Research On Data Forwording Scheme And Content Caching Strategy In Mobile Opportunistic Networks

Along with the deep exploiting of society,people find that due to the geographical conditions or infrastructures limitation,stable connected link status cannot be maintained in such specific environment.Mobile Opportunistic Networks(MONs)utilize the store-carry-forward scheme to transmit packets,in order to deal with the intermittently connected links,which satisfying the requirements of such specific network and application environments.However,there still remain many challenges of MONs development,such as the optimization of data transmission,content placement in the resource constraint nodes,the immediacy and continuity of sensing data,etc.Therefore,how to guarantee the data transmission and content caching efficiency is the key problem of MONs research.In order to deal with the aforementioned challenges,in this paper,we make a study of MONs from two aspects,one is the multi-copy routing scheme and the other is content caching strategy.The main contributions of our work are demonstrated as following:(1)The exploiting of human gathering point for data forwarding scheme.We introduce the sociality analysis under mobile opportunistic networks,consider the influence of human mobility on data communication and put a static node(AP)to assist data spraying.In our work,we analyze the different data transmission phrases and make the corresponding scheme.(2)Previous work employ the accumulative contact ratio to model node mobility,aiming to deal with the deficiency,we propose OPPO,an optimal data allocation scheme which takes the individual contact feature of nodes.OPPO allocates data copies in a proportional way and we analyze the critical conditions of HS and Spray Wait,and then prove the optimal delivery performance of OPPO.(3)Previous work make caching strategy only based on the node mobility,which leading to a limitation of application scenarios,aiming to deal with this problem,in our work,we propose a cooperative caching strategy under the hybrid mobile opportunistic networks by placing an AP in the center of network.Combining the preference of nodes for different data items and node mobility,we divide the mobile nodes in the network into Fetchers and Regulars based on the node utility.In order to improve the content caching success ratio and reduce the content access delay,the contents with high popularity are placed in the Fetchers and the lower ones are in the Regulars.(4)Based on the study of previous work,we discuss the data access delay under “Caching+Routing” overall framework.In the premise of fixed date request strategy and routing scheme,by introducing the data offloading application,we divide the whole data access process into two parts: D2 D communication phase and D2 A communication phase.By modeling the data request process and data transmission process in the two different phases respectively,we finally get the whole data access delay model under the “Caching+Routing” overall framework.In this paper,we research on the routing scheme and caching strategy,centering on the multiple-copy routing scheme and cooperative caching strategy under mobile opportunistic networks respectively.Three related works are demonstrated and validated by the mathematical analysis and experimental evaluations.At last,we model the whole data access delay under the “Caching+Routing” overall framework.