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: "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"
  Abstract: The use of large-scale antenna arrays can bring substantial improvements in energy and/or spectral efficiency to wireless systems due to the greatly improved spatial resolution and array gain. Recent works in the field of massive multiple-input multiple-output (MIMO) show that the user channels decorrelate when the number of antennas at the base stations (BSs) increases, thus strong signal gains are achievable with little interuser interference. Since these results rely on asymptotics, it is important to investigate whether the conventional system models are reasonable in this asymptotic regime. This paper considers a new system model that incorporates general transceiver hardware impairments at both the BSs (equipped with large antenna arrays) and the single-antenna user equipments (UEs). As opposed to the conventional case of ideal hardware, we show that hardware impairments create finite ceilings on the channel estimation accuracy and on the downlink/uplink capacity of each UE. Surprisingly, the capacity is mainly limited by the hardware at the UE, while the impact of impairments in the large-scale arrays vanishes asymptotically and interuser interference (in particular, pilot contamination) becomes negligible. Furthermore, we prove that the huge degrees of freedom offered by massive MIMO can be used to reduce the transmit power and/or to tolerate larger hardware impairments, which allows for the use of inexpensive and energy-efficient antenna elements.

Connected through hyperedge HE-1 (induced by source paper "on the pilot contamination attack in multi cell multiuser massive mimo networks"):
  with members:
    - "pilot spoofing attack by multiple eavesdroppers"
    - "multiple antennas secure transmission under pilot spoofing and jamming attack"
    - "active attack on user load achieving pilot design in massive mimo networks"
    - "user load analysis and pilot sequence design for multi cell massive mimo networks"
    - "the world s first real time testbed for massive mimo design implementation and validation"
    - "multi cell multiuser massive mimo networks user capacity analysis and pilot design"
    - "massive mimo pilot retransmission strategies for robustification against jamming"
    - "subverting massive mimo by smart jamming"

Connected through hyperedge HE-2 (induced by source paper "multiple antenna technologies for beyond 5g"):
  with members:
    - "intelligent reflecting surface versus decode and forward how large surfaces are needed to beat relaying"
    - "robust trajectory and resource allocation design for secure uav aided communications"
    - "a new look at cell free massive mimo making it practical with dynamic cooperation"
    - "scalability aspects of cell free massive mimo"
    - "cascaded channel estimation for large intelligent metasurface assisted massive mimo"
    - "robust and secure wireless communications via intelligent reflecting surfaces"
    - "channel estimation for intelligent reflecting surface assisted multiuser communications framework algorithms and analysis"
    - "resource allocation for secure irs assisted multiuser miso systems"

Connected through hyperedge HE-3 (induced by source paper "hardware distortion correlation has negligible impact on ul massive mimo spectral efficiency"):
  with members:
    - "massive mimo has unlimited capacity"
    - "can hardware distortion correlation be neglected when analyzing uplink se in massive mimo"
    - "out of band radiation from antenna arrays clarified"
    - "spatial characteristics of distortion radiated from antenna arrays with transceiver nonlinearities"
    - "performance characterization of a real time massive mimo system with los mobile channels"
    - "throughput analysis of massive mimo uplink with low resolution adcs"
    - "achievable uplink rates for massive mimo with coarse quantization"
    - "impact of spatial filtering on distortion from low noise amplifiers in massive mimo base stations"

Connected through hyperedge HE-4 (induced by source paper "a regression approach to certain information transmission problems"):
  with members:
    - "learning to detect"
    - "mmwave beam prediction with situational awareness a machine learning approach"
    - "deep learning based channel estimation for beamspace mmwave massive mimo systems"
    - "one bit ofdm receivers via deep learning"
    - "deepcode feedback codes via deep learning"
    - "learning the mmse channel estimator"
    - "a model driven deep learning network for mimo detection"
    - "a two step learning and interpolation method for location based channel database"

Connected through hyperedge HE-5 (induced by source paper "transmission strategies for cell free massive mimo with limited capacity fronthaul links"):
  with members:
    - "cell free massive mimo with limited backhaul"
    - "spectral and energy efficiency of cell free massive mimo systems with hardware impairments"
    - "spectral efficiency of multipair massive mimo two way relaying with hardware impairments"
    - "on the total energy efficiency of cell free massive mimo"
    - "channel hardening and favorable propagation in cell free massive mimo with stochastic geometry"
    - "energy efficiency in cell free massive mimo with zero forcing precoding design"
    - "analysis and design of secure massive mimo systems in the presence of hardware impairments"
    - "cell free massive mimo versus small cells"

Connected through hyperedge HE-6 (induced by source paper "average sep optimal precoding for correlated massive mimo with zf detection an asymptotic analysis"):
  with members:
    - "large scale fading decoding in cellular massive mimo systems with spatially correlated channels"
    - "massive mimo has unlimited capacity"
    - "performance analysis for massive mimo downlink with low complexity approximate zero forcing precoding"
    - "joint pilot design and uplink power allocation in multi cell massive mimo systems"
    - "the world s first real time testbed for massive mimo design implementation and validation"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-7 (induced by source paper "channel estimation in massive mimo under hardware non linearities bayesian methods versus deep learning"):
  with members:
    - "max min rate of cell free massive mimo uplink with optimal uniform quantization"
    - "hardware distortion correlation has negligible impact on ul massive mimo spectral efficiency"
    - "massive mu mimo ofdm uplink with hardware impairments modeling and analysis"
    - "learning the mmse channel estimator"
    - "an introduction to deep learning for the physical layer"
    - "throughput analysis of massive mimo uplink with low resolution adcs"
    - "impact of spatial filtering on distortion from low noise amplifiers in massive mimo base stations"
    - "rate splitting to mitigate residual transceiver hardware impairments in massive mimo systems"

Connected through hyperedge HE-8 (induced by source paper "intelligent reflecting surface irs enabled covert communications in wireless networks"):
  with members:
    - "multi antenna covert communications in random wireless networks"
    - "enabling secure wireless communications via intelligent reflecting surfaces"
    - "beyond massive mimo the potential of data transmission with large intelligent surfaces"
    - "on covert communication with noise uncertainty"
    - "what will 5g be"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "limits of reliable communication with low probability of detection on awgn channels"

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)