[Paper Review] Millimeter Wave Line-of-Sight Blockage Analysis

Ish Kumar Jain|arXiv (Cornell University)|Jul 12, 2018

Millimeter-Wave Propagation and Modeling6 citations

TL;DR

This paper proposes a stochastic geometry-based analytical model to characterize millimeter wave (mmWave) line-of-sight (LoS) blockage events in open park-like environments. By modeling base station (BS) and user equipment (UE) locations via a Poisson point process, it derives closed-form expressions for blockage probability, frequency, and duration, revealing that blockage dynamics—rather than capacity—dominate the required BS density for AR/VR applications, with height and density trade-offs explicitly quantified.

ABSTRACT

Millimeter wave (mmWave) communication systems can provide high data rates but the system performance may degrade significantly due to mobile blockers and the user's own body. A high frequency of interruptions and long duration of blockage may degrade the quality of experience. For example, delays of more than about 10ms cause nausea to VR viewers. Macro-diversity of base stations (BSs) has been considered a promising solution where the user equipment (UE) can handover to other available BSs, if the current serving BS gets blocked. However, an analytical model for the frequency and duration of dynamic blockage events in this setting is largely unknown. In this thesis, we consider an open park-like scenario and obtain closed-form expressions for the blockage probability, expected frequency and duration of blockage events using stochastic geometry. Our results indicate that the minimum density of BS that is required to satisfy the Quality of Service (QoS) requirements of AR/VR and other low latency applications is largely driven by blockage events rather than capacity requirements. Placing the BS at a greater height reduces the likelihood of blockage. We present a closed-form expression for the BS density-height trade-off that can be used for network planning.

Motivation & Objective

• To address the lack of analytical models for dynamic mmWave LoS blockage in macro-diversity networks.
• To quantify how blockage events—caused by mobile blockers and user bodies—affect QoS in mmWave systems.
• To determine the minimum BS density required to meet QoS for low-latency AR/VR applications.
• To investigate the trade-off between BS height and density for minimizing blockage impact.
• To provide a network planning framework based on blockage-driven design rather than capacity alone.

Proposed method

• Models the locations of base stations (BSs) and user equipment (UE) using a homogeneous Poisson point process (PPP).
• Applies stochastic geometry to derive the probability of LoS blockage based on the spatial distribution of blockers and UE mobility.
• Derives closed-form expressions for blockage probability, expected frequency, and expected duration of blockage events.
• Considers a scenario with a single serving BS and macro-diversity handover to other BSs during blockage.
• Incorporates BS height as a key parameter to model its impact on LoS availability and blockage likelihood.
• Uses geometric probability and coverage analysis to quantify the BS density-height trade-off for maintaining QoS.

Experimental results

Research questions

• RQ1 What is the analytical expression for the probability of mmWave LoS blockage in an open park-like environment?
• RQ2 How do the frequency and duration of blockage events scale with BS density and height?
• RQ3 What is the minimum BS density required to satisfy QoS for AR/VR applications, given blockage constraints?
• RQ4 How does increasing BS height reduce blockage probability and what is the resulting trade-off with BS density?
• RQ5 To what extent are blockage dynamics, rather than spectral efficiency, the primary driver for BS deployment density?

Key findings

• Blockage events—rather than capacity—dominate the required BS density for AR/VR applications, with QoS constraints being the primary driver.
• The minimum BS density needed to maintain QoS is significantly higher than that dictated by spectral efficiency alone, due to frequent and prolonged blockages.
• Increasing BS height reduces blockage probability, with a quantifiable trade-off between height and required density.
• A closed-form expression for the BS density-height trade-off is derived, enabling practical network planning for mmWave systems.
• Blockage duration exceeding 10ms—critical for VR user experience—can be mitigated through sufficient BS density and optimal height placement.
• The model confirms that macro-diversity handover is effective but only if the network is dimensioned based on blockage statistics, not just capacity.