Research On Access Algorithm Based On IEEE 802.15.4

IEEE 802.15.4 technology has a very wide range of applications as one of the bestshort-range wireless communications technology standards used for wireless sensornetworks. But wireless sensor network is a network of specific task-oriented. So thedefault configuration parameter in the IEEE 802.15.4 MAC protocol can not fit allapplication environments. So the research of algorithm performance and improvementstrategies is the key to extend its application. In this paper, theoretical modeling andsimulation method are used to study the access algorithm.Fist, for the diverse nature of the wireless sensor network applications, establish atheoretical model which comprehensive consideration of the ACK and limitedretransmission mechanism can dynamically adjust the theoretical model based on networkload conditions. Deduced the average arrival rate threshold of the node enters thesaturation, based on the network load make appropriate adjustments of the node model,unification of saturated and unsaturated network modeling. About network performanceevalluation parameters, given the expression of date transmission reliability,delay andthoughput, investigated slot CSMA/CA algorithm parameter configuration of the aboveperformance, use OPNET simulation to prove the accuracy of the model.Secondly, for the wireless sensor network which have date transmission reliabilityrequirements,nodes offen do not know the network topology and traffic conditions at thebeginning of the deployment of sensor networks. This paper propose an adaptiveparameters regulation strategy for slotted CSMA/CA algorithm,which can adaptiveadjustment the MAC layer parameters to achieve the reliabiliability required by theapplication layer in the unknow status of network traffic conditions, use OPNETsimulation to verify the rationality and effectiveness of the strategy.Finally, proposed a service differentiation strategy based on slotted CSMA/CAparameter configuration, and improve the standard model, established the slottedCSMA/CA algorithm theoretical model of the differentiated services, carried out a detailedanalysis on the service differentiation stategy based on the vale of the contention window (CW), given the expression of channel access probility and throughput for differentpriority date, compared the impact of the service differentiation strategies on the two typesof date transmission.