RMS Delay Spread Research Articles

Measurements of Building Transmission Loss and Delay Spread at 2.5 GHz

This paper presents the results of measurements of signal transmission loss at 2.5 GHz through 10 urban buildings. This allows the characterization of different types of buildings by effective attenuation constants and consideration of the contribution of the transmitted signal in microcell coverage predictions. Power delay profiles (PDPs) of the received signal were also measured and used to determine the time dispersion parameters of the channel, including the mean excess delay and the rms delay spread.

CHARACTERIZATION OF AN OFF-BODY CHANNEL AT 2.45 GHZ IN AN UNDERGROUND MINE ENVIRONMENT

Underground mines are challenging environments for off-body wireless communication, since the signal propagation is majorly affected by small scale and large scale fading. The use of multiple antennas at the transmitter and the receiver sides is a known technique to combat fading and enhance capacity. In this paper, the channel parameters of a 2 × 2 Multiple-Input Multiple- Output (MIMO) off-body system are investigated in an underground gold mine and compared to the Single-Input Single-Output (SISO) system parameters. Measurement campaigns were conducted using monopole antennas at a center frequency of 2.45 GHz for both Line Of Sight (LOS) and None Line of Sight (NLOS) scenarios. The measured frequency responses are converted into impulse responses through an Inverse Fourier Transform (IFT). The results show that for a constant transmitted power, the path loss exponents at NLOS are smaller than their counterpart values at LOS. The channel capacity values decrease as the propagation distance increases and when the link is obstructed at NLOS. The RMS delay spread is generally increasing with distance for both LOS and NLOS situations. When a fixed Signal-to-Noise Ratio (SNR) is assumed, MIMO topologies improved the SISO capacity by roughly 8 bps/Hz. The channel characterization results demonstrate that the MIMO configurations provided a remarkable improvement in terms of capacity, coherence bandwidth, and time delay spread compared to the SISO topologies.

Inter-Floor Wide Band Radio Channel Measurements and Simulation Applying Saleh-Valenzuela Model

This paper explores the accuracy of Saleh-Valenzuela (SV) statistical simulation model in time of arrival domain (ToA) applied on inter-floor wide band indoor radio channels. In order to extract the model parameters, an extensive measurement campaign was performed inside a modern building by applying vector network analyzer method at frequency of 1.8 GHz. The measurement results are presented in form of path loss exponent and delay spread statistics for each number-of-floors (NOF) distance between the antennas (up to 4). Path loss exponent was found to be around 3 for antennas on a same floor and around 5.5 for any other case when antennas were on separated floors. CDFs of rms delay spread may be divided into two groups: the first group is made of single-floor (SF) case and distanced-floors (DF) cases (three or more floors separated antennas) which showed similarities performing median value at 20 ns. For neighboring-floors (NF) cases (one and two floors separation) this value was increased to 35 ns. SV simulation, run with the extracted parameters, assessed delay spread statistics sufficiently good for the first group of CDFs. In order to assess the second group results, it was necessary to introduce simple corrections in SV model application.

Analysis of the LED Lamp Arrangement for Uniformity of Illumination in Indoor VLC System

LED lamp arrangement is a critical issue in indoor visible light communication (VLC) system. In this paper, we analyze the illumination distribution under the arrangement of <TEX>$2{\times}3$</TEX> and propose a method to find the optimal lamp arrangement. The method, based on the MIMO (Multiple Input/Multiple Output) system model and taking the first order reflection into consideration, enables accurate analysis of the arrangement of the LED lamps for any room. The studies show that under the optimal arrangement the uniformity of illumination is improved from 0.55 to 0.86, which guarantees that users can get almost equal lighting effects, no matter where they locate themselves. At the same time, the RMS delay spread distribution which is used to evaluate the inter-signal-interference (ISI) is analyzed, and the simulation results indicate that the optimal arrangement also can improve the communication quality by reducing the fluctuation of the RMS delay spread.

