Distributed downlink beamforming with cooperative base stations

Boon Loong Ng*, Jamie S. Evans, Stephen V. Hanly, Defne Aktas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

167 Citations (Scopus)


In this paper, we consider multicell processing on the downlink of a cellular network to accomplish "macrodiversity" transmit beamforming. The particular downlink beamformer structure we consider allows a recasting of the downlink beamforming problem as a virtual linear mean square error (LMMSE) estimation problem. We exploit the structure of the channel and develop distributed beamforming algorithms using local message passing between neighboring base stations. For 1-D networks, we use the Kalman smoothing framework to obtain a forward-backward beamforming algorithm. We also propose a limited extent version of this algorithm that shows that the delay need not grow with the size of the network in practice. For 2-D cellular networks, we remodel the network as a factor graph and present a distributed beamforming algorithm based on the sum-product algorithm. Despite the presence of loops in the factor graph, the algorithm produces optimal results if convergence occurs.

Original languageEnglish
Pages (from-to)5491-5499
Number of pages9
JournalIEEE Transactions on Information Theory
Issue number12
Publication statusPublished - 2008
Externally publishedYes


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