Research On Transmission Control Scheme For Media Access In Data Gathering Sensor Networks

With the development of communication and computer technology, Ubiquitous Computing, as one kind of computing mode in 21st Century, has been obtaining more and more attentions. Wireless Sensor Networks (WSNs), as a typical application of Ubiquitous Computing System, has become the research hotspot of international industry and academia due to the great value of applications to military scouting, industry control, forest fire monitoring, medical ward and space exploration.WSNs, not simply connecting the sensors into networks, integrating sensoring, embed computing, distributed information processing and wireless communication, can collaborate with real-time monitoring, data sensing and acquiring of the network distributed area, process the acquired data and send the detail processed data to the user.As one of the new complex networks, WSNs has some particular features in application: the energy, computing ability and storage capacity of the nodes are limited, and sometimes it is difficult to replace the battery due to the physical limitations. Therefore, the energy-efficient design has become the researching hotspot of WSNs. In this paper, we first study several classical MAC protocols for WSNs. And than, after discussed the data gathering WSN, which is expected to be wide-applied in the future, we address two high efficient transmission control mechanism for MAC.In the paper, we first discuss the CSMA mechanism. As a wireless network, in the design of CSMA mechanism for WSN, the characteristics of wireless channel also have to be considered. Based on the detailed analyses to data gathering applications, we study the CSMA mechanism, and the point is backoff mechanism. Here we point out that the classical backoff mechanisms are not feat data gathering WSNs, and then we give some modification to them. At last, we carry out a simulation. Comparison and observations are presented and analyzed.Then, we have a study to the data gathering tree and point out a even-load data gathering tree can enhance the performance of MAC protocols, decrease the probability of data collision, enhance throughput, decrease network delay, and also can reduce the energy consumption,extend the life of network. So in this paper we consider the construction of data gathering tree as a important mechanism for MAC protocol. We discuss some data gathering tree construction protocols and detailed in EGTP (Even-load data Gathering Tree construction Protocol), which can make the load even between nodes in the same layer and can extend the network's life. This protocol also can reduce the collision and enhance the throughput. At last, we give a simulation to EGTP and then run a MAC protocol in the tree constructed by EGTP. Comparison and observations are presented and analyzed.