human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "user association in massive mimo hetnets"
  Abstract: Massive multiple-input–multiple-output (MIMO) and small cell are both recognized as key technologies for the future fifth-generation wireless systems. In this paper, we investigate the problem of user association in a heterogeneous network (HetNet) with massive MIMO and small cells, where the macro base station (BS) is equipped with a massive MIMO, and the picocell BSs are equipped with regular MIMOs. We first develop centralized user association algorithms with proven optimality, considering various objectives such as rate maximization, proportional fairness, and joint user association and resource allocation. We then develop a repeated game model, which leads to distributed user association algorithms with proven convergence to the Nash equilibrium. We demonstrate the efficacy of these optimal schemes by comparing with several greedy algorithms through simulations.

Connected through hyperedge HE-1 (induced by source paper "an efficient requirement aware attachment policy for future millimeter wave vehicular networks"):
  with members:
    - "a tutorial on beam management for 3gpp nr at mmwave frequencies"
    - "toward intelligent vehicular networks a machine learning framework"
    - "hybrid spectrum sharing in mmwave cellular networks"
    - "millimeter wave vehicular communication to support massive automotive sensing"
    - "initial access in 5g mmwave cellular networks"
    - "tractable model for rate in self backhauled millimeter wave cellular networks"
    - "millimeter wave cellular wireless networks potentials and challenges"
    - "millimeter wave channel modeling and cellular capacity evaluation"

Connected through hyperedge HE-2 (induced by source paper "downlink user association and uplink scheduling for energy harvesting users in software defined mobile networks"):
  with members:
    - "energy efficient precoding design for swipt in mimo two way relay networks"
    - "greendelivery proactive content caching and push with energy harvesting based small cells"
    - "energy efficiency in massive mimo based 5g networks opportunities and challenges"
    - "software defined and virtualized future mobile and wireless networks a survey"

Connected through hyperedge HE-3 (induced by source paper "applications of economic and pricing models for resource management in 5g wireless networks a survey"):
  with members:
    - "an auction approach to spectrum management in hetnets"
    - "applications of economic and pricing models for wireless network security a survey"
    - "caching incentive design in wireless d2d networks a stackelberg game approach"
    - "breaking the economic barrier of caching in cellular networks incentives and contracts"
    - "distributed optimization of hierarchical small cell networks a gnep framework"
    - "spectrum and infrastructure sharing in millimeter wave cellular networks an economic perspective"
    - "caching as a service small cell caching mechanism design for service providers"
    - "user association in 5g networks a survey and an outlook"

Connected through hyperedge HE-4 (induced by source paper "wireless power transfer in massive mimo aided hetnets with user association"):
  with members:
    - "user association in 5g networks a survey and an outlook"
    - "joint downlink cell association and bandwidth allocation for wireless backhauling in two tier hetnets with large scale antenna arrays"
    - "millimeter wave energy harvesting"
    - "performance analysis of simultaneous wireless information and power transfer with ambient rf energy harvesting"
    - "why to decouple the uplink and downlink in cellular networks and how to do it"
    - "5g cellular key enabling technologies and research challenges"
    - "millimeter wave power transfer and information transmission"
    - "throughput optimization for massive mimo systems powered by wireless energy transfer"

Connected through hyperedge HE-5 (induced by source paper "boost base station on off switching strategy for energy efficient massive mimo hetnets"):
  with members:
    - "harvest the potential of massive mimo with multi layer techniques"
    - "what will 5g be"
    - "massive mimo and small cells improving energy efficiency by optimal soft cell coordination"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "user association for load balancing in heterogeneous cellular networks"
    - "green cellular networks a survey some research issues and challenges"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-6 (induced by source paper "harvest the potential of massive mimo with multi layer techniques"):
  with members:
    - "boost base station on off switching strategy for energy efficient massive mimo hetnets"
    - "multipair full duplex relaying with massive arrays and linear processing"
    - "large scale mimo versus network mimo for multicell interference mitigation"
    - "massive mimo for next generation wireless systems"
    - "massive mimo and small cells improving energy efficiency by optimal soft cell coordination"
    - "electromagnetic lens focusing antenna enabled massive mimo performance improvement and cost reduction"
    - "achieving massive mimo spectral efficiency with a not so large number of antennas"

Connected through hyperedge HE-7 (induced by source paper "interference management in massive mimo hetnets a nested array approach"):
  with members:
    - "boost base station on off switching strategy for energy efficient massive mimo hetnets"
    - "harvest the potential of massive mimo with multi layer techniques"
    - "what will 5g be"
    - "massive mimo meets hetnet interference coordination through spatial blanking"
    - "massive mimo and small cells improving energy efficiency by optimal soft cell coordination"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-8 (induced by source paper "user association with maximizing sum energy efficiency for massive mimo enabled heterogeneous cellular networks"):
  with members:
    - "distributed pricing based user association for downlink heterogeneous cellular networks"
    - "optimal user cell association for massive mimo wireless networks"
    - "user association for load balancing in heterogeneous cellular networks"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.IT(Information Theory)