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: "secrecy sum rate maximization in non orthogonal multiple access"
  Abstract: Non-orthogonal multiple access (NOMA) has been recognized as a promising technique for providing high data rates in 5G systems. This letter is to study physical layer security in a single-input single-output (SISO) NOMA system consisting of a transmitter, multiple legitimate users and an eavesdropper. The aim of this letter is to maximize the secrecy sum rate (SSR) of the NOMA system subject to the users’ quality of service (QoS) requirements. We firstly identify the feasible region of the transmit power for satisfying all users’ QoS requirements. Then we derive the closed-form expression of an optimal power allocation policy that maximizes the SSR. Numerical results are provided to show a significant SSR improvement by NOMA compared with conventional orthogonal multiple access (OMA).

Connected through hyperedge HE-1 (induced by source paper "physical layer security for noma transmission in mmwave drone networks"):
  with members:
    - "secure users oriented downlink miso noma"
    - "uav communications for 5g and beyond recent advances and future trends"
    - "enhancing physical layer security for noma transmission in mmwave drone networks"
    - "beamforming design and power allocation for secure transmission with noma"
    - "exploiting inter user interference for secure massive non orthogonal multiple access"
    - "on the design of secure non orthogonal multiple access systems"
    - "enhancing the physical layer security of non orthogonal multiple access in large scale networks"

Connected through hyperedge HE-2 (induced by source paper "secure relaying in non orthogonal multiple access trusted and untrusted scenarios"):
  with members:
    - "on the spectral efficiency and security enhancements of noma assisted multicast unicast streaming"
    - "enhancing the physical layer security of non orthogonal multiple access in large scale networks"
    - "cooperation with an untrusted relay a secrecy perspective"
    - "the secrecy capacity region of the gaussian mimo multi receiver wiretap channel"

Connected through hyperedge HE-3 (induced by source paper "a survey of rate optimal power domain noma schemes for enabling technologies of future wireless networks"):
  with members:
    - "generalized coordinated multipoint gcomp enabled noma outage capacity and power allocation"
    - "what role can noma play in massive mimo"
    - "uav data collection over noma backscatter networks uav altitude and trajectory optimization"
    - "uav communications for 5g and beyond recent advances and future trends"
    - "when full duplex wireless meets non orthogonal multiple access opportunities and challenges"
    - "on optimizing vlc networks for downlink multi user transmission a survey"
    - "beam design and user scheduling for nonorthogonal multiple access with multiple antennas based on pareto optimality"
    - "spatial modulation assisted multi antenna non orthogonal multiple access"

Connected through hyperedge HE-4 (induced by source paper "secure communications in a unified non orthogonal multiple access framework"):
  with members:
    - "exploiting full half duplex user relaying in noma systems"
    - "user association and resource allocation in unified noma enabled heterogeneous ultra dense networks"
    - "securing downlink non orthogonal multiple access systems by trusted relays"
    - "a unified framework for non orthogonal multiple access"
    - "edge computing aware noma for 5g networks"
    - "impact of non orthogonal multiple access on the offloading of mobile edge computing"
    - "secure communications in noma system subcarrier assignment and power allocation"
    - "performance analysis of noma with fixed gain relaying over nakagami m fading channels"

Connected through hyperedge HE-5 (induced by source paper "securing downlink massive mimo noma networks with artificial noise"):
  with members:
    - "energy efficient joint user rb association and power allocation for uplink hybrid noma oma"
    - "energy efficient power allocation in uplink mmwave massive mimo with noma"
    - "exploiting inter user interference for secure massive non orthogonal multiple access"
    - "optimal resource allocation for power efficient mc noma with imperfect channel state information"
    - "power domain non orthogonal multiple access noma in 5g systems potentials and challenges"
    - "energy efficient power allocation in millimeter wave massive mimo with non orthogonal multiple access"
    - "resource allocation for downlink noma systems key techniques and open issues"
    - "noma in 5g systems exciting possibilities for enhancing spectral efficiency"

Connected through hyperedge HE-6 (induced by source paper "secure users oriented downlink miso noma"):
  with members:
    - "exploiting inter user interference for secure massive non orthogonal multiple access"
    - "secure communications in noma system subcarrier assignment and power allocation"
    - "relay selection for cooperative noma"
    - "on the spectral efficiency and security enhancements of noma assisted multicast unicast streaming"
    - "optimal joint power and subcarrier allocation for full duplex multicarrier non orthogonal multiple access systems"
    - "on the design of secure non orthogonal multiple access systems"
    - "energy efficient transmission design in non orthogonal multiple access"
    - "physical layer security in millimeter wave cellular networks"

Connected through hyperedge HE-7 (induced by source paper "secure beamforming in miso noma backscatter device aided symbiotic radio networks"):
  with members:
    - "symbiotic radio a new communication paradigm for passive internet of things"
    - "enhancing the physical layer security of non orthogonal multiple access in large scale networks"

Connected through hyperedge HE-8 (induced by source paper "non orthogonal multiple access for 5g and beyond"):
  with members:
    - "downlink non orthogonal multiple access with limited feedback"
    - "optimal user scheduling and power allocation for millimeter wave noma systems"
    - "coordinated multi point comp transmission in downlink multi cell noma systems models and spectral efficiency performance"
    - "low complexity receiver for multi level polar coded modulation in non orthogonal multiple access"
    - "massive non orthogonal multiple access for cellular iot potentials and limitations"
    - "power domain non orthogonal multiple access noma in 5g systems potentials and challenges"
    - "modulation and multiple access for 5g networks"
    - "robust beamforming techniques for non orthogonal multiple access systems with bounded channel uncertainties"

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)