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C. Mecklenbräuker, A. Paier, T. Zemen, G. Matz, A. Molisch:
"On Temporal Evolution of Signal Subspaces in Vehicular MIMO Channels in the 5 GHz Band";
Talk: Joint Workshop on Coding and Communications (JWCC), St. Helena (CA), USA (invited); 2008-10-26 - 2008-10-28; in: "Joint Workshop on Coding and Communications (JWCC 2008)", (2008).

We study the temporal evolution of the singular value decomposition of vehicular 4x4 MIMO channel measurements H(t) in the 5.2 GHz band for a selected single OFDM subcarrier. First, we estimate the number of relevant singular values 0 <= p(t) <= 4 for each sampling time t by applying the minimum descriptive length (MDL) criterion. The MDL criterion is used here as an estimator for the time-variant dimension p(t) of the dominant "signal" subspace. Then we characterize the dynamics of the estimated dominant singular subspaces by the principal angles between the corresponding subspaces at times t and t + ∆ where ∆ is the channel sounder´s MIMO channel acquisition period which defines the resolution in the Doppler domain. These principal angles are closely related to covariances and measures of dependency. When principal angles are evaluated for pairs of column spaces of matrices, the principal angles describe
canonical correlations of a matrix pair. Ultimately, we wish to describe the evolution of the dominant singular vectors as trajectories in the (complex) Stiefel manifold and the corresponding evolution of the dominanant subspaces as trajectories in the (complex) Grassmann manifold.

vehicular communications, time-variant, Stiefel manifold, Grassmann manifold, principle angle

http://publik.tuwien.ac.at/files/PubDat_166707.pdf

Project Head Gerald Matz:
Multiple Access Space-Time Coding Testbed