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Unitary isotropically distributed inputs are not capacity-achieving for large-MIMO fading channels

Wei Yang (Institutionen för signaler och system, Kommunikationssystem) ; Giuseppe Durisi (Institutionen för signaler och system, Kommunikationssystem) ; Erwin Riegler
2012 IEEE International Symposium on Information Theory, ISIT 2012. Cambridge, MA,1 - 6 July 2012 p. 1717-1721. (2012)
[Konferensbidrag, refereegranskat]

We analyze the capacity of Rayleigh block-fading multiple-input multiple-output (MIMO) channels in the noncoherent setting and prove that unitary space-time modulation (USTM) is not capacity-achieving when the total number of antennas exceeds the coherence time of the fading channel. This situation is relevant for MIMO systems with large antenna arrays (large-MIMO systems). Our result settles a conjecture by Zheng & Tse (2002) in the affirmative. The capacity-achieving input signal, which we refer to as Beta-variate space-time modulation (BSTM), turns out to be the product of a unitary isotropically distributed random matrix, and a diagonal matrix whose nonzero entries are distributed as the eigenvalues of a Beta-distributed random matrix of appropriate size. Numerical results illustrate that using BSTM instead of USTM in large-MIMO systems yields a rate gain as large as 13% for SNR values of practical interest.


Finalist for student best paper award



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Denna post skapades 2012-06-06. Senast ändrad 2016-10-28.
CPL Pubid: 158592

 

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