Deterministic Channel Model Research Articles

Wide-Aperture MIMO via Reflection off a Smooth Surface

This paper provides a deterministic channel model for a scenario where wireless connectivity is established through a reflection off a smooth planar surface of an infinite extent. The developed model is rigorously built upon the physics of wave propagation and is as precise as tight are the unboundedness and smoothness assumptions on the surface. This model allows establishing how line-of-sight multiantenna communication is altered by a reflection off an electrically large surface, a situation of high interest for mmWave and terahertz frequencies.

Channel modeling based on multilayer artificial neural network in metro tunnel environments

AbstractTraditional deterministic channel modeling is accurate in prediction, but due to its complexity, improving computational efficiency remains a challenge. In an alternative approach, we investigated a multilayer artificial neural network (ANN) to predict large‐scale and small‐scale channel characteristics in metro tunnels. Simulated high‐precision training datasets were obtained by combining measurement campaign with a ray tracing (RT) method in a metro tunnel. Performance on the training data was used to determine the number of hidden layers and neurons of the multilayer ANN. The proposed multilayer ANN performed efficiently (10 s for training; 0.19 ms for prediction), and accurately, with better approximation of the RT data than the single‐layer ANN. The root mean square errors (RMSE) of path loss (2.82 dB), root mean square delay spread (0.61 ns), azimuth angle spread (3.06°), and elevation angle spread (1.22°) were impressive. These results demonstrate the superior computing efficiency and model complexity of ANNs.

Measurement and Ray Tracing Simulation with Urban Microcell Environments at 28GHz Band

In this study, we investigate outdoor propagation measurements performed in an industrial park environment at 28.3 GHz band. The propagation characteristics were evaluated with the measurement result regarding the path loss characteristics. Ray tracing simulation was also studied and compared with the measurement data to evaluate the quantitative accuracy of ray tracing in millimeter-wave band wireless propagations. Ray tracing, whose accuracy was evaluated based on a comparison with the measurement results, can aid in the theoretical design of the coverage area and deterministic channel modeling.

Researching on the Deterministic Channel Models for Urban Microcells Considering Diffraction Effects

Deterministic channel models, such as the three-dimensional (3D) ray launching method, can yield wireless channel parameters. In the non-line-of-sight (NLOS) propagation, the outdoor 3D ray launching method that considers diffraction effects is more accurate than the one that does not. While considering the diffraction effect, obtaining the diffraction point is challenging. This paper proposed a method for determining diffracted rays using the receiving sphere method in 3D ray launching. The diffraction point is determined using the shortest distance method between two straight lines, and the signal loss from the transmitting to receiving antennas is obtained. Furthermore, experiments on a millimeter wave in a microcell scenario were performed. The test results of the wireless channel parameters were compared with theoretical calculations. The results obtained via the 3D ray launching method that only considers the specular reflection and direct rays agree with the experimental results in the line-of-sight (LOS); furthermore, they generate larger errors compared with the experimental results in the NLOS. The results obtained via the 3D ray launching method that considers the direct ray, reflected rays, and diffracted rays agree with the experimental results both in the LOS and NLOS. Therefore, the 3D ray launching method that considers the diffraction effect can improve the prediction accuracy of the millimeter wave channel parameters in a microcell.

A Symbolic Encapsulation Point as Tool for 5G Wideband Channel Cross-Layer Modeling.

Considering that networks based on New Radio (NR) technology are oriented to provide services of desired quality (QoS), it becomes questionable how to model and predict targeted QoS values, especially if the physical channel is dynamically changing. In order to overcome mobility issues, we aim to support the evaluation of second-order statistics of signal, namely level-crossing rate (LCR) and average fade duration (AFD) that is missing in general channel 5G models. Presenting results from our symbolic encapsulation point 5G (SEP5G) additional tool, we fill this gap and motivate further extensions on current general channel 5G. As a matter of contribution, we clearly propose: (i) anadditional tool for encapsulating different mobile 5G modeling approaches; (ii) extended, wideband, LCR, and AFD evaluation for optimal radio resource allocation modeling; and (iii) lower computational complexity and simulation time regarding analytical expression simulations in related scenario-specific 5G channel models. Using our deterministic channel model for selected scenarios and comparing it with stochastic models, we show steps towards higherlevel finite state Markov chain (FSMC) modeling, where mentioned QoS parameters become more feasible, placing symbolic encapsulation at the center of cross-layer design. Furthermore, we generate values within a specified 5G passband, indicating how it can be used for provisioningoptimal radio resource allocation.

