Dynamic popularity driven caching optimization at base station

Caching at base station (BS) has attracted significant research efforts for future wireless networks. Most existing works are based on the assumption of static content catalogue and stationary popularity distribution, which however is far away from the reality as recently reported in the literature. In this paper, we take the popularity dynamics into account, and study the caching policy at BS for a traffic model consisting of two categories of contents respectively with long and short lifespans. By modeling the two categories of contents with Independent Reference Model (IRM) and Shot Noise Model (SNM), we formulate a cache resource allocation problem to maximize the total cache hit ratio for both categories of contents, which gives rise to a hybrid proactive and reactive caching policy. We solve the problem numerically for general case and provide closed-form solutions for several special cases. Numerical and simulation results demonstrate remarkable performance gain of the proposed caching policy over non-hybrid caching polices.