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: "energy efficient optimization for physical layer security in multi antenna downlink networks with qos guarantee"
  Abstract: In this letter, we consider a multi-antenna downlink network where a secure user (SU) coexists with a passive eavesdropper. There are two design requirements for such a network. First, the information should be transferred in a secret and efficient manner. Second, the quality of service (QoS), i.e. delay sensitivity, should be take into consideration to satisfy the demands of real-time wireless services. In order to fulfill the two requirements, we combine the physical layer security technique based on switched beam beamforming with an energy-efficient power allocation. The problem is formulated as the maximization of the secrecy energy efficiency subject to delay and power constraints. By solving the optimization problem, we derive an energy-efficient power allocation scheme. Numerical results validate the effectiveness of the proposed scheme.

Connected through hyperedge HE-1 (induced by source paper "enabling security and high energy efficiency in the internet of things with massive mimo hybrid precoding"):
  with members:
    - "joint optimization of computation and communication power in multi user massive mimo systems"
    - "secure massive mimo systems with limited rf chains"
    - "energy efficiency optimization of 5g radio frequency chain systems"
    - "physical layer security in heterogeneous cellular networks"
    - "large scale mimo relaying techniques for physical layer security af or df"
    - "jamming aided secure communication in massive mimo rician channels"
    - "on the secrecy outage capacity of physical layer security in large scale mimo relaying systems with imperfect csi"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"

Connected through hyperedge HE-2 (induced by source paper "physical layer service integration in 5g potentials and challenges"):
  with members:
    - "fundamental green tradeoffs progresses challenges and impacts on 5g networks"
    - "an overview of sustainable green 5g networks"
    - "gsvd based precoding in mimo systems with integrated services"
    - "robust artificial noise aided transmit design for multi user miso systems with integrated services"
    - "wireless powered communication opportunities and challenges"
    - "multi antenna relay aided wireless physical layer security"
    - "enhancing wireless information and power transfer by exploiting multi antenna techniques"
    - "simultaneous wireless information and power transfer in modern communication systems"

Connected through hyperedge HE-3 (induced by source paper "secrecy energy efficiency of mimome wiretap channels with full duplex jamming"):
  with members:
    - "multi tenant c ran with spectrum pooling downlink optimization under privacy constraints"
    - "exploiting full duplex receivers for achieving secret communications in multiuser miso networks"
    - "softnull many antenna full duplex wireless via digital beamforming"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"
    - "hardware impairments aware transceiver for full duplex massive mimo relaying"
    - "multi objective optimization for robust power efficient and secure full duplex wireless communication systems"
    - "joint design of optimal cooperative jamming and power allocation for linear precoding"
    - "robust beamforming for secure communication in systems with wireless information and power transfer"

Connected through hyperedge HE-4 (induced by source paper "physical layer security in wireless ad hoc networks under a hybrid full half duplex receiver deployment strategy"):
  with members:
    - "safeguarding decentralized wireless networks using full duplex jamming receivers"
    - "optimal power allocation for artificial noise under imperfect csi against spatially random eavesdroppers"
    - "physical layer security in millimeter wave cellular networks"
    - "physical layer security in heterogeneous cellular networks"
    - "hybrid full half duplex system analysis in heterogeneous wireless networks"
    - "improving physical layer secrecy using full duplex jamming receivers"
    - "enhancing secrecy with multi antenna transmission in wireless ad hoc networks"
    - "on the throughput cost of physical layer security in decentralized wireless networks"

Connected through hyperedge HE-5 (induced by source paper "secure transmission of delay sensitive data over wireless fading channels"):
  with members:
    - "secure communications in the presence of a buffer aided wireless powered relay with self energy recycling"
    - "a survey on wireless security technical challenges recent advances and future trends"
    - "joint power control in wiretap interference channels"
    - "cross layer scheduling for ofdma based cognitive radio systems with delay and security constraints"
    - "opportunistic secrecy with a strict delay constraint"
    - "secure wireless communication and optimal power control under statistical queueing constraints"
    - "secure communication in the low snr regime"
    - "analysis of energy efficiency in fading channels under qos constraints"

Connected through hyperedge HE-6 (induced by source paper "secrecy energy efficient robust beamforming in wireless networks of information and energy transfer"):
  with members:
    - "waveform design for wireless power transfer"
    - "path following algorithms for beamforming and signal splitting in rf energy harvesting networks"
    - "wireless information and power transfer nonlinearity waveform design and rate energy tradeoff"
    - "communications and signals design for wireless power transmission"
    - "cooperative non orthogonal multiple access with simultaneous wireless information and power transfer"
    - "simultaneous wireless information and power transfer in modern communication systems"
    - "wireless networks with rf energy harvesting a contemporary survey"
    - "power allocation strategies in energy harvesting wireless cooperative networks"

Connected through hyperedge HE-7 (induced by source paper "joint power and subcarrier allocation for multicarrier full duplex systems"):
  with members:
    - "power efficient resource allocation for mc noma with statistical channel state information"
    - "optimal joint power and subcarrier allocation for mc noma systems"
    - "on the spectral efficiency of massive mimo systems with low resolution adcs"
    - "robust resource allocation for full duplex cognitive radio systems"
    - "achievable rate of rician large scale mimo channels with transceiver hardware impairments"
    - "power efficient resource allocation for full duplex radio distributed antenna networks"
    - "secure massive mimo transmission with an active eavesdropper"
    - "multi objective optimization for robust power efficient and secure full duplex wireless communication systems"

Connected through hyperedge HE-8 (induced by source paper "large scale mimo relaying techniques for physical layer security af or df"):
  with members:
    - "linear precoding of data and artificial noise in secure massive mimo systems"
    - "multi antenna relay aided wireless physical layer security"
    - "robust beamforming for secure communication in systems with wireless information and power transfer"
    - "on the secrecy outage capacity of physical layer security in large scale mimo relaying systems with imperfect csi"
    - "exploiting large scale mimo techniques for physical layer security with imperfect channel state information"
    - "performance analysis for physical layer security in multi antenna downlink networks with limited csi feedback"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "optimal relay selection for physical layer security in cooperative wireless networks"

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)