Ad Hoc Network Qos In Key Technologies

The Mobile Ad hoc network (MANET) is a dynamic and self-organized network system with temporary network topology, which is composed of mobile stations with wireless transceivers and receivers. Each mobile station can serve not only as a communication terminal but also as a router node. And the data packet is relayed hop-by-hop between two adjacent nodes, without any supports of infrastructure. The distinguish features of the network, such as convenience, flexibility, mobility, self-organization and connecting at any time or any location etc, make Ad hoc network deployed broadly in many military area, civil area and commercial area such as battle communication, disaster relief, emergency rescue, temporary meeting, intelligent transport, exploration and so on. Nowadays, Ad hoc network is a hot research area in home and abroad and has broad prospect.With the increasingly application of the Ad hoc network, the demanding for supporting different quality of service (QoS) in the network arises. Especially the audio, video and real time data communication applications require strict QoS guarantee such as delay, delay jitter, priority differentiation and Bandwidth Allocation. Although the multi-hop and distribution feature makes the Ad hoc network's constructing more convenient and flexible, it also makes QoS supporting a huge challenge. Because of the distributed free contention access mode in Medium Access Control (MAC) layer, the limited transmission range, asynchronous station clock, not understanding fully about network status and frequent changing of network topology by node moving in Ad hoc network, many QoS technology used in fixed network and some mobile wireless network with point center facility can not be transplanted to Ad hoc network directly. So QoS guarantee is a difficulty for Ad hoc researchers. In Ad hoc network, solving QoS problem in a certain layer is impossible because there are too much influence among protocol layers. So, every protocol layer must offer QoS support technology. As a result, this dissertation conducts in-depth and systematical research in network layer, MAC layer and transport layer of the Ad hoc network, when participating in National Natural Science Fund Project 60372101 and 60772109, and makes some innovative research results:1. Briefly introduces the history of Ad hoc, analyze the characteristic, the main hot spots, application future, development trend of Ad hoc networks, and then present the research background, contents and innovations of this dissertation. 2. Mainly discusses the protocol stack structure of Ad hoc networks, concludes the present research on transport layer, network layer and MAC layer, and describes the QoS guarantee model in Ad hoc network.3. Firstly proposes a multi-path routing protocol TRND-AODV to enhance the routing stability and avoid congestion in Ad hoc, which can realize node disjoint multi-path routing in one routing process. Based on this routing algorithm, a network model and a node disjoint multi-path routing protocol AODLS are proposed, through combining the routing techniques in Ad hoc with the label fast-forwarding techniques in MPLS. It makes the Ad hoc can adapt to the mobile MPLS network.4. Using the slow start window principle in TCP congestion control scheme, a MAC backoff algorithm called MISSD for IEEE 802.11 DCF is proposed, to enhance the node fairness and the network bandwidth utilization. And then in order to improve the network congestion status and achieve or approach the optimum performance in different network scale, a self-adaptive backoff algorithm SAOP based on Optimum Parameter approaching is proposed, which can be applied to WLAN well.5. Summarizes the reason that increasing of low priority data stream influence high priority throughput in WLAN, then two self-adaptive multiple priority algorithm named SAQMR and MRDCW are proposed to protect high priority quality of service better by using RTS multiple reservation priority differentiating and inspecting network status to adjust algorithm parameter dynamically.6. To avoid the relay congestion and guarantee high priority QoS in Ad hoc, a multi-hop network QoS model named WMHQ and adaptive cooperation channel access algorithm named QAC-EDCA with three layer priority mechanism, multi-hop coordination mechanism and reception avoiding Strategy are proposed through analyzing the influence on each other of multi-hop nodes in Ad hoc surrounding.7. Analyzes the problem of transport layer protocol TCP existing in Ad hoc network, a cross-layer solution is proposed, which transfer the TCP-ACK. packet through the CFCA algorithm.Through the research above, the aim of this dissertation is to provide a complete QoS solution mechanism from the MAC layer to transport layer for Ad hoc networks.