A power adjustment based eICIC algorithm for hyper-dense HetNets considering the alteration of user association

This paper evaluates power adjustment based enhanced inter-cell interference coordination （eICIC） problem in the hyper-dense HetNet under the practical serving cell selection rule where each user selects the base station with the strongest received signal power as its serving cell while the alteration of the serving cell happens during the power adjusting process. In this paper, the eICIC problem is solved by cooperatively adjusting the transmission power of all small cells. A power adjustment method based on modified particle swarm optimization （MPSO） is proposed to tackle the NP-hard eICIC problem caused by the alteration of the serving cell, and considering the drawbacks of MPSO, an improved MPSO is proposed for effective algorithm. Local search and multi-restart process are introduced in the improved MPSO based eICIC algorithm to guarantee the local and then global optimality, and the convergence conditions and the global optimality are proved by mathematical deduction to guide the selection of the parameters. Simulations show that, while considering the fifty-picocell case as an example, the proposed improved MPSO based eICIC algorithm can increase the system throughput by 66.0% compared with the full power transmission, and compared with the existing schemes which do not alter the serving cells, the proposed algorithm can improve the system throughput by 32.2%. By improving MPSO, the consequent algorithm costs less iteration time to achieve higher system throughput, and it is effective and feasible to solve the eICIC problem in the hyper-dense HetNet.