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: "mimo beamforming for secure and energy efficient wireless communication"
  Abstract: Considering a multiple-user multiple-input multiple-output channel with an eavesdropper, this letter develops a beamformer design to optimize the energy efficiency in terms of secrecy bits per Joule under secrecy quality-of-service constraints. This is a very difficult design problem with no available exact solution techniques. A path-following procedure, which iteratively improves its feasible points by using a simple quadratic program of moderate dimension, is proposed. Under any fixed computational tolerance, the procedure terminates after finitely many iterations, yielding at least a locally optimal solution. Simulation results show the superior performance of the obtained algorithm over other existing methods.

Connected through hyperedge HE-1 (induced by source paper "energy efficient cooperative secure transmission in multi uav enabled wireless networks"):
  with members:
    - "secrecy energy efficiency maximization for uav enabled mobile relaying"
    - "uav aided offloading for cellular hotspot"
    - "securing uav communications via joint trajectory and power control"
    - "energy minimization for wireless communication with rotary wing uav"
    - "robust trajectory and transmit power design for secure uav communications"
    - "secure uav communication with cooperative jamming and trajectory control"
    - "placement optimization of uav mounted mobile base stations"
    - "joint trajectory and communication design for multi uav enabled wireless networks"

Connected through hyperedge HE-2 (induced by source paper "cell free massive mimo networks optimal power control against active eavesdropping"):
  with members:
    - "on the total energy efficiency of cell free massive mimo"
    - "energy efficiency in cell free massive mimo with zero forcing precoding design"
    - "mimo secret communications against an active eavesdropper"
    - "cell free massive mimo versus small cells"
    - "cell free massive mimo uniformly great service for everyone"
    - "secure massive mimo transmission with an active eavesdropper"
    - "secret key agreement with large antenna arrays under the pilot contamination attack"
    - "physical layer security for massive mimo an overview on passive eavesdropping and active attacks"

Connected through hyperedge HE-3 (induced by source paper "beamforming optimization for physical layer security in miso wireless networks"):
  with members:
    - "robust chance constrained optimization for power efficient and secure swipt systems"
    - "secrecy energy efficiency optimization for miso and siso communication networks"
    - "secrecy wireless information and power transfer with miso beamforming"
    - "toward energy efficient 5g wireless communications technologies"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "coordinated beamforming for multiuser miso interference channel under rate outage constraints"
    - "spatially selective artificial noise aided transmit optimization for miso multi eves secrecy rate maximization"
    - "outage probability and outage based robust beamforming for mimo interference channels with imperfect channel state information"

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)