On the Optimality of Linear Multiuser MIMO Beamforming for a
Two-User Two-Input Multiple-Output Broadcast System
and Robert W. Heath, Jr.
In this letter, the asymptotic optimality of
a jointly optimized linear multiuser beamforming system with two transmit and
many receive antennas for the fading multiple-input multiple-output (MIMO)
Gaussian broadcast channel is investigated. We derive the asymptotic sum
capacity of the independent and identically-distributed (i.i.d.) MIMO broadcast
channel and the asymptotic sum rate of a linear multiuser beamforming system
with respect to the number of receive antennas per user, where two users are
served with a zero-interference constraint. Based on this result, we show that
linear multiuser beamforming with many receive antennas can asymptotically
achieve the sum capacity of the two-user i.i.d. MIMO broadcast channel even
without opportunistic scheduling gain. Numerical results confirm that as the
number of receive antennas increases the sum rate of linear multiuser
beamforming system converges to the sum capacity.
IEEE Signal Processing Letters, vol. 16, no. 2, pp. 117-120, Feb. 2009.
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