# ABSTRACT

# How Much Does Transmit
Correlation Affect the Sum-Rate of MIMO
Broadcast Channels?

In this talk, we consider
the effect of spatial correlation between
transmit antennas on the sum-rate capacity
of the MIMO broadcast channel (i.e., downlink
of a cellular system). Specifically, for
a system with a large number of users n,
we analyze the scaling laws of the sum-rate
for the dirty paper coding (DPC) and for
different types of beamforming transmission
schemes. When the channel is i.i.d., it
has been shown that for large number of
users n, the sum rate is equal to M*loglog(n)
+ M*log SNR where M is the number of transmit
antennas.

When the channel exhibits
some spatial correlation with a covariance
matrix R, we show that this results in an
SNR hit that depends on 1) the multiuser
broadcast technique and 2) on the eigenvalues
of the correlation matrix R. In this talk,
we quantify the hit resulting from spatial
correlation to the sum-rate of DPC, beam-forming
with channel whitening, random beam-forming,
and deterministic beam-forming.

This is a joint work with
Masoud Sharif (Boston University) and Babak
Hassibi (California Institute of Technology)