Link-Signature-Based Discriminatory Channel Estimation (LS-DCE) for Physical Layer Security in Stationary and Mobile OFDM Transceivers

In this work, we propose a physical layer security (PLS) scheme for orthogonal frequency-division multiplexing (OFDM) based transceivers, termed link-signature-based discriminatory channel estimation (LS-DCE). The proposed scheme exploits the space-time uniqueness of the channel responses (i.e. link-signatures) at different transceiver pairs to facilitate a reliable signal reception at legitimate receivers, while equivocating reception at non-legitimate adversaries. While most PLS studies focus on transmitted data to provide such an equivocation, LS-DCE focuses on channel estimations. Since the quality of estimates impacts the overall performance, LS-DCE facilitates distinctive detection error probabilities by enforcing a poor channel estimation at non-legitimate receivers as compared to legitimate ones. To validate the effectiveness of the proposed scheme, analytical, simulated, and experimental evaluations are performed. First, a theoretical analysis is established in terms of the probability of bit error (PBE) at the legitimate and non-legitimate receivers. Then, indoor/outdoor stochastic and deterministic channel models are adopted using correlated Nakagami-m simulation model and software-defined radio (SDR) testbed, respectively. With $-10\,{\rm dB}$ signal-to-noise ratio (SNR), it is found that a spatial correlation $\leq 0.1$ between the legitimate and non-legitimate channels results in an average PBE of 0.48, 0.48, and 0.49 for BPSK, QPSK, and 16-QAM, respectively, at the non-legitimate receiver; and 0.45, 0.46, and 0.48 with $\text{50}\,{\rm dB}$ SNR.

Electromagnetic Parameter Calibration for a Broadband Ray-Launching Simulator With SAGE Algorithm for Millimeter-Wave Communications

The millimeter-wave (mmWave) communication is a promising solution to future high-speed data transmission. To study the impact of its wireless channel, a ray-launching simulator is developed to generate deterministic channel models according to realistic scenario descriptions. For such channel modeling, the material parameters play an important role in the electromagnetic numerical computing of multi-path components (MPCs) and should be calibrated according to channel measurement results. Our contribution in this paper is three-fold: we conduct the channel measurement in an indoor scenario for extracting mmWave channel characteristics, apply the Hungarian algorithm to pair measured and simulated propagation MPCs and apply the SAGE algorithm for the parameter calibration of materials impacting on the MPCs. Note that the proposed material parameter calibration method is general for the various radio propagation environment, not limited by the indoor or outdoor scenarios. Moreover, it avoids independent measurement of specific materials in a given scenario, thus greatly reducing the difficulty of obtaining material parameters. The result shows that the space alternating generalized expectation-maximization (SAGE) algorithm achieves a good match between measurement and simulation with a reasonable computational effort.

Channel capacity model in urban areas at 20–70 GHz for 5G systems

ABSTRACTIn this paper, a millimeter-wave (mm-W)–multiple-input multiple-output (MIMO) channel model is introduced for the fifth-generation (5G) of microcellular communication systems. This deterministic channel model is based on reflection phenomena, which is a dominated propagation mechanism at mm-W communication systems. The model analyzes the channel capacity (CP) based on some important factors including frequency, absorption atmosphere, polarization, materials of surfaces and distance between the transmitter and the receiver. Four urban scenarios are considered in the analyses which are based on real urban constructions. Finally, Measurement data that have been conducted on the other work validate the theoretical analysis and demonstrate that the proposed model can be used to predict CP in urban areas for 5G systems.

