PCI Planning with Reassignment Budget in Ultra-Dense Networks

The physical cell identity (PCI) is a critical parameter in wireless networks, enabling user equipment (UE) to uniquely identify cells and mitigate inter-cell interference during communication. However, the proliferation of base stations in modern networks has complicated the proper assignment of PCIs, as it requires avoiding multiple types of PCI conflicts, such as PCI collision, mod-3 collision, and confusion. Existing methods generally focus on addressing single PCI conflicts and involve reassigning PCIs for all cells, which can lead to significant data exchange overhead in large-scale networks. To address these challenges, this paper tackles the PCI planning problem by introducing a PCI reassignment budget as a constraint to minimize overall network interference. A penalty-based double-loop PCI planning algorithm is proposed, where the outer loop optimizes penalty parameters derived from the constraints, and the inner loop combines a block coordinate descent (BCD) approach with a proposed concave-convex procedure to optimize PCI assignments. Simulation results demonstrate the effectiveness of the proposed method in significantly reducing network interference compared to existing approaches.