Ad Hoc Network Layered Protocol And Cross-layer Design

Ad hoc networks are wireless communication systems with special structure; they don't depend on any fixed facilities, but depend on mutually cooperation of the nodes with several hops. They have the characteristics of self organization, distribution, dynamic state etc., so they can be deployed in complicate environment and perform data communication. Mobile Ad hoc network is an important branch of mobile communication. It is used in the military tactics, urgent service, disasters recover etc. It arouses high attention of many military sections, industrial fields and academic circles.However, comparing to other traditional communication networks, Ad hoc networks have the characteristics of self organization, dynamic topology, routing in several hops, transmission in the wireless condition etc. So a special protocol stack is required to be designed for it. In this thesis, the data link layer, network layer, transportation layer and cross-layer design of Ad hoc networks are analysised and researched respectively. The main contributions are introduced as follows:Chapter 1 introduces the history, characteristics, key technology and hot problems of Ad hoc networks. Research background, contribution and structure of this thesis are also presented in this chapter.Chapter 2 introduces the IEEE 802.11 and IEEE 802.11e and proposes an AEDCA (Adaptive EDCA) with traffic balance and QoS guarantee. This mechanism still adopts contention window (CW) to control deliver probability, and involves Token Bucket Algorithm (TBA) computing the multiple factor (MF) to balance the traffic, and follows the QoS mechanism used in IEEE 802.11e EDCA.Ad hoc network is subjected to bandwidth, delay, jitter, frame loss, etc. As a result, high class service is not suitable for transmission sometimes. This situation makes network congestion and low throughput, and unfair problem raised by high class service not sharing the bandwidth resource. An improved EDCA (IEDCA) mechanism with services differentiations is proposed. Channel resistance coefficient is introduced to compute the collision probability in this algorithm, considering the wireless characteristics.The parameters setting of active queue management (AQM) in Ad hoc networks is correspondence to the network, and has important impact on the stability and dynamic state function. We proposed an ANNPID algorithm to solve the problem of parameters setting of PID algorithm. Chapter 3 introduces the Ad hoc network routing protocols, including proactive routing, reactive routing and hybrid routing. We proposed a hybrid IAODV routing protocol with multipath and PA characteristics. It has the source routing feature of PA characteristics, allowing nodes listening and recording the route information. This method increased the size of data packet, but decreased the transmission times. The route table is established in route discovery process, and maintains the route to prevent expiration. The overhead of route discovery process is reduced by using multipath.Chapter 4 introduces basic congestion control mechanism in the transportation layer: slow start, congestion avoidance, fast retransmission and fast recovery. Aiming at the characteristic of the wireless link, three methods of improvement of TCP can be implemented: end-to-end solution, wired-wireless-combined TCP solution, TCP with data link improvement solution. Based on the introduction of the three main improve methods, the simulation of the main end-to-end TCP algorithms is done. The result proves the best performance of SACK algorithm.Chapter 5 introduces the cross-layer design in Ad hoc network and its common design method. The convex optimizing theory in Ad hoc network and its common application is then introduced.We proposed a cross-layer design in multimedia service. Delay is critical problem for delay-constrained service such as VoIP. Explicit congestion notice (ECN) is used to propose a joint transportation and data link layer adaptive TCP mechanism. Adaptive TCP involves frame delay (FD) as the criterion to judge the packet loss. TCP transmitting window is fixed as long as the FD satisfy our criterion, even though packet loss is high. We suppose that the packet loss is caused by wireless bit error not network congestion.Based on the convex optimizing theory used in wireless resource allocation, we are able to optimize the network performance through adjust parameter cross layer. We utilize cross-layer design and joint source code, power control, end-to-end delay allocation to set up a math mode to maximize the quality of video. Then our algorithm is proved can converge to the best value through theory discussion.Chapter 6 is the conclusion. We summarize the whole thesis, and discuss our further research.