  This paper presents outdoor wideband small-scale spatial fading and
autocorrelation measurements and results in the 73 GHz millimeter-wave (mmWave)
band conducted in downtown Brooklyn, New York. Both directional and
omnidirectional receiver (RX) antennas are studied. Two pairs of transmitter
(TX) and RX locations were tested with one line-of-sight (LOS) and one
non-line-of-sight (NLOS) environment, where a linear track was employed at each
RX to move the antenna in half-wavelength increments. Measured data reveal that
the small-scale spatial fading of the received signal voltage amplitude are
generally Ricean-distributed for both omnidirectional and directional RX
antenna patterns under both LOS and NLOS conditions in most cases, except for
the log-normal distribution for the omnidirectional RX antenna pattern in the
NLOS environment. Sinusoidal exponential and typical exponential functions are
found to model small-scale spatial autocorrelation of the received signal
voltage amplitude in LOS and NLOS environments in most cases, respectively.
Furthermore, different decorrelation distances were observed for different RX
track orientations, i.e., for different directions of motion relative to the
TX. Results herein are valuable for characterizing small-scale spatial fading
and autocorrelation properties in multiple-input multiple-output (MIMO) systems
for fifth-generation (5G) mmWave frequencies.
