Cache Replacement in CoMP-Based Multi-Cell Networks with Unknown Content Popularity

In this paper, we propose a new two-phase mixed cache replacement and content delivery framework for the online content delivery phase of a time-slotted coordinated multipoint (CoMP)-based multi-cell system with unknown content popularity. In our framework, the caches are updated according to only the last requests of users and channel state information (CSI) at the end of each time slot. To this end, we formulate the problem of finding efficient joint cache replacement strategy (CRS) and user association for a backhaul limited network to minimize the total backhaul traffic and maximize the total network throughput while guaranteeing the quality-of-service (QoS) requirement of users. The formulated problem is an integer nonlinear programming problem that is nonconvex and NPhard. In this regard, we propose a locally optimal approach based on sequential programming which has polynomial time complexity. For the delivery phase, we also propose an efficient user association policy determined in a similar way to the CRS algorithm. Simulation results show significant performance gains in terms of sum-rate of users and total backhaul traffic by our proposed online CRS compared to the traditional offline caching approaches.