Rapid Fading Due to Human Blockage in Pedestrian Crowds at 5G Millimeter-Wave Frequencies (1709.05883v2)

Abstract: Rapidly fading channels caused by pedestrians in dense urban environments will have a significant impact on millimeter-wave (mmWave) communications systems that employ electrically-steerable and narrow beamwidth antenna arrays. A peer-to-peer (P2P) measurement campaign was conducted with 7-degree, 15-degree, and 60-degree half-power beamwidth (HPBW) antenna pairs at 73.5 GHz and with 1 GHz of RF null-to-null bandwidth in a heavily populated open square scenario in Brooklyn, New York, to study blockage events caused by typical pedestrian traffic. Antenna beamwidths that range approximately an order of magnitude were selected to gain knowledge of fading events for antennas with different beamwidths since antenna patterns for mmWave systems will be electronically-adjustable. Two simple modeling approaches in the literature are introduced to characterize the blockage events by either a two-state Markov model or a four-state piecewise linear modeling approach. Transition probability rates are determined from the measurements and it is shown that average fade durations with a -5 dB threshold are 299.0 ms for 7-degree HPBW antennas and 260.2 ms for 60-degree HPBW antennas. The four-state piecewise linear modeling approach shows that signal strength decay and rise times are asymmetric for blockage events and that mean signal attenuations (average fade depths) are inversely proportional to antenna HPBW, where 7-degree and 60-degree HPBW antennas resulted in mean signal fades of 15.8 dB and 11.5 dB, respectively. The models presented herein are valuable for extending statistical channel models at mmWave to accurately simulate real-world pedestrian blockage events when designing fifth-generation (5G) wireless systems.

• The paper conducts empirical measurements at 73.5 GHz in Brooklyn to assess rapid signal fading caused by human blockage in pedestrian crowds at 5G millimeter-wave frequencies.
• Using Markov and piecewise linear models, the study found narrower beams like 70 HPBW experience longer fade durations (299 ms) and greater attenuation (15.8 dB) than wider beams like 600 HPBW.
• Results highlight the need for adaptive beamforming, rapid beam switching, and antenna planning using the fade depth model to mitigate human blockage effects in dense urban 5G mmWave deployments.

Insightful Overview of 5G Millimeter-Wave Frequencies and Human Blockage

The paper "Rapid Fading Due to Human Blockage in Pedestrian Crowds at 5G Millimeter-Wave Frequencies" by MacCartney et al. provides an in-depth exploration of the adverse effects of human blockage on millimeter-wave (mmWave) communications, specifically at the 5G frequency of 73.5 GHz. The primary focus is to assess the impact of pedestrians in densely populated urban environments on mmWave signal fading, leveraging empirical data and simple modeling techniques to enhance the fidelity of 5G communication systems.

Due to the high frequencies utilized in 5G mmWave communications, mmWave bands inherently exhibit greater susceptibility to obstructions such as human bodies. This can cause rapid signal fluctuations, requiring detailed paper to facilitate robust network architecture and service quality assurance. This paper's approach is to conduct controlled peer-to-peer measurements in a heavily trafficked open square in Brooklyn, New York, with beams detailed by half-power beamwidths (HPBW) of $7^\circ$, $15^\circ$, and $60^\circ$.

Empirical Methodology and Results

The paper's robust methodology incorporated precise measurements of a live urban environment to simulate real-world scenarios where pedestrian blockages are prevalent. With 1 GHz of bandwidth at 73.5 GHz frequency, a key focus was on fade durations and signal attenuation caused by human obstructions. Two modeling frameworks, a two-state Markov model and a four-state piecewise linear model, were employed to analyze fading events.

1. Two-State Markov Model Results:
   • The transition probability rate from the unshadowed to shadowed states remained approximately constant across HPBW settings at around 0.2 transitions per second.
   • Notably, the average fade duration was extended for narrower beamwidths, with a $7^\circ$ HPBW exhibiting mean fades lasting 299 ms compared to 260 ms for a $60^\circ$ HPBW.
2. Four-State Piecewise Linear Model Results:
   • The asymmetric nature of signal strength decay and rise times was noted, which is significantly influenced by non-linear pedestrian movement paths.
   • Wider beamwidths correlated with more substantial decay and rise rates. However, the mean attenuation in signal strength was inversely proportional to beamwidth, as the $7^\circ$ HPBW antenna revealed mean signal fades of 15.8 dB compared to 11.5 dB with a $60^\circ$ HPBW.

Implications and Future Directions

The results underscore the necessity of accounting for human blockage in mmWave real-world deployment, providing critical empirical data to validate and extend existing statistical models. Given the substantial variance in signal behavior due to pedestrian movement, the implementation of adaptive beamforming and the development of sophisticated signal processing algorithms are crucial for optimizing network resilience.

The linear model of fade depth versus HPBW offers engineers a useful tool for planning antenna configuration to mitigate signal attenuation effects in dense urban settings. Equally crucial are the implications for 5G hardware, emphasizing a design paradigm that optimizes for rapid beam switching to avoid prolonged obstruction and ensure consistent connectivity.

Moving forward, future research should center on expanding measurement campaigns to include various urban environments and exploring the impact of larger crowd densities on signal behavior. Additionally, assessing the interplay between different frequency bands could yield further insights into cross-band interference and enhancement strategies. These efforts will be pivotal in refining 5G infrastructure capable of withstanding diverse real-world conditions intrinsic to urban landscapes.