Fractional Reuse Partitioning for MIMO Networks

Inter-cell interference diminishes the performance of wireless cellular networks, hence interference management by cooperation of basestations should be employed to combat interference and increase spectral efficiency. Contrary to full cooperation, which renders the network into a super-cell with distributed antennas, we investigate a form of weak cooperation: transmission strategies among the basestations are coordinated, which requires a minor overhead, while the users treat interference of other cells as noise. Although our results are not restricted to reuse partitioning, we assume a set of strategies, each corresponding to a different reuse factor, and assign orthogonal resources to each strategy. Basestation cooperation is realized by dynamically adjusting the resource allocation, so-called fractional reuse partitioning, while the capacity achieving single-cell strategies are employed in each cell in order to optimally manage intra-cell interference exploiting all degrees of freedom offered by multiple antennas at the transmitter and receiver. Efficient operation of a cellular communications network requires interference management in order to achieve high data rates including rate assignment matched to the user demands, which we formulate as network utility maximization problem. We put special emphasis on the popular utilities sum-rate and proportional fairness, either with or without additional quality of service constraints. Finally, we illustrate the performance gain of our method by providing system level simulation results for a three sectorized cellular network with nineteen sites.