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: "achieving secrecy without knowing the number of eavesdropper antennas"
  Abstract: The existing research on physical layer security commonly assumes the number of eavesdropper antennas to be known. Although this assumption allows one to easily compute the achievable secrecy rate, it can hardly be realized in practice. In this paper, we provide an innovative approach to studying secure communication systems without knowing the number of eavesdropper antennas by introducing the concept of spatial constraint into physical layer security. Specifically, the eavesdropper is assumed to have a limited spatial region to place (possibly an infinite number of) antennas. From a practical point of view, knowing the spatial constraint of the eavesdropper is much easier than knowing the number of eavesdropper antennas. We derive the achievable secrecy rates of the spatially-constrained system with and without friendly jamming. We show that a non-zero secrecy rate is achievable with the help of a friendly jammer, even if the eavesdropper places an infinite number of antennas in its spatial region. Furthermore, we find that the achievable secrecy rate does not monotonically increase with the jamming power, and hence, we obtain the closed-form solution of the optimal jamming power that maximizes the secrecy rate.

Connected through hyperedge HE-1 (induced by source paper "artificial noise injection for securing single antenna systems"):
  with members:
    - "on secrecy metrics for physical layer security over quasi static fading channels"
    - "artificial noise aided secrecy information and power transfer in ofdma systems"
    - "secure on off transmission design with channel estimation errors"
    - "improving physical layer secrecy using full duplex jamming receivers"
    - "power allocation and time domain artificial noise design for wiretap ofdm with discrete inputs"
    - "rethinking the secrecy outage formulation a secure transmission design perspective"
    - "secure transmission with artificial noise over fading channels achievable rate and optimal power allocation"

Connected through hyperedge HE-2 (induced by source paper "on the design of secure non orthogonal multiple access systems"):
  with members:
    - "on secrecy metrics for physical layer security over quasi static fading channels"
    - "secrecy sum rate maximization in non orthogonal multiple access"
    - "a survey of downlink non orthogonal multiple access for 5g wireless communication networks"
    - "fairness for non orthogonal multiple access in 5g systems"
    - "a general mimo framework for noma downlink and uplink transmission based on signal alignment"
    - "on the performance of non orthogonal multiple access in 5g systems with randomly deployed users"
    - "secure on off transmission design with channel estimation errors"
    - "large system analysis of linear precoding in miso broadcast channels with confidential messages"

Connected through hyperedge HE-3 (induced by source paper "artificial noise aided secure transmission in wiretap channels with transmitter side correlation"):
  with members:
    - "linear precoding of data and artificial noise in secure massive mimo systems"
    - "location based beamforming for enhancing secrecy in rician wiretap channels"
    - "artificial noise aided secure multi antenna transmission with limited feedback"
    - "physical layer security for massive mimo an overview on passive eavesdropping and active attacks"
    - "optimization of code rates in sisome wiretap channels"
    - "improving physical layer secrecy using full duplex jamming receivers"
    - "spatially selective artificial noise aided transmit optimization for miso multi eves secrecy rate maximization"
    - "on the design of artificial noise aided secure multi antenna transmission in slow fading channels"

Connected through hyperedge HE-4 (induced by source paper "location based beamforming and physical layer security in rician wiretap channels"):
  with members:
    - "artificial noise aided secure transmission in large scale spectrum sharing networks"
    - "location based beamforming for enhancing secrecy in rician wiretap channels"
    - "jamming aided secure communication in massive mimo rician channels"
    - "location based beamforming for rician wiretap channels"
    - "on the design of artificial noise aided secure multi antenna transmission in slow fading channels"
    - "secure transmission with multiple antennas ii the mimome wiretap channel"
    - "the secrecy capacity of the mimo wiretap channel"

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)