Polling Access Protocols Analysis Of Wireless Sensor Network And OPNET Simunation

As a new type of communication network, Wireless sensor network has realized the function of the link between the real world and the human world. It also becomes a bridge while people cognizing and monitoring the physical world. However, the communication distance, computing ability and energy of single node is quite limited. In the other hand, the nodes are applied in random way and organized in Ad hoc mode which is different from traditional network. So the research on WSN now became hot spot in communication technology. Wireless sensor network are widely adopted in intelligent household, smart grid, medical care, security high iron, etc. As a result, it’s hard to form unified standard in WSN. Ever since last century, the research on both hardware platform and each layer’s protocols haven’t stopped. The protocols in each layer is the key point,they decided the which way should apply when processing data and they also guarantee the performance of transmission. The medium Access Control (MAC) protocol is in the second layer of WSN. It’s responsible for the access way of nodes and it’s the foundation of the network communication. So how to design suitable protocol for different use of WSN has become the key point. With the development of technology, many new ideas have been adopted in WSN, but different MAC protocols emphasis on different network performance, optimization index and demand. So there’s no universal MAC protocol, at the same time, the study and the research on this field still have a long way to go.Now wireless sensor network MAC agreement research mainly divided into based on competition, scheduling and mixed three mechanism. Polling way as a kind of important scheduling channel access way based on early in the industrial revolution began to further research, and because of its control mode in fairness, real-time, and the good performance of reliability, so that in the industrial automation control, computer time multiplex, network communication protocol, especially in communication network MAC agreement in a wide range of applications. The PCF IEEE802.11polling mechanism is the network communication in the typical application of MAC agreement, for voice, video and data real-time demand higher business to offer better quality service and performance. But because of its previous application and didn’t really pay attention to energy dissipation problems, so PCF direct application to in wireless sensor network.In this paper, the IEEE802.11PCF was improved, the dormancy mechanism joined in node, and puts forward a polling-based MAC simulation experiment module S-PCF, and system modeling and simulation, the simulation results prove S-PCF greatly reduced the PCF polling mechanism of energy consumption, improve the life cycle of the node. The research of the theory of polling predecessors had already done a lot of work and effort, basically can be divided into threshold service, limited (K=1) service and full service three basic types, S-PCF is based on polling the control strategy of the access mechanism, this paper of S-PCF established the mathematical model, with embedded markov chain and probability generating function as the mathematical tools to accurately the agreement definition and analysis, system model using limited (K=1) service, by a central server and N a node of the process control, mainly includes three:node of the group arrival process information, center of service process, server between the nodes of the conversion process and node dormancy query process. At the same time calculation one order characteristics and second order characteristics, get the average queue length and system average wait for delay theoretical results.Then, using the OPNET simulation platform of S-PCF simulation experiment module for network simulation, in the network time delay, energy consumption and network throughput analysis in three aspects of traditional PCF and S-PCF. Can come into dormancy mechanism S-PCF in energy conservation in much better than traditional PCF, at the same time because of the delay is small bring dormancy network, the network throughput and network delay are basically the same.