This contribution provides experimental evidence for the two-wave with diffuse power (TWDP) fading model. We have conducted two indoor millimetre wave measurement campaigns with directive horn antennas at both link ends. One horn antenna is mounted in a corner of our laboratory, while the other is steerable and scans azimuth and elevation. Our first measurement campaign is based on scalar network analysis with 7 GHz of bandwidth. Our second measurement campaign obtains magnitude and phase information, additionally sampled directionally at several positions in space. This second measurement campaign is limited to 2 GHz bandwidth. We apply Akaike's information criterion to decide whether Rician fading sufficiently explains the data or the generalized TWDP fading model is necessary. Our results indicate that the TWDP fading hypothesis is favoured over Rician fading in situations where the steerable antenna is pointing towards reflecting objects or is slightly misaligned at line-of-sight. We demonstrate TWDP fading in several different domains, namely, frequency, space, and time.
The authors of @cite_22 investigated a simple wall scattering scenario and analysed how fading scales with various antenna directivities and different bandwidths. Increasing directivity @cite_22 , as well as increasing bandwidth @cite_22 @cite_19 , results in an increased Rician K-factor. The authors of @cite_74 analysed fading at @math ,GHz with high gain horn antennas on both link ends. They observe high Rician K-factors even at NLOS . This effect is explained by spatial filtering of directive antennas, as they suppress many multipath components @cite_22 . Outdoor measurements in @cite_1 @cite_7 , show a graphical agreement with the Rice fit, but especially Fig. 10 in @cite_7 might be better explained as TWDP fading.
@cite_22 @cite_7 @cite_1 @cite_19 @cite_74
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In the present paper we analyse small-scale fading of reflections at 60 GHz using different antennas and bandwidths. The aim is to investigate the deterministic property of the channel in view of modelling and deployment of systems with larger bandwidths and higher directivity. We have investigated the scattering effect of a reflection on a wall emulating a beam-former in a NLOS condition. The results show that the distribution of the amplitudes fit better with a Rician than a Rayleigh distribution. Furthermore, we show that an increasing bandwidth and directivity increases the k-factor, supporting the idea of deterministic paths apart from the LOS. 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. A wireless channel is always composed of both deterministic and stochastic multi-path components. A high Rician K-factor increases the contribution of deterministic channel components, thereby reducing the significance of stochastic parts of a channel. This paper focus at the investigative analysis of K-factor and fading depth to analyze the deterministic behavior of a channel under a certain bandwidth. In this paper, 4 different propagation setups have been studied including a LOS, reflections from black board and wall are considered due to their different surface roughness and double bounce reflections from both surfaces. It has been observed that in all propagation cases, small scale fading depth asymptotically converges towards zero dB whereby K-factor increases with bandwidth. Results also show that the de-polarization of a signal increases its amplitude fading. This effect is much more significant at lower bandwidths but an increase in bandwidth reduces the difference in fade depths between polarized and depolarized signals. These observations lead to a conclusion that channel tend to be more deterministic at higher bandwidths. This paper presents small-scale fading measurements for 28 GHz outdoor millimeter-wave ultrawideband channels using directional horn antennas at the transmitter and receiver. Power delay profiles were measured at half-wavelength spatial increments over a local area (33 wavelengths) on a linear track in two orthogonal receiver directions in a typical base-to-mobile scenario with fixed transmitter and receiver antenna beam pointing directions. The voltage path amplitudes are shown to follow a Rician distribution, with K-factor ranging from 9 - 15 dB and 5 - 8 dB in line of sight (LOS) and non-line of sight (NLOS) for a vertical-to-vertical co- polarized antenna scenario, respectively, and from 3 - 7 dB in both LOS and NLOS vertical-to- horizontal cross-polarized antenna scenario. The average spatial autocorrelation functions of individual multipath components reveal that signal amplitudes reach a correlation of 0 after 2 and 5 wavelengths in LOS and NLOS co-polarized V-V antenna scenarios. The models provided are useful for recreating path gain statistics of millimeter- wave wideband channel impulse responses over local areas, for the study of multi-element antenna simulations and channel estimation algorithms.