Research On Key Technologies Of MAC In Wireless Ad Hoc Networks

The media access control protocol is one of the key technologies in wireless mobile ad hoc networks, whose main function is sharing the limited wireless channel among nodes reasonably and efficiently. The MAC protocol has a significant effect on most of the important network performances, such as throughput, time delay and fairness etc. But, non-centralized, distributed network architecture and limited energy of nodes make it unfeasible to use some existing MAC protocols designed for wired networks, centralized cell system or distributed one-hop network. Presently, the design of MAC protocols is a research hotspot, which exerts a tremendous fascination on researchers.Using the limited wireless channel efficiently is the most basic and important requirement for all kinds of networks. In the distributed one-hop network only one pair of nodes is allowed to communicate at a certain time. So, the efficiency of wireless channel depends heavily on how many packets are transmitted successfully in a certain time. That is the so called time efficiency. But in multi-hop networks, several pair of nodes can transmit simultaneously when there is no collision. Consequently, the efficiency of spatial field is a crucial factor that influents the channel efficiency, which should be paid more attention to.More over, there are mainly three different transmission models in one hop link. Point to point is the uppermost model that supports unicast data. Point to multi-point is another important model that used in transmission of broadcast data. Multi-point to point is a new model brought forwards in cooperative communication recently. Because the differences among these three models, it is necessary to explore how to improve the efficiency of wireless channel in ad hoc networks.This paper centers on research of the above-mentioned three transmission models and places special emphasis on the key technologies of media access control protocol from the aspects of improving spatial efficiency and time efficiency. The main contributions of this paper can be summarized as follows:1. A new idea for the designing of MAC protocols ----good-mannered MAC (gmMAC) is brought forward in this paper. The core idea of gmMAC is that each node self-consciously enforces or reduces the ability of accessing channel based on the different influences on network performance. Thus lighten the degree of selfishness and greed which dramatically degrades the network throughput, time delay and etc. in most of the traditional MAC protocols based on random competition mechanism. The condition of improving network performance by gmMAC and the best control method is given based on theoretic analysis.2. Based on the idea of gmMAC, a bi-direction edge effectual interference gmMAC(bee-gmMAC) algorithm is also presented in this paper. By defining the interference coefficient of edge ei with respect to node h, every edge can get its own effectual interference. The effect of a bi-direction edge on throughput is the gist that node controls its MAP. If the effect of an edge on throughput is serious, the sender will decrease the MAP. Otherwise, the sender increases the MAP. Simulation results show it can increase the network throughput markedly.3. A novel adaptive reliable broadcast/multicast MAC protocol (ARBMAC) is proposed. The idea comes into being based on the broadcast/multicast cost function, which is achieved by analyzing different realizations of reliable broadcast/multicast. According to the function, the method with minimum broadcast /multicast cost in different scenes can be got. Thus, the protocol could select the optimal realization adaptively in various scenarios. Extensive analysis and simulation results validate the reliability and efficiency of it.4. To improve the efficiency of reliable broadcast/ multicast MAC protocol in wireless multi-hop network, a location aid algorithm to eliminate redundant nodes (LARE) is put forward. Using the neighbor geographical location information, according to the principle of equivalent collision region, the algorithm could reduce redundant nodes from receivers, which is unnecessary for acknowledgement. Thus, the minimum acknowledgement nodes set is got. Extensive analysis and simulation results verify the reliability and efficiency of it.5. A reliable coherent cooperation cross-layer MAC Protocol is also presented in this paper, which is called CCMAC. By using channel explore, CCMAC provides real time channel radiate and eclipse gene. This is the necessary condition to ensure in-phase addition of singles coming from the sender and partner. Move over CCMAC can eliminate "cooperative cavity" by embedding selection of partner in the phase of data distribution. "One-step reservation" and "timely acknowledgement and adjacent retransmission" are the main rules for the communication process. Simulation results validate the time delay and efficiency of it.6. A new method to support smooth transition between synchronized protocol and asynchronous protocol is given. When there are some asynchronous nodes in a synchronized network, it can ensure the uninterrupted communication.7. A flexible designing frame of MAC protocol is also given, which can wipe off the tightly coupling between protocols and applications.