Multidevice Map-Constrained Fingerprint-Based Indoor Positioning Using 3-D Ray Tracing

This paper studies the use of deterministic channel modeling through 3-D ray tracing (RT) for constructing device-independent radiomaps for Wi-Fi RSSI-based fingerprinting indoor positioning, applicable to different devices. Device heterogeneity constitutes a limitation in fingerprint-based approaches and also constructing radiomaps through extensive in situ measurement campaigns is laborious and time-consuming even with a single device let alone the need for radiomaps constructed using multiple different devices. This paper tackles both challenges through the use of 3-D RT for radiomap generation in conjunction with data calibration using a small set of device-specific measurements to make the radiomap device independent. The efficiency of this approach is evaluated using simulations and measurements in terms of the time spent to generate the radiomap, the amount of device-specific data required for calibration, and in terms of the achievable positioning accuracy. Potential accuracy improvements in the RT-based indoor positioning process are further investigated, by studying the use of map constraints into the algorithm in the form of a priori probabilities. In this approach, a route probability factor (RPF), which reflects the likelihood of a user being in various locations inside the environment is used. The outcome of the evaluation process, which includes a study of different RPF distributions, indicates the validity of the approach, demonstrated by a reduction in the positioning error for various devices. The versatility of this approach is also demonstrated for different scenarios, different devices, and by considering different device-handling conditions.

Broadband Wireless Channel in Composite High-Speed Railway Scenario: Measurements, Simulation, and Analysis

The rapid development of high-speed railway (HSR) and train-ground communications with high reliability, safety, and capacity promotes the evolution of railway dedicated mobile communication systems from Global System for Mobile Communications-Railway (GSM-R) to Long Term Evolution-Railway (LTE-R). The main challenges for LTE-R network planning are the rapidly time-varying channel and high mobility, because HSR lines consist of a variety of complex terrains, especially the composite scenarios where tunnels, cuttings, and viaducts are connected together within a short distance. Existing researches mainly focus on the path loss and delay spread for the individual HSR scenarios. In this paper, the broadband measurements are performed using a channel sounder at 950 MHz and 2150 MHz in a typical HSR composite scenario. Based on the measurements, the pivotal characteristics are analyzed for path loss exponent, power delay profile, and tap delay line model. Then, the deterministic channel model in which the 3D ray-tracing algorithm is applied in the composite scenario is presented and validated by the measurement data. Based on the ray-tracing simulations, statistical analysis of channel characteristics in delay and Doppler domain is carried out for the HSR composite scenario. The research results can be useful for radio interface design and optimization of LTE-R system.

Soft‐output MMSE MIMO detector under different channel estimation models

This study considers the effect of channel estimation error (CEE) on the soft-output bit log-likelihood ratio (LLR) in a multiple-input–multiple-output detection system which the source sends their quadrature amplitude modulation to the detector through Rayleigh fading channels. The new expressions of LLR with maximum-likelihood CE for deterministic channel model and minimum mean square error (MMSE) CE for random channel model are obtained separately for linear MMSE receiver using known pilot-symbol-aided CE. Meanwhile, the optimal power allocation between training and data transmissions for these two different LLR expressions, which attends to get the maximum ratio of signal and interference plus noise ratio, are obtained under the total transmitting power constraints. Numerical results show that the power allocation ratio sets to be ∼0.5 is optimal for two new different LLRs at the same total power and system noise. Moreover, the derived LLR expressions match the simulation result and outperform the conventional system without the consideration of CEE and optimal power allocation. Meanwhile, the system performance is better than the existing research with the consideration of CE.

TIME DOMAIN AND FREQUENCY DOMAIN DETERMINISTIC CHANNEL MODELING FOR TUNNEL/MINING ENVIRONMENTS

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments - one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.

