The paper Computational Framework for Optimal Robust Beamforming in Coordinated Multicell Systems presented at the Fourth International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP 2011) sponsored by IEEE received the Best Paper Award.

This research is a result of collaboration between researchers Emil Björnson and Mats Bengtsson at the Royal Institute of Technology, Stockholm and SnT researcher Gan Zheng and Björn Ottersten.
The paper deals with a new computational framework that optimizes multiuser multi-cell system performance. Multiuser systems are limited by interference, requiring considerations between optimizing total performance and guaranteeing individual users’ quality of service at the same time.
Most resource allocation problems in wireless systems are non-convex, meaning that the optimal solution cannot be obtained in polynomial time. Thus, only heuristic suboptimal strategies can be applied in practice. It is very important to compute the optimal solution and to use it as a benchmark for suboptimal algorithms.
The paper proposes a new branch-reduce -and-bound algorithm that systematically solves such non-convex problems to global optimality. The main contribution lies in the fact that the algorithm substantially reduces the complexity and shows a better convergence behavior than previous algorithms.
The proposed algorithm was applied for performance benchmarking in realistic multi-cell systems with 20 users in Stockholm, Sweden.