Alfred O. Hero

Alfred O. Hero, III

EECS Department

University of Michigan

Thursday, April 20
4:00 - 5:00 P.M.
Room 1311 EECS

Cut-off Rate and Signal Design for the Rayleigh Fading Space-Time Channel


We consider the computational cut-off rate and its implications on signal design for the complex Rayleigh flat fading spatio-temporal (multiple-antenna) communications channel under a peak power constraint. Different characterizations of the optimal rate-achieving signal constellation are obtained. For arbitrary finite dimension, the optimal constellation must admit an equalizer distribution, i.e., a positive set of signal probabilities which equalizes the conditional decoding error probabilities. When the number of signal matrices in the constellation is less than the ratio of the number of time samples to the number of transmit antennas, the optimal cut-off rate attaining constellation is a set of equiprobable mutually-orthogonal unitary matrices. When the SNR is below a specified threshold the matrices in the constellation are rank one and the cutoff rate is achieved by applying all transmit power to a single antenna and using orthogonal signaling. Implications on the achievable rate region for space-time coding in diffuse vs. specular multi-path channels will be discussed.

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