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: "physical layer security in mimo backscatter wireless systems"
  Abstract: Backscatter wireless communication is an emerging technique widely used in low-cost and low-power wireless systems, especially in passive radio frequency identification (RFID) systems. Recently, the requirement of high data rates, data reliability, and security drives the development of RFID systems, which motivates our investigation on the physical layer security of a multiple-input multiple-output (MIMO) RFID system. In this paper, we propose a noise-injection precoding strategy to safeguard the system security with the resource-constrained nature of the backscatter system taken into consideration. We first consider a multi-antenna RFID tag case and investigate the secrecy rate maximization (SRM) problem by jointly optimizing the energy supply power and the precoding matrix of the injected artificial noise at the RFID reader. We exploit the alternating optimization method and the sequential parametric convex approximation method, respectively, to tackle the non-convex SRM problem and show an interesting fact that the two methods are actually equivalent for our SRM problem with the convergence of a Karush–Kuhn–Tucker point. To facilitate the practical implementation for resource-constrained RFID devices, we propose a fast algorithm based on projected gradient. We also consider a single-antenna RFID tag case and develop a low-complexity algorithm, which yields the global optimal solution. Simulation results show the superiority of our proposed algorithms in terms of the secrecy rate and computational complexity.

Connected through hyperedge HE-1 (induced by source paper "wireless powered asynchronous backscatter networks with sporadic short packets performance analysis and optimization"):
  with members:
    - "modeling and analysis of cellular networks using stochastic geometry a tutorial"
    - "backscatter communications for the internet of things a stochastic geometry approach"
    - "full duplex backscatter interference networks based on time hopping spread spectrum"
    - "some new research trends in wirelessly powered communications"
    - "massive machine type communications in 5g physical and mac layer solutions"
    - "wirelessly powered backscatter communication networks modeling coverage and capacity"
    - "wireless powered communication opportunities and challenges"
    - "a stochastic geometry framework for asynchronous full duplex networks"

Connected through hyperedge HE-2 (induced by source paper "ambient backscatter communications a contemporary survey"):
  with members:
    - "cooperative ambient backscatter communications for green internet of things"
    - "pixelated vlc backscattering for self charging indoor iot devices"
    - "wirelessly powered backscatter communications waveform design and snr energy tradeoff"
    - "lora backscatter enabling the vision of ubiquitous connectivity"
    - "backscatter communications for internet of things theory and applications"
    - "ambient backscatter networking a novel paradigm to assist wireless powered communications"
    - "backscatter multiplicative multiple access systems fundamental limits and practical design"
    - "scatter radio receivers for extended range environmental sensing wsns"

Connected through hyperedge HE-3 (induced by source paper "resource allocation strategies for secure wpcn multiantenna multicasting systems"):
  with members:
    - "wireless powered communication networks an overview"
    - "optimum wirelessly powered relaying"
    - "harvest then cooperate wireless powered cooperative communications"
    - "robust beamforming for secure communication in systems with wireless information and power transfer"
    - "massive mimo multicasting in noncooperative cellular networks"
    - "wireless powered cooperative communications via a hybrid relay"
    - "user cooperation in wireless powered communication networks"
    - "secrecy wireless information and power transfer with miso beamforming"

Connected through hyperedge HE-4 (induced by source paper "beamforming and power splitting designs for an aided secure multi user mimo swipt systems"):
  with members:
    - "transceiver design to maximize the weighted sum secrecy rate in full duplex swipt systems"
    - "wireless powered communication opportunities and challenges"
    - "robust beamforming for secure communication in systems with wireless information and power transfer"
    - "secure beamforming for mimo broadcasting with wireless information and power transfer"
    - "secrecy wireless information and power transfer with miso beamforming"
    - "power efficient and secure multiuser communication systems with wireless information and power transfer"
    - "application of smart antenna technologies in simultaneous wireless information and power transfer"
    - "spatially selective artificial noise aided transmit optimization for miso multi eves secrecy rate maximization"

Connected through hyperedge HE-5 (induced by source paper "inference from randomized transmissions by many backscatter sensors"):
  with members:
    - "wirelessly powered backscatter communications waveform design and snr energy tradeoff"
    - "detection algorithms for communication systems using deep learning"
    - "ambient backscatter communications a contemporary survey"
    - "full duplex backscatter interference networks based on time hopping spread spectrum"
    - "wirelessly powered backscatter communication networks modeling coverage and capacity"
    - "multi antenna wireless energy transfer for backscatter communication systems"

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)