Abstract:
We explicitly construct an irreducible four-dimensional unitary
representation of the Lie group SU(2) and use it for the construction
of high-rate unitary space-time codes for four transmit antennas. The
tools we use are invariant integration on the group to unitarize the
representation, and dense spherical codes on the three-dimensional
sphere. Our construction calls for the design of such spherical codes
in which the angle between any two points is well separated from 120
degrees. We give a partial solution to this restricted design problem
and use numerical optimization techniques to optimize our solution.
Status:
Submitted to IEEE Trans. Info. Theory, October 2000.
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