Comparisons of Channel Parameters and Models for Urban Microcells at 2 GHz and 5 GHz [Wireless Corner

The goal of this paper was to find the differences of the channel models and parameters as well as the correlations of the channel parameters between 2 GHz and 5 GHz with 100 MHz bandwidth when measurements were performed in exactly the same routes for urban microcells. The path-loss models and shadow fading were studied by using single-input single-output (SISO) measurements. The channel characteristics were investigated by the rms delay spread, rms angular spread, shadow fading, Ricean factor, number of clusters, cross-polar discrimination, and channel capacities using both SISO and MIMO (multiple-input multiple-output) measurements. Static measurements at 5 GHz were also performed in both micro- and macro-cells to investigate clustering effects. Moreover, the channel models and parameters were compared with WINNER work to test their validity in urban microcells. The main conclusion was that the 2 GHz and 5 GHz frequencies can have different propagation behaviors causing the independent channel parameters. However, it was found that their coherence bandwidths were highly correlated. The WINNER path-loss models over-estimate the path losses, both in the line-of-sight (LOS) and non-line-of-sight (NLOS) street canyons where strong guided waves exist. Irrespective of carrier frequencies, the channel parameters offered by WINNER may roughly estimate the channel by implementing its generic model.

Angular and RMS delay spread modeling in view of THz indoor communication systems

AbstractFuture wireless communication systems will most likely be operated at carrier frequencies above 300 GHz, where the indoor radio channel behaves entirely differently compared to legacy radio communication frequencies. Being highly relevant for system performance evaluations and channel modeling, the spatial as well as the temporal dispersions are studied for a representative office wireless LAN scenario in this paper. Ray tracing serves as the means for the accurate simulation of the THz radio wave propagation. Simple stochastic models are derived to approximate and reproduce the distance‐dependent behavior of the angular spread as well as of the RMS delay spread. Based on the results, the maximum symbol rates achievable without any intersymbol interference are quantified and can be shown to reach up to several 100 GSymbols/s provided that highly directive antennas are used.

Multiple Scattering in Rain and Fog on Free-Space Optical Links

The multiple scattering effects of light propagation in rain and fog are investigated by means of numerical Monte Carlo photon propagation simulations. Rain and fog consisting of water droplets are described by realistic drop size distributions with parameters related to physical parameters of hydrometeors such as rain intensity, liquid water content, effective droplet radius of fog and atmospheric visibility. Simulations show that optical attenuation due to rain is about two times lower than predicted by single scattering approach. Fog attenuation is also reduced for the lowest visibilities. An impulse response of optical channel in rain and fog is obtained and the explicit models for the delay spread dependence are provided. Under realistic conditions, the RMS delay spread due to rain on 1 km long free space optics (FSO) path is limited below 10 ps. Moderate and dense fog can cause the delay spread about 50 ps or more. Frequency characteristics of the FSO channel impaired by rain and fog are given.

Statistical Characterization of the Indoor Low-Voltage Narrowband Power Line Communication Channel

This paper presents a novel statistical characterization of the indoor low-voltage (LV) narrowband power line communication (PLC) channel in CENELEC and FCC/ARIB bands. Experimental measurements of electrical network complex transfer functions were used to determine, for the frequency range up to 500 kHz, the statistics of the average channel gain, the delay spread parameters, the coherence bandwidth and the channel capacity. The average measured channel attenuation exhibits values between 16.36 and 26.95 dB with a mean of 20.75 dB in the frequency band from 10 to 500 kHz. The root mean square (rms) delay spread has a mean value of 2.12 μs with 90% of the channels revealing values below 3.20 μs. The minimum coherence bandwidth at 0.9 correlation level is of 1.23 kHz and the mean channel capacity is of 5.32 Mbps. The lognormal behavior is confirmed and justified for the rms delay spread but not for the average channel gain. The negative correlation between these two parameters is examined, and the relationships between the different studied metrics are also explored.

Deterministic and Experimental Indoor mmW Channel Modeling

This letter presents an extensive multidimensional analysis of line-of-sight (LOS) experimental data and simulations at 60 GHz over a 9-GHz bandwidth. Numerical versions of the measured multiple-input-multiple-output (MIMO) channel transfer functions were obtained with a ray-tracing engine that includes single-order diffuse scattering. The received power, RMS delay spread (DS), and maximum excess delay (MED) computed from both measured and simulated data indicate that diffuse scattering improves ray-tracing-based modeling. Moreover, the multipath components (MPCs) extracted from both sets of data using the high-resolution estimator RiMAX were statistically compared. The analysis of the results shows that even a raw description of the environment can be used to predict millimeter-wave (mmW) propagation with ray tracing.

