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: "performance analysis of massive mimo for cell boundary users"
  Abstract: In this paper, we consider massive multiple-input–multiple-output systems for both downlink and uplink scenarios, where three radio units connected via one digital unit support multiple user equipments at the cell-boundary through the same radio resource, i.e., the same time–frequency slot. For downlink transmitter options, the study considers zero forcing (ZF) and maximum ratio transmission (MRT), whereas for uplink receiver options, it considers ZF and maximum ratio combining (MRC). For the sum rate of each of these, we derive simple closed-form formulas. In the simple but practically relevant case where uniform power is allocated to all downlink data streams, we observe that, for the downlink, vector normalization is better for ZF whereas matrix normalization is better for MRT. For a given antenna and user configuration, we also analytically derive the signal-to-noise-ratio level below which MRC should be used instead of ZF. Numerical simulations confirm our analytical results.

Connected through hyperedge HE-1 (induced by source paper "a retrodirective wireless power transfer scheme for ambient backscatter systems"):
  with members:
    - "design of ambient backscatter training for retrodirective wireless power transfer"
    - "retrodirective large antenna energy beamforming in backscatter multi user networks"
    - "retrodirective multi user wireless power transfer with massive mimo"
    - "modulation in the air backscatter communication over ambient ofdm carrier"
    - "joint wireless information and energy transfer with reduced feedback in mimo interference channels"
    - "energy beamforming with one bit feedback"
    - "joint beamforming design for multi user wireless information and power transfer"
    - "optimized training design for wireless energy transfer"

Connected through hyperedge HE-2 (induced by source paper "design of ambient backscatter training for retrodirective wireless power transfer"):
  with members:
    - "retrodirective large antenna energy beamforming in backscatter multi user networks"
    - "retrodirective multi user wireless power transfer with massive mimo"
    - "next generation backscatter communication systems techniques and applications"
    - "ambient backscatter communications a contemporary survey"
    - "modulation in the air backscatter communication over ambient ofdm carrier"
    - "inter technology backscatter towards internet connectivity for implanted devices"
    - "communications and signals design for wireless power transmission"
    - "wireless powered communication opportunities and challenges"

Connected through hyperedge HE-3 (induced by source paper "ultrareliable and low latency communication techniques for tactile internet services"):
  with members:
    - "map based millimeter wave channel models an overview guidelines and data"
    - "multiple access for 5g new radio categorization evaluation and challenges"
    - "relationship between cross polarization discrimination xpd and spatial correlation in indoor small cell mimo systems"
    - "compact full duplex mimo radios in d2d underlaid cellular networks from system design to prototype results"
    - "rf lens embedded massive mimo systems fabrication issues and codebook design"
    - "degrees of freedom of full duplex cellular networks with reconfigurable antennas at base station"
    - "filtered ofdm enabler for flexible waveform in the 5th generation cellular networks"
    - "prototyping real time full duplex radios"

Connected through hyperedge HE-4 (induced by source paper "channel shortening by large multiantenna precoding in ofdm"):
  with members:
    - "time frequency selective mimo precoding for ofdm with insufficient cp"
    - "ofdm without cp in massive mimo"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-5 (induced by source paper "5g massive mimo architectures self backhauled small cells versus direct access"):
  with members:
    - "performance analysis for practical unmanned aerial vehicle networks with los nlos transmissions"
    - "performance of massive mimo self backhauling for ultra dense small cell deployments"
    - "performance of dynamic and static tdd in self backhauled millimeter wave cellular networks"
    - "uplink sounding reference signal coordination to combat pilot contamination in 5g massive mimo"
    - "joint backhaul access analysis of full duplex self backhauling heterogeneous networks"
    - "analysis of massive mimo enabled downlink wireless backhauling for full duplex small cells"
    - "the new frontier in ran heterogeneity multi tier drone cells"
    - "performance impact of los and nlos transmissions in dense cellular networks"

Connected through hyperedge HE-6 (induced by source paper "dft based hybrid beamforming multiuser systems rate analysis and beam selection"):
  with members:
    - "performance analysis of mixed adc massive mimo systems over rician fading channels"
    - "hybrid analog digital precoding revisited under realistic rf modeling"
    - "on the number of rf chains and phase shifters and scheduling design with hybrid analog digital beamforming"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "uplink achievable rate for massive mimo systems with low resolution adc"
    - "millimeter wave mimo with lens antenna array a new path division multiplexing paradigm"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"

Connected through hyperedge HE-7 (induced by source paper "location aided pilot contamination avoidance for massive mimo systems"):
  with members:
    - "massive mimo has unlimited capacity"
    - "mitigating pilot contamination through location aware pilot assignment in massive mimo networks"
    - "spatially common sparsity based adaptive channel estimation and feedback for fdd massive mimo"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "smart pilot assignment for massive mimo"
    - "massive mimo for next generation wireless systems"
    - "optimizing multi cell massive mimo for spectral efficiency how many users should be scheduled"
    - "blind pilot decontamination"

Connected through hyperedge HE-8 (induced by source paper "retrodirective large antenna energy beamforming in backscatter multi user networks"):
  with members:
    - "retrodirective multi user wireless power transfer with massive mimo"
    - "some new research trends in wirelessly powered communications"
    - "communications and signals design for wireless power transmission"
    - "on the efficiency of far field wireless power transfer"
    - "multi antenna wireless energy transfer for backscatter communication systems"
    - "energy beamforming with one bit feedback"
    - "optimized training design for wireless energy transfer"
    - "mimo broadcasting for simultaneous wireless information and power transfer"

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)