure brings control overheads,the thesis puts forward amechanism with GTS request sending out in prior by setting different parameters forGTS requests and normal data.In IEEE802.15.4standard,superframe has a fixed active and sleep period,whichwill influence the other traffic when meets the needs of real-time traffic.The thesis putsforward a duty-cycle adaption scheme, which dynamically adjust duty-cycle accordingto the different traffic and the network load,which can make the network goodperformance when meet the needs of real-time application.Finally,The simulation in NS2tests and verifies that the improvement on MACprotocol is suitable for real-time traffic while with good performance on whole network.