Multi-antenna downlink transmission with individual SINR receiver constraints for cellular wireless systems

We study the downlink of an interference-limited multi-user system employing M transmit antennas at the base station and K independent single-antenna receivers. The second-order channel statistics are assumed to be known at the transmitter. Recent results show that the transmission of parallel data streams is rendered inefficient by noise and co-channel interference. For such a scenario, beamforming performs close to the optimal strategy. Assuming strict transmission delay constraints, a fair sharing of resources is required. In addition the total transmission power must not exceeded a certain threshold. This leads to the problem of minimizing the transmission power while satisfying certain SINR requirements for each user. In this paper we propose a new optimization scheme for the given problem. The algorithm is computationally efficient and always converges to the global optimum. Infeasible scenarios can be detected in an early stage. This makes the algorithm well suited for application together with resource management.