A simple joint beamforming and power control algorithm for multi-user MIMO wireless networks

We consider the joint optimization of transmitted power, receive and transmit beamforming vectors for multi-user MIMO wireless networks. Specifically, they are optimized such that the total transmit power is minimized while satisfying SINR requirements of all links. We first analytically show that maximum ratio transmission (MRT) beamforming is asymptotically optimal for the low SINR region and the corresponding optimal transmit power vector is element-wise minimal. We then propose a simple joint optimization algorithm tailored for cellular downlinks by exploiting network duality, which is applicable over a wide range of SINR. The proposed algorithm can be readily implemented in a distributed fashion since it requires only local adaptive beamforming at the receivers, a simple power control loop, and minimal feedback of the channel state information. Also, the algorithm achieves a performance close to that of centralized iterative optimization algorithms, and outperforms other decentralized approaches that have been previously proposed.