Caching Policy Toward Maximal Success Probability and Area Spectral Efficiency of Cache-enabled HetNets

TL;DR

This paper derives optimal caching policies in cache-enabled HetNets to maximize success probability and area spectral efficiency, analyzing the impact of system parameters and comparing with traditional HetNets.

Contribution

It introduces a probabilistic caching framework using stochastic geometry to optimize caching policies for success probability and ASE in HetNets.

Findings

Optimal caching probability varies with system parameters.

Helper density can be reduced by increasing cache size.

Existence of an optimal helper density for maximum ASE.

Abstract

In this paper, we investigate the optimal caching policy respectively maximizing the success probability and area spectral efficiency (ASE) in a cache-enabled heterogeneous network (HetNet) where a tier of multi-antenna macro base stations (MBSs) is overlaid with a tier of helpers with caches. Under the probabilistic caching framework, we resort to stochastic geometry theory to derive the success probability and ASE. After finding the optimal caching policies, we analyze the impact of critical system parameters and compare the ASE with traditional HetNet where the MBS tier is overlaid by a tier of pico BSs (PBSs) with limited-capacity backhaul. Analytical and numerical results show that the optimal caching probability is less skewed among helpers to maximize the success probability when the ratios of MBS-to-helper density, MBS-to-helper transmit power, user-to-helper density, or the rate requirement are small, but is more skewed to maximize the ASE in general. Compared with traditional HetNet, the helper density is much lower than the PBS density to achieve the same target ASE. The helper density can be reduced by increasing cache size. With given total cache size within an area, there exists an optimal helper node density that maximizes the ASE.