Spatial Channel Model Research Articles

Cell Selection Technique for Millimeter-Wave Cellular Systems with Hybrid Beamforming.

In this paper, a cell selection technique for millimeter-wave (mm-wave) cellular systems with hybrid beamforming is proposed. To select a serving cell, taking into account hybrid beamforming structures in a mm-wave cellular system, the angles of arrival and departure for all candidate cells need to be estimated in the initialization stage, requiring a long processing time. To enable simultaneous multi-beam transmissions in a multi-cell environment, a cell and beam synchronization signal (CBSS) is proposed to carry beam IDs in conjunction with cell IDs. A serving cell maximizing the channel capacity of the hybrid beamformer is selected with the estimated channel information and the optimum precoder. The performance of the proposed technique is evaluated by a computer simulation with a spatial channel model in a simple model of a mm-wave cellular system. It is shown by simulation that the proposed technique with the CBSS can significantly reduce the processing time for channel estimation and cell selection, and can achieve additional gains in channel capacity, or in bit error rate, compared to that obtained by conventional techniques.

Characterization of 3D Elliptical Spatial Channel Model for MIMO Mobile-to-Mobile Communication Environment

In this paper, we develop three dimensional (3D) elliptical cylindrical geometrical channel model for multiple-input–multiple-output mobile-to-mobile communication environments. It is assumed that both the mobile nodes are surrounded by uniformly distributed infinite number of scatterers sprinkled over the surfaces of an elliptical-based cylindrical shapes. The mobile nodes are located at the centers of the bottom surfaces of elliptical cylinders and both the mobile nodes are equipped with low-elevated multiple antenna arrays. The proposed model is designed for urban areas, where mostly the mobile subscribers reside and are on the move. This model takes into account the effect of multiple antenna array attributes, roadside infrastructure, the dimensions of the propagation medium, transmit–receiver distance and the velocity of mobile nodes. Using the proposed channel model, expressions for the joint and marginal cross correlation functions are derived for non-isotropic scattering environments. The derived expression are simulated for various parameters to verify their effect on the antenna correlations. The obtained correlation graph is compared with measured data that confirms a close agreement with it. Finally, by changing various parameters of the proposed channel model, some existing 2D and 3D channel models are deduced.

Connecting a City by Wireless Backhaul: 3D Spatial Channel Characterization and Modeling Perspectives

The backhaul forwards aggregated traffic from massive users, machines, and sensors to the core network, and is the key infrastructure to facilitate a smart city. The beamforming and spatial multiplexing technologies enable the wireless multipoint-to-point backhaul to connect dense small cell eNodeBs (eNBs) and macrocell eNBs. Because the spatial characteristics of the backhaul channels, such as the angular power spectra and spreads, determine the interference and capacity performance of the backhaul links, accurate 3D channel modeling is vital for the evaluation and comparison of candidate proposals. In this article, the concepts and methodology of spatial channel modeling are first introduced, and the state-of-the-art models developed by the standardization bodies in recent years are surveyed. Then we present a field measurement campaign on the 3D backhaul channels in an urban street, including the channel sounder implementation, field measurement, multipath parameter estimation, and propagation modeling. The Rx of the sounder (emulating a donor eNB) was installed on the rooftop of a five-story building, and the Tx was located along a street and at different altitudes to emulate a relay eNB. The channel angular power spectra in the elevation and azimuth domains were measured, and the impact by the relay�s distance and altitude on the angular spreads was evaluated. In addition, a Laplace model is proposed for the power spectra in both domains. This article not only explains the methodology and implementation of the spatial channel measurement, but also reveals the urban wireless backhaul channel characteristics which are useful for the design and deployment of wireless backhaul for a smart city.

Opportunistic Polarization-Matching for Multiuser Polarized MISO Downlink

Channel imperfections, obstacles, and the unpredictable movements of user equipment can create polarization-mismatch at the receiving antenna, which decreases the power of the received signal in practical wireless communications. In such environments, performance can be improved by opportunistic polarization-matching via dual-polarized (DP) transmitters for limited feedback systems. In this letter, we demonstrate the performance enhancement obtained from opportunistic polarization-matching between a DP transmitter and randomly rotated single-polarized (SP) receivers via a proposed DP multiple-input and SP single-output spatial channel model.

A Framework of Automatic Clustering and Tracking for Time-Variant Multipath Components

A framework of automatic clustering and tracking algorithm is proposed for the multipath components (MPCs) in time-variant radio channels. The algorithm is based on the channel dynamics in time domain and is able to reflect the birth and death behaviors of MPCs naturally. The proposed algorithm is validated by a ray-tracer and the spatial channel model extension simulations. Compared with other existing clustering algorithms, the proposed framework is able to cluster the time-varying MPCs and track the clusters with high accuracy and low complexity.

