Cache Placement in Fog-RANs: From Centralized to Distributed Algorithms

Abstract

To deal with the rapid growth of high-speed and/or ultra-low latency data traffic for massive mobile users, fog radio access networks (Fog-RANs) have emerged as a promising architecture for next-generation wireless networks. In Fog-RANs, the edge nodes and user terminals possess storage, computation and communication functionalities to various degrees, which provides high flexibility for network operation, i.e., from fully centralized to fully distributed operation. In this paper, we study the cache placement problem in Fog-RANs, by taking into account flexible physical-layer transmission schemes and diverse content preferences of different users. We develop both centralized and distributed transmission aware cache placement strategies to minimize users' average download delay subject to the storage capacity constraints. In the centralized mode, the cache placement problem is transformed into a matroid constrained submodular maximization problem, and an approximation algorithm is proposed to find a solution within a constant factor to the optimum. In the distributed mode, a belief propagation based distributed algorithm is proposed to provide a suboptimal solution, with iterative updates at each BS based on locally collected information. Simulation results show that by exploiting caching and cooperation gains, the proposed transmission aware caching algorithms can greatly reduce the users' average download delay.

Edge Cache-Assisted Secure Low-Latency Millimeter-Wave Transmission

“…Edge caching has attracted increasing attention recently. Some woks focused on the delivery strategies [19]- [22] and others studied the cache placement problems [23]- [26]. Specifically, in [19], Tao et al proposed to form a multicast group for users requesting the same content, so that these users can be jointly served by the same group of RRHs.…”

“…Furthermore, the authors analyzed the obtained EE gain brought by cache. Based on the flexible physicallayer transmission and the diverse requirements of different users, Liu et al [23] studied the cache placement problem, and proposed centralized and distributed cache strategies to minimize the download delay. In [24], Zheng et al applied the cache technique to a distributed relay system, and proposed a hybrid cache scheme to minimize the outage probability.…”

Cooperative caching in fog radio access networks: a graph‐based approach

“…Let M = {1, 2, · · · , m, · · · , M } denote the F-AP set. Assume that neighboring F-APs can share files and cooperate with each other [15]. Whether two F-APs can cooperate or not depends on how well they satisfy some certain rules.…”

A Decomposition Framework for Optimal Edge-Cache Leasing

“…Tuholukova, Neglia and Spyropoulos [24] investigate optimal content placement for joint transmission schemes in small cell networks. Other works on CoMP include [25] and [26]. Liu et al [21] develop a distributed content placement algorithm for different transmission schemes.…”

“…The weights can represent the downlink throughput between a user and a CBS (other work with the same objective is [25]). For such a weights choice, the channel quality between m and s is a constant value h m,s that depends on a reference distance and the path loss exponent.…”