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: "transmitter optimization for achieving secrecy capacity in gaussian mimo wiretap channels"
  Abstract: We consider a Gaussian multiple-input multiple-output (MIMO) wiretap channel model, where there exists a transmitter, a legitimate receiver and an eavesdro pper, each node equipped with multiple antennas. We study the problem of finding the optimal input covariance m atrix that achieves secrecy capacity subject to a power constraint, which leads to a non-convex optimization problem that is in general difficult to solve. Existing results for this problem address the case in which the transmitter and the legitimate receiver have two antennas each and the eavesdropper has one antenna. For the general cases, it has been shown that the optimal input covariance matrix has low rank when the difference between the Grams of the eavesdropper and the legitimate receiver channel matrices is indefinite or semi-definite, while it may have low rank or full rank when the difference is positive defi nite. In this paper, the aforementioned nonconvex optimization problem is investigated. In particular, for the multiple-input single-output (MISO) wiretap channel, the optimal input covariance matrix is obtained in closed form. For general cases, we derive the necessary conditions for the optimal input covariance matrix consisting of a set of equations. For the case in which the transmitter has two antennas, the derived necessary conditions can result in a closed form solution; For the case in which the difference between the Grams is indefinite and has all negative eigenvalues except one positive eigenvalue, t he optimal input covariance matrix has rank one and can be obtained in closed form; For other cases, the solution is proved to be a fixed point of a mapping from a convex set to itself and an iterative procedure is provided to search for it. Numerical results are presented to illustrate the proposed theoretic al findings.

Connected through hyperedge HE-1 (induced by source paper "a rotation based method for precoding in gaussian mimome channels"):
  with members:
    - "noma an information theoretic perspective"
    - "optimal beamforming for gaussian mimo wiretap channels with two transmit antennas"
    - "optimal signaling for secure communications over gaussian mimo wiretap channels"
    - "an algorithm for global maximization of secrecy rates in gaussian mimo wiretap channels"
    - "full rank solutions for the mimo gaussian wiretap channel with an average power constraint"
    - "cooperative jamming for secure communications in mimo relay networks"
    - "towards the secrecy capacity of the gaussian mimo wire tap channel the 2 2 1 channel"
    - "the secrecy capacity of the mimo wiretap channel"

Connected through hyperedge HE-2 (induced by source paper "optimal beamforming for gaussian mimo wiretap channels with two transmit antennas"):
  with members:
    - "optimal signaling for secure communications over gaussian mimo wiretap channels"
    - "an algorithm for global maximization of secrecy rates in gaussian mimo wiretap channels"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "full rank solutions for the mimo gaussian wiretap channel with an average power constraint"
    - "on secrecy rate analysis of mimo wiretap channels driven by finite alphabet input"
    - "secure transmission with multiple antennas ii the mimome wiretap channel"
    - "towards the secrecy capacity of the gaussian mimo wire tap channel the 2 2 1 channel"
    - "the secrecy capacity of the mimo wiretap channel"

Connected through hyperedge HE-3 (induced by source paper "on the compound mimo wiretap channel with mean feedback"):
  with members:
    - "the secrecy capacity of compound gaussian mimo wiretap channels"
    - "secrecy results for compound wiretap channels"
    - "secure transmission with multiple antennas ii the mimome wiretap channel"
    - "the secrecy capacity of the mimo wiretap channel"

Connected through hyperedge HE-4 (induced by source paper "rank deficient solutions for optimal signaling over wiretap mimo channels"):
  with members:
    - "an algorithm for global maximization of secrecy rates in gaussian mimo wiretap channels"
    - "on the optimal precoding for mimo gaussian wire tap channels"
    - "secrecy results for compound wiretap channels"
    - "secure transmission with multiple antennas ii the mimome wiretap channel"
    - "towards the secrecy capacity of the gaussian mimo wire tap channel the 2 2 1 channel"
    - "secure communication in the low snr regime"
    - "the secrecy capacity of the mimo wiretap channel"

Connected through hyperedge HE-5 (induced by source paper "optimal signaling for secure communications over gaussian mimo wiretap channels"):
  with members:
    - "secure transmission with multiple antennas ii the mimome wiretap channel"
    - "towards the secrecy capacity of the gaussian mimo wire tap channel the 2 2 1 channel"
    - "the secrecy capacity of the mimo wiretap channel"

Connected through hyperedge HE-6 (induced by source paper "energy efficiency in secure multi antenna systems"):
  with members:
    - "energy efficient scheduling and power allocation in downlink ofdma networks with base station coordination"
    - "real and complex monotone communication games"
    - "on secrecy capacity of fast fading mimome wiretap channels with statistical csit"
    - "on the design of artificial noise aided secure multi antenna transmission in slow fading channels"
    - "on secrecy rate of the generalized artificial noise assisted secure beamforming for wiretap channels"
    - "framework for link level energy efficiency optimization with informed transmitter"
    - "explicit solution of worst case secrecy rate for miso wiretap channels with spherical uncertainty"
    - "information theoretically secret key generation for fading wireless channels"

Connected through hyperedge HE-7 (induced by source paper "the secrecy capacity of compound gaussian mimo wiretap channels"):
  with members:
    - "on the continuity of the secrecy capacity of compound and arbitrarily varying wiretap channels"
    - "secrecy results for compound wiretap channels"
    - "finite snr diversity multiplexing tradeoff via asymptotic analysis of large mimo systems"
    - "mimo wiretap channels with arbitrarily varying eavesdropper channel states"
    - "secure transmission with multiple antennas ii the mimome wiretap channel"
    - "on the compound mimo broadcast channels with confidential messages"
    - "the secrecy capacity of the mimo wiretap channel"

Connected through hyperedge HE-8 (induced by source paper "an algorithm for global maximization of secrecy rates in gaussian mimo wiretap channels"):
  with members:
    - "secure transmission with multiple antennas ii the mimome wiretap channel"
    - "towards the secrecy capacity of the gaussian mimo wire tap channel the 2 2 1 channel"
    - "secure communication in the low snr regime"
    - "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)