Exploiting Tradeoff Between Transmission Diversity and Content Diversity in Multi-Cell Edge Caching

Caching in multi-cell networks faces a well-known dilemma, i.e., to cache same contents among multiple edge nodes to enable transmission cooperation/diversity for higher transmission efficiency, or to cache different contents to enable content diversity for higher cache hit rate. In this work, we introduce a partition-based caching to exploit the tradeoff between transmission diversity and content diversity in a multi-cell edge caching networks with single user only. The performance is characterized by the system average outage probability, which can be viewed as weighted sum between cache hit outage probability and cache miss probability. We show that (i) In the low SNR region, the edge nodes are encouraged to cache more fractions of the most popular files so as to better exploit the transmission diversity for the most popular content; (ii) In the high SNR region, the edge nodes are encouraged to cache more files with less fractions of each so as to better exploit the content diversity.