Stan X. Lu

Measurement-based angular characterization for 72 GHz propagation channels in indoor environments

In this paper, channel measurement campaigns at center frequency of 72 GHz with 2 GHz bandwidth conducted by Huawei company are introduced. The transmitter and receiver make use of similar horn antennas which are rotated step by step in the directional domains to capture the frequency spectra of spatial channels in line-of-sight and non-line-of-sight scenarios of indoor environments. The data is applied to extract the statistics of composite and cluster angular spreads in the azimuth and elevation of arrival. The variation of the angular spreads with respect to the distance between the transmitter and receiver is also investigated. A preliminary channel model is provided based on the analysis results. It is found that the directional dispersion of 72 GHz indoor channels is more sparse than those obtained in lower frequencies. The observations of less composite and cluster angular spreads imply that spatial beamforming techniques are preferable in either backhaul transmission cases or user-specific applications.

Channel modeling based on random propagation graphs for high speed railway scenarios

In this paper, a channel modeling method based on random-propagation-graph is elaborated, validated, and applied to characterizing time-variant channels observed in typical environments for high-speed railway wireless communications. The advantage of the proposed method is that the frequency-tempo-spatial channel coefficients, as well as the multi-dimensional channel impulse responses in delay, Doppler frequency, direction of arrival (i.e. azimuth and elevation of arrival) and direction of departure are calculated analytically for specific environments. The validation of the proposed method is performed by comparing the statistics of two large-scale parameters obtained with those described in the well-established standards. Finally, stochastic geometry-based models in the same format as the well-known spatial channel model enhanced (SCME) are generated by using the proposed method for the high-speed scenarios in the rural, urban, and suburban environments.

Angular spread measurement and modeling for 3D MIMO in urban macrocellular radio channels

When planar antenna arrays are introduced at the base stations (BSs) of cellular networks, accurate modeling of the spatial radio channel in there-dimension (3D) will become crucial. In this paper, a field measurement campaign was conducted to characterize the 3D spatial propagation to the BS in urban street canyon environments. Using a wideband channel sounder with two uniform planar antenna arrays, the angular spread (AS) in both azimuth and elevation domains at the BS was measured with the user equipment (UE) located at 100 different positions in LOS scenario and 95 positions in NLOS scenario. Contrary to the expected simple correlation between the large-scale fading (like path loss) and AS, our measurements have shown much more complicated relationship between AS and the surrounding environment. It is demonstrated that, in LOS scenario, the AS has positive correlation with the UE-to-BS distance in wide street, but negative correlation in narrow street. In NLOS scenario, the correlation between AS and the transceiver distance is positive when the UE is too close to a building to have “Quasi-LOS” path (diffracted over the building roof) propagation. However, if “Quasi-LOS” path is strengthened, the correlation is reversed. These observations lead to the need of more sophisticated models on the angular characteristics in urban radio channels. Based on the collected data, we also present the Laplacian distribution models of AS in both azimuth and elevation domains.

Measurement and modeling of indoor channels in elevation domain for 3D MIMO applications

The 3-dimensional multi-input-multi-output (3D MIMO) scheme is one of the enabling technologies for next generation mobile communications and is expected to increase the capacity considerably by realizing the beamforming in the elevation domain. With the small cell architecture, 3D MIMO may be deployed in indoor environments. Thus 3D spatial measurement and characterization of the indoor channels are critical, which have been rarely conducted. In this paper, indoor channel measurements are performed at 2.6 GHz in typical hall and corridor environments including both line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. Using a sounder with two uniform planer antenna arrays, spatial channel responses were captured at about 200 positions. The multipath channel impulse responses (CIR) are extracted and the angle-of-arrival of each propagation path is estimated jointly in azimuth and elevation domains. Then the distributions and models of the incident angles and angular power distribution in the elevation domain are established. Our measurements and proposed models can support the design and simulation of 3D MIMO working in the indoor environment in the next generation cellular networks.

Antenna De-Embedded Characterization for 13–17-GHz Wave Propagation in Indoor Environments

High-gain directional antennas such as pyramidal horns have been widely used in higher frequency band channel measurements. Channel models established based on directional channel observations are antenna-specific and subject to the direction-scanning method adopted. To de-embed the impact of the antennas responses from propagation channels, an array signal model is proposed that formulates the received signals as the outputs of a virtual array generated via antenna rotating. We first show by simulations that high-resolution parameter estimation methods, such as the space-alternating generalized expectation-maximization (SAGE) algorithm derived based on this model, are applicable to extract multipath components. The results are system-independent provided the antenna-rotating strategy satisfies certain conditions. Then, measurements conducted by using two types of horn antennas for characterizing 13–17-GHz wave propagation in a laboratory demonstrate the de-embedding effect by using the proposed scheme.

