  Sub-Terahertz frequencies (frequencies above 100 GHz) have the potential to
satisfy the unprecedented demand on data rate on the order of hundreds of Gbps
for sixth-generation (6G) wireless communications and beyond. Accurate beam
tracking and rapid beam selection are increasingly important since antenna
arrays with more elements generate narrower beams to compensate for additional
path loss within the first meter of propagation distance at sub-THz
frequencies. Realistic channel models for above 100 GHz are needed, and should
include spatial consistency to model the spatial and temporal channel evolution
along the user trajectory. This paper introduces recent outdoor urban microcell
(UMi) propagation measurements at 142 GHz along a 39 m $\times$ 12 m
rectangular route (102 m long), where each consecutive and adjacent receiver
location is 3 m apart from each other. The measured power delay profiles and
angular power spectrum at each receiver location are used to study spatial
autocorrelation properties of various channel parameters such as shadow fading,
delay spread, and angular spread along the track. Compared to the correlation
distances reported in the 3GPP TR 38.901 for frequencies below 100 GHz, the
measured correlation distance of shadow fading at 142 GHz (3.8 m) is much
shorter than the 10-13 m as specified in 3GPP; the measured correlation
distances of delay spread and angular spread at 142 GHz (both 12 m) are
comparable to the 7-10 m as specified in 3GPP. This result may guide the
development of a statistical spatially consistent channel model for frequencies
above 100 GHz in the UMi street canyon environment.
