Congruence Decomposition with Neural Block Solvers for Large-Scale PCI Assignment
Authors: Yeqing Qiu, Chengpiao Huang, Ye Xue, Akang Wang, Fan Xu, Zhipeng Jiang, Dong Zhang, Ruoyu Sun, Qingjiang Shi, Zhi-Quan Luo
Organizations: School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, China, and Shenzhen Research Institute of Big Data, Shenzhen, China · Shenzhen Research Institute of Big Data, Shenzhen, China · Department of Industrial Engineering and Operations Research, Columbia University, New York, USA · School of Intelligent Systems Engineering, Sun Yat-sen University, Shenzhen, China · School of Data Science, The Chinese University of Hong Kong, Shenzhen, China · College of Electronic and Information Engineering, Tongji University, Shanghai, China · School of Mathematical Sciences, University of Chinese Academy of Sciences, Beijing, China · Huawei Technologies, Shenzhen, China
Physical Cell Identity (PCI) assignment is essential for interference management in dense 5G networks. As cellular networks scale, PCI reuse becomes unavoidable, which may cause collisions, confusions, and multiple forms of modular interference. Jointly mitigating these effects gives rise to a large-scale, multi-objective combinatorial optimization problem that is difficult to solve efficiently at practical network scales. In this work, we propose a congruence decomposition framework with neural block solvers for large-scale PCI assignment. The proposed decomposition exploits the arithmetic structure of PCI values to decouple multiple modular interference objectives into a collection of blockwise Min-k-Partition subproblems, followed by a graph coloring procedure to resolve PCI conflicts. For the resulting NP-hard Min-k-Partition subproblems, we develop neural block solvers by parameterizing their relaxed quadratic formulations with graph neural networks, enabling efficient optimization at large scales. Discrete assignments are recovered through conditional expectation rounding with theoretical guarantees. Experiments on synthetic cellular graphs and real-world 5G networks show that the proposed method consistently outperforms existing modular-interference-aware baselines in modular interference reduction, conflict elimination, and computational efficiency.
Figures & tables
Mod- p
Typical interference source
Reference
mod-3
Primary and Secondary Synchronization Signal reuse
[ 1 , 2 ]
mod-4
Physical Broadcast Channel Demodulation Reference Signal reuse
[ 1 , 3 ]
mod-6
Uplink and Downlink Demodulation Reference Signal pattern reuse
[ 1 , 11 ]
mod-30
Zadoff–Chu root group reuse in PUCCH, PUSCH, SRS, and PRACH
[ 1 , 31 ]
TABLE I : Common modular interference types in 5G PCI assignment.
Fig. 1 : This figure illustrates the modular interference, collisions, and confusions of PCI assignment in a 5G wireless network, where each sector denotes a cell and the number inside indicates its assigned PCI value.
Fig. 2 : (a) Hierarchical congruence decomposition of Zp into prime-power coefficient blocks. (b) The resulting multi-modular decomposition for PCI assignment simultaneously addressing mod- 3 , mod- 4 , mod- 6 , and mod- 30 interferences.
Fig. 3 : The Evaluation Results on RGG(N,r) with N∈{500,1000,2000} and r∈{0.05,0.1,0.2} of different scales.
RGG(N,r)
Density
Max Clique
Avg. Degree
Clustering Coef.
(500,0.05)
0.01
6.45
3.78
0.53
(500,0.1)
0.03
13.65
14.48
0.62
(500,0.2)
0.11
30.45
52.69
0.65
(1000,0.05)
0.01
9.70
7.54
0.60
(1000,0.1)
0.03
20.45
28.85
0.62
(1000,0.2)
0.11
53.05
105.29
0.65
TABLE II : Structural statistics of the random geometric graphs used in our experiments (averaged over 20 instances per setting).
Methods
Coll. & Conf.
Inter.
Time (s)
GGC [ 29 , 5 ]
0
122392610
3.20
Genetic [ 14 ]
226
111035257
3649.26
MA-NWS [ 3 ]
128
62123830
7520.81
RGP [ 23 ]
372
53833127
2423.40
MMD-PMD [ 22 ]
0
53505001
2969.44
MMD-GPO
0
51999927
1452.26
TABLE III : The evaluation results on the real-world data.