The correlation properties of subchannel fading for non-continuous carrier aggregation based on indoor ultra-wideband measurement

The new multichannel/multicarrier technologies have drawn great attention recently to support high data rate in mobile multiple-access environments, such as the carrier aggregation (CA) as a part of 4G LTE-Advanced enhancement. On the way to the development of multicarrier technologies, there is a considerable need to understand and utilize the correlation properties of distinct subchannels, which, however, has not been reported in the literature. Based on the extensive indoor ultra-wideband (UWB) channel measurement, this paper develops a new approach to analyze the correlation of the large and small-scale fading of arbitrarily separated subchannels. The approach avoids the high complexity and cost of the conventionally probing the multiple subchannels simultaneously using channel sounders which would be too complicated to implement. We first propose a modified CLEAN algorithm to reliably extract channel impulse responses (CIRs) from the measured pulse response waveforms with substantially varying noise floor. Then the cross-correlation of the fading of two distinct subchannels, the autocorrelation of the fading of a single subchannel and the correlation of the multipath profile over a small area are analyzed. The study has revealed how significantly the channel response would change when the receiver travels from room to room or just over a distance of dozen of wavelength, and how two separated subchannels are correlated. In our view, the acquired new insights on subchannel correlations could provide guidelines for efficient designs and performance predictions of multicarrier communication systems.

Automatic data segmentation based on statistical hypothesis testing for stochastic channel modeling

In order to extract the statistical characteristics of propagation channels, multiple impulse responses of the channels are measured and saved e.g. in terms of cycles or bursts. In the case where measurements are performed in time-variant environments, the received signals need to be divided into multiple segments. It is essential to perform the data segmentation reasonably in order to guarantee that each segment contains the observations of the same stationary process. In this contribution, we first show experimentally the impact of the number of data bursts per segment on the clustering results. Then a novel Kolmogorov-Smirnov hypothesis-testing-based approach is proposed for automatically determining the number of bursts in each segment. The applicability of this approach is evaluated using indoor channel measurement data. The results obtained show that the number of bursts in a segment follows lognormal distributions with parameters dependent on the environments and the mobilities of the transmitter, receiver and the scatterers during the measurement campaigns.

Semi-deterministic modeling of diffuse scattering component based on propagation graph theory

Graph theory-based channel modeling is an efficient approach to simulate multipath propagation taking into account the reverberation of electromagnetic waves. In this contribution, without modifying the modeling framework, we proposed a semi-deterministic graph modeling approach by associating the scatterers with realistic environment objects, and by calculating the coefficients of the propagation paths on the base of a proven diffuse scattering theory. An isolated office building scenario is adopted to illustrate the procedure of the proposed method. The performance is thus evaluated by comparing the simulated power-delay-profiles (PDPs) with ray-tracing and real channel measurement data. The results illustrate that the proposed method can accurately predict both the decaying slopes and the diffuse tails of the PDPs.

Propagation Characteristic for Indoor E-Band Wideband Channels

Abstract- We discuss the measured propagation characteristics of E-Band radio signals measured in indoor office and closed meeting room scenarios for LOS (Line-of-Sight) and NLOS (Non-Line-of-Sight) conditions. A new wideband channel sounder with 2 GHz bandwidth (i.e. 72 GHz ~ 74 GHz) was used for the propagation measurements. In both the LOS and NLOS scenarios, a horn antenna with 40° HPBW was used at the transmitter and a scanned directional horn antenna with 10° HPBW was used at the receiver. These measurement results show a path loss exponent of about 2.1 for LOS and 3.4 for NLOS respectively. These measurements are quite similar to the values observed for the traditional cellular frequency bands below 6 GHz. The measurements confirm the suitability of E Band radio channels for future 5G applications indoors, and serve to guide the design of future millimeter-wave mobile communication radio systems.

Measurement and Analytical Study of the Correlation Properties of Subchannel Fading for Noncontiguous Carrier Aggregation

The new multichannel/multicarrier technologies can potentially support much higher data rates in mobile multiple-access environments, such as carrier aggregation (CA) defined in the fourth-generation Long-Term Evolution Advanced enhancement. The correlation properties of noncontiguous subchannels are critical for the performance of CA, including cell coverage, frequency diversity, and channel state estimation. This paper has studied the correlation of the large-scale fading (LSF) and small-scale fading (SSF) of arbitrarily separated subchannels by realistic channel measurement and analytical modeling. We first obtain the subchannel correlation from the ultrawideband (UWB) channel measurement. This new approach avoids probing multiple subchannels simultaneously with channel sounders, which would be prohibitively complicated. The cross correlation of two distinct subchannels and the autocorrelation of a single subchannel are evaluated. Second, a new propagation model for the Nakagami-m fading in a multipath environment is proposed. The frequency-domain level crossing rate (FD-LCR) is defined and derived based on the propagation model. Then, a Markov chain for the frequency fading of the wideband channel is established, which can generate the correlated gain/power of subchannels in a wide bandwidth. Therefore, this model can be used as a fast simulator of CA over correlated subchannels. Finally, the cross correlation coefficients (CCCs) between two Nakagami-m fading subchannels obtained from the measurement and the proposed Markov model are compared with the analytical results in the literature. This paper provides important insights into the fading correlation of the multicarrier channels and can be applied to the design and simulation of indoor/outdoor multicarrier communications.