Proposed Channel Simulator Research Articles

Fast simulation of high-speed railway fading channel using finite-state Markov models

The design and performance evaluation of the high-speed railway (HSR) communications are inseparable from the accurate and efficient high-speed channel simulator. The variation on path loss, shadowing and fast fading are the key characteristics of HSR channels. Although finite-state Markov chain (FSMC) channel models have been extensively investigated to describe fading channels, most of the previous channel simulators cannot reflect all the above key characteristics. In this paper, we propose a novel FSMC model based on channel simulator with the path loss, shadowing and fast fading in HSR. The accurate closed-form expression of state transition probabilities between channel states is derived to break the simplified assumption of first-order Markov chain. To validate the accuracy of the new FSMC channel simulator, the comparison analysis between the proposed channel simulator and the actual measurements are provided.

A Novel 3D Non-Stationary Wireless MIMO Channel Simulator and Hardware Emulator

In this paper, a new WINNER+-based 3-D non-stationary geometry-based stochastic model (GBSM) for multiple-input multiple-output channels is proposed, as well as extended evolving algorithms of time-variant channel parameters. Meanwhile, important statistical properties of the channel model, i.e., time-variant autocorrelation function, time-variant cross-correlation function, and time-variant Doppler power spectrum density are derived and analyzed. Moreover, we propose an efficient hardware implementation method, namely, sum-of-frequency-modulation (SoFM) method, to generate non-stationary channel coefficients. By utilizing compact hardware architecture with SoFM modules, the proposed 3-D non-stationary GBSM is realized on a field-programmable gate array hardware platform. Simulations and hardware measurement results demonstrate that our proposed channel simulator and emulator can get more accurate and realistic Doppler frequency than those of the existing models. In addition, hardware measurements of statistical properties are also well consistent with the corresponding theoretical ones, which verify the correctness of both the hardware emulation scheme and theoretical derivations.

A Novel Wideband MIMO Car-to-Car Channel Model Based on a Geometrical Semi-Circular Tunnel Scattering Model

In this paper, we present a wideband multiple-input multiple-output (MIMO) car-to-car (C2C) channel model based on a geometrical semi-circular tunnel (SCT) scattering model. From the geometrical SCT scattering model, a reference channel model is derived under the assumption of single-bounce scattering in line-of-sight (LOS) and non-LOS (NLOS) propagation environments. In the proposed reference channel model, it is assumed that an infinite number of scatterers are randomly distributed on the tunnel wall. Starting from the geometrical scattering model, the time-variant transfer function (TVTF) is derived, and its correlation properties in time, frequency, and space are studied. Expressions are presented for the space–time–frequency cross-correlation function (STF-CCF), the two-dimensional (2D) space CCF, the 2D time–frequency CCF (TF-CCF), the temporal autocorrelation function (ACF), and the frequency correlation function (FCF). Owing to the semi-circular geometry, we reduced the originally threefold integrals to double integrals in the computations of the correlation functions, which simplifies the numerical analysis considerably. From the TVTF characterizing the reference model, an efficient sum-of-cisoid (SOC) channel simulator is derived. Numerical results show that both the temporal ACF and the FCF of the SOC channel simulator match very well with those of the reference model. A validation of the proposed model has been done by fitting the delay spread of the reference model to that of the measured channel, which demonstrates an excellent agreement. The proposed channel simulator allows us to evaluate the performance of C2C communication systems in tunnel environments.

Higher Rank Principal Kronecker Model for Triply Selective Fading Channels With Experimental Validation

This paper proposes a higher rank principal Kronecker model (PKM) for simulating triply selective fading channels. To construct the PKM, the channel correlation matrices are decomposed using the higher order singular value decomposition (HOSVD) method. The proposed PKM-HOSVD model improves upon the original Kronecker model by using higher rank approximation of the channel correlation matrices rather than the rank-1 approximation. The proposed PKM-HOSVD model was validated by extensive field experiments conducted for 4 $\times$ 4 multiple-input–multiple-output (MIMO) systems in both indoor and outdoor environments. The carrier frequencies used included 800 MHz, 2.2 GHz, and 5.2 GHz. The channel correlation matrices calculated from the measured channel coefficients were then decomposed via the proposed PKM-HOSVD method. The quality of the decomposition was evaluated by not only the mean square error but also the correlation matrix distance. These results indicate that many practical channels must use higher rank approximation rather than the commonly used rank-1 approximation (or the Kermoal method) to achieve satisfactory decomposition accuracy. In addition, the predicted channel capacity by the proposed channel simulation model achieves better accuracy than the original rank-1 channel simulation model.

Joint Shadowing Process in Urban Peer-to-Peer Radio Channels

For multihop and ad hoc networks, a conventional 1-D channel model cannot capture the spatial correlation of the shadowing processes. This paper investigates the joint spatial correlation property of the shadowing process for peer-to-peer (P2P) radio links in urban environments. When a fixed base station is assumed, statistical analysis reveals that the shadowing process is mainly a result of spatial displacement at the mobile station (MS). Furthermore, the joint correlation property of the MS-MS channel shows that MS displacements at each end of the P2P link have an independent and equal effect on the correlation coefficient. A sum-of-sinusoids simulation model is proposed to generate the joint correlation shadowing process for urban P2P radio channels. The performance of the proposed channel simulator is analyzed in terms of the autocorrelation and joint correlation function of the simulated shadowing process. Simulations illustrate that the proposed model is able to output deterministic shadowing with a normal distribution (in decibels) and the desired correlation properties. It is thus suitable for use in system-level simulations, such as the evaluation of routing and radio resource management algorithms in ad hoc or mesh networks.

A two-dimensional channel simulation model for shadowing processes

A Gaussian random process with a given power spectral density (PSD) function can be modeled as a sum of sinusoids (SOS), and has been widely used to simulate Rayleigh-fading communication channels. The conventional one-dimensional (1D) channel model cannot capture the spatial correlation of shadowing processes. We here develop a two-dimensional (2D) SOS-based channel model to simulate the shadowing process. Three methods to fit the PSD of the simulated process to the true channel's PSD are explored. Performance of the proposed channel simulator is analyzed in terms of the autocorrelation function of the simulated shadowing process. Simulations illustrate the potential of the proposed channel simulation model.

Enhanced correlated shadowing generation in channel simulation

An enhanced method of generating a shadow fading for mobile radio channel simulation is proposed. It is verified that simulated samples satisfy the properties of variance, autocorrelation and cross-correlation. The proposed channel simulation method can be utilized for evaluating the performances in mobile communication systems where the exchange of interactive information between uplink and downlink channels is required.

Design of high-speed simulation models for mobile fading channels by using table look-up techniques

This paper describes a procedure for the design of fast simulation models for Rayleigh fading channels. The presented method is based on an efficient implementation of Rice's sum of sinusoids by using table look-up techniques. The proposed channel simulator is composed of a few numbers of adders, storage elements, and simple modulo operators, whereas time-consuming operations like multiplications and trigonometric operations are not required. Such a multiplier-free simulation model is introduced as a high-speed channel simulator. It is shown that the high-speed channel simulator can be interpreted as a finite state machine which generates deterministic output envelope sequences with approximately Rayleigh distribution. The statistical properties of the designed high-speed channel simulator are investigated analytically and compared with the statistics of the underlying Rayleigh reference model. Results of experiments for measuring the speed of the presented and other types of channel simulators are also presented.