PCI Planning Based on Binary Quadratic Programming in LTE/LTE-A Networks

Abstract

In recent years, interference has played an increasingly significant part in bulkier and denser Long Term Evolution (LTE/LTE-Advanced) networks. Though intra-cell interference is successfully improved by Orthogonal Frequency Division Multiple Access (OFDMA), inter-cell interference (ICI) could cause a degradation of throughput and significantly impact Signal-to-Noise-Ratio (SINR) in the downlink (DL) network. Physical Cell ID (PCI) planning, an effective approach to eliminate ICI, is required to reduce collision, confusion and mod q interference, where q = 3 for Single-Input Single-Output (SISO) system, and q = 6 for Multiple-Input Multiple-Output (MIMO) system. In this study, a new definition of neighborhood relations was proposed based on the measurement report (MR) data in the actual network. Binary quadratic programming (BQP) model was built for PCI planning through a series of model deductions and mathematical proofs. Since BQP is known as NP-hard, a heuristic Greedy algorithm was proposed and its low complexity both in time and space can ensure large-scale computing. Finally, based on the raw data extracted from the actual SISO system network and the simulation calculation of MATLAB, the experimental results demonstrated that Greedy algorithm not only eliminates conflict and confusion completely, but also reduces the mod 3 interference of 26.213% more than the baseline scheme and far more than the improvement ratio of 4.436% given by the classical graph coloring algorithm.

Cluster-Based Hybrid Approach for PCI Configuration and Optimization in 5G EN-DC Heterogeneous Networks

“…(1) PCI Self-Configuration (2) OAM sends PCI list to all connected eNBs (3) Central eNB assign PCI to itself according to PCI list (8) PCI Optimization: eNBs and gNBs check PCI collisions and confusions according to their cell type (9) 4) Central eNB assign PCIs to gNBs within its cluster according to eNBList (5) Base stations exchange information with neighbor cells through X2/Xn interface and consultation mechanism, then update neighbor relations accordingly (6) Update eNB_NRList, gNB_NRList, eNBList, gNBList then store the information in the central eNB (7) Central eNB exchange information with its neighbor eNBs through X2 interface…”

“…These developments in network densification and heterogeneous systems have emphasized the importance of autoconfiguration and optimization of radio parameters, such as Physical Cell Identity (PCI) [3][4][5]. PCI serves as a critical cell identifier in LTE networks, and improper assignment can lead to challenges such as PCI collisions, confusions, and 𝑚𝑜𝑑 𝑞 interference [4,[6][7][8]. The limited number of available PCIs (504 in LTE, 1008 in 5G NR) further complicates the management in ultra-dense network environments, with the deployment of small cells alongside traditional macro cells adding to the complexity [2,9].…”