[Paper Review] Large-Scale Parameters of Spatio-Temporal Short-Range Indoor Backhaul Channels at 140 GHz

Sinh Le Hong Nguyen, Katsuyuki Haneda+3 more|arXiv (Cornell University)|Sep 28, 2020

Millimeter-Wave Propagation and Modeling22 references39 citations

TL;DR

This paper presents 140 GHz indoor channel sounding measurements in a shopping mall and an airport check-in hall to estimate omni-directional large-scale parameters (pathloss, delay spread, azimuth spread) for short-range backhaul links and compares them with 3GPP NR InH models.

ABSTRACT

The use of above-100 GHz radio frequencies would be one of promising approaches to enhance the fifth-generation cellular further. Any air interface and cellular network designs require channel models, for which measured evidence of largescale parameters such as pathloss, delay and angular spreads, is crucial. This paper provides the evidence from quasi-static spatiotemporal channel sounding campaigns at two indoor hotspot (InH) scenarios at 140 GHz band, assuming short-range backhaul connectivity. The measured two InH sites are shopping mall and airport check-in hall. Our estimated omni-directional large-scale parameters from the measurements are found in good match with those of the Third Generation Partnership Project (3GPP) for new radios (NR) channel model in InH scenario, despite the difference of assumed link types and radio frequency range. The 3GPP NR channel model is meant for access links and said to be valid up to 100 GHz, while our measurements cover shortrange backhaul scenarios at 140 GHz. We found more deviation between our estimated large-scale parameters and those of the 3GPP NR channel model in the airport than in the shopping mall.

Motivation & Objective

• Motivate exploration of above-100 GHz bands for short-range indoor backhaul in 5G+ contexts.
• Provide measured evidence for large-scale channel parameters (pathloss, delay spread, azimuth spread) at 140 GHz.
• Assess how measured parameters align with 3GPP NR InH models despite link-type differences.
• Highlight differences between shopping mall and airport environments and implications for channel modeling.

Proposed method

• Use a quasi-static spatio-temporal channel sounder at 140 GHz with a VNA, up-/down-converters, and RF-over-fiber to extend range.
• Perform measurements at two indoor hotspot sites (shopping mall and airport check-in hall) with elevated Tx/Rx heights and LOS-dominant links.
• Estimate multipath parameters (alpha_l, phi_l, tau_l) from peak detection of the PADP using an antenna gain-de-embedding approach (G_a = 19 dBi).
• Derive omni-directional large-scale parameters (pathloss, delay spread, azimuth spread) from estimated multipath parameters and compare with 3GPP NR InH LOS model (frequency substituted to 140 GHz).
• Address instability of the sounder transfer function by calibration and consider dynamic range limits in parameter estimation.

Experimental results

Research questions

• RQ1 What are the omni-directional large-scale parameters (pathloss, delay spread, azimuth spread) for 140 GHz indoor short-range backhaul channels in shopping mall and airport environments?
• RQ2 How well do the 140 GHz measurements agree with the 3GPP NR InH LOS model parameters (with frequency terms adjusted to 140 GHz) for indoor hotspot scenarios?
• RQ3 Do the two indoor sites exhibit different levels of deviation from the 3GPP NR model, and what environments contribute to these differences?
• RQ4 What are the practical implications of measured long-delay multipaths and angular spread for high-frequency indoor backhaul design?

Key findings

• Pathloss at 140 GHz in the shopping mall matches the LOS model within +0.9 dB on average (std 3.6 dB).
• Delay spread in the shopping mall matches the LOS model within +1.3 ns on average (std 8.5 ns).
• Azimuth spreads in the shopping mall match within +18.0° (AoD) and −0.2° (AoA) on average (std 11.6°).
• In the airport, pathloss matches the LOS model within −0.9 dB (std 3.6 dB).
• Airport shows much larger delay spread (mean 54 ns, std 40 ns) than the LOS model, due to long-delayed multipaths, and azimuth spread is generally smaller than LOS model expectations (mean differences: AoD −13.4°, AoA 4.8°; std 9.1°).
• Overall, 3GPP NR InH LOS model agrees better with the shopping mall than with the airport measurements at 140 GHz.