A method and apparatus for increasing in the data rate of a multiple-input and/or
multiple-output system that has frequency selective fading by using training sequences
with both low normalized auto-correlation and low normalized cross-correlation.
Both 1) the sum of the square of the normalized auto-correlation of each training
sequence over an auto-correlation window and 2) the sum of the square of the normalized
cross-correlation of each pair of the training sequences over a cross-correlation
window, are significantly less than unity. In one embodiment of the invention the
training sequences are shifted versions of each other, and the low normalized cyclic-auto-correlation
of cyclic sequences is significantly less than unity, with each cyclic sequence
being N, N=N-;L+1, symbols of one of the at least two training
sequences. In another embodiment, the training sequences are ones where the trace
of the inverse of the product of the matrix of training sequences' symbols and
the conjugate transpose of this matrix is low. The matrix is a function of the
number of symbols over which multipaths of significant power can arrive, the number
of training sequences, and the number of symbols in a training sequence. More particularly
the matrix is a block-toeplitzmatrix composed of the training symbols.
