Optimization and Analysis of Probabilistic Caching in N -Tier Heterogeneous Networks

• Published in: IEEE transactions on wireless communications Vol. 17; no. 2; pp. 1283 - 1297
• Main Authors: Li, Kuikui, Yang, Chenchen, Chen, Zhiyong, Tao, Meixia
• Format: Journal Article
• Language: English
• Published: IEEE 01.02.2018
• Subjects: Caching; density-caching tradeoff; Fading channels; Heterogeneous networks; Optimization; power-caching tradeoff; Probabilistic logic; Relays; wireless HetNets; Wireless networks
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2017.2777483

In this paper, we study the probabilistic caching for an N-tier wireless heterogeneous network (HetNet) using stochastic geometry. A general and tractable expression of the successful delivery probability (SDP) is first derived. We then optimize the caching probabilities for maximizing the SDP in the high signal-to-noise ratio regime. The problem is proved to be convex and solved efficiently. We next establish an interesting connection between N-tier HetNets and single-tier networks. Unlike the single-tier network where the optimal performance only depends on the cache size, the optimal performance of N-tier HetNets depends also on the base station (BS) densities. The performance upper bound is, however, determined by an equivalent single-tier network. We further show that with uniform caching probabilities regardless of content popularities, to achieve a target SDP, the BS density of a tier can be reduced by increasing the cache size of the tier when the cache size is larger than a threshold; otherwise, the BS density and BS cache size can be increased simultaneously. It is also found analytically that the BS density of a tier is inverse to the BS cache size of the same tier and is linear to BS cache sizes of other tiers.