Gerd Sommerkorn

Identification of time-variant directional mobile radio channels

For the identification of the time-variant, directional structure of the mobile radio channel impulse response, a broadband vector channel sounder is described. The measurement procedure relies on periodic multifrequency excitation signals, correlation processing and joint delay-azimuth superresolution based on the ESPRIT algorithm. Problems of imperfect receiver and antenna performance and antenna array calibration methods are discussed. Results of multidimensional correlation analyses of various channel scenarios in the time-frequency-spatial domain and the corresponding Doppler-delay-angular domain are represented.

MIMO vector channel sounder measurement for smart antenna system evaluation

For the simulation and design of smart antenna transmission principles in mobile radio, precise knowledge of the time-variant directional multipath structure in various radio environments is required. In this paper, a new real-time multiple-input-multiple-output (MIMO) vector radio channel sounder is described, which uses multiple antennas at the transmitter as well as at the receiver position. The proposed MIMO measurement principle can be effectively exploited to estimate the propagation direction at both ends of the wireless link simultaneously, and thus, dramatically enhance overall resolution of the multiple path parameters. Applying a proper antenna architecture and the multidimensional unitary ESPRIT algorithm, joint superresolution estimation of the direction of departure (DOD), time- delay of arrival (TDOA), Doppler shift, and direction of arrival (DOA) of the propagating waves becomes possible. The measured results can also be used directly for the simulation of combined transmit-receive diversity (MIMO) transmission principles and space-time (ST) adaptive receivers in a multi-user scenario. Results based on measurements in different locations are referenced, including a complicated indoor environment as is typical for industrial WLAN applications.

Array measurement of the double-directional mobile radio channel

We describe a novel technique to measure the double-directional mobile radio channel. The channel is called double-directional since it includes directional spreading at both link ends, namely the base station and the mobile station. We use a double-array multiplexing technique consisting of a switched linear array at the receiver and a virtual array at the transmitter site. The measured microcellular scenarios are an open and a closed courtyard with different transmitter positions. The data are evaluated with an alternating estimation and beamforming technique that relies on (Unitary) ESPRIT estimation of positional parameters and subsequent beamforming for complex weight extraction. Usage of a two-axis crossed array at the transmitter site avoids forward-backward ambiguity. The presented exemplary results show a good agreement of the extracted directional information with the physical environment and give an indication of its scattering properties.

Joint estimation of DoD, time-delay, and DoA for high-resolution channel sounding

The detailed knowledge of the directional characteristics of the mobile radio channel is required to develop directional channel models and to design efficient smart antenna concepts for future mobile radio systems. In this paper, we present a high-resolution estimation scheme for the directional channel parameters from dual antenna array based channel sounding measurements. Since 360/spl deg/ azimuth coverage seems reasonable at the mobile station (MS), the utilization of a circular uniform beam antenna array at this place is proposed. Moreover, a transformation is described making this array suitable for high resolution angle estimation with ESPRIT. With this approach, the joint estimation of direction of departure, time-delay, and direction of arrival using 3-D Unitary ESPRIT is derived. Finally, we propose a procedure for the model order estimation and discuss some calibration issues.

Multidimensional high-resolution channel sounding in mobile radio

Multidimensional high resolution channel sounding is a method of wave propagation analysis, channel modeling, and link performance evaluation in mobile radio. For this application antenna array architecture design, calibration, and a maximum likelihood channel parameter estimation framework (RIMAX) is described. Depending on the available measured dimensions, the algorithm estimates the four coefficients of the polymetric path weight matrix, the direction of arrival, the direction of departure, the time delay of arrival, and the Doppler-shift of the specular paths. Moreover, the parameters of a statistical model of the dense multipath components resulting from distributed diffuse scattering are estimated. Additional reliability measures are calculated to enhance the robustness of the estimate.

3D-Antenna Array Model for IST-WINNER Channel Simulations

The IST-WINNER channel model (WIM) offers a complete channel model description in a sense of large-scale as well as small-scale effects in MIMO radio-channel for B3G system designs. This paper proposes the extension of 1D regular array structures being currently supported within WIM (uniform linear array - ULA) to arbitrary 3D antenna arrays. Arbitrary antenna structures are necessary for both modelling and validation purposes since antenna arrays define the spatial dimension of the radio-channel. General 3D antenna array description also embeds polarization concepts that are becoming important for modelling of 3D rotation of antenna array. In this paper two different strategies of using 3D antenna arrays in channel model simulations are proposed and discussed. Both methods are compared in terms of the computational complexity and their suitability for the current WIM channel model implementation.

Large Scale Parameter for the WINNER II Channel Model at 2.53 GHz in Urban Macro Cell

This paper presents results of wide band channel measurements at 2.53 GHz for a representative urban macro cell environment in Ilmenau, Germany. The extensive channel sounding campaign covered the MIMO radio links from 22 mobile tracks to 3 different base stations and 1 relay station. The results presented in this paper provide insight into the large scale parameter analysis of the power, delay domain, including the transmission loss and the statistical distributions of the shadow fading, narrowband k-factor and delay spread. Large scale parameters from angle domain (azimuth and elevation) are derived based on the high resolution multipath parameter estimation (RIMAX). Furthermore the cross correlation of these parameters are investigated and compared to state-of-the-art channel models as from the IST-WINNER.

Characterization of the directional mobile radio channel in industrial scenarios, based on wideband propagation measurements

The object of this paper is to provide data from wideband directional channel measurements carried out at 5.2 GHz in two different industrial scenarios. The channel is characterized by the temporal, azimuthal and Doppler characteristics under LOS and non-LOS situations. The results give insight into the propagation behavior for this type of environment and reveal that the installation of wireless LANs in industrial scenarios imposes important requirements on the system design.

MIMO capacities for different antenna array structures based on double directional wide-band channel measurements

We present an approach for investigating the performance of generic multiple-input multiple-output (MIMO) wireless systems in a realistic way using wideband real-time propagation measurements of the double-directional radio channel. Applying a multidimensional high-resolution channel parameter estimation procedure the descriptive parameters for any relevant propagation path including the path weights, time-delay, Doppler shift and the propagation directions at both ends of the wireless link are extracted simultaneously from the measurement data. from the estimated parameter sets then a local reconstruction of the multidimensional wave fields in the vicinity of the measured aperture volumes in time, space and frequency is possible. Since this way the measurement antenna properties are excluded from the channel, the influence of a variety of application specific array architectures can be investigated. Here, we use this synthesis approach to analyze the performance of given target systems with smart antennas in terms of the resulting channel capacities and eigenvalue distributions.

MIMO measurement and joint M-D parameter estimation of mobile radio channels

We describe a measurement and parameter identification procedure for the mobile radio propagation channel which includes the azimuth directions of the propagating waves at both link ends, elevation at the base station, time delay, and Doppler shift. The measurement is based on a broadband, real-time multiple-input-multiple-output radio channel sounder. At the mobile station a circular uniform beam array (CUBA) is used which covers 360/spl deg/ viewing angle whereas at the base station a uniform rectangular array (URA) is deployed. We derive the underlying data model and propose a multidimensional joint parameter estimation procedure from measurements which is based on the M-D ESPRIT algorithm. The resolution of coherent paths by subspace smoothing and the reduction of measurement errors by device calibration procedures is addressed.