Block diagonalization with interference control for energy efficient downlink

Block diagonalization is a linear precoding technique which eliminates the multi-user interference at the transmitter side by creating parallel orthogonal single user links. In this technique, the transmit diversity order is fixed for each user and only power can be controlled to satisfy SINR requirements. This restricts the degrees of freedom available for resource allocation and limits the energy efficiency of the power allocation schemes performed by the base-station. In this contribution we present a new extension to block diagonalization where spatial degrees of freedom can also be adjusted in addition to power and bandwidth. With this new technique, it is possible to serve multiple users with different rate requirements by tolerating a controllable amount of interference. The amount of interference is controlled through an algebraic parameter that can be tuned in order to allow energy efficient power allocation.