Large Scale Parameters and Double-Directional Characterization of Indoor Wideband Radio Multipath Channels at 11 GHz

This paper presents the large scale parameters of wideband multipath channels based on extensive measurement campaigns in various indoor environments. The measurements were conducted with a wideband multiple-input multiple-output (MIMO) channel sounder having a bandwidth of 400 MHz at 11 GHz which is a challenging frequency for future mobile systems. In particular, polarization characteristics of path-loss, shadowing, cross-polarization power ratio (XPR), delay spread and coherence bandwidth are characterized. The measurement results show that the path-loss exponents range between 2.0 and 3.0 for none-line-of-sight (NLoS), 0.36 and 1.5 for LoS, respectively. Vertically and horizontally polarized transmissions have almost same path-gain, but in some corridor-room NLoS environments, the path-loss for HH is significantly large. In most cases, the RMS delay spreads are less than 20 and 50 ns for NLoS and LoS, respectively, and the average coherence bandwidth is less than 30 MHz. The Rician K-factors range between 2 and 3 dB for cross-polarization, and in large Hall environments, those for co-polarization are greater than 6.0 dB with 10% probability. Finally, some dominant propagation mechanism and site-specific behaviors are illustrated using the double-directional measurement results.

Simulation and Analysis of Indoor Visible Light Propagation Characteristics Based on the Method of SBR/Image

The indoor visible light propagation characteristics are simulated and analyzed using the method of SBR/Image (shooting and bounding ray tracing/Image). A good agreement is achieved between the results simulated and the results given in published literature. So the correctness of the method has been validated. Some propagation parameters are obtained in the simulation, such as the indoor received power distribution, statistical distribution of phase angle of received power, RMS (root mean square) delay spread, direction of arrival, and Doppler shift. The foundation for the wireless network coverage of indoor visible light communication system is provided by the analysis of the above results.

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.

OFDM Error Floor Prediction in a Small-Time-Dispersion Channel

In this paper, a novel error floor prediction model is proposed for estimating the peak performance of the OFDM transmission in a small-time-dispersion environment--typically indoor. The obtained analytical formula involves both the accordingly modified common channel time-dispersion parameters such as the rms delay spread, but distinct for the advanced and delayed multipath echoes (with respect to the chosen sampling instant), as well as the OFDM signal-specific parameters. The validity of the model was confirmed by the results of the corresponding Monte-Carlo simulations.

Broadband over Power Lines Systems Convergence: Multiple-Input Multiple-Output Communications Analysis of Overhead and Underground Low-Voltage and Medium-Voltage BPL Networks

This review paper reveals the broadband potential of overhead and underground low-voltage (LV) and medium-voltage (MV) broadband over power lines (BPL) networks associated with multiple-input multiple-output (MIMO) technology. The contribution of this review paper is fourfold. First, the unified value decomposition (UVD) modal analysis is introduced. UVD modal analysis is a new technique that unifies eigenvalue decomposition (EVD) and singular value decomposition (SVD) modal analyses achieving the common handling of traditional SISO/BPL and upcoming MIMO/BPL systems. The validity of UVD modal analysis is examined by comparing its simulation results with those of other exact analytical models. Second, based on the proposed UVD modal analysis, the MIMO channels of overhead and underground LV and MV BPL networks (distribution BPL networks) are investigated with regard to their inherent characteristics. Towards that direction, an extended collection of well-validated metrics from the communications literature, such as channel attenuation, average channel gain (ACG), root-mean-square delay spread (RMS-DS), coherence bandwidth (CB), cumulative capacity, capacity complementary cumulative distribution function (CCDF), and capacity gain (GC), is first applied in overhead and underground MIMO/LV and MIMO/MV BPL channels and systems. It is found that the results of the aforementioned metrics portfolio depend drastically on the frequency, the power grid type (either overhead or underground, either LV or MV), the MIMO scheme configuration properties, the MTL configuration, the physical properties of the cables used, the end-to-end distance, and the number, the electrical length, and the terminations of the branches encountered along the end-to-end BPL signal propagation. Third, three interesting findings concerning the statistical properties of MIMO channels of distribution BPL networks are demonstrated, namely, (i) the ACG, RMS-DS, and cumulative capacity lognormal distributions; (ii) the correlation between RMS-DS and ACG; and (iii) the correlation between RMS-DS and CB. By fitting the numerical results, unified regression distributions appropriate for MIMO/BPL channels and systems are proposed. These three fundamental properties can play significant role in the evaluation of recently proposed statistical channel models for various BPL systems. Fourth, the potential of transformation of overhead and underground LV/BPL and MV/BPL distribution grids to an alternative solution to fiber-to-the-building (FTTB) technology is first revealed. By examining the capacity characteristics of various MIMO scheme configurations and by comparing these capacity results against SISO ones, a new promising urban backbone network seems to be born in a smart grid (SG) environment.

