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ABSTRACT: Distributed antenna systems (DAS) has been adopted in both indoor and outdoor wireless communications for benefits of reducing the power consumption and enhancing system capacity owing to spatial multiplexing gains. The capacity of a DAS system is partially determined by the cross-correlation of the large-scale fading of multiple links in the system. In this contribution, we use experimental data collected in an indoor environment to investigate the influences of different constellations of the transmit and receive antennas on the channel capacity when the DAS system is deployed within a building. We found that the capacity decreases dramatically when the line-of-sight propagation appears in the constellation. When the spacing of the antennas decreases to 1 meter, the large-scale similarity among the antennas leads to high cross-correlations and as a result, the capacity drops. These observations provide insights for characterization of distributed channels in indoor environments.
Antennas and Propagation (EUCAP), Proceedings of the 5th European Conference on; 05/2011
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ABSTRACT: Spatial auto- and cross-correlation characteristics of propagation channels are investigated for four indoor scenarios using measurement data. In addition to the well-known spatial auto-correlation effect, significant cross-correlation between channels is also observed. We found that non-zero spatial cross-correlation among channels may occur in three scenarios with possibly different mechanisms. These results should be considered when establishing realistic models for the spatial cross-correlation behavior of channels.
Wireless Communications and Signal Processing (WCSP), 2010 International Conference on; 11/2010
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ABSTRACT: In this contribution, we derive the spread function and power spectrum of the so-called "relay channel'' along which electromagnetic waves propagate from a source station to a destination station via multiple amplify-and-forward (AF) relay stations. These results show analytically that the propagation over such a relay channel can be influenced by the propagation in individual "hops'' and the responses of the relay stations. Furthermore, we find that the uncorrelated-scattering assumption is inapplicable for the AF-relay channels in the case where the relay stations receive and retransmit signals using mulitple antennas. We propose to simulate the relay channels by three steps: i) selecting channel models for individual "hops''; ii) defining the correlations of model parameters among the hops; and iii) constructing realizations of relay channels by taking into account the responses of relay stations, which are specified by considering the response of antennas and the relay mode according to system configurations. We also show in this contribution that the spreads of a multi-relay channel in delay, Doppler frequency and directions are lower-bounded by the weighted summation of the spreads of individual source-relay-destination channels.
Vehicular Technology Conference Fall (VTC 2010-Fall), 2010 IEEE 72nd; 10/2010
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ABSTRACT: In this contribution, we investigate the applicability of using multiple propagation paths to estimate the temporal auto-correlation function and the coherence time of wireless propagation channels. The Space-Alternating Generalized Expectation-maximization (SAGE) algorithm is applied for extracting the paths from measurement data. It is found that the channel auto-correlation function and coherence time computed based on the path parameters are biased. A simple method is proposed for correction of the biases. Experimental investigations are conducted to evaluate the effectiveness of the method.
Communications and Networking in China (CHINACOM), 2010 5th International ICST Conference on; 09/2010
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Proceedings of the 72nd IEEE Vehicular Technology Conference, VTC Fall 2010, 6-9 September 2010, Ottawa, Canada; 01/2010
