How Many Transmit Antennas to Use in a MIMO Interference Channel

TL;DR

This paper investigates the optimal number of transmit antennas in a multi-user MIMO interference channel, demonstrating that transmitting a single data stream per user maximizes outage capacity without channel state information.

Contribution

It shows that transmitting a single data stream per user is optimal for outage capacity and sum capacity in multi-user MIMO channels without channel state information at transmitters.

Findings

Single data stream per user maximizes outage capacity.

Single data stream also maximizes sum outage capacity.

Optimality holds with sufficient number of users.

Abstract

The problem of finding the optimal number of data streams to transmit in a multi-user MIMO scenario, where both the transmitters and receivers are equipped with multiple antennas is considered. Without channel state information at any transmitter, with a zero-forcing receiver each user is shown to transmit a single data stream to maximize its own outage capacity in the presence of sufficient number of users. Transmitting a single data stream is also shown to be optimal in terms of maximizing the sum of the outage capacities in the presence of sufficient number of users.