Marko Milojevic

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.

Channel Modeling for Multiple Satellite Broadcasting Systems

In this contribution we present the results of a study on land mobile satellite channel models for satellite systems with multiple satellites. The slow fading of our channel model for several satellites is based on a Markov channel state model for joint processes while the probability density function (PDF) of the signal amplitude within each state is fitted to the Loo distribution. The correlation between two satellite channels and the channel spatial autocorrelation have also been studied. We show that a channel state model that uses a Markov state model of order one or of a fixed higher order is not appropriate if the state duration is of very high importance, which can be the case in the process of system planning. Therefore, we propose a dynamic higher order Markov state model for joint processes that depends on the current state duration. This approach models precisely any PDF of the channel state duration for both single and multiple satellite broadcasting systems while having a significantly lower computational complexity than a fixed higher order Markov model. It models the channel states of the whole system correctly, as well as the channel states of each satellite observed independently. It is able to capture the state correlation between multiple satellites. We also study possible approximations of the proposed models in order to reduce their computational complexity while having a good PDF match. Our channel state models are validated by measurements.

Tensor-based framework for the prediction of frequency-selective time-variant MIMO channels

In this contribution we propose a tensor-based framework for the prediction of time-variant frequency-selective multiple-input multiple-output (MIMO) channels from noisy channel estimates. This method performs the prediction in a transformed domain obtained via the higher order singular value decomposition (HOSVD), namely on the transformed tensor elements. This is followed by the inverse transformation of the predicted transformed tensor elements onto a basis corresponding to the signal subspace. To verify our strategy, we compare the results in terms of the normalized mean square error using a known prediction method, e.g., a Wiener filter, applied to the transformed tensor elements with the identical method applied directly to the channel coefficients. The results of our investigation show that the tensor-based prediction method outperforms the direct prediction method. Although we concentrate in this contribution on the prediction in the time domain, this framework can also be used for the estimation in other domains.

Experimental Evaluation of Correlation Properties of Large Scale Parameters in an Indoor LOS Environment

The primary goal of this paper is through examining a set of measurement data to show that the spatial variation properties of large scale parameters can well be expressed by the exponential decaying function, as proposed by Algans et al. (2002), but with quite a small decorrelation distance. The large scale parameters include large scale fading and delay spread as well as azimuth spreads at the transmitter and receiver sides. Furthermore, it is also shown that the cross correlation between the large scale parameters is relatively small, only being -0.54 between large scale fading and delay spread, while being almost 0 for the others. The measurement data obtained in an indoor LOS scenario in the campus of Technische Universitat Ilmenau was used for this purpose.

Path loss and Wideband Channel Model Parameters for WINNER Link and System Level Evaluation

In this paper double-directional wideband channel measurements at 5.2 GHz and 120 MHz bandwidth for hot spot outdoor and indoor scenarios are presented. Statistical analysis based on the measurements derive spatial and temporal parameters for the recently published WINNER1 channel model. The focus is on channel models for link level evaluation and radio network planning, whereby the tapped delay line model as well as the path loss model are used.

A subspace-based channel model for frequency selective time variant MIMO channels

In this contribution we propose a subspace-based channel model suitable to represent frequency selective time variant MIMO channels. This approach captures the true nature of the MIMO channel maintaining the spatial correlation present between the antenna arrays. Correlation in time and frequency is conserved as well. The decomposition into eigenmodes, which form the channel subspace, gives an interesting interpretation of the channels eigenstructure. These investigations lead to a very efficient method to synthesize new channels with the same correlation in time, frequency and space of a reference channel. The model allows the interpolation of a channel in order to retrieve more samples in frequency and time to perform statistical analysis such as bit error rate and capacity curves. In addition the model allows the generation of new random channels with the same spatial, time, and frequency correlations of a reference channel, which, for instance, could be obtained from measurements.

Impact of the Receive Antenna Arrays on Spatio-Temporal Availability in Satellite-to-Indoor Broadcasting

This contribution presents the results of our study on spatio-temporal availability in satellite-to-indoor broadcasting. We compare the performance of single and multiple antenna arrays consisting of theoretical and measured antennas with various polarimetric radiation patterns and coupling effects for different satellite elevation angles. The spatial satellite to indoor channels are obtained by a 3D ray tracing engine and by a geometry-based channel modeling tool. The temporal fluctuations of the channels are modeled by the PDF of a truncated normal distribution and are based on satellite-to-indoor measurements. The additional antennas at the receiver reduce both the spatial and the temporal variability of the received power, leading to a significant reduction of the transmit power required to achieve the same target availability. The simulation results suggest that the spatial correlation in the line-of-sight room area is higher than in the non-line-of-sight room area. In the line-of-sight areas, the best performance is achieved by multiple circularly polarized receive antennas. For elevations higher than 50 in the non-line-of-sight areas, a combination of horizontally and vertically (orthogonal) polarized antennas shows the best performance, especially if high availabilities are considered. Furthermore, the influence of coupling effects between closely spaced receive antennas on the availability is studied. In general, antenna coupling effects should be handled by increasing the required link margin. The influence of the temporal changes due to a person movement on the availability is found to be not very significant.

Channel state modeling for single and multiple satellite broadcasting systems

In this contribution, we present the results of a study of the Probability Density Function (PDF) of the state durations in satellite broadcasting systems. We show that a channel state model that uses a Markov state model of order one is not appropriate if the state duration is of high importance, which can be the case in the process of system planning. In this case, a dynamic higher order Markov state model can be used. We study the modeling of the channel state duration for both single and multiple satellite broadcasting systems. In case of multiple satellite systems the channel state modeling is performed based on a dynamic higher order Markov channel state model for joint processes that depends on the current state duration. This approach is able to model the channel states of the whole system correctly, as well as the channel states of each satellite observed independently, showing the ability of capturing the state correlation between multiple satellites. Moreover, we introduce a reduced complexity channel state generation algorithm based on the PDF of the state duration. Our channel state models are validated with measurements of the Satellite Digital Audio Radio Services (S-DARS) system XM Radio carried out on various locations in the USA and Canada.

Measurement based satellite to outdoor channel modeling for multiple satellite systems

In this contribution we present the results of a study on satellite to outdoor channel modeling for satellite systems with multiple satellites. Our model for several satellites is based on a first order Markov channel state model for joint processes. The probability density function (PDF) of the signal amplitude within each state is fitted to the Loo distribution. The parameters of our model are based on the simultaneous measurements of the Satellite Digital Audio Radio services (S-DARS) systems XM Radio and Sirius carried out on various locations in the USA and Canada. All channel model parameters are estimated for four different measured environments. We also study the channel state duration, the correlation between two satellite channels, and the channel spatial autocorrelation. The probability density functions of these parameters are approximated with analytical expressions. The correlation properties between two channels and the state duration indicate that significant diversity gains are possible in multiple satellite systems.

Spatio-Temporal Availability in Satellite-to-Indoor Broadcasting

This contribution studies the spatio-temporal availability of satellite links inside typical indoor environments. The spatio-temporal satellite-to-indoor channels are obtained by a 3D ray tracing engine and by a geometry-based channel modeling tool. In this paper the temporal fluctuations of the channels have been modeled based on satellite-to-indoor measurements. Here the performance of single as well as multiple receive antennas with different polarimetric radiation patterns are compared for different satellite elevation angles. The results show that additional antennas placed at the receiver reduce both the spatial and temporal variability of the received power, leading to a significant reduction in transmit power necessary for the same target availability.