Design considerations of conventional angle diversity receivers for indoor optical wireless communications

Abstract A conventional angle diversity receiver uses multiple receiving elements that are oriented in different directions, where each element employs its own filter and nonimaging concentrator, such as a compound parabolic concentrator (CPC) or hemispheric lens. In this paper, a study of the design of a conventional receiver structure using angle diversity that offers improved performance with respect to the infrared channel characteristics is presented. To this end, a recently proposed model for the effective signal collection area of a conventional angle diversity receiver that more closely approximates real behaviour than the ideal model is used. The inclusion of this model in a Monte Carlo ray-tracing algorithm allows us to investigate the effects of conventional receiver parameters on the main infrared channel parameters, such as path loss and rms delay spread. Furthermore, in order to determine the number of receiver elements, the outage probability and the average error probability are also considered. Based on the results, a conventional angle diversity receiver composed of seven elements is proposed, with one of them oriented towards the ceiling, and six angled at a 56° elevation with a 60° separation in azimuth. For each element, a CPC with a 50° field of view must be used.

Feasibility of a Millimeter-Wave MIMO System for Short-Range Wireless Communications in an Underground Gold Mine

The performance of multiple-input-multiple-output (MIMO) system operating at the 60 GHz band is investigated based on experimental data in a real underground mine gallery. However, the millimeter wave (mmW) channels face some challenges such as high propagation loss. In order to overcome this issue, a planar microstrip antenna array has been designed, and fabricated. Moreover, the effect of miners' activity in the vicinity of the short-range wireless link is studied. Statistical parameters of the propagation channel, such as RMS delay spread, path loss, K-factor, channel correlation and capacity are extracted and analyzed. Results suggest that miners presence substantially affects both received power and time dispersion parameters and should therefore be considered when developing underground mine wireless networks in the unlicensed 60-GHz band.

SFN channel measurements in Brazil

In this paper, field measurements carried out in a suburban SFN network with two synchronized transmitters are reported. It is found that the radio signal coverage of the distributed transmission scheme is distinctly improved when compared to a single transmitter system. The path loss gain and improvement associated to the SFN scheme are obtained as well as the multipath channel parameters including the mean and RMS delay spread. A tapped delay line is used to model the average power delay profile (PDP) in the distributed transmission cases and shows rather different features than the single transmission case.

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.

Channel characteristics of MIMO–WLAN communications at 60 GHz for various corridors

Abstract A comparison of 4 × 4 multiple-input multiple-output wireless local area network wireless communication characteristics for six different geometrical shapes is investigated. These six shapes include the straight shape corridor with rectangular cross section, the straight shape corridor with arched cross section, the curved shape corridor with rectangular cross section, the curved shape corridor with arched cross section, the L-shape corridor, and the T-shape corridor. The impulse responses of these corridors are computed by applying shooting and bouncing ray/image (SBR/Image) techniques along with inverse Fourier transform. By using the impulse response of these multipath channels, the mean excess delay, root mean square (RMS) delay spread for these six corridors can be obtained. Numerical results show that the capacity for the rectangular cross section corridors is smaller than those for the arched cross section corridors regardless of the shapes. And the RMS delay spreads for the T-and the L-shape corridors are greater than the other corridors.

Antenna Beam-Forming for a 60 GHz Transceiver System

The main target of a 60 GHz transceiver system is to obtain data rates close to gigabits per second (Gbps) over short distances. The 60 GHz suffers from severe pathloss, inter-symbol interference (ISI) and a limited link budget. In order to improve the link budget, beamforming techniques are utilized. Antenna beamforming, i.e., combining signals from multiple receive antennas is one of the crucial aspects of the 60 GHz transceiver system. Adaptive antenna arrays are considered for the beamforming. A single carrier with frequency domain equalization (SC-FDE) is used for the modulation. In order to suppress the ISI, a cyclic prefix (CP) is used in SC-FDE. The effects of the physical parameters of antenna arrays on the RMS delay spread and BER have been investigated in LOS/NLOS condition. An algorithm for radio frequency (RF) level beamforming is proposed. The effects of perfect channel and non-perfect channel on the BER have been investigated using the proposed beamforming algorithm. The effects of the antenna array physical parameters on the BER using the proposed beamforming lgorithm have also been investigated. It was seen that the BER improves after the implementation of the new beamforming algorithm. The 60 GHz band shows severe ISI which is improved by using the proposed beamforming algorithm.