Autonomous Algorithms for Centralized and Distributed Interference Coordination: A Virtual Layer Based Approach

Interference mitigation techniques are essential for improving the performance of interference limited wireless networks. In this paper, we introduce novel interference mitigation schemes for wireless cellular networks with space division multiple access (SDMA). The schemes are based on a virtual layer that captures and simplifies the complicated interference situation in the network and that is used for power control. We show how optimization in this virtual layer generates gradually adapting power control settings that lead to autonomous interference minimization. Thereby, the granularity of control ranges from controlling frequency sub-band power via controlling the power on a per-beam basis, to a granularity of only enforcing average power constraints per beam. In conjunction with suitable short-term scheduling, our algorithms gradually steer the network towards a higher utility. We use extensive system-level simulations to compare three distributed algorithms and evaluate their applicability for different user mobility assumptions. In particular, it turns out that larger gains can be achieved by imposing average power constraints and allowing opportunistic scheduling instantaneously, rather than controlling the power in a strict way. Furthermore, we introduce a centralized algorithm, which directly solves the underlying optimization and shows fast convergence, as a performance benchmark for the distributed solutions. Moreover, we investigate the deviation from global optimality by comparing to a branch-and-bound-based solution.Comment: revised versio

Downlink beamforming and resource allocation in multicell MISO-OFDMA systems

International audienceWe study the downlink beamforming (DLBF) and resource optimisation problem in multicell multi-input single-output orthogonal frequency division multiple access (MISO-OFDMA) systems. This is a mixed combinatorial, nonlinear and nonconvex optimisation problem. By using uplink downlink duality, we propose an efficient suboptimal algorithm. This algorithm provides beamformers and allocates subcarriers and power to different users in the network with minimum message passing between the transmitting base stations. DLBF and resource optimisation algorithm for single-cell MISO-OFDMA systems can be obtained as a special case of the multicell algorithm. Simulation results reveal the performance gains provided by the proposed algorithm