Decentralized Precoding for Multicell MIMO Downlink


Winston W. L. Hoy, Tony Q. S. Quek, Sumei Sun, and Robert W. Heath, Jr.


Submitted to IEEE Transactions on Wireless Communications, March 2010.


Interference is becoming a performance limiting factor in dense cellular networks with aggressive frequency reuse. Cooperation among base stations is a promising approach for improving data rates by eliminating or mitigating interference. For the downlink, the highest spectral efficiency gains are achieved through precoding with full coordination, which requires complete channel state information (CSI) and data be shared among base stations (BSs). In this paper, we propose distributed precoding techniques for MIMO cellular networks. Unlike prior work, the main feature of our precoders is that each base station designs its own precoder without requiring data or downlink CSI of links from other BSs. Furthermore, our precoders tackle both inside-cell and outside-cell interference in a decentralized manner. Since CSI is unlikely to be perfect, we study the effect of imperfect CSI on our proposed precoders and propose a robust precoder in the presence of CSI uncertainty. Simulations show that our proposed methods enjoy a rate increase with SNR similar to multicell joint dirty paper coding in the high SNR regime due to effective interference mitigation. Numerical results reflect the sensitivity of each proposed precoder with respect to the the imperfectness in the available CSI.