Ultra-wideband millimeter-wave (mmWave) propagation measurements were conducted in the 28-and 73-GHz frequency bands in a typical indoor office environment in downtown Brooklyn, New York, on the campus of New York University. The measurements provide large-scale path loss and temporal statistics that will be useful for ultra-dense indoor wireless networks for future mmWave bands. This paper presents the details of measurements that employed a 400 Megachips-per-second broadband sliding correlator channel sounder, using rotatable highly directional horn antennas for both co-polarized and crosspolarized antenna configurations. The measurement environment was a closed-plan in-building scenario that included a line-of-sight and non-line-of-sight corridor, a hallway, a cubicle farm, and adjacent-room communication links. Well-known and new single-frequency and multi-frequency directional and omnidirectional large-scale path loss models are presented and evaluated based on more than 14 000 directional power delay profiles acquired from unique transmitter and receiver antenna pointing angle combinations. Omnidirectional path loss models, synthesized from the directional measurements, are provided for the case of arbitrary polarization coupling, as well as for the specific cases of co-polarized and cross-polarized antenna orientations. The results show that novel large-scale path loss models provided here are simpler and more physically based compared to previous 3GPP and ITU indoor propagation models that require more model parameters and offer very little additional accuracy and lack a physical basis. Multipath time dispersion statistics for mmWave systems using directional antennas are presented for co-polarization, crosspolarization, and combined-polarization scenarios, and show that the multipath root mean square delay spread can be reduced when using transmitter and receiver antenna pointing angles that result in the strongest received power. Raw omnidirectional path loss data and closed-form optimization formulas for all path loss models are given in the Appendices.

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This paper studies radio propagation mechanisms that impact handoffs, air interface design, beam steering, and MIMO for 5G mobile communication systems. Knife edge diffraction (KED) and a creeping wave linear model are shown to predict diffraction loss around typical building objects from 10 to 26 GHz, and human blockage measurements at 73 GHz are shown to fit a double knifeedge diffraction (DKED) model which incorporates antenna gains. Small-scale spatial fading of millimeter wave received signal voltage amplitude is generally Ricean-distributed for both omnidirectional and directional receive antenna patterns under both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions in most cases, although the log-normal distribution fits measured data better for the omnidirectional receive antenna pattern in the NLOS environment. Small-scale spatial autocorrelations of received voltage amplitudes are shown to fit sinusoidal exponential and exponential functions for LOS and NLOS environments, respectively, with small decorrelation distances of 0.27 cm to 13.6 cm (smaller than the size of a handset) that are favorable for spatial multiplexing. Local area measurements using cluster and route scenarios show how the received signal changes as the mobile moves and transitions from LOS to NLOS locations, with reasonably stationary signal levels within clusters. Wideband mmWave power levels are shown to fade from 0.4 dB/ms to 40 dB/s, depending on travel speed and surroundings.

Abstract-This paper presents 28 GHz and 73 GHz millimeterwave propagation measurements performed in a typical office environment using a 400 Megachip-per-second broadband sliding correlator channel sounder and highly directional steerable 15 dBi (30• beamwidth) and 20 dBi (15 • beamwidth) horn antennas. Power delay profiles were acquired for 48 transmitter-receiver location combinations over distances ranging from 3.9 m to 45.9 m with maximum transmit powers of 24 dBm and 12.3 dBm at 28 GHz and 73 GHz, respectively. Directional and omnidirectional path loss models and RMS delay spread statistics are presented for line-of-sight and non-line-of-sight environments for both co-and cross-polarized antenna configurations. The LOS omnidirectional path loss exponents were 1.1 and 1.3 at 28 GHz and 73 GHz, and 2.7 and 3.2 in NLOS at 28 GHz and 73 GHz, respectively, for vertically-polarized antennas. The mean directional RMS delay spreads were 18.4 ns and 13.3 ns, with maximum values of 193 ns and 288 ns at 28 GHz and 73 GHz, respectively.Index Terms-Millimeter-wave; 28 GHz; 73 GHz; indoor propagation; indoor environment; path loss; RMS delay spread; close-in free space reference model; polarization.

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This paper presents 73 GHz wideband outdoor foliage and ground reflection measurements. Propagation measurements were made with a 400 Megachips-per-second sliding correlator channel sounder, with rotatable 27 dBi (7 • halfpower beamwidth) horn antennas at both the transmitter and receiver, to study foliage-induced scattering and de-polarization effects, to assist in developing future wireless systems that will use adaptive array antennas. Signal attenuation through foliage was measured to be 0.4 dB/m for both co-and cross-polarized antenna configurations. Measured ground reflection coefficients for dirt and gravel ranged from 0.02 to 0.34, for incident angles ranging from 60 • to 81 • (with respect to the normal incidence of the surface). These data are useful for link budget design and site-specific (ray-tracing) models for future millimeter-wave communications systems.

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This paper presents large-scale path loss models based on extensive ultra-wideband millimeter-wave propagation measurements performed at 28 GHz and 73 GHz in three typical indoor office layouts -namely: corridor, open-plan, and closedplan. A previous study combined all indoor layouts together, while this study separates them for site-specific indoor large-scale path loss model analysis. Measurements were conducted using a 400 megachips-per-second broadband sliding correlator channel sounder with 800 MHz first null-to-null RF bandwidth for 48 transmitterreceiver location combinations with distances ranging 3.9 m to 45.9 m for both co-and cross-polarized antenna configurations in lineof-sight and non-line-of-sight environments. Omnidirectional path loss values were synthesized from over 14,000 directional power delay profiles and were used to generate single-frequency and multi-frequency path loss models for combined, co-, and crosspolarized antennas. Large-scale path loss models that include a cross-polarization discrimination factor are provided for crosspolarized antenna measurements. The results show the value of using the close-in free space reference distance single and multifrequency path loss models, as they offer simplicity (less parameters) in path loss calculation and prediction, without sacrificing accuracy. Moreover, the current 3GPP floating-intercept path loss model only requires a simple and subtle modification to convert to the close-in free space reference distance models.