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: "wireless physical layer security with imperfect channel state information a survey"
  Abstract: Physical layer security is an emerging technique to improve the wireless communication security, which is widely regarded as a complement to cryptographic technologies. To design physical layer security techniques under practical scenarios, the uncertainty and imperfections in the channel knowledge need to be taken into consideration. This paper provides a survey of recent research and development in physical layer security considering the imperfect channel state information (CSI) at communication nodes. We first present an overview of the main information-theoretic measures of the secrecy performance with imperfect CSI. Then, we describe several signal processing enhancements in secure transmission designs, such as secure on-off transmission, beamforming with artificial noise, and secure communication assisted by relay nodes or in cognitive radio systems. The recent studies of physical layer security in large-scale decentralized wireless networks are also summarized. Finally, the open problems for the on-going and future research are discussed.

Connected through hyperedge HE-1 (induced by source paper "blind channel separation in massive mimo system under pilot spoofing and jamming attack"):
  with members:
    - "jamming resistant receivers for the massive mimo uplink"
    - "physical layer security for massive mimo an overview on passive eavesdropping and active attacks"

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 "boundaries as an enhancement technique for physical layer security"):
  with members:
    - "temporal correlation of interference and outage in mobile networks over one dimensional finite regions"
    - "stochastic geometry based comparison of secrecy enhancement techniques in d2d networks"
    - "temporal correlation of interference in bounded mobile ad hoc networks with blockage"
    - "distribution of cell size in bounded voronoi tesselations with application to secure local connectivity"
    - "device to device millimeter wave communications interference coverage rate and finite topologies"
    - "physical layer security in heterogeneous cellular networks"
    - "physical layer security in three tier wireless sensor networks a stochastic geometry approach"
    - "analyzing the impact of access point density on the performance of finite area networks"

Connected through hyperedge HE-4 (induced by source paper "boundaries can enhance physical layer security at high data rates"):
  with members:
    - "temporal correlation of interference and outage in mobile networks over one dimensional finite regions"
    - "physical layer security in wireless ad hoc networks under a hybrid full half duplex receiver deployment strategy"
    - "stochastic geometry based comparison of secrecy enhancement techniques in d2d networks"
    - "temporal correlation of interference in bounded mobile ad hoc networks with blockage"
    - "physical layer security in heterogeneous cellular networks"
    - "physical layer security in three tier wireless sensor networks a stochastic geometry approach"
    - "improving physical layer security in wireless communications using diversity techniques"
    - "analyzing the impact of access point density on the performance of finite area networks"

Connected through hyperedge HE-5 (induced by source paper "artificial noise aided biobjective transmitter optimization for service integration in multi user mimo broadcast channel"):
  with members:
    - "gsvd based precoding in mimo systems with integrated services"
    - "robust artificial noise aided transmit design for multi user miso systems with integrated services"
    - "what will 5g be"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "physical layer multicasting by stochastic transmit beamforming and alamouti space time coding"
    - "spatially selective artificial noise aided transmit optimization for miso multi eves secrecy rate maximization"
    - "new results on multiple input multiple output broadcast channels with confidential messages"
    - "precoder design for physical layer multicasting"

Connected through hyperedge HE-6 (induced by source paper "securing wireless communications of the internet of things from the physical layer an overview"):
  with members:
    - "a survey on wireless security technical challenges recent advances and future trends"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "robust beamforming for security in mimo wiretap channels with imperfect csi"
    - "fuzzy extractors how to generate strong keys from biometrics and other noisy data"

Connected through hyperedge HE-7 (induced by source paper "robust artificial noise aided transmit design for multi user miso systems with integrated services"):
  with members:
    - "safeguarding decentralized wireless networks using full duplex jamming receivers"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "physical layer multicasting by stochastic transmit beamforming and alamouti space time coding"
    - "outage constrained robust secure transmission for miso wiretap channels"
    - "new results on multiple input multiple output broadcast channels with confidential messages"
    - "precoder design for physical layer multicasting"
    - "robust secure transmission in miso channels based on worst case optimization"
    - "optimal and robust transmit designs for miso channel secrecy by semidefinite programming"

Connected through hyperedge HE-8 (induced by source paper "on secrecy metrics for physical layer security over quasi static fading channels"):
  with members:
    - "performance assessment and design of finite length ldpc codes for the gaussian wiretap channel"
    - "rethinking the intercept probability of random linear network coding"
    - "probability estimates for fading and wiretap channels from ideal class zeta functions"
    - "secure on off transmission design with channel estimation errors"
    - "coding with scrambling concatenation and harq for the awgn wire tap channel a security gap analysis"
    - "secret sharing ldpc codes for the bpsk constrained gaussian wiretap channel"
    - "ldpc code design for the bpsk constrained gaussian wiretap channel"
    - "rethinking the secrecy outage formulation a secure transmission design perspective"

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)