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: "energy efficient time synchronization based on asynchronous source clock frequency recovery and reverse two way message exchanges in wireless sensor networks"
  Abstract: We consider energy-efficient time synchronization in a wireless sensor network where a head node is equipped with a powerful processor and supplied power from outlet, and sensor nodes are limited in processing and battery-powered. It is this  asymmetry  that our study focuses on; unlike most existing schemes to save the power of all network nodes, we concentrate on battery-powered sensor nodes in minimizing energy consumption for time synchronization. We present a time synchronization scheme based on asynchronous source clock frequency recovery and reverse two-way message exchanges combined with measurement data report messages, where we minimize the number of message transmissions from sensor nodes while achieving sub-microsecond time synchronization accuracy through propagation delay compensation. We carry out the performance analysis of the estimation of both measurement time and clock frequency with lower bounds for the latter. Simulation results verify that the proposed scheme outperforms the schemes based on conventional two-way message exchanges with and without clock frequency recovery in terms of the accuracy of measurement time estimation and the number of message transmissions and receptions at sensor nodes as an indirect measure of energy efficiency.

Connected through hyperedge HE-1 (induced by source paper "a beaconless asymmetric energy efficient time synchronization scheme for resource constrained multi hop wireless sensor networks"):
  with members:
    - "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"
    - "asynchronous source clock frequency recovery through aperiodic packet streams"
    - "analysis study of time synchronization protocols in wireless sensor networks"

Connected through hyperedge HE-2 (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:
    - "efficient single hop time synchronization protocol for randomly connected wsns"
    - "asynchronous source clock frequency recovery through aperiodic packet streams"

Connected through hyperedge HE-3 (induced by source paper "optimal message bundling with delay and synchronization constraints in wireless sensor networks"):
  with members:
    - "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"

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)