Path-Loss Channel Models for Receiver Spatial Diversity Systems at 2.4 GHz

This article proposes receiver spatial diversity propagation path-loss channel models based on real-field measurement campaigns that were conducted in a line-of-site (LOS) and non-LOS (NLOS) indoor laboratory environment at 2.4 GHz. We apply equal gain power combining (EGC), coherent and noncoherent techniques, on the received signal powers. Our empirical data is used to propose spatial diversity propagation path-loss channel models using the log-distance and the floating intercept path-loss models. The proposed models indicate logarithmic-like reduction in the path-loss values as the number of diversity antennas increases. In the proposed spatial diversity empirical path-loss models, the number of diversity antenna elements is directly accounted for, and it is shown that they can accurately estimate the path-loss for any generalized number of receiving antenna elements for a given measurement setup. In particular, the floating intercept-based diversity path-loss model is vital to the 3GPP and WINNER II standards since they are widely utilized in multi-antenna-based communication systems.

Phased Array Radar-Based Channel Modeling and Sparse Channel Estimation for an Integrated Radar and Communication System

An integrated radar and communication system can cooperatively form a radar-communication network with significantly enhanced efficiency and considerably less occupied hardware resources. Such a system exhibits great advantages compared with traditional individual radar and communication modes. Numerous papers have proposed achieving the integrated functions based on phased array radar, whereas the channel modeling and channel estimation problems concerning communications are seldom discussed in the literature. In this paper, we propose a ray-cluster-based spatial channel model and a sounding channel estimation scheme realized on the existing hardware of phased array radar. Considering the correlation, we model the channel by comparing the difference between adjacent antennas, and we present the response vector of the antenna array. We analyze the number of beams that are needed to cover the space, and we present the sequence of directional beamforming vectors when sounding the channel. Redundant dictionary matrices are utilized to present the channel as a sparse signal recovery problem, in which the spatial sparsity is leveraged for performance enhancement. A sparsity adaptive matching pursuit (SAMP)-based compressed sensing tool is exploited for the sparse recovery problem and compared with the conventional least squares (LS) algorithm. The experimental results demonstrate that our proposed scheme can effectively solve the channel estimation problem in the integrated radar and communication system with reduced complexity, and it outperforms LS by 25% when considering mean square error (MSE) performance in general.

Research on Spatial Channel Model for Vehicle-to-Vehicle Communication Channel in Roadside Scattering Environment

In this paper, an extension of spatial channel model (SCM) for vehicle-to-vehicle (V2V) communication channel in roadside scattering environment is investigated for the first time theoretically and by simulations. Subsequently, to efficiently describe the roadside scattering environment and reflect the nonstationary properties of V2V channels, the proposed SCM V2V model divides the scattering objects into three categories of clusters according to the location of effective scatterers by introducing critical distance. We derive general expressions for the most important statistical properties of V2V channels, such as channel impulse response, power spectral density, angular power density, autocorrelation function, and Doppler spread of the proposed model. The impact of vehicle speed, traffic density, and angle of departure, angle of arrival, and other statistical performances on the V2V channel model is thoroughly discussed. Numerical simulation results are presented to validate the accuracy and effectiveness of the proposed model.

On the Field Emulation Techniques in Over-the-Air Testing: Experimental Throughput Comparison

In this letter, we compare two field emulation techniques, namely plane-wave synthesis (PWS) and prefading signal synthesis (PFS) for multiple-input-multiple-output over-the-air (MIMO OTA) testing of mobile terminals in an anechoic chamber equipped with multiple probes. The comparison is performed in terms of measured throughput. The measurements were performed under urban microcellular scenario of the spatial channel model extended and at Long Term Evolution lower band 20. A practical mobile terminal is used as a test device. The throughput of four different browsing positions of the mobile terminal utilizing both emulation techniques has been measured. Results shows that at a fixed median throughput, the differences of the downlink channel power between the PFS and PWS techniques are small and are in the range of 0.2-1.0 dB for different browsing positions of the mobile terminal. The PWS and PFS techniques are equally capable of emulating the target field inside the test zone and are suitable for the MIMO OTA antenna testing based on anechoic chambers equipped with multiple probes.

