Performance Modeling Of Data Transmission In Opportunistic Network With Limited Resources

Opportunistic network is a novel kind of Mobile Ad hoc Networks, which takesfull advantage of the opportunistic contacts to transfer data. Thanks to its distinguishedfeature of dynamic networking, opportunistic networks have demonstrated verypromising application prospect in many areas including wildlife tracing, emergencynetworking, battlefield communications, inter-stellar communication, etc.Due to the high node mobility and low node density, opportunistic networks arecharacterized by frequent and long duration partitions. In opportunistic networks, adirect end-to-end path between source and destination may not exist. Instead, mobilenodes opportunistically exchange data when they are in the transmission range of eachother. All the nodes work in a "store-wait-forward" mode which allows the messages tobe transmitted hop-by-hop instead of end-to-end as in other traditional networks. It isessential to investigate the data transmission characteristics through carefully theoreticalanalysis, in order to design an optimal protocol to support the hop-by-hop transmission.In addition, the resources in mobile nodes, including transmission capacity, buffer andenergy, are usually limited. Therefore, in this thesis, we are focused on the performancemodeling of data transmission in opportunistic networks with limited resources. Themain achievements and contributions of our work can be summarized as follows.(1) In opportunistic networks, link duration is a main factor in determining thetransmission capacity between two encounter nodes. Existing researches usually assumethat a node is able to immediately discover the nodes which move into its transmissionrange and ignore the influence of neighbor discovery mechanism (or contact probingmechanism). Therefore, in this thesis, we carefully investigate the impact of contactprobing mechanism on link duration, and thus the transmission capacity of opportunisticnetworks. Based on that, we derive the theoretical node throughput and energyconsumption, and explore their tradeoff. In addition, we provide a framework tocompute the optimal contact probing frequency under energy limitation.(2) In maritime networks, the communication links are characterized by highdynamics due to fluctuating sea surface conditions and ship mobility. Some researchershave considered using opportunistic network to improve the performance of datatransmission in maritime circumstance. So far previous research work usually uses simulation to evaluate the transmission performance in maritime opportunistic networks.In this thesis, we develop a theoretical model to analyze the data transmission processbetween encountering ships in the seaway. We fist construct a model to describe the shipencountering probability. Then, we use this model to analyze the packet delivery ratiofrom ships to the base station. Based on the data of tracing the ships navigating in arealistic seaway, we develop a simulator and validate the theoretical models. In addition,by comparing the performance of opportunistic transmission protocol and traditionalend-to-end transmission protocol, we validate that opportunistic transmission canimprove the performance of data transmission in maritime networks.(3) Recently, network coding has been proposed as a promising approach toimprove data transmission efficiency in opportunistic networks. In this thesis, wedevelop an analytical model to evaluate the performance of Random Linear NetworkCoding (RLNC) based epidemic routing in opportunistic networks. So far exisitingrelated work considers only one unicast communication session existing in the network.In our model, we develop a more general model which considers multiple unicastsessions competing for limited transmission capacity. This model is more closed torealistic situations. Based on that, we compare the data transmission delay in RLNCbased routing protocol with that of conventional routing protocol under differentnetwork settings. Numerical results demonstrate that significant performanceimprovement for data transmission in opportunistic networks can be achieved byemploying network coding.(4) In the data transmission process of opportunistic networks, mobile nodesusually need to store and forward a large number of packets, which consumessubstantial buffer and energy resources of the nodes. Thus, in this thesis, we useprobabilistic forwarding protocol to reduce the number of packet copies which aregenerated in the transmission process. We develop a theoretical model to analyze thedata transmission process of probabilistic forwarding in opportunistic networks. Inaddition, we use this model to evaluate the impact of different forwarding probabilitieson transmission performance.Our research results of this thesis provide a general tool for performance evaluationof data transmission in opportunistic networks and some useful guidelines for designingdata transmission protocols with good performance in opportunistic networks.