Distributed Storage Scheme Based On Repairable Fountain Code In Heterogeneous Device-to-Device Network

With the rapid growth of global mobile data,the spectrum resources of mobile communications and the burden of base stations are facing great pressure and challenges.The device-to-device communication(D2D)allows the user terminal to multiplex the spectrum resources of the cellular system,and the devices can directly communicate with each other without forwarding through the base station.D2 D communication alleviates the burden on the base station and improves the spectrum efficiency of the cellular system.At the same time,for the reliable storage problem of massive data,the existing mobile device's powerful storage and computing capabilities are used to distribute the file content to multiple mobile devices,which can satisfy the frequent download of data in nodes within the network.It achieves the goal of users to quickly access important business data and improves data transmission efficiency.In a D2 D network,when a mobile device storing data is unavailable,it is necessary to repair the lost data in time to ensure the and stability of the system.Therefore,the redundant fault-tolerant technologies of distributed storage systems have potential practical value in D2 D storage networks.Traditional redundancy fault-tolerant technologies,such as replication,erasure codes,or regenerating codes,although the reliability of the system is guaranteed to a certain extent,the problem of waste of storage resources,excessive bandwidth cost,and number of help nodes is still unavoidable.Moreover,the heterogeneity of D2 D networks has become an inevitable development trend of 5G communication networks in the future.Due to the different transmission capabilities of the devices between different areas in actual applications,communication cost imbalance and energy waste for D2 D distributed data storage networks need to be resolved.Aiming at the application problem of data fault-tolerance technology in the above D2 D distributed data storage network,this paper aims to reduce the communication cost of data download and repair,and introduce the repairable fountain code into the D2 D distributed data storage network to solve the reliable storage and timely repair problems of data in heterogeneous D2 D network.Our main research contents and contributions are as follows:The repairable fountain codes(RFC)are a family of fountain codes with distributed storage properties.RFCs are proposed in recent years on the basis of traditional channel coding.This paper first elaborates the encoding and decoding process of the repairable fountain codes.And we analyze the characteristics of the RFCs.We analyze the performaces of RFCs on distributed storage in detail and compare the performances with the traditional schemes such as replication,erasure codes and regenerating codes.These efforts lay the groundwork for the study of D2 D distributed data storage technology in heterogeneous networks.Secondly,for a D2 D data storage scenario composed of two sets of mobile devices with different transmission capabilities under the coverage of one base station,this paper designs the unequal repair locality codes based on RFC(URL-RFC)according to the rateless property of the RFCs and the repair locality of O(logk).The encoding,decoding,repair and other processes are described.And the performance of equal and unequal locality repairable fountain codes in the system model is analyzed and compared.The superiority of the URL-RFC scheme in the heterogeneous D2 D data storage network is verified by simulation.Finally,for the characteristics of base station miniaturization in the future,we propose a system model with RFC in hierarchical heterogeneous D2 D distributed data storage network.By considering and analyzing the working process of the model,we derive the performance formula of data downloading and repairing cost in the case of a certain repair interval.And for the model,we design the URL-RFC and its repair strategy under the hierarchical heterogeneous network model.The communication costs between URL-RFC scheme and other schemes are compared.The simulation shows that URL-RFC can better adapt to hierarchical heterogeneous D2 D distributed data storage network when mobile devices or the micro base stations have heterogeneity.