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: "ultra dense networks is there a limit to spatial spectrum reuse"
  Abstract: The aggressive spatial spectrum reuse (SSR) by network densification using smaller cells has successfully driven the wireless communication industry onward in the past decades. In our future journey toward ultra-dense networks (UDNs), a fundamental question needs to be answered. Is there a limit to SSR? In other words, when we deploy thousands or millions of small cell base stations (BSs) per square kilometer, is activating all BSs on the same time/frequency resource the best strategy? In this paper, we present theoretical analyses to answer such question. In particular, we find that both the signal and interference powers become bounded in practical UDNs with a non-zero BS-to-UE antenna height difference and a finite UE density, which leads to a constant capacity scaling law. As a result, there exists an optimal SSR density that can maximize the network capacity. Hence, the limit to SSR should be considered in the operation of future UDNs.

Connected through hyperedge HE-1 (induced by source paper "a brief history on the theoretical analysis of dense small cell wireless networks"):
  with members:
    - "optimal base station antenna downtilt in downlink cellular networks"
    - "sinr and throughput of dense cellular networks with stretched exponential path loss"
    - "wireless powered dense cellular networks how many small cells do we need"
    - "inter operator base station coordination in spectrum shared millimeter wave cellular networks"
    - "downlink cellular network analysis with los nlos propagation and elevated base stations"
    - "performance impact of base station antenna heights in dense cellular networks"
    - "modeling infrastructure sharing in mmwave networks with shared spectrum licenses"
    - "spatially correlated content caching for device to device communications"

Connected through hyperedge HE-2 (induced by source paper "optimal base station antenna downtilt in downlink cellular networks"):
  with members:
    - "performance analysis of ultra dense networks with elevated base stations"
    - "performance impact of base station antenna heights in dense cellular networks"
    - "joint tilt angle adaptation and beamforming in multicell multiuser cellular networks"
    - "energy efficiency optimization of 5g radio frequency chain systems"
    - "please lower small cell antenna heights in 5g"
    - "performance impact of los and nlos transmissions in dense cellular networks"
    - "spatial spectrum and energy efficiency of random cellular networks"
    - "towards 1 gbps ue in cellular systems understanding ultra dense small cell deployments"

Connected through hyperedge HE-3 (induced by source paper "performance analysis for practical unmanned aerial vehicle networks with los nlos transmissions"):
  with members:
    - "dynamic base station repositioning to improve spectral efficiency of drone small cells"
    - "please lower small cell antenna heights in 5g"
    - "unmanned aerial vehicle with underlaid device to device communications performance and tradeoffs"
    - "performance impact of los and nlos transmissions in dense cellular networks"
    - "drone small cells in the clouds design deployment and performance analysis"

Connected through hyperedge HE-4 (induced by source paper "optimum interference management in underlay inband d2d enhanced cellular networks"):
  with members:
    - "on the performance of practical ultra dense networks the major and minor factors"
    - "a stochastic geometric analysis of device to device communications operating over generalized fading channels"
    - "the intensity matching approach a tractable stochastic geometry approximation to system level analysis of cellular networks"
    - "performance impact of los and nlos transmissions in dense cellular networks"
    - "towards 1 gbps ue in cellular systems understanding ultra dense small cell deployments"
    - "an analytical framework for device to device communication in cellular networks"
    - "spectrum sharing for device to device communication in cellular networks"
    - "power control for d2d underlaid cellular networks modeling algorithms and analysis"

Connected through hyperedge HE-5 (induced by source paper "on the performance of multi tier heterogeneous cellular networks with idle mode capability"):
  with members:
    - "on the performance of practical ultra dense networks the major and minor factors"
    - "study on the idle mode capability with los and nlos transmissions"
    - "energy efficient cell activation user association and spectrum allocation in heterogeneous networks"
    - "towards 1 gbps ue in cellular systems understanding ultra dense small cell deployments"
    - "analysis on cache enabled wireless heterogeneous networks"
    - "heterogeneous cellular networks with flexible cell association a comprehensive downlink sinr analysis"
    - "user association for load balancing in heterogeneous cellular networks"
    - "coverage and economy of cellular networks with many base stations"

Connected through hyperedge HE-6 (induced by source paper "ultra dense networks a new look at the proportional fair scheduler"):
  with members:
    - "study on the idle mode capability with los and nlos transmissions"
    - "heterogeneous cellular networks with spatio temporal traffic delay analysis and scheduling"
    - "performance impact of los and nlos transmissions in dense cellular networks"
    - "towards 1 gbps ue in cellular systems understanding ultra dense small cell deployments"
    - "5g ultra dense cellular networks"
    - "study on scheduling techniques for ultra dense small cell networks"
    - "coverage and economy of cellular networks with many base stations"

Connected through hyperedge HE-7 (induced by source paper "analysis of device to device communications in uplink cellular networks with lognormal fading"):
  with members:
    - "towards 1 gbps ue in cellular systems understanding ultra dense small cell deployments"
    - "d2d enhanced heterogeneous cellular networks with dynamic tdd"
    - "an analytical framework for device to device communication in cellular networks"
    - "performance impact of los and nlos transmissions in small cell networks"
    - "power control for d2d underlaid cellular networks modeling algorithms and analysis"
    - "analytical modeling of uplink cellular networks"
    - "a tractable approach to coverage and rate in cellular networks"

Connected through hyperedge HE-8 (induced by source paper "a tractable framework for the analysis of dense heterogeneous cellular networks"):
  with members:
    - "stability and dynamic control of underlay mobile edge networks"
    - "sinr and throughput of dense cellular networks with stretched exponential path loss"
    - "performance limits of network densification"
    - "modeling and analysis of cellular networks using stochastic geometry a tutorial"
    - "poisson cluster process based analysis of hetnets with correlated user and base station locations"
    - "user association in 5g networks a survey and an outlook"
    - "tractable framework for the analysis of general multi tier heterogeneous cellular networks"
    - "gaussian approximation for the downlink interference 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.NI(Networking and Internet Architecture)