Beamforming with relays in heterogeneous networks based on correlation knowledge

Considering a network with a frequency reuse one where intercell interference is a limiting factor, an unfair distribution of the signal-to-interference-plus-noise ratio (SINR) for different users results. A method to improve the SINR is fair multicell max-min beamforming (MBF). In addition to intercell interference, shadow fading is another performance limiting factor. Strongly shadowed users can decrease the performance of all jointly scheduled users if fairness is desired. To overcome this shadow fading effect, this paper investigates one-way half-duplex decode-and-forward relays in combination with MBF. The user is served only by the relay in the second hop and in the first hop only BS transmits the signal to the relay. In large networks, obtaining instantaneous channel state information (CSI) is difficult, therefore, the algorithm proposed in this paper is based on long-term CSI in the form of correlation knowledge. In addition to sum rate performance energy efficiency becomes a much more important issue. This paper proposes an algorithm which can achieve a higher performance as networks without relays with 20% reduced transmit power.