Research On Key Technologies In Mobile Ad Hoc Networks

Due to the characteristics such as indepent of infrastructure, self-organized and fast deployment, mobile ad hoc networks (MANETs) play a more and more important role in many aspects of people's daily life. The wide application prospect of MANETs stimulates the energetical development of relevant research. Under this background, this dissertation carries out deep research and study on several important problems of MANETs. These problems include multi-channel transmission power control MAC protocol, MAC and routing protocols utilize the characteristic of wireless channel, and the base of many security and QoS techniques used in MANETs - packet classification algorithm. The main contributions of this dissertation are as follows:1. The history, main characteristic, application prospect, and research hotspot of MANETs are reviewed as well as the MAC protocols of wireless local area networks and MANETs. We introduce the distribution coordination function (DCF) of IEEE 802.11, including two access mechanisms: the basic mechanism and the RTS/CTS (Request to Send/ Clear to Send) mechanism.2. Existing multi-channel transmission power control MAC protocols for MANETs, e.g. DCA-PC, suffer from the low utilization of control channel and the interference of communications using large power to the lower ones. To solve this problem, DDCA-PC, an enhanced protocol is proposed. DDCA-PC allows transmitting the control frames by lower power, and constrains the communications using large power in a dedicated channel. Simulation results indicate that compared to the DCA-PC protocol, DDCA-PC achieves a significant increase in the network throughput, while decreases the energy consumption also.3. To efficiently exploit the inherent characteristics of radio channels, a clustered opportunistic routing protocol - CORP (Clustered Opportunistic Routing Protocol)—is proposed. CORP forwards data packet by broadcasting it firstly, then selects the most appropriate node among the nodes received this packet to forward it further. As a result CORP can use long and unreliable radio links which would not be used by traditional protocols. The experiment results show that the proposed protocol presents significant performance improvements, in particular in the average transmission numbers and the network throughput.4. A packet classification algorithm named Adaptive Bitmap RFC which have been optimized for Intel IXP2xxx network processor architecture is proposed. We study the implementation issues of how an adaptive classification algorithm can be efficiently implemented on a multi-core and multithreaded NPU architecture. Our algorithm combines best traits of recursive flow classification (RFC) algorithm and bitmap compression, and multiply instruction substitution techniques to achieve deterministic classification performance while keeping the memory growth checked. Although we experiment on the Intel IXP2xxx series network processor, the same high-performance can be achieved on other similar NPU architectures.