BLAST training : Estimating Channel Characteristics for High-Capacity Space-Time Wireless

Abstract

BLAST (Bell Labs Layered Space-Time) is a multiple-antenna communication scheme whose outage capacity in a Rayleigh flat fading environment grows linearly with the minimum of the number of transmit and receive antennas, with no increase in bandwidth or transmitted power. Based on its knowledge of the matrix of propagation coefficients, the receiver performs two critical operations: nulling and cancellation, that in effect create independent virtual subchannels. Assume that the receiver estimates the propagation matrix from a known set of transmitted training signals, and then uses the estimate as though it were correct for nulling and cancellation. How much training is needed for satisfactory operation? The optimal training signals are orthogonal with respect to time among the transmit antennas, and each transmit antenna is fed equal energy. Errors in estimating the propagation matrix manifest themselves as crosstalk among the virtual subchannels. If its magnitude is too large, the cro...

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