Study On Wireless Multiple Access Control And Multicast Routing In Ad Hoc Networks

Multiple access control (MAC) and wireless ad hoc networks are two hot spots of research in the field of wireless communications. Despite of their promising prospects, both of them encounter a lot of challenges. Multiple access control (MAC), which provides a mechanism of sharing the channel resource efficiently, is one of the key techniques to enhance the utilization of channel resource. An ad hoc network, which is a self-organizing wireless network composed of mobile terminals, does not rely on any preexisting infrastructure. Since many applications in an ad hoc network require the cooperation among multiple users, multicast routing plays an important role. This paper deals with the MAC techniques in wireless access networks with a central access point (CAP), and multicast routing in ad hoc networks. Meanwhile, in consideration of the self-similar nature of traffic in communication networks, the queueing system of an ON/OFF traffic source with heavy-tailed distribution is discussed, because the aggregating traffic of a mass of such traffic sources exhibits self-similarity. The main research works and results are listed as follows.1. Two algorithms for queueing analysis are proposed. The first one, which is based on the method of phases, aims to analyze the queueing system of an ON/OFF traffic source, whose ON and OFF time-length distributions are heavy-tailed. The second one can estimate number of users in ON state as well as their respective bandwidth available. Thus, with the combination of these two algorithms, performance of the MUPMA protocol in terms of the throughput and average packet queueing time can be evaluated.2. A modified user-dependent perfect-scheduling multiple access protocol (MUPMA) is proposed. MUPMA protocol characterizes its access algorithm, which specifies a certain number of minislots at the end of each frame to accommodate access requests from activated users, and the number can be adjusted dynamically according to the degree of collisions. Based on MUPMA protocol, a QoS-supporting UPMA protocol, QUPMA protocol, is present. QUPMA has a unique frame structure and a priority-based access algorithm, which guarantee both the access and the transmission of real-time traffic prior to those of non-real-time traffic. In addition, a study on the influence of different traffic types on the properties of MUPMA protocol is conducted.3. A region-based multicast routing protocol (RMRP) for ad hoc networks is proposed. RMRP adopts a position-based partition algorithm, which divides the coverage area of an ad hoc network into a set of overlapped regions. RMRP protocol consists of two parts: the local multicast algorithm for multicasting within regions, and the global multicast algorithm for multicasting among regions. These two algorithms are proactive and reactive, respectively. Thus, RMRP operates in a hybrid proactive/reactive manner,by means of which it can not only reduce the latency to search multicast group members and establish corresponding paths, but also restrain the overhead due to the increment of network scale or multicast group size from increasing very fast.