Abstract
Comparisons of outdoor Urban Microcell (UMi) large-scale path loss models, root mean square (RMS) delay spreads (DS), angular spreads (AS), and the number of spatial beams for extensive measurements performed at 28, 38, 73, and 142 GHz are presented in this letter. Measurement campaigns were conducted from 2011–2020 in downtown Austin, Texas, Manhattan (New York City), and Brooklyn, New York with communication ranges up to 930 m. Key similarities and differences in outdoor wireless channels are observed when comparing the channel statistics across a wide range of frequencies from millimeter-wave to sub-THz bands. Path loss exponents (PLEs) are remarkably similar over all measured frequencies, when referenced to the first meter free space path loss, and the RMS DS and AS decrease as frequency increases. The similar PLEs from millimeter-wave to THz frequencies imply that spacing between cellular base stations will not have to change as carrier frequencies increase towards THz, since wider bandwidth channels at sub-THz or THz carrier frequencies will cover similar distances because antenna gains increase quadratically with increasing frequency when the physical antenna area remain constant.
Highlights
Inspired by the success of 5G commercial deployments at millimeter wave and sub-6 GHz frequencies, futuristic wireless communication systems (e.g., 6G and beyond) will likely utilize sub-THz and THz frequencies above 100 GHz to provide much higher data rates (Tbps) with near-zero latency [1]–[3], and global coverage with unmanned aerial vehicles (UAV), high altitude platform stations (HAPS), satellites, terrestrial and maritime stations [4], ushering in innovative applications such as autonomous vehicles/drones, wireless cognition, and precise localization with centimeterlevel accuracy [4], [5]
Compared to our previous work in [17,18,19,20,21], which presented outdoor Urban Microcell (UMi) channel statistics of path loss and root mean square (RMS) delay spread, this letter introduces new findings of outdoor time and angular statistics (RMS angle of arrival (AOA)/angle of departure (AOD) spread, average number of AOA/AOD directions, and RMS delay spread) at frequencies from 28-142 GHz, which will be useful for multiple-input multiple-output (MIMO) rank analysis and capacity predictions for future sub-THz systems
28 GHz, 11 ns at 38 GHz, 23 ns at 73 GHz, and 9 ns at 142 GHz, which are all larger than the RMS delay spreads in NLOSBest and LOS boresight scenarios across all four frequencies bands, since for UMi NLOS scenarios there is likely more than one dominant multipath
Summary
Inspired by the success of 5G commercial deployments at millimeter wave (mmWave) and sub-6 GHz frequencies, futuristic wireless communication systems (e.g., 6G and beyond) will likely utilize sub-THz and THz frequencies above 100 GHz to provide much higher data rates (Tbps) with near-zero latency [1]–[3], and global coverage with unmanned aerial vehicles (UAV), high altitude platform stations (HAPS), satellites, terrestrial and maritime stations [4], ushering in innovative applications such as autonomous vehicles/drones, wireless cognition, and precise localization with centimeterlevel accuracy [4], [5]. Recent work in [16] presented 142 GHz outdoor Urban Microcell (UMi) radio propagation measurements for LOS and NLOS scenarios with coverage ranges up to 117 m. This letter presents a comprehensive comparison of outdoor urban wireless channels using transmitting base station antenna heights that varied between 4 and 36 m above ground in four frequency bands from 28 to 142 GHz in UMi environments for both LOS and NLOS scenarios with coverage ranges up to 930 m, based on extensive outdoor radio propagation measurements conducted from 2011 to 2020. Compared to our previous work in [17,18,19,20,21], which presented outdoor UMi channel statistics of path loss and RMS delay spread, this letter introduces new findings of outdoor time and angular statistics (RMS AOA/AOD spread, average number of AOA/AOD directions, and RMS delay spread) at frequencies from 28-142 GHz, which will be useful for multiple-input multiple-output (MIMO) rank analysis and capacity predictions for future sub-THz systems. The methods to compute the multipath numbers, the corresponding channel-gain, RMS delay spread, and RMS angular spread can be found in [12]
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