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: "toward a tractable delay analysis in ultra dense networks"
  Abstract: Meeting the diverse delay requirements of emerging wireless applications is one of the most critical goals for the design of ultradense networks. Though the delay of point-to-point communications has been well investigated using classical queueing theory, the delay of multi-point to multi-point communications, such as in ultradense networks, has not been explored in depth. The main technical difficulty lies in the interacting queues problem, in which the service rate is coupled with the statuses of other queues. In this article, we elaborate on the main challenges in the delay analysis in ultradense networks. Several promising approaches, such as introducing the dominant system and the simplified system, to bypass these difficulties are proposed and summarized to provide useful guidance.

Connected through hyperedge HE-1 (induced by source paper "energy efficient optimization of wireless powered 5g full duplex cellular networks a mean field game approach"):
  with members:
    - "tradeoff between delay and physical layer security in wireless networks"
    - "distributed user association in energy harvesting small cell networks a probabilistic bandit model"
    - "ultra dense small cell networks turning density into energy efficiency"
    - "fronthauling for 5g lte u ultra dense cloud small cell networks"
    - "heterogeneous cellular networks with spatio temporal traffic delay analysis and scheduling"
    - "5g ultra dense cellular networks"
    - "energy harvesting small cell networks feasibility deployment and operation"
    - "mean field energy games in wireless networks"

Connected through hyperedge HE-2 (induced by source paper "secure communication in dynamic wireless ad hoc networks"):
  with members:
    - "k connectivity in random key graphs with unreliable links"
    - "tradeoff between delay and physical layer security in wireless networks"
    - "directional cell search delay analysis for cellular networks with static users"
    - "connectivity in secure wireless sensor networks under transmission constraints"
    - "on topological properties of wireless sensor networks under the q composite key predistribution scheme with on off channels"
    - "physical layer security in cellular networks a stochastic geometry approach"
    - "on the throughput cost of physical layer security in decentralized wireless networks"
    - "information propagation speed in mobile and delay tolerant networks"

Connected through hyperedge HE-3 (induced by source paper "a new small world iot routing mechanism based on cayley graphs"):
  with members:
    - "ultra reliable low latency communications in autonomous vehicular networks"
    - "tradeoff between delay and physical layer security in wireless networks"
    - "joint optimization of computation and communication power in multi user massive mimo systems"
    - "coverage and handoff analysis of 5g fractal small cell networks"
    - "cache aided non orthogonal multiple access"
    - "energy efficiency evaluation of cellular networks based on spatial distributions of traffic load and power consumption"
    - "capacity analysis of a multi cell multi antenna cooperative cellular network with co channel interference"
    - "throughput delay reliability tradeoff with arq in wireless ad hoc networks"

Connected through hyperedge HE-4 (induced by source paper "delay analysis in full duplex heterogeneous cellular networks"):
  with members:
    - "tradeoff between delay and physical layer security in wireless networks"
    - "modeling and performance analysis of full duplex communications in cache enabled d2d networks"
    - "full duplex device to device collaboration for low latency wireless video distribution"
    - "hybrid duplex switching in heterogeneous networks"
    - "hybrid full half duplex system analysis in heterogeneous wireless networks"
    - "heterogeneous cellular networks with flexible cell association a comprehensive downlink sinr analysis"

Connected through hyperedge HE-5 (induced by source paper "sir coverage analysis in cellular networks with temporal traffic a stochastic geometry approach"):
  with members:
    - "cell edge aware precoding for downlink massive mimo cellular networks"
    - "modeling and analysis of cellular networks using stochastic geometry a tutorial"
    - "packet throughput analysis of static and dynamic tdd in small cell networks"
    - "spatiotemporal stochastic modeling of iot enabled cellular networks scalability and stability analysis"
    - "unified stochastic geometry modeling and analysis of cellular networks in los nlos and shadowed fading"
    - "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"

Connected through hyperedge HE-6 (induced by source paper "tradeoff between delay and physical layer security in wireless networks"):
  with members:
    - "when mmwave communications meet network densification a scalable interference coordination perspective"
    - "secure transmission with large numbers of antennas and finite alphabet inputs"
    - "5g software defined vehicular networks"
    - "heterogeneous cellular networks with spatio temporal traffic delay analysis and scheduling"
    - "secure massive mimo transmission with an active eavesdropper"
    - "5g ultra dense cellular networks"
    - "performance laws of large heterogeneous cellular networks"
    - "cross layer scheduling for ofdma based cognitive radio systems with delay and security constraints"

Connected through hyperedge HE-7 (induced by source paper "spatiotemporal model for uplink iot traffic scheduling random access paradox"):
  with members:
    - "tradeoff between delay and physical layer security in wireless networks"
    - "modeling and analysis of cellular networks using stochastic geometry a tutorial"
    - "the meta distribution of the sir for cellular networks with power control"
    - "random access analysis for massive iot networks under a new spatio temporal model a stochastic geometry approach"
    - "spatiotemporal stochastic modeling of iot enabled cellular networks scalability and stability analysis"
    - "lte lte a random access for massive machine type communications in smart cities"
    - "on the evaluation of lte random access channel overload in a smart city scenario"
    - "analytical modeling of interference aware power control for the uplink of heterogeneous cellular networks"

Connected through hyperedge HE-8 (induced by source paper "delay analysis of random scheduling and round robin in small cell networks"):
  with members:
    - "sir coverage analysis in cellular networks with temporal traffic a stochastic geometry approach"
    - "ultra dense networks a new look at the proportional fair scheduler"
    - "packet throughput analysis of static and dynamic tdd in small cell networks"
    - "spatiotemporal stochastic modeling of iot enabled cellular networks scalability and stability analysis"
    - "heterogeneous cellular networks with spatio temporal traffic delay analysis and scheduling"
    - "the meta distribution of the sir in poisson bipolar and cellular networks"
    - "study on scheduling techniques for ultra dense small cell networks"
    - "what will 5g be"

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)