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Propagation Measurement System and Approach at 140 GHz-Moving to 6G and Above 100 GHz
Yunchou Xing, Theodore S. Rappaport
TL;DR
Above-100-GHz radio channels lack the measurement base available below 100 GHz, despite wider unused bandwidth. The paper reviews D-band propagation, designs a 140 GHz wideband sounder, and reports preliminary material-penetration measurements while proposing broader indoor campaigns. Its measurements validate free-space path loss at 140 GHz, quantify increasing penetration loss with frequency, and support future indoor channel modeling.
Problem
Radio-channel knowledge above 100 GHz is limited, even though wider unused bandwidth slots are available for wireless applications.
Method
The paper reviews D-band measurements, provides a 140 GHz wideband channel-sounder architecture, and proposes indoor propagation and material-penetration measurements.
Results
140 GHz measured path loss agrees with Friis free-space loss and the 1 m-reference CI model, while penetration loss increases from 28 to 73 to 140 GHz.
Takeaways & Limitations
The measurements and planned campaign will support statistical indoor channel models across frequencies, antenna configurations, and polarizations.
Abstract
from arXiv · showhide
With the relatively recent realization that millimeter wave frequencies are viable for mobile communications, extensive measurements and research have been conducted on frequencies from 0.5 to 100 GHz, and several global wireless standard bodies have proposed channel models for frequencies below 100 GHz. Presently, little is known about the radio channel above 100 GHz where there are much wider unused bandwidth slots available. This paper summarizes wireless communication research and activities above 100 GHz, overviews the results of previously published propagation measurements at D-band (110-170 GHz), provides the design of a 140 GHz wideband channel sounder system, and proposes indoor wideband propagation measurements and penetration measurements for common materials at 140 GHz which were not previously investigated.
I. INTRODUCTION
Research and standards activity below 100 GHz has produced extensive measurements and channel models, while radio-channel knowledge above 100 GHz remains limited despite wider unused bandwidth.
- 15 Gbps peak rates were demonstrated using 4 × 4 handset phased arrays with 200 m base-station spacing.
- Extensive measurements at 28, 38, 60, and 73 GHz support channel models proposed for frequencies below 100 GHz.
- Above 100 GHz, wider unused bandwidth slots motivate research into future indoor, outdoor, rural, and fixed wireless applications.
II. MOVING TO 6G AND FREQUENCIES ABOVE 100 GHZ
Activity above 100 GHz spans spectrum regulation, communications research, and potential high-bandwidth applications, with atmospheric absorption varying substantially by frequency.
- The 120, 183, 325, and 380 GHz bands are suited to very close-in links because atmospheric absorption increases rapidly beyond a few meters.
- The 77, 140, and 240 GHz bands have 1 dB or less additional atmospheric loss per kilometer and are suitable for longer-range broadband applications.
- The FCC proposed licensed, unlicensed, and experimental access across spectrum above 95 GHz, while Japan allocated 18 GHz from 116 to 134 GHz for broadcasting.
- Fiber replacement is motivated by high installation and maintenance costs in rural areas, where broadband wireless links could provide comparable rates with lower latency than fiber.
III. PROPAGATION IN D-BAND (110-170 GHZ)
Prior D-band measurements used VNA-based sounders to characterize path loss and multipath, while the NYU system supports wideband directional measurements over longer and shorter channel conditions.
- A 140 GHz shopping-mall sounder provided 130 dB dynamic range and 4 GHz bandwidth over measurable distances of 3–65 m.
- At 140 GHz, path-loss slope and variation were similar to 28 GHz measurements apart from additional free-space path loss.
- 140 GHz measurements averaged 5.9 clusters and 3.8 multipath components per cluster, fewer than the corresponding 28 GHz averages of 7.9 and 5.4.
- Four indoor directional path-loss models produced LOS path-loss exponents near 2.0, while multi-frequency CIF and ABG models showed better PLE and standard-deviation stability.
IV. A NOVEL 140 GHZ CHANNEL SOUNDER SYSTEM
The paper presents a 140 GHz wideband channel sounder and verifies its free-space path-loss measurements, then applies it to indoor penetration measurements of common materials.
- Channel sounder system: The dual-conversion 140 GHz sounder supports wideband sliding-correlator and real-time spread-spectrum modes for long-distance and short-range channel measurements.The modes target angular/delay spread, Doppler, and rapidly fading characterization.
- Channel sounder system: The transmitter generates a 142 GHz RF signal and radiates it through a 27 dBi rotatable horn antenna with 8° beamwidth in azimuth and elevation.The RF signal is amplified before transmission, and image frequencies are filtered by a 140 GHz bandpass filter.
- Channel sounder system: The receiver downconverts the signal and correlates its I/Q baseband outputs with an offset-rate PN sequence to obtain processing gain.The processing gain increases acquisition time to the order of tens of milliseconds.
- Channel sounder system: The system measures dual-directional information by sweeping gimbaled antennas through 360° in azimuth and 120° in elevation at 1° steps, but its range is reduced by 0 dBm output power.The lower output power is attributed to limited amplifier technology at 140 GHz.
- Free-space path loss: At 1–5 m separations, measured 140 GHz free-space path loss agrees with Friis FSPL and the 1 m-reference CI model, while the 73-to-140 GHz difference is 5.85 dB.The measured 5.85 dB difference is close to the 5.66 dB theoretical Friis value, indicating high channel-sounder accuracy.
- Indoor penetration measurements: At 140 GHz, average penetration loss is 14 dB/cm for clear glass and 1.04 dB/cm for drywall, exceeding the corresponding 28 and 73 GHz values.Measurements included clear glass, a glass door, and drywall samples with multiple thicknesses and locations.
VI. PLANNED INDOOR PROPAGATION MEASUREMENTS
The planned 140 GHz campaign will measure broadband propagation in a multipath-rich office environment to support frequency-dependent channel modeling, spatial consistency, and localization studies.
- Measurements will cover hallways, meeting rooms, cubicle offices, laboratories, and open areas on the ninth floor of 2 MetroTech Center.
- The campaign will collect data across locations and antenna polarizations for a frequency-dependent broadband statistical channel model compatible with NYUSIM.It will combine new 140 GHz measurements with existing 28 and 73 GHz indoor data.
- Forty-eight TX-RX combinations will reuse prior 28 and 73 GHz measurement locations, spanning 3.9 to 45.9 m.
- The 4 GHz RF-bandwidth campaign will support channel modeling, precise localization algorithms, and spatial consistency analysis for smooth local channel transitions.
VII. CONCLUSION
The paper reviews above-100 GHz research and D-band measurements, presents a 140 GHz channel sounder, and reports preliminary material penetration measurements while proposing indoor measurements for statistical modeling.
- The paper summarizes above-100 GHz research and rulemakings, reviews D-band propagation measurements, and provides the NYU WIRELESS 140 GHz channel-sounder architecture.
- Preliminary 140 GHz penetration-loss measurements for various building materials are compared with measurements at 28 and 73 GHz.
- Planned 140 GHz indoor measurements will combine with prior 28 and 73 GHz data to form statistical indoor channel models across antenna configurations, polarizations, and frequencies.
- The processed data and resulting models are intended to support indoor mmWave network design, position-localization studies, and future gigabyte WiFi with Internet of Things.