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Structured unitary space-time autocoding constellations

Marzetta, Thomas L. and Hassibi, Babak and Hochwald, Bertrand M. (2002) Structured unitary space-time autocoding constellations. IEEE Transactions on Information Theory, 48 (4). pp. 942-950. ISSN 0018-9448.

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We previously showed that arbitrarily reliable communication is possible within a single coherence interval in Rayleigh flat fading as the symbol duration of the coherence interval and the number of transmit antennas grow simultaneously. This effect, where the space-time signals act as their own channel codes, is called autocoding. For relatively short (e.g., 16-symbol) coherence intervals, a codebook of independent isotropically random unitary space-time signals theoretically supports transmission rates that are a significant fraction of autocapacity with an extremely low probability of error. The exploitation of space-time autocoding requires the creation and decoding of extraordinarily large constellations-typically L = 2^80. We make progress on the first part of the problem through a random, but highly structured, constellation that is completely specified by log2 L independent isotropically distributed unitary matrices. The distinguishing property of this construction is that any two signals in the constellation are pairwise statistically independent and isotropically distributed. Thus, the pairwise probability of error, and hence the union bound on the block probability of error, of the structured constellation is identical to that of a fully random constellation of independent signals. We establish the limitations of an earlier construction through a subsidiary result that is interesting in its own right: the square (or for that matter, any integer power greater than one) of an isotropically random unitary matrix is not isotropically random, with the sole exception of the one-by-one unitary matrix.

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Additional Information:© Copyright 2002 IEEE. Reprinted with permission. Manuscript received June 13, 2000; revised June 16, 2001. Communicated by M.L. Honig, Associate Editor for Communications.
Subject Keywords:Eigenvalues of random matrices, multiple antennas, Rayleigh flat fading, space–time autocoding, unitary space–time modulation, wireless communication
Issue or Number:4
Record Number:CaltechAUTHORS:MARieeetit02
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9023
Deposited By: Archive Administrator
Deposited On:22 Oct 2007
Last Modified:02 Oct 2019 23:56

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