Study On End-to-End Transmission In Ad Hoc Networks With Communication And Computing Collaboration

Ad Hoc networks are characterized by limited bandwidth,multiple hops,and dynamic topology changes due to the time-varying wireless channel being susceptible to interference and the high mobility of network nodes,which results in a high link frame error rate and serious packet loss during end-to-end transmission.Especially in wireless networks,the traditional TCP protocol cannot distinguish the specific causes of packet loss,and attribute it to network congestion.Frequent congestion control makes TCP performance deteriorate seriously.The digital fountain code technology provides an idea for solving the serious packet loss problem in wireless networks by virtue of the rateless characteristics.However,due to the bottleneck link restriction and the lack of an effective congestion control method for the rateless code,the transmission efficiency of the traditional fountain code technology is limited.In addition,the service transmission requirements in the Ad Hoc network are constantly increasing,but the actual available resources of the network have not increased.The traditional end-to-end transmission method cannot provide differentiated services for heterogeneous services,resulting in low utilization of network resources.Therefore,there is an urgent need for an end-to-end transmission method that can break through the network bottleneck link restriction,adapt to the characteristics of the Ad Hoc network and provide targeted services for different services.Focusing on the above problem,in this thesis,an end-to-end transmission method is designed to support the end-to-end transmission requirements of different services in Ad Hoc networks.First of all,this paper adopts the method of carrying cross-layer parameters in routing packets to construct and maintain the network traffic map with a small cost,and further reduces the cost of maintaining the traffic map by using the fisheye routing technology;Secondly,based on the traffic graph constructed by each node,a distributed method is used to select the appropriate intelligent node proxy transmission on the path to overcome the restriction of the bottleneck link on the end-to-end transmission performance.Specifically,for services with Qo S requirements,with the optimization goals of maximizing throughput and minimizing delay,the throughput requirements can be met by selecting several transmission sub-flows and the combination of intelligent nodes on each sub-flow;For services without Qo S requirements,the optimization goal is to maximize the probability of successful transmission of encoded packets,and idle computing nodes are selected as intelligent nodes to effectively utilize network idle resources and ensure that the transmission performance of high-priority services is not damaged.Then,based on the intelligent node which has been selected,this paper proposes a split-coding transmission strategy Split-CT(Split-Coding Transmission)for unicast and multicast.On the one hand,the intelligent node adopts the strategy of forwarding while decoding to ensure the transmission efficiency;On the other hand,the relay node forwards the encoded packet to improve the decoding efficiency of the destination,and overcome the problem of low decoding efficiency caused by the loss of the encoded packet;Finally,based on the available bandwidth information of each link obtained from the traffic map,the funnel algorithm is used to control the source-end fountain code packet sending rate to solve the problem that the rateless code is easy to aggravate network congestion.In order to verify the performance of the proposed method,we use the NS-3 simulation tool to evaluate the performance of Split-CT.The results show that for unicast services,Split-CT is suitable for the scenarios where the source service has high throughput,poor network link quality,more transmission hops,and mobility,in these scenarios,compared with the traditional TCP protocol and CT,Split-CT can significantly improve end-to-end throughput and reduce transmission delay on the basis of ensuring service transmission requirements;For multicast services,compared with MUDP,Split-CT can effectively improve the probability of successful packet transmission and ensure the reliability of transmission.