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: "collaborative relay beamforming for secrecy"
  Abstract: In this paper, collaborative use of relays to form a beamforming system and provide physical-layer security is investigated. In particular, decode-and-forward (DF) and amplify-and-forward (AF) relay beamforming designs under total and individual relay power constraints are studied with the goal of maximizing the secrecy rates when perfect channel state information (CSI) is available. In the DF scheme, the total power constraint leads to a closed-form solution, and in this case, the optimal beamforming structure is identified in the low and high signal-to-noise ratio (SNR) regimes. The beamforming design under individual relay power constraints is formulated as an optimization problem which is shown to be easily solved using two different approaches, namely semidefinite programming and second-order cone programming. A simplified and suboptimal technique which reduces the computation complexity under individual power constraints is also presented. In the AF scheme, not having analytical solutions for the optimal beamforming design under both total and individual power constraints, an iterative algorithm is proposed to numerically obtain the optimal beamforming structure and maximize the secrecy rates. Finally, robust beamforming designs in the presence of imperfect CSI are investigated for DF-based relay beamforming, and optimization frameworks are provided

Connected through hyperedge HE-1 (induced by source paper "effective optimization criteria and relay selection algorithms for physical layer security in multiple antenna relay networks"):
  with members:
    - "widely linear precoding for large scale mimo with iqi algorithms and performance analysis"
    - "direction finding algorithms based on joint iterative subspace optimization"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "buffer aided relaying with adaptive link selection fixed and mixed rate transmission"
    - "multiuser diversity for secrecy communications using opportunistic jammer selection secure dof and jammer scaling law"
    - "adaptive distributed space time coding based on adjustable code matrices for cooperative mimo relaying systems"
    - "joint relay and jammer selection for secure two way relay networks"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-2 (induced by source paper "an efficient precoder design for multiuser mimo cognitive radio networks with interference constraints"):
  with members:
    - "beamforming and rate allocation in miso cognitive radio networks"
    - "cooperative multi cell block diagonalization with per base station power constraints"
    - "exploiting multi antennas for opportunistic spectrum sharing in cognitive radio networks"
    - "on peak versus average interference power constraints for protecting primary users in cognitive radio networks"
    - "weighted sum rate optimization for cognitive radio mimo broadcast channels"
    - "capacity limits of cognitive radio with distributed and dynamic spectral activity"

Connected through hyperedge HE-3 (induced by source paper "a survey on wireless security technical challenges recent advances and future trends"):
  with members:
    - "relay selection for wireless communications against eavesdropping a security reliability trade off perspective"
    - "improving physical layer security in wireless communications using diversity techniques"
    - "securing physical layer communications for cognitive radio networks"
    - "secrecy outage and diversity analysis of cognitive radio systems"
    - "security versus reliability analysis of opportunistic relaying"
    - "what will 5g be"
    - "intercept probability analysis of cooperative wireless networks with best relay selection in the presence of eavesdropping attack"
    - "optimal relay selection for physical layer security in cooperative wireless networks"

Connected through hyperedge HE-4 (induced by source paper "study of tomlinson harashima precoding strategies for physical layer security in wireless networks"):
  with members:
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "buffer aided relaying with adaptive link selection fixed and mixed rate transmission"
    - "multiuser diversity for secrecy communications using opportunistic jammer selection secure dof and jammer scaling law"
    - "adaptive distributed space time coding based on adjustable code matrices for cooperative mimo relaying systems"
    - "joint relay and jammer selection for secure two way relay networks"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "the secrecy capacity of the mimo wiretap channel"

Connected through hyperedge HE-5 (induced by source paper "network simplification for secure af relaying"):
  with members:
    - "secure transmission in amplify and forward diamond networks with a single eavesdropper"
    - "analog network coding in general snr regime"
    - "wireless network simplification the gaussian n relay diamond network"
    - "relay beamforming strategies for physical layer security"
    - "discrete memoryless interference and broadcast channels with confidential messages secrecy rate regions"
    - "a simple cooperative diversity method based on network path selection"

Connected through hyperedge HE-6 (induced by source paper "study of opportunistic cooperation techniques using jamming and relays for physical layer security in buffer aided relay networks"):
  with members:
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "buffer aided relaying with adaptive link selection fixed and mixed rate transmission"
    - "multiuser diversity for secrecy communications using opportunistic jammer selection secure dof and jammer scaling law"
    - "adaptive distributed space time coding based on adjustable code matrices for cooperative mimo relaying systems"
    - "joint relay and jammer selection for secure two way relay networks"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "the secrecy capacity of the mimo wiretap channel"

Connected through hyperedge HE-7 (induced by source paper "mimo df relay beamforming for secrecy with artificial noise imperfect csi and finite alphabet"):
  with members:
    - "power allocation in mimo wiretap channel with statistical csi and finite alphabet input"
    - "robust secure transmission in miso channels based on worst case optimization"
    - "on secrecy rate analysis of mimo wiretap channels driven by finite alphabet input"
    - "on cooperative relaying schemes for wireless physical layer security"
    - "secrecy capacity of the gaussian wire tap channel with finite complex constellation input"
    - "the secrecy capacity of the mimo wiretap channel"
    - "mutual information and minimum mean square error in gaussian channels"

Connected through hyperedge HE-8 (induced by source paper "joint design of optimal cooperative jamming and power allocation for linear precoding"):
  with members:
    - "robust secure transmission in miso channels based on worst case optimization"
    - "on cooperative relaying schemes for wireless physical layer security"
    - "power and subcarrier allocation for physical layer security in ofdma based broadband wireless networks"
    - "cooperative jamming for secure communications in mimo relay networks"
    - "solutions for the mimo gaussian wiretap channel with a cooperative jammer"
    - "discrete memoryless interference and broadcast channels with confidential messages secrecy rate regions"

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)