Caching and bandwidth allocation policy optimization in heterogeneous networks

Caching at wireless edge is a promising way to support the explosive growth of traffic load. In this paper, we jointly optimize the caching and bandwidth allocation policy in a cache-enabled heterogeneous network, where macro base stations (BSs) each with high capacity backhaul but not cache and helpers each with cache are random located. Probabilistic caching and random bandwidth allocation are considered. We derive the closed-form expression of successful offloading probability, which is defined as the probability that a user is associated with helpers with the date rate greater than a threshold. The joint optimal problem is not concave in general case. Nonetheless, when the density of helpers is large, the joint global optimum can be obtained, where the optimal bandwidth allocation needs one-dimensional search and the optimal caching policy is with closed-form expression. Numerical results show that the offloading gain can be significantly improved by the joint optimization.