Wireless Self-organizing Network Mac Protocol

Wireless Ad Hoc networks is a distributed self-organized network that is composed of wireless mobile nodes, without fixed infrastructure, robust and deployed quickly. It is especially attractive to military tactical and disastrous rescue cases and remote regions.The MAC protocol is important for the achievement of QoS supported by up layers in wireless Ad Hoc networks. It is the direct controller for sending and receiving all the controlling message and data packet. MAC protocol play the important roll in the communication QoS,network capacity and the complication of the wirless terminals. Because of the specialty of the Ad Hoc networks, the traditional mutiple address access technology based on sharing broadcast channel can not be applied directly in the Ad Hoc networks. The mobile terminals access the channel by the base station in the cellular wireless communication system. However, the Ad Hoc networks doesn't have the controlling center like the base station. So the design of the MAC protocol becomes the current hot topics in the field of wireless Ad Hoc networks.This paper is focused on MAC protocols in wireless Ad Hoc networks. At first, The network's character, application environment and research hot topics are introduced. Then, we introduce and analyze IEEE 802.11 protocol, which is broadly applied in the MAC layer of wireless Ad Hoc networks. We employ Markov model to analyze the system performance of IEEE 802.11 DCF in saturation networks and find that the size of contention window has great impact on the system performance. We deduce the relationship formulation of throughput, media access delay and energy consumption in saturation networks and give a compositive evaluation. Moreover, the performance problems is analyzed and simulated, when IEEE 802.11 DCF is applied in ad hoc networking environment. The problems include exposede terminal problem,unfairness access problem,the decrease of throughput and unstability of TCP layer. So, we propose a dynamic backoff algorithm for MAC protocol in ad hoc network. The simulation results show that compared with the original IEEE 802.11 protocol, the proposed algorithms achieve better system performance in fairness and throughput. Next, the characteristics of energy consumption with MAC protocols in wireless sensor network is researched, meanwhile which are classified. We compare and analyze the typical protocols of them in the metric of energy consumption, average packet delay and packet delivery ratio. We give the conclusion that they are suitable for different application circumstances by comparing the simulation results. We pay a attention to achieving different performances for different specific application environment. For example, we focus on the throughput and fairness for the terminals which have certain process capacity and on the energy saving for the sensor network used for special application. At last we summarize the current MAC protocol techniques and discuss their future development.