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: "efficient single hop time synchronization protocol for randomly connected wsns"
  Abstract: This letter develops a single-hop fast accurate and energy-efficient time synchronization protocol for wireless sensor networks. The protocol is designed to operate in harsh environments and is based on a resistive electrical network metaphor. It treats the nodes’ times as the states of a discrete decentralized unconditionally stable dynamical system. The synchronizer monitors the evolution of these states during the transient phase to determine the instant at which the time encoded by a state is close to the master node time. The procedure can yield high quality time estimates with accuracies that are fractions of the communication cycle. The synchronization method is developed and its capabilities are demonstrated by simulation and physical experiments on the MICA-Z wireless sensor network.

Connected through hyperedge HE-1 (induced by source paper "on the practical implementation of propagation delay and clock skew compensated high precision time synchronization schemes with resource constrained sensor nodes in multi hop wireless sensor networks"):
  with members:
    - "energy efficient time synchronization based on asynchronous source clock frequency recovery and reverse two way message exchanges in wireless sensor networks"
    - "asynchronous source clock frequency recovery through aperiodic packet streams"

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)