Tradeoff Caching Strategy of the Outage Probability and Fronthaul Usage in a Cloud-RAN

In this paper, a tradeoff content caching strategy is proposed to jointly minimize the cell average outage probability and fronthaul usage in a cloud radio access network. At first, an accurate closed-form expression of the outage probability conditioned on the user's location is presented, and the cell average outage probability is obtained through the composite Simpson's integration. The caching strategy for jointly optimizing the cell average outage probability and fronthaul usage is then formulated as a weighted sum minimization problem, which is a nonlinear 0-1 integer problem. Two heuristic algorithms are proposed to solve the problem. First, a genetic algorithm (GA)-based approach is proposed. Numerical results show that the performance of the proposed GA-based approach with significantly reduced computational complexity is close to the optimal performance achieved by an exhaustive-search-based caching strategy, and the GA-based approach can improve the performance by up to 47.5% on average than the typical probabilistic caching strategy. Second, in order to further reduce the computational complexity, a mode selection approach is proposed. Numerical results show that this approach can achieve near-optimal performance over a wide range of weighting factors through a single computation.