This paper considers a multicell downlink channel in which multiple basestations (BSs) cooperatively serve users by jointly precoding shared datatransported from a central processor over limited-capacity backhaul links. Wejointly design the beamformers and BS-user link selection so as to maximize thesum rate subject to user-specific signal-to-interference-noise (SINR)requirements, per-BS backhaul capacity and per-BS power constraints. Asexisting solutions for the considered problem are suboptimal and theiroptimality remains unknown due to the lack of globally optimal solutions, wecharacterized this gap by proposing a globally optimal algorithm for theproblem of interest. Specifically, the proposed method is customized from ageneric framework of a branch and bound algorithm applied to discrete monotonicoptimization. We show that the proposed algorithm converges after a finitenumber of iterations, and can serve as a benchmark for existing suboptimalsolutions and those that will be developed for similar contexts in the future.In this regard, we numerically compare the proposed optimal solution to acurrent state-of-the-art, which show that this suboptimal method only attains70% to 90% of the optimal performance.
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