Research On Cross Layer Design Of Wireless Network Based On Delay Optimization

With the rapid development of wireless network, the type of communication service also change a lot, the proportion of voice communication are declining gradually, and multimedia services are increasing in outbreaks of type. This change resulted in further expansion of the contradictions between the wireless network resource and Quality of Service (QoS). Nowadays the speed of wireless resources development can not adjust to the increase of the communication demand, This phenomenon probably will exist for many years, the disadvantages of traditional layered structure of wireless network system for this kind of phenomenon will gradually grow.In addition, the development trend of the wireless network technology is higher transmission rate and higher movement speed, and the channel environment has become more complex. Just putting the effort on improvement of the wireless network transmission speed unilaterally, it is difficult for researchers and not a very good way to solve the problems in the wireless network. We should think over and make a complete and careful analysis to solve a complex problem. The current big problems in the wireless network include the low transmission rate (relative to the wired network), channel interference, the instability of link, continual congestion, the spectrum utilization rate is not high, information exchange between the layers in wireless network is not smooth and so on. In recent years, many researchers used cross layer techniques to solve this problem and get some good result, but how to cross the layers and select the key point to study or design is becoming a big debate in recent years. There are two kinds of main research direction:one is focus on the cross layer problem based on the TCP congestion control; the other one is trying to solve the problem based on the self-adaptive link. This paper took use of the advantages of both research trend and synthesize their characteristics, and proposes a cross layer design method based on reducing the delay to improve QoS of the wireless network.For a variety of loss of wireless network packet, for the first time using convex optimization theory to do the convergence analysis for link packet loss and congestion packet loss, and the results showed that link packet loss for the convergence of network delay is better than congestion packet loss.According to the above conclusions, the study for delay mainly was carried in the link layer, detected the energy efficiency and transmission rate of the three kinds of model of hybrid automatic repeat request (HARQ). With the consecutive improving of wireless transmission equipment and technology, the quality of wireless channel has also been greatly improved, and an improved method based on the HARQII model is suggested. The improved method is designed for the phenomenon of the link packet loss, the simulation for it get some very good results. At the same time, considering the mechanism of HARQ in different groups, using reliable retransmission strategy not only effectively alleviate the effects of the wireless link fading on the performance of TCP, but also reduce the congestion packet loss and network delay.According to the complexity and time-varying characteristics of the wireless network, the paper studied how to use the combined adaptive modulation and coding (AMC), power control, HARQ control to maximize the quality of multimedia stream receiving. The proposed framework is based on the use of first-order two-dimensional discrete time Markov chains (DTMCs) jointly modeling the AMC scheme and the amplitude and rate of change of the wireless channel fading envelope. The behavior of the scheduler is embedded into the multidimensional PHY layer Markov model through the use of a service-vacation process. Depends on the effective bandwidth theory to simulate the packet arrival queue and effective energy theory to simulate the reaction of the PHY/MAC behavior, the DTMC-based and effective bandwidth/capacity-based approaches are analyzed and compared in a cross-layer design aiming at maximizing the average throughput of the system where constraints on the maximum tolerable average packet loss and delay are to be reduced, and through the simulation the paper proved better effect than current protocol.With the gradual way of thinking, in solving the congestion, the most important problem of wireless network, the paper used the convex optimization theory to find out the implementation point of optimal solution and optimization purposes, and achieved local optimization through the improvement of relevant protocol of link layer, and then proposed a cross layer model of wireless network based on the local optimization to realize the global optimization.