Edge Caching in Dense Heterogeneous Cellular Networks With Massive MIMO-Aided Self-Backhaul

This paper focuses on edge caching in dense heterogeneous cellular networks, in which small base stations (SBSs) with limited cache size store the popular contents, and massive multiple-input multiple-output (MIMO)-aided macro base stations provide wireless self-backhaul when SBSs require the non-cached contents. Our aim is to address the effects of cell load and hit probability on the successful content delivery (SCD) and present the minimum required base station density for avoiding the access overload in an arbitrary small cell and backhaul overload in an arbitrary macrocell. The achievable rate of massive MIMO backhaul without any downlink channel estimation is derived to calculate the backhaul time, and the latency is also evaluated in such networks. The analytical results confirm that hit probability needs to be appropriately selected in order to achieve SCD. The interplay between cache size and SCD is explicitly quantified. It is theoretically demonstrated that when non-cached contents are requested, the average delay of the non-cached content delivery could be comparable to the cached content delivery with the help of massive MIMO-aided self-backhaul, if the average access rate of cached content delivery is lower than that of self-backhauled content delivery. Simulation results are presented to validate our analysis.

本文聚焦于密集异构蜂窝网络中的边缘缓存，在该网络中，缓存大小有限的小型基站（SBS）存储热门内容，而当SBS需要未缓存的内容时，大规模多输入多输出（MIMO）辅助的宏基站提供无线自回程。我们的目的是解决小区负载和命中概率对成功内容交付（SCD）的影响，并给出避免任意小小区接入过载和任意宏小区回程过载所需的最小基站密度。推导了在无下行链路信道估计情况下大规模MIMO回程的可实现速率以计算回程时间，并对这类网络中的延迟也进行了评估。分析结果证实，为了实现SCD，需要适当选择命中概率。缓存大小与SCD之间的相互作用得到了明确量化。从理论上证明，当请求未缓存的内容时，如果缓存内容交付的平均接入速率低于自回程内容交付的平均接入速率，在大规模MIMO辅助自回程的帮助下，未缓存内容交付的平均延迟可能与缓存内容交付的平均延迟相当。给出了仿真结果以验证我们的分析。