Performance of transmit beamforming for interference mitigation with random codebooks

In this paper, we study the interference mitigation capability of Transmit Beamforming (TBF) when used to combat cross-layer interference in a two-tier Heterogeneous Network (Het-Net) scenario. Since generic practical codebook designs are not known when TBF is applied for interference mitigation purposes, a randomly generated codebook is used as a simple way to provide a lower bound performance for any efficient (deterministic) codebook design. Closed-form expressions for the rate performance are derived when altruistic TBF is applied to mitigate interference with different number of transmit antennas and feedback bit resolutions. Our analysis reveals that the use of additional feedback bits has potential to provide more performance gain at lower outage probability regimes (when compared to higher outage probability ones). In addition, for random codebooks with a fixed number of feedback bits, the number of transmit antennas does not have a notable effect on the interference mitigation capability of an altruistic TBF scheme.