# ABSTRACT

**
Scaling
Laws of Multiple Antenna (Group)
Broadcast Channels**

Broadcast (or point to multipoint)
communication has attracted a lot of
research recently. In this talk we
consider the scaling laws for two
broadcast scenarios.

In the
first part of the 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.
We quantify this hit for DPC and various
beamforming techniques.

In the
second part of the talk, we consider the
multiple antenna group broadcast channel
where a base station is to transmit to a
group of users and where the users' pool
is divided into K groups, each group of
which is interested in common
information. Such a situation occurs for
example in digital audio and video
broadcast where the users are divided
into various groups according to the
shows they are interested in. We study
the scaling laws of the sum-rate in the
large number of users and/or large
number of antennas regimes.
Intuitively, the group broadcast
capacity should decrease with the number
of users. We show that in order to
achieve a constant rate per user, the
number of transmit antennas should scale
at least logarithmically with the number
of users.

This is a
joint work with Masoud Sharif (Boston
University), Amir Dana (Qualcomm
Corporation), and Babak Hassibi
(California Institute of Technology)