Distributed Beamforming for the Multicell Sparsely-Spread MC-CDMA Downlink

We propose a beamforming technique for the multicell downlink of a multicarrier code division multiple access (MC-CDMA) system with sparse signatures. We propose a distributed beamforming algorithm using the sum-product algorithm. The distributed beamforming algorithm converges very quickly to the centralized beamforming solution, minimizing the delay associated with computation of the transmit vector. The complexity of distributed beamforming depends on the number of base stations (BSs) that are in range of each user, not on the size of the entire network.