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 with optimal power and training duration allocation"
  Abstract: We consider the uplink of massive multicell multiple-input multiple-output systems, where the base stations (BSs), equipped with massive arrays, serve simultaneously several terminals in the same frequency band. We assume that the BS estimates the channel from uplink training, and then uses the maximum ratio combining technique to detect the signals transmitted from all terminals in its own cell. We propose an optimal resource allocation scheme which jointly selects the training duration, training signal power, and data signal power in order to maximize the sum spectral efficiency, for a given total energy budget spent in a coherence interval. Numerical results verify the benefits of the optimal resource allocation scheme. Furthermore, we show that more training signal power should be used at low signal-to-noise ratio (SNRs), and vice versa at high SNRs. Interestingly, for the entire SNR regime, the optimal training duration is equal to the number of terminals.

Connected through hyperedge HE-1 (induced by source paper "spectral efficiency of mixed adc massive mimo"):
  with members:
    - "a comparison of hybrid beamforming and digital beamforming with low resolution adcs for multiple users and imperfect csi"
    - "spatial characteristics of distortion radiated from antenna arrays with transceiver nonlinearities"
    - "throughput analysis of massive mimo uplink with low resolution adcs"
    - "channel estimation and performance analysis of one bit massive mimo systems"
    - "impact of spatial filtering on distortion from low noise amplifiers in massive mimo base stations"
    - "performance analysis of mixed adc massive mimo systems over rician fading channels"
    - "uplink performance of wideband massive mimo with one bit adcs"
    - "mixed adc massive mimo"

Connected through hyperedge HE-2 (induced by source paper "hybrid processing design for multipair massive mimo relaying with channel spatial correlation"):
  with members:
    - "secure massive mimo systems with limited rf chains"
    - "spectral and energy efficiency of multi pair massive mimo relay network with hybrid processing"
    - "framework of channel estimation for hybrid analog and digital processing enabled massive mimo communications"
    - "massive mimo with imperfect channel covariance information"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "channel covariance estimation in massive mimo frequency division duplex systems"
    - "hybrid beamforming for massive mimo a survey"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"

Connected through hyperedge HE-3 (induced by source paper "channel estimation and performance analysis of one bit massive mimo systems"):
  with members:
    - "throughput analysis of massive mimo uplink with low resolution adcs"
    - "uplink performance of wideband massive mimo with one bit adcs"
    - "mixed adc massive mimo"
    - "on the spectral efficiency of massive mimo systems with low resolution adcs"
    - "channel estimation and uplink achievable rates in one bit massive mimo systems"
    - "performance of the wideband massive uplink mimo with one bit adcs"
    - "low power analog to digital conversion in millimeter wave systems impact of resolution and bandwidth on performance"
    - "one bit massive mimo channel estimation and high order modulations"

Connected through hyperedge HE-4 (induced by source paper "pilot power allocation through user grouping in multi cell massive mimo systems"):
  with members:
    - "power allocation schemes for multicell massive mimo systems"
    - "channel estimation in massive mimo systems"
    - "uplink pilot and data power control for single cell massive mimo systems with mrc"
    - "massive mimo with non ideal arbitrary arrays hardware scaling laws and circuit aware design"
    - "multipair full duplex relaying with massive arrays and linear processing"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "dealing with interference in distributed large scale mimo systems a statistical approach"
    - "massive mimo multicasting in noncooperative cellular networks"

Connected through hyperedge HE-5 (induced by source paper "on reusing pilots among interfering cells in massive mimo"):
  with members:
    - "cell free massive mimo versus small cells"
    - "no downlink pilots are needed in tdd massive mimo"
    - "interference management in 5g reverse tdd hetnets with wireless backhaul a large system analysis"
    - "a multi cell mmse precoder for massive mimo systems and new large system analysis"
    - "5g ultra dense cellular networks"
    - "when pilots should not be reused across interfering cells in massive mimo"
    - "massive mimo performance evaluation based on measured propagation data"
    - "smart pilot assignment for massive mimo"

Connected through hyperedge HE-6 (induced by source paper "optimal pilot and payload power control in single cell massive mimo systems"):
  with members:
    - "massive mimo with multi cell mmse processing exploiting all pilots for interference suppression"
    - "uplink pilot and data power control for single cell massive mimo systems with mrc"
    - "massive mimo performance evaluation based on measured propagation data"
    - "multiobjective signal processing optimization the way to balance conflicting metrics in 5g systems"
    - "joint optimization of power allocation and training duration for uplink multiuser mimo communications"
    - "optimal design of energy efficient multi user mimo systems is massive mimo the answer"
    - "massive mimo for maximal spectral efficiency how many users and pilots should be allocated"
    - "scaling up mimo opportunities and challenges with very large arrays"

Connected through hyperedge HE-7 (induced by source paper "on hybrid pilot for channel estimation in massive mimo uplink"):
  with members:
    - "superimposed pilots are superior for mitigating pilot contamination in massive mimo part i theory and channel estimation"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"
    - "blind pilot decontamination"
    - "massive mimo for maximal spectral efficiency how many users and pilots should be allocated"
    - "five disruptive technology directions for 5g"
    - "scaling up mimo opportunities and challenges with very large arrays"

Connected through hyperedge HE-8 (induced by source paper "multipair two way half duplex relaying with massive arrays and imperfect csi"):
  with members:
    - "performance analysis and scaling law of mrc mrt relaying with csi error in massive mimo systems"
    - "multipair full duplex relaying with massive arrays and linear processing"
    - "massive mimo for next generation wireless systems"
    - "multi pair amplify and forward relaying with very large antenna arrays"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "relay selection and resource allocation for two way df af cognitive radio networks"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "optimal beamforming for two way multi antenna relay channel with analogue network coding"

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)