Experimental Evaluation of User Influence on Test Zone Size in Multi-Probe Anechoic Chamber Setups

Over-the-air (OTA) radiated testing for multiple-input multiple-output (MIMO) capable mobile terminals has been actively discussed in the standardization in recent years, where multi-probe anechoic chamber (MPAC) method has been selected, together with the radiated two-stage method. The supported test zone size is a key parameter to determine for an MPAC design, and the test zone size is restricted by the number of OTA antennas. A larger test zone would necessitate more OTA antennas, each port of which is driven by an expensive channel emulator radio frequency interface. Results available in the literature are typically limited to free space scenarios, where no user effect in the vicinity of MIMO terminal is present. There is a concern whether or not the test zone size should encompass the user phantom, together with the mobile terminal in the MPAC setup. To address this issue, an extensive measurement campaign was carried out in this paper. Two realistic long term evolution mockups were designed and their performance were evaluated under standard spatial channel models with and without the presence of user phantom. The measurement results have shown that the nearby user phantom can significantly affect the MIMO performance. However, its impact on the test zone size of the MPAC system is negligible, since emulation accuracy in terms of received power, branch power ratio, antenna correlation, and measured throughput under the target and the emulated channels is not affected by the presence of user phantom. Moreover, results measured with the synthetic MPAC method generally match those obtained with the reference two-stage method. These findings are valuable inputs for the ongoing MIMO OTA harmonization work in the standardization.

Construction of a Generalized DFT Codebook Using Channel-Adaptive Parameters

Discrete Fourier transform (DFT)-based codebooks are known to work efficiently for spatially correlated channels produced by uniform linear arrays. Although the long-term codebooks are selected to suit to channel correlation characteristics, such selections may not be optimal for the given channel of the target user equipment (UE), due to the specific structure and constraints of the codebook in use. In this letter, we propose a generalized DFT-based codebook structure employing variable parameters to provide enhanced resolution of codevectors and adjustable spacing among them. The proposal includes the Release 10 codebook of LTE-advanced as a special case, with added flexibility via parameter configurations. When tested over the 3GPP spatial channel model, the new codebook exhibits significant gains over existing ones, outperforming the LTE-advanced codebook in entire UE locations within the sector.

Experimental Evaluation of MIMO Terminals With User Influence in OTA Setups

User influence, together with propagation environments and antenna designs, determines how well multiple-input–multiple-output (MIMO) terminals operate in true usage conditions. In this letter, we investigate to what extent the user influence affects the performance of a realistic MIMO terminal under various reproduced spatial channel models in a practical 3-D multiprobe anechoic chamber setup. A terminal mock-up, operating at 2.55 GHz, together with a realistic user phantom was used, and channel models with different spatial and polarization profiles, device under test with different operation modes and orientation angles were tested.

Spatial Characterization for High-Speed Railway Channels Based on Moving Virtual Array Measurement Scheme

In this letter, spatial channel characterization in highspeed railway (HSR) scenarios is investigated using a moving virtual array measurement approach. Based on the wideband single-antenna measurements conducted on high-speed railway (HSR) in China and the moving virtual array measurement scheme, 1 × 3 single-input-multiple-output channel impulse responses are generated. Spatial characteristics in the obstructed viaduct and deep cutting scenarios, focusing on angle of arrival, angle spread, and spatial correlation, are analyzed. The obtained results can fulfill the gap of HSR spatial channel models and provide helpful reference for the assessment of HSR multiantenna technologies.

Analytical spatial correlation analysis based on the hierarchical angle model for uniform linear and circular antenna arrays

In this study, an analytical analysis of normalised spatial correlation based on a hierarchical angle model for uniform linear array (ULA) and uniform circular array (UCA) over clustered narrowband multiple-input multiple-output channels is presented. The clustered channel has independent multiple paths, each of which is a cluster consisting of a number of independent subpaths, constructing a hierarchical angle structure. Unlike most of existing analysis methods that employ various simplification to the hierarchical angle, in this study, the hierarchical angle is expressed as a function of bivariate random variables. This formulation can include the simplified models as special cases. Assuming the angle of departure and angle of arrival of each subpath are independent, a closed-form spatial correlation expression between transmit and receive antennas of ULA or UCA is derived. Simulation results show that the theoretical spatial correlation matches well with the simulated one with channel data generated from the 3GPP spatial channel model for different scenarios.

