[Paper Review] Analysis of Human-Body Blockage in Urban Millimeter-Wave Cellular Communications

Margarita Gapeyenko, Andrey Samuylov+8 more|arXiv (Cornell University)|Apr 16, 2016

Millimeter-Wave Propagation and Modeling10 references4 citations

TL;DR

This paper proposes a novel stochastic geometry-based model to analytically characterize human-body blockage in urban mmWave networks, modeling humans as randomly positioned cylinders with variable heights and radii. The key contribution is the derivation of blockage probability as a function of transmitter-receiver separation, antenna heights, and human density, revealing an optimal transmitter height that minimizes path loss and maximizes signal reliability in dense urban environments.

ABSTRACT

The use of extremely high frequency (EHF) or millimeter-wave (mmWave) band has attracted significant attention for the next generation wireless access networks. As demonstrated by recent measurements, mmWave frequencies render themselves quite sensitive to "blocking" caused by obstacles like foliage, humans, vehicles, etc. However, there is a dearth of analytical models for characterizing such blocking and the consequent effect on the signal reliability. In this paper, we propose a novel, general, and tractable model for characterizing the blocking caused by humans (assuming them to be randomly located in the environment) to mmWave propagation as a function of system parameters like transmitter-receiver locations and dimensions, as well as density and dimensions of humans. Moreover, the proposed model is validated using a ray-launcher tool. Utilizing the proposed model, the blockage probability is shown to increase with human density and separation between the transmitter-receiver pair. Furthermore, the developed analysis is shown to demonstrate the existence of a transmitter antenna height that maximizes the received signal strength, which in turn is a function of the transmitter-receiver distance and their dimensions.

Motivation & Objective

• To address the lack of analytical models for human-body blockage in mmWave urban communications.
• To develop a general, tractable framework that accounts for non-infinitesimal receiver dimensions and random human body parameters.
• To identify system design insights, particularly the optimal transmitter height, for minimizing blockage and path loss.
• To validate the analytical model against detailed ray-launching simulations for real-world accuracy.

Proposed method

• Modeling human blockers as cylinders with random height (normally distributed) and diameter (uniformly distributed), whose centers follow a Matern hard-core point process.
• Replacing the Matern process with an equivalent Poisson point process for tractable analysis using tools from stochastic geometry and renewal theory.
• Deriving blockage probability for both infinitesimal and interval (non-infinitesimal) receivers using line-of-sight (LoS) path interruption criteria.
• Defining three blockage events: partial, half, and full blockage, based on the number of blocked lines across the Rx aperture.
• Using a ray-launching simulator to validate analytical results across varying Tx-Rx distances, human densities, and receiver sizes.
• Applying the model to derive the optimal transmitter height that minimizes average path loss for a given Tx-Rx separation.

Experimental results

Research questions

• RQ1 What is the analytical probability of line-of-sight blockage caused by randomly distributed humans in urban mmWave networks?
• RQ2 How do receiver size, transmitter height, and human density jointly affect blockage probability?
• RQ3 Does a transmitter height exist that minimizes path loss, and how does it scale with Tx-Rx distance?
• RQ4 How accurate is the proposed analytical model compared to high-fidelity ray-launching simulations?
• RQ5 How does the blockage probability differ between point and interval receivers of finite size?

Key findings

• The blockage probability increases with both human density and transmitter-receiver separation distance.
• An optimal transmitter height exists that minimizes average path loss, and this height is proportional to the Tx-Rx separation distance.
• For a given separation, the blockage probability decreases as the ratio of receiver length to mean blocker diameter increases.
• The analytical model shows close agreement with ray-launching simulations, with maximum absolute deviation less than 0.1 for a 10 cm receiver.
• At large distances, blockage probability plateaus due to high likelihood of encountering blockers along the LoS path.
• The probability of blockage decreases exponentially with increasing transmitter height, especially at shorter distances.