On the Sublinear Behavior of Massive Multi User MIMO Sum Rate for Deterministic Channel Models

This paper studies the behavior of the sum-rate of outdoor multi-user multiple input multiple output systems, where a uniform linear array is utilized at the base station (BS), as the number of BS antennas and the number of users increase. Two schemes are studied for the downlink, the zero-forcing and the maximum ratio transmission (MRT). To begin with, the channel matrix is described deterministically using direct scattering theory. Its matrix elements are the Fourier coefficients of functions that have a physical significance, being connected to the geometry of the environment. For the case when the energy is not arriving at the BS from every spatial direction, we prove for the ZF scheme that the achievable sum-rate behavior is sublinear in the number of antennas at the BS. For the MRT scheme, we prove that there is a link between the sum-rate and the distribution of the users in the city. To numerically evaluate the sum-rate for a given city, schematically described by its streets and its buildings, we introduce a model for the Fourier coefficients of the aforementioned functions, which mixes geometrical and statistical ingredients. We randomly distribute high buildings that will act as strong scatterers and look at the influence of their number on the sum-rate. With the ZF scheme, we perform the calculations for the case where the number of BS antennas, $M_{T}$ , is equal to the number of users, $M_{R}$ , and for the case where $M_{T}$ is larger than $M_{R}$ . We observe that the sum-rate first increases linearly with the number of BS antennas, and becomes sublinear after $M_{T}$ reaches a certain value. The threshold depends on the number of high buildings. With the MRT scheme, the calculations confirm the theoretical predictions, and the sum-rate is greater if the users are spread over all of the city.

Ray-Based Statistical Propagation Modeling for Indoor Corridor Scenarios at 15 GHz

According to the demands for fifth-generation (5G) communication systems, high frequency bands (above 6 GHz) need to be adopted to provide additional spectrum. This paper investigates the characteristics of indoor corridor channels at 15 GHz. Channel measurements with a vector network analyzer in two corridors were conducted. Based on a ray-optical approach, a deterministic channel model covering both antenna and propagation characteristic is presented. The channel model is evaluated by comparing simulated results of received power and root mean square delay spread with the corresponding measurements. By removing the impact of directional antennas from the transmitter and receiver, a path loss model as well as small-scale fading properties for typical corridors is presented based on the generated samples from the deterministic model. Results show that the standard deviation of path loss variation is related to the Tx height, and placing the Tx closer to the ceiling leads to a smaller fluctuation of path loss.

Assessment of the Contribution of Time Reversal on a UWB Localization System for Railway Applications

UWB radio has the potential to offer good performance in terms of localization precision. Time Reversal channel pre-filtering facilitates signal detection and also helps to increase the received energy in a targeted area. This paper assesses the quantitative and qualitative contributions of the Time Reversal (TR) technique associated with an Ultra Wideband (UWB) localization system applied to a railway odometry problem. The analytical and simulation results for Power Delay Profile, equivalent channel model and focusing gain of the TR-UWB are given. The contribution of the TR technique associated with UWB radio to enhance the localization resolution is analysed. To perform these studies, and to be representative of the proposed railway application, a deterministic channel model is used. The analytical simulation and experimental results show that time reversal has very promising characteristics regarding its association with the UWB in terms of localization error. These results also indicate that the TR-UWB technique delivers improved performance over UWB only localization approach, that could benefit the development of the proposed railway application.

Simulation and Measurement-Based Vehicle-to-Vehicle Channel Characterization: Accuracy and Constraint Analysis

In this paper, a deterministic channel model for vehicle-to-vehicle (V2V) communication, is compared against channel measurement data collected during a V2V channel measurement campaign using a channel sounder. Channel metrics such as channel gain, delay and Doppler spreads, eigenvalue decomposition and antenna correlations are derived from the ray tracing (RT) simulations as well as from the measurement data obtained from two different measurements in an urban four-way intersection scenario. The channel metrics are compared separately for line-of-sight (LOS) and non-LOS (NLOS) situation. Most power contributions arise from the LOS component (if present) as well as from multipaths with single bounce reflections. Measurement and simulation results show a very good agreement in the presence of LOS, as most of the received power is contributed from the LOS component. In NLOS, the difference is large because the ray tracer is unable to capture some of the multi bounced propagation paths that are present in the measurements. Despite the limitations of the ray-based propagation model identified in this work, the model is suitable to characterize the channel properties in a sufficient manner.

