Efficient Edge Caching In Fog Radio Access Networks

With the massive influx of mobile devices and new data services into the network,the global mobile data traffic is growing in a rapid trend,which brings huge load pressure on wireless communication network,or even causes network congestion.Although the data traffic volume in the network is very large,research shows that nearly 80% of traffic loads come from the top 10% popular contents in the network,which means that there exist a large number of duplicate content transmissions in the network.Thus,by utilizing edge caching technology,popular contents in the network can be cached closer to end users,which will bring many advantages.O n one hand,users' content requests can be processed efficiently at the edge network to decrease the average download time for users.On the other hand,many repeated content transmission in the core network can be avoided so as to alleviate the traffic load pressure of the network.In this context,we focus on studying efficient edge caching in fog radio access network.Fog computing is the complement and extension of cloud computing,and fog radio access network deploys many fog access points with fog computing,caching and communication capabilities at the edge network,so as to promote edge processing by invoking distributed resources at the network edge on demand.Firstly,we consider a non-cooperative content caching system model in fog radio access networks.In this model,the total storage cache storages of the access layer are limited,and we consider the scenario where the average latency for users to obtain the requested content is mainly affected by the content transmission latency.By studying the relationship between the number of deployed fog access points,cache storage allocation and content caching strategies,we propose an efficient edge caching strategy jointly based on the deployment of fog access point and content placement.MATLAB simulation results demonstrate that the proposed strategy can efficiently decrease the average latency of obtaining the requested contents compared with some benchmark caching strategies.Further,we will consider another scenario where the content request traffic processing capabilities of fog access points are limited and content requests can not be processed as soon as they arrives at the fog access points,then the average latency for users to obtain the requested content will mainly include waiting latency in the queue and traffic processing latency.By utilizing the queue theory,the content request traffic model at the fog access points is introduced,which mainly includes the traffic arriving and processing procedure,and then a cooperative edge caching framework is established.Based on this framework,we propose a kind of traffic-aware and cooperative edge caching strategy,under the constraints of both limited cache storages and traffic processing capabilities.Then aiming at optimizing the average latency,the optimization problem for this proposed caching strategy is formulated,which can be proved to be a convex optimization problem.Next,to solve this problem,a caching algorithm based on alternating direction multiplier method is designed.By utilizing the designed algorithm,we obtain the optimal proposed caching strategy.Finally,in the MATLAB simulation process,it can be demonstrated that compared with traditional algorithm,the designed algorithm can guarantee correctness with a faster convergence rate.Moreover,compared with existing cache strategies,the proposed optimal edge caching strategy can effectively reduce the average latency for users to obtain the requested contents.