9:30, SPCOM-P4.1
MUTUAL COUPLING EFFECTS ON THE CAPACITY OF MULTIELEMENT ANTENNA SYSTEMS
T. SVANTESSON, A. RANHEIM
A study of the capacity of multiple element antenna systems is presented, with particular emphasis on the effect that mutual coupling between the antenna elements has on the capacity. The results presented here shows, contrary to some earlier claims, that correlation between different channel coefficients as a function of antenna spacing, can in fact decrease when the mutual coupling effect is accounted for. As a consequence, capacity also improves. A realistic channel model is used to perform simulations to support these claims.

9:30, SPCOM-P4.2
MODELING AND CAPACITY OF REALISTIC SPATIAL MIMO CHANNELS
A. SAYEED
Accurate and tractable channel modeling is critical to realizing the full potential of antenna arrays in wireless communications. In this paper we propose a framework for modeling multi-antenna multipath channels based on the notion of virtual spatial angles. The virtual angles are fixed a priori and are determined by the number of antennas at the transmitter and receiver and the spacing between the antennas. The model essentially corresponds to a coordinate transformation via fixed spatial basis functions at the transmitter and receiver. The resulting linear virtual channel representation encompasses all existing models and provides a natural link between the physical propagation environment and the channel statistics induced by it. For any given scattering environment, the model facilitates realistic estimates of channel capacity and clearly reveals the two key parameters affecting capacity: the number of parallel channels and the level of diversity.

9:30, SPCOM-P4.3
A WIRELESS MIMO CHANNEL PROBING APPROACH FOR ARBITRARY ANTENNA ARRAYS
B. JEFFS, E. PYPER, B. HUNTER
This paper introduces a method for experimentally probing indoor wireless channels to compute MIMO transfer function matrices, H. The data is gathered using rotating transmit and receive antennas to observe the multipath ray structure of the channel. H can be computed for any arbitrary transmit and receive array sizes and geometries using the single probe data set. Esitmating $\bf H$ is crucial for space time coding communications algorithm performance analysis. Example results are presented.

9:30, SPCOM-P4.4
SPATIAL CHARACTERIZATION OF THE MIMO WIRELESS CHANNEL: EXPERIMENTAL DATA ACQUISITION AND ANALYSIS
M. JENSEN, J. WALLACE
Detailed performance assessment of space-time coding algorithms in realistic channels is critically dependent upon accurate knowledge of the wireless channel spatial characteristics. This paper presents an experimental measurement platform capable of providing the channel transfer matrix for indoor and outdoor wireless communications scenarios. The system allows direct measurement of key multiple input multiple output parameters for 16 transmit and 16 receive antennas. The basic hardware blocks are outlined, and the data post-processing algorithms are presented. Representative data showing channel capacity and spatial correlation for several indoor sites are provided.

9:30, SPCOM-P4.5
WIRELESS INDOOR CHANNEL MODELING: STATISTICAL AGREEMENT OF RAY TRACING SIMULATIONS AND CHANNEL SOUNDING MEASUREMENTS
G. GERMAN, Q. SPENCER, A. SWINDLEHURST, R. VALENZUELA
A statistical space-time model for indoor wireless propagation based on empirical measurements is compared with results from the deterministic ray-tracing simulation tool WiSE for the same environment. Excellent agreement is found in terms of the distributions of arrival times and angular spread for both modeling approaches. The WiSE package is also use to synthesize MIMO channel matrices and determine the theoretical capacity available in the tested environments. It is found that, for narrowband channels, the spatial clustering of the multipaths limits the capacity gains associated with increased array size.

9:30, SPCOM-P4.6
SPACE-TIME CORRELATION MODELING OF MULTIELEMENT ANTENNA SYSTEMS IN MOBILE FADING CHANNELS
A. ABDI, M. KAVEH
For the analysis and design of multielement antenna systems in mobile fading channels, we need a model for the space-time cross correlation among the links of the multiple-input multiple-output (MIMO) channel. In this paper we propose a general space-time cross correlation function for narrowband Rayleigh fading MIMO channels, where various parameters of interest such as angle spreads at the base station and the user, the distance between the base station and the user, mean directions of the signal arrivals, array configurations, and Doppler spread are all taken into account. The new space-time cross correlation function includes all the relevant parameters of the MIMO narrowband Rayleigh fading channel in a clean compact form, suitable for both simulation and mathematical analysis. It also covers many known correlation models as special cases. We demonstrate the utility of the new space-time correlation model by clarifying the limitations of a widely-accepted correlation model for MIMO fading channels.

9:30, SPCOM-P4.7
ASYMPTOTIC CAPACITY OF SPACE-TIME CODING FOR ARBITRARY FADING: A CLOSED FORM EXPRESSION USING GIRKO'S LAW
U. SAKOGLU, A. SCAGLIONE
Several works addressed the problem of deriving the asymptotic capacity of a wireless system with space diversity in random fading. However, the theory of random matrices was never used in evaluating the asymptotic optimal performance in closed form. By increasing the number of transmit and receive antennas the resulting capacity tend to be a stable value independent of the fading realization. This surprising result is a consequence of Girko's law, stating that the asymptotic distribution of the eigenvalues of a random matrix, with independent identically distributed zero mean complex entries, is a circle. The conditions on the probability density function of the matrix entries are satisfied by the majority of random non-line of sight fading models. Using this theory in this paper we derive the close form expression for the asymptotic capacity of a system with transmit and receive diversity, assuming independent flat fading for each transmit-receive antenna link, with equal distribution. Our formula fits the numerical results even if the number of transmit an receive antennas as small as ten.

9:30, SPCOM-P4.8
WIDE BAND CHANNEL CHARACTERISATION IN COLOURED NOISE USING THE REVERSIBLE JUMP MCMC
J. LAROCQUE, J. REILLY
This paper presents a novel approach for characterizing wideband (CDMA) multiple dimensional channels for the wireless environment in arbitrarily coloured additive Gaussian noise. This characterization is sufficient for the specification of optimal multichannel space-time receivers. The proposed solution is defined in the Bayesian framework and uses the Reversible Jump Markov Chain Monte Carlo (MCMC) method to obtain estimates of the number of scatterers,their directions of arrival and their times of arrival. The developed method is applied to simulated and real measured data to verify the performance of the approach.