Autonomous uplink intercell interference coordination in OFDMA-based wireless systems

The inter-cell interference (ICI) problem in OFDMA-based wireless systems becomes a major impediment to attaining high rates particularly for cell-edge users in reuse-1 systems. Interference mitigation techniques attempt to combat ICI by using proper resource allocation schemes. Using centralized algorithms is not practical, particularly in HetNet environments, as these algorithms require intensive signaling, interference, and channel state information that may not always be practically available. In this paper, we present a framework for autonomous uplink ICIC in OFDMA-based wireless systems. The framework is based on imposing an overall interference limit for each cell. We use the proportional fair algorithm for resource block assignment and the power allocation problem is formulated as a maximization of the sum of the signal to leakage and noise ratio (SLNR) subject to the cell interference on other cells below a certain threshold. We propose a suboptimal closed form method, and an iterative allocation using Newton's method. These schemes do not need coordination between the cells where the resource allocation can completely be performed autonomously. Simulations show that relaxing the interference constraints improves the performance of the two proposed algorithms which exhibit better performance than the trivial equal power allocation. Comparison with a centralized scheme that uses global information shows good performance with acceptable degradation in the spectral efficiency which decreases as the interference limit increases.