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: "hetnets and massive mimo modeling potential gains and performance analysis"
  Abstract: We consider a heterogeneous cellular network (HetNet) where a macrocell tier with a large antenna array base station (BS) is overlaid with a dense tier of small cells (SCs). We investigate the potential benefits of incorporating a massive MIMO BS in a TDD-based HetNet and we provide analytical expressions for the coverage probability and the area spectral efficiency using stochastic geometry. The duplexing mode in which SCs should operate during uplink macrocell transmissions is optimized. Furthermore, we consider a reverse TDD scheme, in which the massive MIMO BS can estimate the SC interference covariance matrix. Our results suggest that significant throughput improvement can be achieved by exploiting interference nulling and implicit coordination across the tiers due to flexible and asymmetric TDD operation.

Connected through hyperedge HE-1 (induced by source paper "user centric interference nulling in downlink multi antenna heterogeneous networks"):
  with members:
    - "the mean interference to signal ratio and its key role in cellular and amorphous networks"
    - "user centric intercell interference nulling for downlink small cell networks"
    - "a tractable model for noncoherent joint transmission base station cooperation"
    - "analysis and optimization of inter tier interference coordination in downlink multi antenna hetnets with offloading"
    - "massive mimo meets hetnet interference coordination through spatial blanking"
    - "location aware cross tier coordinated multipoint transmission in two tier cellular networks"
    - "a stochastic geometry analysis of inter cell interference coordination and intra cell diversity"
    - "interference coordination random clustering and adaptive limited feedback"

Connected through hyperedge HE-2 (induced by source paper "energy efficiency in massive mimo based 5g networks opportunities and challenges"):
  with members:
    - "massive mimo performance evaluation based on measured propagation data"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "energy efficient antenna selection and power allocation for large scale multiple antenna systems with hybrid energy supply"
    - "massive mimo meets hetnet interference coordination through spatial blanking"
    - "optimal design of energy efficient multi user mimo systems is massive mimo the answer"
    - "massive mimo and small cells improving energy efficiency by optimal soft cell coordination"
    - "energy efficient optimization for wireless information and power transfer in large scale mimo systems employing energy beamforming"
    - "scaling up mimo opportunities and challenges with very large arrays"

Connected through hyperedge HE-3 (induced by source paper "degrees of freedom of uplink downlink multiantenna cellular networks"):
  with members:
    - "degrees of freedom of full duplex multiantenna cellular networks"
    - "real interference alignment exploiting the potential of single antenna systems"
    - "cellular interference alignment"
    - "genie tree and degrees of freedom of the symmetric mimo interfering broadcast channel"
    - "on the feasibility of linear interference alignment for mimo interference broadcast channels with constant coefficients"
    - "genie chain and degrees of freedom of symmetric mimo interference broadcast channels"
    - "degrees of freedom of mimo cellular networks decomposition and linear beamforming design"
    - "regularized zero forcing interference alignment for the two cell mimo interfering broadcast channel"

Connected through hyperedge HE-4 (induced by source paper "analysis and optimization of inter tier interference coordination in downlink multi antenna hetnets with offloading"):
  with members:
    - "spectral efficiency of dynamic coordinated beamforming a stochastic geometry approach"
    - "the mean interference to signal ratio and its key role in cellular and amorphous networks"
    - "user centric intercell interference nulling for downlink small cell networks"
    - "an overview of load balancing in hetnets old myths and open problems"
    - "massive mimo meets hetnet interference coordination through spatial blanking"
    - "energy efficiency of cross tier base station cooperation in heterogeneous cellular networks"
    - "location aware cross tier coordinated multipoint transmission in two tier cellular networks"
    - "a stochastic geometry analysis of inter cell interference coordination and intra cell diversity"

Connected through hyperedge HE-5 (induced by source paper "the feasibility of interference alignment for reverse tdd systems in mimo cellular networks"):
  with members:
    - "feasibility of interference alignment for the mimo interference channel"
    - "degrees of freedom of uplink downlink multiantenna cellular networks"
    - "cellular interference alignment"
    - "the feasibility conditions for interference alignment in mimo networks"
    - "on the degrees of freedom of asymmetric mimo interference broadcast channels"
    - "on the feasibility of linear interference alignment for mimo interference broadcast channels with constant coefficients"
    - "regularized zero forcing interference alignment for the two cell mimo interfering broadcast channel"
    - "on the degrees of freedom achievable through interference alignment in a mimo interference channel"

Connected through hyperedge HE-6 (induced by source paper "statistical modeling and probabilistic analysis of cellular networks with determinantal point processes"):
  with members:
    - "studying the sinr process of the typical user in poisson networks by using its factorial moment measures"
    - "the ginibre point process as a model for wireless networks with repulsion"
    - "wireless networks appear poissonian due to strong shadowing"
    - "downlink mimo hetnets modeling ordering results and performance analysis"
    - "load aware modeling and analysis of heterogeneous cellular networks"
    - "modeling heterogeneous network interference using poisson point processes"
    - "modeling and analysis of k tier downlink heterogeneous cellular networks"
    - "series expansion for interference in wireless 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)