Analysis of challenges in the application of deterministic wireless channel modelling in the implementation of WLAN-based indoor location system in large complex scenarios

This paper describes user location and tracking on indoor scenarios based on the pattern recognition of IEEE 802.11 signal strength measurements by means of a fuzzy inference system. Signal fluctuation makes difficult and imprecise the trilateration of the user location, so we propose the use of fuzzy techniques to deal with such imprecision. To implement the location system, deterministic wireless channel characterisation is obtained by means of in–house implemented 3D ray launching code. Several scenarios are analysed, since their size strongly impacts on algorithm convergence. The limitations and solution, based on subdivision of the scenario in sub–zones, are analysed and applied to the case of a new emergency hospital complex in Navarra. Simulation and measurement results are presented showing good agreement. The results can aid in the determination of an optimised WiFi–based location system providing efficient positioning and communication services in complex indoor scenarios.

Analysis and Comparison of Deterministic Power Line Channel Modeling Methods

Indoor broadband power line communications (PLC) use home grid as communication media. Many applications exist such as data sharing and internet access. However, the performances achieved differ widely from a home to another because of differences in electrical installations. A software tool able to qualify any household grid versus power line might be developed. There is no today undeniable model and many frameworks exist. To make an informed choice, this paper analyzes and compares frequent deterministic modeling: chain matrices, multipath, infinite impulse response (IIR) filters, and electrical circuits. Multipath model proved to be the most accurate despite its implementation challenge. Chain matrices and electrical circuits are very sensitive to the uncertainty of the propagation coefficient and the impedance characteristic of power cables. Chain matrices and IIR filters based methods are unable to predict accurately the level of a fading due to both two derivations.

Application of Polynomial Chaos to Quantify Uncertainty in Deterministic Channel Models

A non-intrusive formulation of the polynomial chaos method is applied to quantify the uncertainties in deterministic models of the indoor radio channel. Deterministic models based on the finite-difference time-domain (FDTD) method and ray tracing are examined. Various sources of parameter uncertainty are considered, including randomness in the material properties, building geometry, and the spatial location of transmitting and receiving antennas. The polynomial chaos results are confirmed against Monte Carlo simulations and experimental measurements. The analysis shows the expected variation in the sector-averaged path loss can be considerable for relatively small input parameter uncertainties, leading to the conclusion that a single simulation run using `nominal values' may be insufficient to adequately characterize the indoor radio channel.

Interference Alignment: From Degrees of Freedom to Constant-Gap Capacity Approximations

Interference alignment is a key technique for communication scenarios with multiple interfering links. In several such scenarios, interference alignment was used to characterize the degrees of freedom of the channel. However, these degree-of-freedom capacity approximations are often too weak to make accurate predictions about the behavior of channel capacity at finite signal-to-noise ratios (SNRs). The aim of this paper is to significantly strengthen these results by showing that interference alignment can be used to characterize capacity to within a constant gap. We focus on real, time-invariant, frequency-flat X-channels. The only known solutions achieving the degrees of freedom of this channel are either based on real interference alignment or on layer-selection schemes. Neither of these solutions seems sufficient for a constant-gap capacity approximation. In this paper, we propose a new communication scheme and show that it achieves the capacity of the Gaussian X-channel to within a constant gap. To aid in this process, we develop a novel deterministic channel model. This deterministic model depends on the 1/2 log (SNR) most-significant bits of the channel coefficients rather than only the single most-significant bit used in conventional deterministic models. The proposed deterministic model admits a wider range of achievable schemes that can be translated to the Gaussian channel. For this deterministic model, we find an approximately optimal communication scheme. We then translate this scheme for the deterministic channel to the original Gaussian X-channel and show that it achieves capacity to within a constant gap. This is the first constant-gap result for a general, fully-connected network requiring interference alignment.