Research On The MAC Layer And Related Technology Of Wireless AD HOC Networks

Wireless Ad hoc networks are composed of a group of terminals without fixed infrastructure assisted for a specific target. It is commonly used in military battlefield, disaster relief, remote field and so on, owing to its separate network, distributed, self-organizing, multi-hop communication, and network survivability characteristics. However, the development of the Internet of Things and civilian needs has made this technology penetrate into various aspects of civilian communication, such as environmental monitoring, wireless access, smart home, vehicular communication, acting as the short-range transmission technology of sensing layer.Meanwhile, in the practical applications, people not only satisfy with the data transmission, but also voice, video and other multimedia service, which require higher quality of service (QoS) and higher-speed data transmission. In Ad hoc networks, medium access control (MAC) is the controller of radio channel access, and responsible for the efficient sharing of radio resources between nodes. It can directly affect the transmission performance and quality of service, and also has a great impact on the design of upper-layer protocols. So it is of great significance for the study of new technologies in the MAC layer.This article is part of results of the project "Adaptive reconfigurable Ad hoc networks with sensing function" funded by National Nature and Science Fund Committee, and "Research and implementation of wireless Ad hoc experimental platform" funded by Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, and "Autonomous control technology of broadband mobile communications" funded by the General Staff Department. It focuses on the QoS and high-capacity data transmission in the practical application from the perspective of MAC layer and related technologies. The main contributions include the following aspects:Firstly, researched on the MAC protocol for QoS-guarenteed. This part analyzed the performance of802.11e EDCA in Ad hoc networks and the parameter optimization method, and proposed a delay estimation model based on the three-dimensional Markov Chain Model and M/G/1queuing theory, which is much closer to802.11e standard. Considering the influence of unsaturated traffic and the virtual collision of different priorities, we deduced the total delay of MAC layer of different traffics, and verified the accuracy of our model by simulation. This research will provide an important basis for related access control mechanism, and contribute to the application of EDCA in Ad hoc networks for the QoS support.Secondly, proposed a Pareto optimal multi-channel multi-interface allocation algorithm. Multi-channel multi-interface technology in MAC layer can improve the throughput greatly. This part studied the channel allocation problem based on the game theory. We extended the existing literature assumptions, and considered the actual situation that the valid throughput for a channel will decrease with the increasement of competing users. By using the decreasing function properties of the utility function, we designed an incentive mechanism in the game, and proposed a Pareto optimal channel allocation algorithm based on the Nash Equilibrium channel allocation, and verified the effectiveness of this algorithm to maximize the network throughput.Thirdly, proposed a mixed strategy channel selection algorithm. Considering the different channel with different data rates due to the quality or technology difference, namely the asymmetric channel characteristics, we built a saturation throughput mathematical model to quantify the utility of each node pair. By analyzing the optimal channel selection policy under different user numbers, a mixed strategy asymmetric channel selection algorithm was proposed based on the mixed Nash Equilibrium. Simulation results showed that this algorithm can maximize each user’s throughput and improve the fairness of channel selection.Fourth, proposed a multi-channel multi-interface cross-layer routing algorithm (MMRM) which was suitable for the mobile Ad hoc networks. Aiming to decrease to the co-channel interference and increase the throughput by using multi-channel multi-interface MAC, we proposed a cross-layer multi-channel multi-interface routing algorithm, which included the link lifetime estimation mechanism, multi-channel link quality awareness, multi-channel spatial diversity. The weighted link lifetime and hop metric was used to select the relatively stable path, and channels with the highest link quality were chosen hop-by-hop. These two processes were loosely coupled to build a flexible cross-layer routing. Algorithm analysis and simulation verified that MMRM can improve the end-to-end throughput and delay performance in a variety of scenarios.Fifth, proposed a multi-channel multi-interface cross-layer opportunistic routing algorithm (MMOR). Multi-channel can improve the network capacity by reducing co-channel interference, and opportunistic delivery offers a great chance to cope with the unreliability of wireless transmissions. By combining these two technologies, we proposed a multi-channel multi-interface opportunistic routing algorithm to increase the network end-to-end throughput and improve the packet delivery performance, which included a two-step scheme to build actual forwarding candidate set, prioritized packet forwarding, cumulative interference strength metric, and a received-oriented opportunistic delivery mechanism. Simulation results showed that MMOR can improve the end-to-end throughput and packet delivery performance.By the researches above, this article can provide both theoretical and technical support for the guarantee of MAC layer QoS and the large amount of data transmission in Ad hoc networks.