Multiple Mobile Terminal Oriented Cooperative File Download Scheme

In recent years,because of the intellectualization,mobile terminal technology come to the peak time of development.Mobile terminals not only have the ability to process complex task,but also have the storage capacity and multiple communication models.Nowadays,the mobile terminals can communicate with external network through cellular mobile communication technology such as GSM,CDMA,3g and 4g or short-range wireless communication technology such as Bluetooth,infrared,WIFI and the near field communication(NFC).Although 3G?4G have been widely used in mobile intelligent terminals(such as smart phones),it still results in long delays when downloading large files.In addition,the limited data traffic also affects mobile terminal users experience for internet.Through short-range wireless communication,collaborative work between multiple mobile terminals can provide service for single mobile terminal.Therefore,finding nearby mobile terminals that are interested in the same file,using their spare cellular data link to download file and transmitting the file segment to each other through the short-range wireless communication become possible.The cooperative file downloading between nearby terminals can effectively save users data traffic,reduce delay,and is called as multiple mobile terminals oriented cooperative file downloading in this paper.In order to achieve the cooperative file downloads scheme between multiple mobile terminals,we introduced the cooperative cache mechanism in the cooperative file download scheme.The cooperative caching mechanism mainly contains the cache discovery,cache admission control,cache replacement and cache consistency maintenance.The most important part is the cache replacement,and we proposed the improved Value-based cache replacement policy,by defining the neighborhood region of terminals and categorizing data items into primary copy and secondary copy dynamically during the process of data transmission.The simulation results show that by introducing the cooperative cache mechanism,file access latency is obviously improved,and the hit ratio is improved.Then,we proposed a novel cooperative file download scheme that based on genetic algorithm.We assumed that the mobile terminals have the ability to access the MANETs and cellular data network at the same time.The cooperative file download scheme mainly contains the following procedure.At first,we use the proxy discovery request and proxy discovery reply to find terminals that are willing to participate in the cooperative downloading,and then retrieve information(such as battery level,download speed)about the terminals.Next,the genetic algorithm is used to select a set of terminals that used for cooperative file downloading,through them original requester can get complete file at the minimum time.The simulation results show that the cooperative file download scheme with genetic algorithm can successfully select collaborative nodes with better performance and effectively reduce file download latency.