Coverage-Rate Tradeoff Analysis in mmWave Heterogeneous Cellular Networks

TL;DR

This paper develops a comprehensive framework to analyze the fundamental tradeoff between coverage probability and link rate in mmWave heterogeneous cellular networks with multiple tiers, revealing the impossibility of maximizing both simultaneously.

Contribution

It introduces a generalized user association scheme and derives analytical expressions for coverage and link rate, highlighting the inherent tradeoff and providing optimal schemes for coverage and rate.

Findings

Coverage-rate tradeoff is fundamental in mmWave HetNets.

Optimal user association schemes for coverage and rate are characterized.

Numerical validation confirms the theoretical tradeoff analysis.

Abstract

In this paper, we first introduce a generalized modeling and analysis framework to explore the fundamental interactions between user association, coverage probability and link rate in a millimeter wave (mmWave) heterogeneous cellular network (HetNet) in which there are multiple tiers of the ultra-high-frequency (UHF) macrocell and small cell base stations (BSs) and a single tier of mmWave small cell BSs. A generalized user association scheme that can cover many path-loss-based user association schemes is proposed and its related probabilistic properties that facilitate the derivations of the coverage probability and link rate are derived. The derived general expressions of the coverage and link rate not only shed light on how to design user association functions in order to maximize the coverage and link rate but also show that it is impossible to devise a user association scheme that maximizes the coverage and link rate at the same time. Namely, there exists a fundamental tradeoff between the coverage and link rate in mmWave HetNets with distinct bandwidths in the UHF and mmWave bands while a user is associating with a BS. We characterize the coverage-optimal and rate-optimal user association schemes and numerically validate their performances and show the coverage-rate tradeoff problem.