Evaluation Of Selfish Nodes' Effects In Opportunistic Networks And Its Application

In the opportunistic network,nodes are supposed to actively participate in the delivery process.However,in the real world,the node could take in an uncooperative manner,namely selfish ways.The selfishness will lead to the poorer performance of the opportunistic network,increasing the delivery delay,and decreasing the delivery probability.The evaluation of the impact of selfish nodes in the opportunistic network has been a research hotspot.This thesis mainly studies how selfishness affects performance of network,how to evaluate the effect of selfishness in the opportunistic network,and how to apply the evaluation scheme.Although there is much research related to evaluation.However most evaluations schemes have the following problems:the scenarios considered in these researches are relatively simple,so the conclusions drawn based on those scenarios are one-sided;the expression of the effects of selfishness are too complex to apply;the analysis has not been further applied.For selfishness further research can be performed and solutions can be achieved by resolving these problems.To solve these problems,the following results have been researched.Firstly,this thesis presents the evaluation based on messages classification.In the case with limitation of TTL and the case without limitation of TTL,average delay and message delivery probability can be derived under random way point model and the impact of selfishness.Secondly,in previous incentive studies,researchers didn't take performance guarantee into account,which usually cause over motivation.In this thesis,the evaluation scheme is applied to get the value of influential parameters for performance guarantee.Thirdly,theoretical analysis scheme presented is not applicable in some situations.As a supplement for analysis of effects,this thesis conducts an experimental analysis of the existing ferries scene,to find that in this scenario,the opportunistic network has robustness and vulnerability.Through experiments,it's found that the single-copy PRoPHET routing,Spray and Wait routing and single-copy Epidemic routing are affected by selfish behavior for their routing strategy.All these researches will help to solve the problem of selfishness.