Study On Some Key Issues In Mobile Ad Hoc Networks

The mobile Ad Hoc network is a wireless system without a fixed (wired or wireless) infrastructure. It is a self-organizing network composed of mobile nodes or users. The chief difference between mobile Ad Hoc networks and conventional cellular technology is the apparent lack of a centralized entity within an Ad Hoc network. There are no base stations or mobile switching centers in an Ad Hoc network. Consequently, all network protocols must operate in a distributed manner. Recently, mobile Ad Hoc network becomes the hot spot of personal communications and Internet due to its flexible and convenient mobility support and continuous seamless multimedia communication.Starting from the intensely active area of research in mobile Ad Hoc networks, multiple access control (MAC) protocols, performance comparison of routing protocols, cost-efficient QoS routing protocol for mobile Ad Hoc networks and the issue about the optimal UDP packet size are studied in this paper. The main research works and results are listed as follows.1. Based on the idea of contention reservation access and polling transmission, User-dependent Perfect-scheduling Multiple Access (UPMA) protocol is presented, which supports both node mobility and multi-hop network architecture. It improves channel utilization greatly and guarantees that a node accesses the channel rapidly. By adopting the protocol in multi-hop wireless ad hoc network, the network performance is simulated and the related results are given. The results show that the UPMA protocol has satisfying network performance which are better than that gotten when CSMA or 802.11 with DCF is used.2. A performance comparison of three routing protocols developed for mobile ad hoc networks is researched. The protocols are: Dynamic Source Routing (DSR), Destination Sequenced Distance Vector (DSDV) and Ad-hoc On demand Distance Vector (AODV). Extensive simulations are made on a scenario where nodes move randomly and the related results are given which can be used in network decision-making process.3. A novel CEQRP (Cost-Efficient QoS Routing Protocol) for mobile Ad Hoc networks is proposed. CEQRP can provide QoS guarantee and is aimed at extending the battery's lifetime at each node by selecting the nodes with a longb attery's remaining lifetime to forward packets. Simulation results show that CEQRP has good network performance. Furthermore, CEQRP shows distinct performance advantages in using a node's electric energy efficiently. 4. The issue about optimal UDP packet size for mobile Ad Hoc networks when transmitting CBR traffic is studied. Extensive simulations are made on a scenario where nodes move randomly with AODV or DSR routing protocol being used. The simulation results show that the type of routing protocols, traffic intension and the BER of the wireless channel are all important factors affecting the optimal UDP packet size.