Distributed Downlink Beamforming in Cellular Networks

We consider a cellular network where base stations can cooperate to determine the signals to be transmitted on the downlink. Using a particular downlink beamformer structure, we recast our downlink beamforming problem as a virtual linear minimum mean square error (LMMSE) estimation problem. Based on this virtual set up, we remodel the network as a factor graph with loops and present a simple distributed cooperative scheme for base stations based on the sum-product algorithm. We study the condition for convergence for the distributed algorithm and demonstrate its performance via simulations.