This paper studies edge caching in dense heterogeneous cellular networks, inwhich small base stations (SBSs) with limited cache size store the popularcontents, and massive multiple-input multiple-output (MIMO) aided macro basestations provide wireless self-backhaul when SBSs require the non-cachedcontents. We address the effects of cell load and hit probability on thesuccessful content delivery (SCD), and evaluate the minimum required basestation density for avoiding the access overload in a small cell and backhauloverload in a macrocell. We demonstrate that hit probability needs to beappropriately selected, in order to achieve SCD. We derive the massive MIMObackhaul achievable rate without downlink channel estimation, to calculate thebackhaul time. We provide important insights on the interplay between cachesize and SCD, and analyze the latency in such networks. We demonstrate thatwhen non-cached contents are requested, the average delay of the non-cachedcontent delivery could be comparable to the cached content delivery with thehelp of massive MIMO aided self-backhaul, if the average access rate of cachedcontent delivery is lower than that of self-backhauled content delivery.Simulation results are presented to validate our analysis.
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