Research On The Medium Access And Power Control Technologies In Mobile Ad Hoc Networks

Mobile Ad Hoc network (MANET) has some advantages such as convenient and quick network setup, high reliability, strong flexibility, without depending on any fixed supporting infrastructure. These advantages make the applications of Ad Hoc network very extensive. With the appearance of numerous intelligentized and miniaturized wireless devices and smart household terminals, their requirements of information share and data exchange accelerate the development of Ad Hoc network and make it one of the current research hotspots. The research of channel access and share, power control, energy protection and routing in mobile Ad Hoc networks are focused on in this dissertation.Firstly, the protocol of medium access control (MAC) in Ad Hoc networks is researched. The multi-hop sharing character of wireless channel, the hidden terminal and exposed terminal problems are analyzed, and a novel dual channel protocol is presented. In this protocol, dual channel and improved handshakes as well as channel reservation are employed to avoid collision in data transmission. The hidden terminal and exposed terminal problems during data transmission are alleviated and the channel utilization ratio is increased. Based on received control packets, nodes use 3 different Network Allocation Vectors (NAV) in control channel or data channel. During data transmission, the hidden terminal can receive data simultaneously and the exposed terminal can also transmit data. The channel throughput performance of the protocol is analyzed and evaluated in heavy traffic networks. A comparison with a RTS/CTS based protocol is given. The results show that the protocol can improve channel throughput in Ad Hoc networks.Secondly, the problem of power control in Ad Hoc networks is analyzed and a power controlled MAC protocol based on IEEE 802.11 is presented. Transmission power and permitted receiving power of messages are comprised in the control packets. By exchanging control information between a pair of communication nodes, their transmission power of data packet is determined and the transmission power of other neighbor nodes is also restricted, which can effectively reduce the interference between hidden terminals and exposed terminals. During data receiving of one node, the protocol also allows its neighbor nodes to transmit. It is compared with the IEEE 802.11 MAC protocol by simulation. The results indicate that the power controlled protocol proposed can improve the end-to-end throughput performance in mobile Ad Hoc networks, while decrease the power consumption of mobile nodes greatly.