A low-complexity joint power control and beamforming algorithm for the downlink of multi-user W-CDMA coordinated systems

The downlink of a system with phase coherent coordination between several base stations is considered throughout this paper. Within the framework of the power minimization problem, two Joint Power Control and Optimal Beamforming (JPCOB) algorithms have already been proposed in previous works. However, one of the major challenges associated with network coordination is the design of algorithms which result in low-complexity requirements as the number of users increases. In this paper, one of the previous JPCOB algorithms is modified in order to obtain a low-complexity solution by reducing the amount of feedback required from single antenna users in the system. The performance of this algorithm is then compared with the previous JPCOB solutions. Simulation results in a W-CDMA scenario show that the low-complexity algorithm equals the performance of the previous solutions for a given number of coordinated base stations. However, it suffers a severe penalty for scenarios with high SINR requirements at the users. In order to overcome this drawback, two iterative schemes based on the particular structure of the matrices involved in the power control updating step are proposed. Moreover, these schemes could be seen as efficient and computationally simple scheduling techniques.