A performance comparison of the SCM and the Onering channel modeling method for MIMO-OFDMA systems

This paper compares two types of channel modeling methods, which are the spatial channel modeling (SCM) and the Onering channel modeling method. These two well-known channel models are proposed for 4G wideband mobile communication networks. To compare the performance of these channel modeling methods, we analyze the properties of the spatial, temporal, frequency correlation functions simulated by using these methods. The correlation functions of the two channel models are compared in the same conditions of antenna arrangements. The simulation and calculation results show that the correlation functions of Onering and SCM channel models are very close to each other if the BS and the MS antenna arrays are parallel and perpendicular to the broadside of MS-BS. In other cases, the correlation functions of the two models are slightly different; however, their shapes are similar. These differences can be explained that the Onering model hardly fully describes all the characteristics of 4G channels as the performance SCM model does. The performance of these channel modeling methods is compared in system simulation level—MIMO-OFDMA systems. The combination SFBC-MMSE is used for spatial channel coding and the signal detection. The simulation results show that the system performance obtained by using these two channel models are comparable, given that the both modeled channels have same parameters and antenna directions. Copyright © 2016 John Wiley & Sons, Ltd.

공간 채널 모델의 통계적 특성을 반영한 다중 랭크 코드북의 설계 및 성능 이득 평가

공간 채널 모델의 통계적 특성을 반영한 다중 랭크 코드북의 설계 및 성능 이득 평가

Including the Angular Domain in the Analysis of Finite Multi-Packet Peer-to-Peer Networks With Uniformly Distributed Sources

This paper presents a mathematical framework for including the angular domain beside the radial one in the theoretical modeling of wireless networks, in which spatial reuse enables the coexistence of multiple single-hop peer-to-peer communications inside a finite region. The proposed model analyzes a scenario where the transmitting sources are uniformly distributed over a disk and the communications are subjected to path-loss attenuation and multipath-fading, considering the actual location of each destination and its antenna system. Different from most of the previous theories in which the coverage probability of a destination is estimated assuming that the destination itself is positioned at the center of the network, in the proposed analysis, the destination location is generic. This generalization, together with the consideration of the spatial channel model and of the actual receiving pattern, allows one to investigate the influence of the angular domain on the statistic of the interference power and on the coverage probability. The conceived theory, which is further verified by Monte Carlo validations, is finally exploited to derive the network transmission capacity, with the purpose to illustrate the possible advantages that may derive from a reliable modeling of the non-isotropic context, in which each destination has to operate realistically.

Proposal on Millimeter-Wave Channel Modeling for 5G Cellular System

This paper presents 28 GHz wideband propagation channel characteristics for millimeter wave (mmWave) urban cellular communication systems. The mmWave spectrum is considered as a key-enabling feature of 5G cellular communication systems to provide an enormous capacity increment; however, mmWave channel models are lacking today. The paper compares measurements conducted with a spherical scanning 28 GHz channel sounder system in the urban street-canyon environments of Daejeon, Korea and NYU campus, Manhattan, with ray-tracing simulations made for the same areas. Since such scanning measurements are very costly and time-intensive, only a relatively small number of channel samples can be obtained. The measurements are thus used to quantify the accuracy of a ray-tracer; the ray-tracer is subsequently used to obtain a large number of channel samples to fill gaps in the measurements. A set of mmWave radio propagation parameters is presented based on both the measurement results and ray-tracing, and the corresponding channel models following the 3GPP spatial channel model (SCM) methodology are also described.

3GPP 3D MIMO channel model: a holistic implementation guideline for open source simulation tools

Massive MIMO and 3D beamforming have been identified as key technologies for future mobile cellular networks. Their investigation requires channel models that consider not only the azimuth- but also the elevation direction. Recently, the 3rd Generation Partnership Project (3GPP) has released a new 3D spatial channel model. It supports planar antenna arrays and enables to scrutinize concepts such as elevation beamforming and full dimension MIMO. A particular challenge is the practical implementation of the model. Dealing with enormous computational complexity requires to design a highly efficient approach. This paper provides a guideline for the practical implementation of the 3GPP 3D model into existing link- and system-level simulation tools. Considering the complexity of the model itself, our main focus is on computational efficiency. We present simulation examples using the proposed procedure with the Vienna LTE-A Downlink System Level Simulator. We measure simulation run times with respect to various network parameters. Our results allow to quantify the increase in complexity, when accounting for the elevation dimension. Moreover, they exhibit general trends when considering a large number of antenna elements per antenna array. We also draw a comparison with the WINNER channel model, which represents the most closely related channel model in 2D.

Spatial and Temporal Characterization of Indoor Millimeter Wave Propagation at 24 GHz

Indoor millimeter wave propagation at the frequency of 24 GHz is studied by experimental methods. Measurements are performed to obtain temporal and spatial channel model using a channel sounder and rotating antennas in a corridor. The measured impulse responses are processed to obtain compact channel model following Saleh-Valenzuela’s model. The responses are compared with those of 5.3 GHz for the same test sites. Angular spread of 24 GHz is found to be smaller than that of 5.3 GHz, while echoes of 24 GHz are found to be longer than those of 5.3 GHz.