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: "a new look at physical layer security caching and wireless energy harvesting for heterogeneous ultra dense networks"
  Abstract: Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low latency through the use of dense sub-6 GHz and millimeter wave (mmWave) small cells with different antenna configurations. Existing work has widely studied spectral and energy efficiency in such networks and shown that high spectral and energy efficiency can be achieved. This article investigates the benefits of heterogeneous ultra-dense network architecture from the perspectives of three promising technologies, i.e., physical layer security, caching, and wireless energy harvesting, and provides enthusiastic outlook towards application of these technologies in heterogeneous ultra-dense networks. Based on the rationale of each technology, opportunities and challenges are identified to advance the research in this emerging network.

Connected through hyperedge HE-1 (induced by source paper "secrecy outage analysis of non orthogonal spectrum sharing for heterogeneous cellular networks"):
  with members:
    - "security reliability tradeoff for distributed antenna systems in heterogeneous cellular networks"
    - "intelligent interference exploitation for heterogeneous cellular networks against eavesdropping"
    - "power domain non orthogonal multiple access noma in 5g systems potentials and challenges"
    - "physical layer security for spectrum sharing systems"
    - "artificial noise aided secure transmission in large scale spectrum sharing networks"
    - "location based beamforming and physical layer security in rician wiretap channels"
    - "physical layer security in millimeter wave cellular networks"
    - "a survey on wireless security technical challenges recent advances and future trends"

Connected through hyperedge HE-2 (induced by source paper "energy harvesting in 5g networks taxonomy requirements challenges and future directions"):
  with members:
    - "spectral and energy efficient wireless powered iot networks noma or tdma"
    - "joint power allocation and beamforming for non orthogonal multiple access noma in 5g millimeter wave communications"

Connected through hyperedge HE-3 (induced by source paper "content placement in cache enabled sub 6 ghz and millimeter wave multi antenna dense small cell networks"):
  with members:
    - "random caching based cooperative transmission in heterogeneous wireless networks"
    - "modeling and analyzing millimeter wave cellular systems"
    - "caching meets millimeter wave communications for enhanced mobility management in 5g networks"
    - "caching policy toward maximal success probability and area spectral efficiency of cache enabled hetnets"
    - "a tractable framework for performance analysis of dense multi antenna networks"
    - "antenna count for massive mimo 1 9 ghz versus 60 ghz"
    - "on optimal geographical caching in heterogeneous cellular networks"
    - "modeling and analysis for cache enabled networks with dynamic traffic"

Connected through hyperedge HE-4 (induced by source paper "single or multiple frames content delivery for robust and secure communication in energy and spectrum efficient 5g networks"):
  with members:
    - "cost effective cache deployment in mobile heterogeneous networks"
    - "fairness and transmission aware caching and delivery policies in ofdma based hetnets"
    - "limited feedback scheme for device to device communications in 5g cellular networks with reliability and cellular secrecy outage constraints"
    - "joint backhaul access analysis of full duplex self backhauling heterogeneous networks"
    - "green ofdma resource allocation in cache enabled cran"
    - "joint hybrid backhaul and access links design in cloud radio access networks"
    - "exploiting device to device communications in joint scheduling of access and backhaul for mmwave small cells"
    - "uplink contention based scma for 5g radio access"

Connected through hyperedge HE-5 (induced by source paper "safeguarding millimeter wave communications against randomly located eavesdroppers"):
  with members:
    - "physical layer security in millimeter wave cellular networks"
    - "physical layer security in heterogeneous cellular networks"
    - "secure communications in millimeter wave ad hoc networks"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "tractable model for rate in self backhauled millimeter wave cellular networks"
    - "millimeter wave cellular wireless networks potentials and challenges"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "enhancing secrecy with multi antenna transmission in wireless ad hoc networks"

Connected through hyperedge HE-6 (induced by source paper "edge caching in dense heterogeneous cellular networks with massive mimo aided self backhaul"):
  with members:
    - "random caching based cooperative transmission in heterogeneous wireless networks"
    - "how much cache is needed to achieve linear capacity scaling in backhaul limited dense wireless networks"
    - "fog radio access networks mobility management interference mitigation and resource optimization"
    - "stochastic content centric multicast scheduling for cache enabled heterogeneous cellular networks"
    - "cache size allocation in backhaul limited wireless networks"
    - "wireless device to device caching networks basic principles and system performance"
    - "wireless caching technical misconceptions and business barriers"
    - "user association in 5g networks a survey and an outlook"

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.NI(Networking and Internet Architecture)