Combinatorial optimization finds the best feasible choices among discrete alternatives in routing, scheduling, graph problems, and resource allocation.
With the increasing computational demands of deep neural network (DNN) inference on resource-constrained devices, DNN partitioning-based device-edge collaborative inference has emerged as a promising paradigm. However, the transmission of intermediate feature data is vulnerable to malicious jamming, which significantly degrades the overall inference performance. To counter this threat, this letter focuses on an anti-jamming collaborative inference system in the presence of a malicious jammer. In this system, a DNN model is partitioned into two distinct segments, which are executed by wireless devices and edge servers, respectively. We first analyze the effects of jamming and DNN partitioning on inference accuracy via data regression. Based on this, our objective is to maximize the system's revenue of delay and accuracy (RDA) under inference accuracy and computing resource constraints by jointly optimizing computation resource allocation, devices' transmit power, and DNN partitioning. To address the mixed-integer nonlinear programming problem, we propose an efficient alternating optimization-based algorithm, which decomposes the problem into three subproblems that are solved via Karush-Kuhn-Tucker conditions, convex optimization methods, and a quantum genetic algorithm, respectively. Extensive simulations demonstrate that our proposed scheme outperforms baselines in terms of RDA.
Mengru Wu, Jiawei Li, Jiaqi Wei +3
College of Information Engineering, Zhejiang University of Technology, Hangzhou 310023, China · School of Communications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China · Department of Electronic and Electrical Engineering, University College London, WC1E 7JE London, U.K. +2
Distributed Constraint Satisfaction Problems (DCSPs) model distributed decision-making in multi-agent systems, where agents assign values to local variables while satisfying shared constraints. However, many DCSP solvers still rely on broad, repeated peer-to-peer communication and are largely reactive, with limited support for strategic coordination or learning. This increases communication overhead, can lead to stagnation, and reduces the success of hard instances. Hence, we propose Dynamic Conflict Clustering-Incomplete (DCC-Incomplete), a repair-based solver that combines conflict-centred decomposition, structured coordination, strategic repair, and lightweight learning for stagnation recovery. DCC-Incomplete groups the unsolved part of the problem into conflict clusters and restricts communication via a coordination layer to agents within the same conflict region. It also introduces memory-guided restart, enabling agents and clusters to pause, revise, and adapt repairs based on neighbouring conflict states. A thorough evaluation of DCC-Incomplete on distributed graph-colouring benchmarks with planted satisfying assignments shows that its memory-guided restart improves the success rate from 37.50% to 61.11%, reduces median runtime from 0.565s to 0.367s, and cuts median communication from 12.493 to 6.503 messages per constraint. These results suggest that dynamic conflict clustering, combined with lightweight strategic and learning-guided repair, improves both communication efficiency and robustness in incomplete DCSP solving.
Raziyeh Moghaddas, Fabio Caraffini
Department of Science and Engineering, Swansea University, Swansea, UK
Neural networks are being increasingly used as heuristics for constraint satisfaction. These neural methods are often recurrent, learning to iteratively refine candidate assignments. In this work, we make explicit the connection between such iterative neural heuristics and Large Neighborhood Search (LNS), and adapt an existing neural constraint satisfaction method-ConsFormer-into an LNS procedure. We decompose the resulting neural LNS into two standard components: the destroy and repair operators. On the destroy side, we instantiate several classical heuristics and introduce novel prediction-guided operators that exploit the model's internal scores to select neighborhoods. On the repair side, we utilize ConsFormer as a neural repair operator and compare the original sampling-based decoder to a greedy decoder that selects the most likely assignments. Through an empirical study on Sudoku, Graph Coloring, and MaxCut, we find that adapting the neural heuristic to an LNS procedure yields substantial gains over its vanilla settings and improves its competitiveness with classical and neural baselines. We further observe consistent design patterns across tasks: stochastic destroy operators outperform greedy ones, while greedy repair is more effective than sampling-based repair for finding a single high-quality feasible assignment. These findings highlight LNS as a useful lens and design framework for structuring and improving iterative neural approaches.
Yudong W. Xu, Wenhao Li, Scott Sanner +1
Department of Mechanical & Industrial Engineering, University of Toronto · Vector Institute