Root Mean Square Delay Spread Values Research Articles

Millimeter Wave Propagation Measurements and Characteristics for 5G System

In future 5G systems, the millimeter wave (mmWave) band will be used to support a large capacity for current mobile broadband. Therefore, the radio access technology (RAT) should be made available for 5G devices to help in distinct situations, for example device-to-device communications (D2D) and multi-hops. This paper presents ultra-wideband channel measurements for millimeter wave bands at 19, 28, and 38 GHz. We used an ultra-wideband channel sounder (1 GHz bandwidth) in an indoor to outdoor (I2O) environment for non-line-of-sight (NLOS) scenarios. In an NLOS environment, there is no direct path (line of sight), and all of the contributed paths are received from different physical objects by refection propagation phenomena. Hence, in this work, a directional horn antenna (high gain) was used at the transmitter, while an omnidirectional antenna was used at the receiver to collect the radio signals from all directions. The path loss and temporal dispersion were examined based on the acquired measurement data—the 5G propagation characteristics. Two different path loss models were used, namely close-in (CI) free space reference distance and alpha-beta-gamma (ABG) models. The time dispersion parameters were provided based on a mean excess delay, a root mean square (RMS) delay spread, and a maximum excess delay. The path loss exponent for this NLOS specific environment was found to be low for all of the proposed frequencies, and the RMS delay spread values were less than 30 ns for all of the measured frequencies, and the average RMS delay spread values were 19.2, 19.3, and 20.3 ns for 19, 28, and 38 GHz frequencies, respectively. Moreover, the mean excess delay values were found also at 26.1, 25.8, and 27.3 ns for 19, 28, and 38 GHz frequencies, respectively. The propagation signal through the NLOS channel at 19, 28, and 38 GHz was strong with a low delay; it is concluded that these bands are reliable for 5G systems in short-range applications.

Shadowing Characterization for 5-GHz Vehicle-to-Vehicle Channels

As one of the most important parts of intelligent transportation systems, vehicle-to-vehicle (V2V) communications have been widely studied because of the potential improvements it can provide in terms of traffic efficiency and traffic safety through various applications. The research on propagation characteristics for V2V channels is of primary importance, and one particular significant topic is shadowing effects induced by obstructing vehicles between transmitter (Tx) and receiver (Rx). In this paper, we present shadowing measurement results for V2V channels in both urban and highway scenarios, in which a truck and a van were used as the obstacles. Channel measurements in the 5-GHz band were performed in both line-of-sight (LOS) and non-LOS (NLOS) conditions, and different relative positions of vehicles on the road were considered. Based on the measured results, statistics for the shadowing loss and the root mean square delay spread (RMS-DS) are provided, and shadowing effects in each case are compared. By utilizing the temporal power delay profile correlation coefficient, the stationarity distance for each case is estimated, and the nonstationarity phenomenon and its relation to the shadowing effect are investigated. The mean value of shadowing loss was found to range from 3.38 to 9.33 dB with standard deviation ranging from 3.20 to 6.98 dB, and a normal distribution can well describe the statistics of the shadowing loss. With smaller RMS-DS values, the highway shows larger shadowing losses than the urban street. Moreover, in any specific scenario (e.g., highway or urban), the shadowing effect is generally closely related to the RMS-DS and stationarity distance: Larger shadowing loss always occurs when RMS-DS is large and average stationarity distance is small.

Channel Measurements and Modeling at 6 GHz in the Tunnel Environments for 5G Wireless Systems

Propagation measurements of wireless channels performed in the tunnel environments at 6 GHz are presented in this paper. Propagation characteristics are simulated and analyzed based on the method of shooting and bouncing ray tracing/image (SBR/IM). A good agreement is achieved between the measured results and simulated results, so the correctness of SBR/IM method has been validated. The measured results and simulated results are analyzed in terms of path loss models, received power, root mean square (RMS) delay spread, Ricean K-factor, and angle of arrival (AOA). The omnidirectional path loss models are characterized based on close-in (CI) free-space reference distance model and the alpha-beta-gamma (ABG) model. Path loss exponents (PLEs) are 1.50–1.74 in line-of-sight (LOS) scenarios and 2.18–2.20 in non-line-of-sight (NLOS) scenarios. Results show that CI model with the reference distance of 1 m provides more accuracy and stability in tunnel scenarios. The RMS delay spread values vary between 2.77 ns and 18.76 ns. Specially, the Poisson distribution best fits the measured data of RMS delay spreads for LOS scenarios and the Gaussian distribution best fits the measured data of RMS delay spreads for NLOS scenarios. Moreover, the normal distribution provides good fits to the Ricean K-factor. The analysis of the abovementioned results from channel measurements and simulations may be utilized for the design of wireless communications of future 5G radio systems at 6 GHz.

Statistical Modelling and Characterization of Experimental mm-Wave Indoor Channels for Future 5G Wireless Communication Networks.

