Receiver cooperation is an effective technique to improve the performance of multi-antenna Gaussian broadcast channels. In practical systems, the transmitter usually has partial channel state information (CSI) via the finite-rate feedback channel. How could receiver cooperation benefit the system performance in this case? In this letter, we propose a low complexity and effective cooperation scheme based on the principle of decode-and-forward (DF) relaying and successive interference cancelation (SIC) to mitigate the residual multiuser interference.
Compared to non-cooperative systems, the proposed scheme brings a twofold benefit: improved chosen space of beamforming vectors and reduced multiuser interference terms. As a result, both degrees-of-freedom gain and power gain can be observed. The degrees-of-freedom gain leads to unbounded throughput with finite feedback rate. The power gain is significant such that the proposed scheme with partial CSI even outperforms the non-cooperative system with perfect CSI in low and moderate signal-to-noise ratio (SNR) region.