  In this paper, we study the problem of optimal scheduling of content
placement along time in a base station with limited cache capacity, taking into
account jointly the offloading effect and freshness of information. We model
offloading based on popularity in terms of the number of requests and
information freshness based on the notion of age of information (AoI). The
objective is to reduce the load of backhaul links as well as the AoI of
contents in the cache via a joint cost function. For the resulting optimization
problem, we prove its hardness via a reduction from the Partition problem.
Next, via a mathematical reformulation, we derive a solution approach based on
column generation and a tailored rounding mechanism. Finally, we provide
performance evaluation results showing that our algorithm provides near-optimal
solutions.
