Abstract
The fog radio access network (F-RAN) is considered an efficient architecture for caching technology as it can support both edge and centralized caching due to the backhauling of the fog access points (F-APs). Successful transmission probability (STP), delay, and energy efficiency (EE) are key performance metrics for F-RAN. Therefore, this paper proposes a proactive cache placement scheme that jointly optimizes STP, delay, and EE in wireless backhauled cache-enabled F-RAN. First, expressions of the association probability, STP, average delay, and EE are derived using stochastic geometry tools. Then, the optimization problem is formulated to obtain the optimal cache placement that maximizes the weighted sum of STP, EE, and negative delay. To solve the optimization problem, this paper proposes the normalized cuckoo search algorithm (NCSA), which is a novel modified version of the cuckoo search algorithm (CSA). In NCSA, after generating the solutions randomly via Lévy flight and random walk, a simple bound is applied, and then the solutions are normalized to assure their feasibility. The numerical results show that the proposed joint cache placement scheme can effectively achieve significant performance improvement by up to 15% higher STP, 45% lower delay, and 350% higher EE over the well-known benchmark caching schemes.
Highlights
Edge caching is an efficient technology to alleviate the traffic congestion, communication delay, and energy consumption [1,2], which is achieved by reducing the data load in the core network by caching the popular contents at the edge devices closer to the end-users
The performance of the edge caching in fog radio network (F-RAN) can be further enhanced by taking advantage of the centralized caching provided by the cloud via backhauling the fog access points (F-APs) with the cloud access points (C-APs), which results in more efficient and flexible caching strategies [2]
This paper addresses the problem of obtaining the optimal cache placement that minimizes the delay or maximizes the successful transmission probability (STP) or EE in wireless backhauled F-RAN, where it is assumed that STP, delay, and EE have equal importance, i.e., the fitness function is evenly weighted
Summary
Edge caching is an efficient technology to alleviate the traffic congestion, communication delay, and energy consumption [1,2], which is achieved by reducing the data load in the core network by caching the popular contents at the edge devices closer to the end-users. The authors of [7,8,9,10,11,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27] did not tackle the wireless backhauling of the F-APs. The F-AP’s optimal cache placement is not addressed in [12,13,14,23,24,25,26,27], the joint optimization of EE and delay is not addressed in [25,26], STP and delay optimization are performed in [25,26] for a cooperative coded caching F-RAN, and the EE is not addressed in [28]. As far as the authors know, the problem of jointly optimizing STP, EE, and delay in uncoded cache-enabled F-RAN has not been addressed before. A multi-objective optimization of STP, EE, and delay in uncoded wireless backhauled cachedenabled F-RAN is proposed in this paper. Required number of time slots to successfully receive content m conditioned on the distance over the link from Fm,0 to u0, from C0 to Fm,0, from Fa,0 to u0 EE of content m when u0 is associated with Fm,0, Fa,0 EE of u0
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