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: "artificial noise aided secure multicast precoding for directional modulation systems"
  Abstract: In multi-cast scenario, all desired users are divided into $K$ groups. Each group receives its own individual confidential message stream. Eavesdropper group aims to intercept $K$ confidential-message streams. To achieve a secure transmission, two secure schemes are proposed: maximum group receive power plus null-space (NS) projection (Max-GRP plus NSP) and leakage. The former obtains its precoding vector per group by maximizing its own group receive power subject to the orthogonal constraint, and its AN projection matrix consist of all bases of NS of all desired steering vectors from all groups. The latter attains its desired precoding vector per group by driving the current confidential message power to its group steering space and reducing its power leakage to eavesdropper group and other $K-1$ desired ones by maximizing signal to leakage and noise ratio (Max-SLNR). And its AN projection matrix is designed by forcing AN power into the eavesdropper steering space by viewing AN as a useful signal for eavesdropper group and maximizing AN to leakage-and-noise ratio (Max-ANLNR). Simulation results show that the proposed two methods are better than conventional method in terms of both bit-error-rate (BER) and secrecy sum-rate per group. Also, the leakage scheme performs better than Max-GRP-NSP , especially in the presence of direction measurement errors. However, the latter requires no channel statistical parameters and thus is simpler compared to the former.

Connected through hyperedge HE-1 (induced by source paper "energy efficient alternating iterative secure structure of maximizing secrecy rate for directional modulation networks"):
  with members:
    - "alternating iterative secure structure between beamforming and power allocation for uav aided directional modulation networks"
    - "robust secure transmission of using main lobe integration based leakage beamforming in directional modulation mu mimo systems"
    - "secure transmission with large numbers of antennas and finite alphabet inputs"
    - "low complexity and high resolution doa estimation for hybrid analog and digital massive mimo receive array"
    - "artificial noise aided secure transmission with directional modulation based on random frequency diverse arrays"
    - "optimal power allocation for artificial noise under imperfect csi against spatially random eavesdroppers"
    - "an overview of sustainable green 5g networks"
    - "secure massive mimo transmission in the presence of an active eavesdropper"

Connected through hyperedge HE-2 (induced by source paper "performance analysis of directional modulation with finite quantized rf phase shifters in analog beamforming structure"):
  with members:
    - "robust secure transmission of using main lobe integration based leakage beamforming in directional modulation mu mimo systems"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "improving physical layer secrecy using full duplex jamming receivers"
    - "millimeter wave beamforming for wireless backhaul and access in small cell networks"
    - "coding the beams improving beamforming training in mmwave communication system"

Connected through hyperedge HE-3 (induced by source paper "two high performance amplitude beamforming schemes for secure precise communication and jamming with phase alignment"):
  with members:
    - "two high performance schemes of transmit antenna selection for secure spatial modulation"
    - "secure transmission with large numbers of antennas and finite alphabet inputs"
    - "interference alignment and soft space reuse based cooperative transmission for multi cell massive mimo networks"
    - "artificial noise aided secure transmission with directional modulation based on random frequency diverse arrays"

Connected through hyperedge HE-4 (induced by source paper "alternating iterative secure structure between beamforming and power allocation for uav aided directional modulation networks"):
  with members:
    - "robust secure transmission of using main lobe integration based leakage beamforming in directional modulation mu mimo systems"
    - "secure transmission with large numbers of antennas and finite alphabet inputs"
    - "joint trajectory and communication design for multi uav enabled wireless networks"
    - "interference alignment and soft space reuse based cooperative transmission for multi cell massive mimo networks"
    - "low complexity and high resolution doa estimation for hybrid analog and digital massive mimo receive array"
    - "overcoming endurance issue uav enabled communications with proactive caching"
    - "energy efficient uav communication with trajectory optimization"
    - "artificial noise aided secure transmission with directional modulation based on random frequency diverse arrays"

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)