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: "low complexity hybrid precoding in massive multiuser mimo systems"
  Abstract: Massive multiple-input multiple-output (MIMO) is envisioned to offer considerable capacity improvement, but at the cost of high complexity of the hardware. In this paper, we propose a low-complexity hybrid precoding scheme to approach the performance of the traditional baseband zero-forcing (ZF) precoding (referred to as full-complexity ZF), which is considered a virtually optimal linear precoding scheme in massive MIMO systems. The proposed hybrid precoding scheme, named phased-ZF (PZF), essentially applies phase-only control at the RF domain and then performs a low-dimensional baseband ZF precoding based on the effective channel seen from baseband. Heavily quantized RF phase control up to 2 bits of precision is also considered and shown to incur very limited degradation. The proposed scheme is simulated in both ideal Rayleigh fading channels and sparsely scattered millimeter wave (mmWave) channels, both achieving highly desirable performance.

Connected through hyperedge HE-1 (induced by source paper "energy efficient hybrid precoding design for integrated multicast unicast millimeter wave communications with swipt"):
  with members:
    - "hybrid precoding based millimeter wave massive mimo noma with simultaneous wireless information and power transfer"
    - "joint optimization of computation and communication power in multi user massive mimo systems"
    - "energy efficient transceiver design for hybrid sub array architecture mimo systems"
    - "energy efficient power allocation in millimeter wave massive mimo with non orthogonal multiple access"
    - "joint base station clustering and beamforming for non orthogonal multicast and unicast transmission with backhaul constraints"
    - "joint beamforming and broadcasting in massive mimo"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "on the spectral efficiency and security enhancements of noma assisted multicast unicast streaming"

Connected through hyperedge HE-2 (induced by source paper "massive mimo asymptotics for ray based propagation channels"):
  with members:
    - "mimo channel hardening a physical model based analysis"
    - "channel hardening in massive mimo a measurement based analysis"
    - "energy efficiency and asymptotic performance evaluation of beamforming structures in doubly massive mimo mmwave systems"
    - "a random access protocol for pilot allocation in crowded massive mimo systems"
    - "uplink analysis of large mu mimo systems with space constrained arrays in ricean fading"
    - "no downlink pilots are needed in tdd massive mimo"
    - "massive mimo ten myths and one critical question"
    - "asymptotic orthogonality analysis of time domain sparse massive mimo channels"

Connected through hyperedge HE-3 (induced by source paper "hybrid combining based on constant phase shifters and active inactive switches"):
  with members:
    - "resolution adaptive hybrid mimo architectures for millimeter wave communications"
    - "are mmwave low complexity beamforming structures energy efficient analysis of the downlink mu mimo"
    - "millimeter wave receiver efficiency a comprehensive comparison of beamforming schemes with low resolution adcs"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "massive mimo combining with switches"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-4 (induced by source paper "channel estimation and hybrid beamforming for reconfigurable intelligent surfaces assisted thz communications"):
  with members:
    - "secure wireless communication via intelligent reflecting surface"
    - "capacity characterization for intelligent reflecting surface aided mimo communication"
    - "intelligent reflecting surface meets ofdm protocol design and rate maximization"
    - "intelligent reflecting surface design for mimo system by maximizing sum path gains"
    - "channel estimation and transmission for intelligent reflecting surface assisted thz communications"
    - "energy efficient multi user miso communication using low resolution large intelligent surfaces"
    - "achievable rate maximization by passive intelligent mirrors"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"

Connected through hyperedge HE-5 (induced by source paper "robustness of low complexity massive mimo architectures against passive eavesdropping"):
  with members:
    - "papr limited precoding in massive mimo systems with reflect and transmit array antennas"
    - "on robustness of massive mimo systems against passive eavesdropping under antenna selection"
    - "glse precoders for massive mimo systems analysis and applications"
    - "stepwise transmit antenna selection in downlink massive multiuser mimo"
    - "scalable and energy efficient millimeter massive mimo architectures reflect array and transmit array antennas"
    - "optimal transmit antenna selection for massive mimo wiretap channels"
    - "asymptotics of nonlinear lse precoders with applications to transmit antenna selection"
    - "asymptotics of transmit antenna selection impact of multiple receive antennas"

Connected through hyperedge HE-6 (induced by source paper "channel estimation and hybrid precoding for distributed phased arrays based mimo wireless communications"):
  with members:
    - "modeling and analyzing millimeter wave cellular systems"
    - "framework of channel estimation for hybrid analog and digital processing enabled massive mimo communications"
    - "5g cellular user equipment from theory to practical hardware design"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "codebook design for millimeter wave channel estimation with hybrid precoding structure"
    - "the world s first real time testbed for massive mimo design implementation and validation"
    - "an overview of transmission theory and techniques of large scale antenna systems for 5g wireless communications"

Connected through hyperedge HE-7 (induced by source paper "two stage analog combining in hybrid beamforming systems with low resolution adcs"):
  with members:
    - "a comparison of hybrid beamforming and digital beamforming with low resolution adcs for multiple users and imperfect csi"
    - "user scheduling for millimeter wave hybrid beamforming systems with low resolution adcs"
    - "resolution adaptive hybrid mimo architectures for millimeter wave communications"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "hybrid architectures with few bit adc receivers achievable rates and energy rate tradeoffs"
    - "millimeter wave receiver efficiency a comprehensive comparison of beamforming schemes with low resolution adcs"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "low power analog to digital conversion in millimeter wave systems impact of resolution and bandwidth on performance"

Connected through hyperedge HE-8 (induced by source paper "joint design of fronthauling and hybrid beamforming for downlink c ran systems"):
  with members:
    - "channel diagonalization for cloud radio access"
    - "stochastic successive convex optimization for two timescale hybrid precoding in massive mimo"
    - "energy efficiency maximization for c rans discrete monotonic optimization penalty and ell _ 0 approximation methods"
    - "hybrid analog digital beamforming for massive mimo systems"
    - "multi user precoding and channel estimation for hybrid millimeter wave systems"
    - "hybrid precoding for massive mimo systems in cloud ran architecture with capacity limited fronthauls"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "subspace estimation and decomposition for large millimeter wave mimo systems"

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)