This paper presents an experimental characterization of millimeter-wave (mm-wave) channels in the 6.5 GHz, 10.5 GHz, 15 GHz, 19 GHz, 28 GHz and 38 GHz frequency bands in an indoor corridor environment. More than 4,000 power delay profiles were measured across the bands using an omnidirectional transmitter antenna and a highly directional horn receiver antenna for both co- and cross-polarized antenna configurations. This paper develops a new path-loss model to account for the frequency attenuation with distance, which we term the frequency attenuation (FA) path-loss model and introduce a frequency-dependent attenuation factor. The large-scale path loss was characterized based on both new and well-known path-loss models. A general and less complex method is also proposed to estimate the cross-polarization discrimination (XPD) factor of close-in reference distance with the XPD (CIX) and ABG with the XPD (ABGX) path-loss models to avoid the computational complexity of minimum mean square error (MMSE) approach. Moreover, small-scale parameters such as root mean square (RMS) delay spread, mean excess (MN-EX) delay, dispersion factors and maximum excess (MAX-EX) delay parameters were used to characterize the multipath channel dispersion. Multiple statistical distributions for RMS delay spread were also investigated. The results show that our proposed models are simpler and more physically-based than other well-known models. The path-loss exponents for all studied models are smaller than that of the free-space model by values in the range of 0.1 to 1.4 for all measured frequencies. The RMS delay spread values varied between 0.2 ns and 13.8 ns, and the dispersion factor values were less than 1 for all measured frequencies. The exponential and Weibull probability distribution models best fit the RMS delay spread empirical distribution for all of the measured frequencies in all scenarios.

Large-scale path loss models and time dispersion in an outdoor line-of-sight environment for 5G wireless communications

This paper presents path loss models and time dispersion parameters for different candidate frequencies above 6GHz for fifth-generation (5G) wireless communications. Three well-known path loss models are compared for single-frequency and multi-frequency schemes: the close-in (CI) free space reference distance model, the floating intercept model (FI), and the alpha-beta-gamma (ABG) model. This paper also proposes a new path loss model to account for frequency attenuation (FA) with distance, which we term the FA path loss model. In this model, we introduce a frequency-dependent attenuation factor XF(f), which directly adds to the CI reference attenuation. Ultra-wideband measurements are conducted for different frequencies in the range of 10–40GHz in an outdoor environment for line-of-sight scenarios. The time dispersion parameters mean excess delay, root mean square delay spread (RMS-DS), and maximum excess delay are estimated. The results reveal that the path loss exponent values for CI models are less than 1.4 in our experimental set-up. For the proposed FA model, with a path loss exponent of 1.4, the XF(f) attenuation factor values are less than 9.7dB. The time dispersion findings from this work reveal that the RMS-DS values varied between 0.1 and 1.7ns.

Characterization of the 5-GHz Elevator Shaft Channel

In this paper we provide channel characterization results for the elevator shaft channel in the 5-GHz band, based upon measurements conducted in four buildings. This channel is of interest for several applications, including WiFi and public safety. Although several authors have provided elevator shaft channel characteristics for lower-frequency bands (255-MHz, 900-MHz, 1.9-GHz), to our knowledge this is the first work that addresses the 5-GHz band. Moreover, prior work has not thoroughly addressed channel characteristics when the elevator car is in motion, whereas here we provide measurement and modeling results for this dynamic condition. Our measurements were of power delay profiles, from which we estimated propagation path loss and root-mean square delay spread (RMS-DS). Path loss exponents were approximately 2.5 in one building and 5.5 in the other three buildings, with standard deviations about the log-distance linear fits equal to approximately 3 dB and 5.5 dB, respectively. Mean RMS-DS values range from approximately 14-60 ns when the elevator car is motionless. Maximum RMS-DS values were 144 ns and 152 ns in the two different types of buildings when the elevator car is moving. The significant differences in these channel characteristics among the four buildings are likely attributable to the distinct physical features of the buildings.

Delay and Doppler Spreads of Nonstationary Vehicular Channels for Safety-Relevant Scenarios

Vehicular communication channels are characterized by a non-stationary time- and frequency-selective fading process due to rapid changes in the environment. The non-stationary fading process can be characterized by assuming local stationarity for a region with finite extent in time and frequency. For this finite region the wide-sense stationarity and uncorrelated-scattering (WSSUS) assumption holds approximately and we are able to calculate a time and frequency dependent local scattering function (LSF). In this paper, we estimate the LSF from a large set of measurements collected in the DRIVEWAY'09 measurement campaign, which focuses on scenarios for intelligent transportation systems. We then obtain the time-frequency-varying power delay profile (PDP) and the time-frequency-varying Doppler power spectral density (DSD) from the LSF. Based on the PDP and the DSD, we analyze the time-frequency-varying root mean square (RMS) delay spread and the RMS Doppler spread. We show that the distribution of these channel parameters follows a bi-modal Gaussian mixture distribution. High RMS delay spread values are observed in situations with rich scattering, while high RMS Doppler spreads are obtained in drive-by scenarios.

Indoor radiated-mode leaky feeder propagation at 2.0 GHz

This paper presents the results of narrow-band and wide-band propagation measurements carried out at 2.0 GHz in an indoor environment using a radiated-mode leaky feeder as the transmitting antenna. The narrow-band measurements were devised to measure attenuation of radio signals and the wide-band techniques to measure multipath impulse responses and their associated root mean square (RMS) delay spread. Analysis of the narrow-band data files shows that the received signal levels in the direction along the feeder generally decay exponentially due to the feeder-specific attenuation. The received signal levels in the direction radial to the feeder decrease slowly, and the distance-power law exponent is found to be smaller than one. The slow and fast variations of the received signal levels are also examined. The results reveal that the slow variations basically follow the log-normal distribution, while the fast variations fit the Rayleigh distribution in the direction parallel to the feeder and the Rician distribution in the direction radial to the feeder, respectively. Analysis of the wide-band data files reveals that the maximum value of the RMS delay spread is 60.6 ns and the RMS delay spread values are less than 42 ns 50% of the time. One therefore can conclude that the indoor channel excited by the radiated-mode leaky feeder has a broad coherent band-width and can support a data rate of up to 3.3 Mb/s without equalization.