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 approach to user scheduling in massive multi user mimo broadcast channels"
  Abstract: In this paper, a new user-scheduling-and-beamforming method is proposed for multi-user massive multiple-input multiple-output (massive MIMO) broadcast channels in the context of two-stage beamforming. The key ideas of the proposed scheduling method are 1) to use a set of orthogonal reference beams and construct a double cone around each reference beam to select `nearly-optimal' semi-orthogonal users based only on channel quality indicator (CQI) feedback and 2) to apply post-user-selection beam refinement with zero-forcing beamforming (ZFBF) based on channel state information (CSI) feedback only from the selected users. It is proved that the proposed scheduling-and-beamforming method is asymptotically optimal as the number of users increases. Furthermore, the proposed scheduling-and-beamforming method almost achieves the performance of the existing semi-orthogonal user selection with ZFBF (SUS-ZFBF) that requires full CSI feedback from all users, with significantly reduced feedback overhead which is even less than that required by random beamforming.

Connected through hyperedge HE-1 (induced by source paper "hybrid beamforming noma for mmwave communications"):
  with members:
    - "a new reconfigurable antenna mimo architecture for mmwave communication"
    - "multi beam noma for hybrid mmwave systems"
    - "reconfigurable antenna multiple access for 5g mmwave systems"
    - "non orthogonal multiple access based on hybrid beamforming for mmwave systems"
    - "non orthogonal multiple access common myths and critical questions"
    - "exploiting multiple antenna techniques for non orthogonal multiple access"
    - "modeling and analyzing millimeter wave cellular systems"
    - "energy efficient power allocation in millimeter wave massive mimo with non orthogonal multiple access"

Connected through hyperedge HE-2 (induced by source paper "security reliability tradeoff for distributed antenna systems in heterogeneous cellular networks"):
  with members:
    - "game based approach for qos provisioning and interference management in heterogeneous networks"
    - "intelligent interference exploitation for heterogeneous cellular networks against eavesdropping"
    - "energy efficiency analysis of heterogeneous cellular networks with extra cell range expansion"
    - "secrecy optimized resource allocation for device to device communication underlaying heterogeneous networks"
    - "safeguarding decentralized wireless networks using full duplex jamming receivers"
    - "optimal beamforming for gaussian mimo wiretap channels with two transmit antennas"
    - "relay selection for wireless communications against eavesdropping a security reliability trade off perspective"
    - "a survey on wireless security technical challenges recent advances and future trends"

Connected through hyperedge HE-3 (induced by source paper "impact of beam misalignment on hybrid beamforming noma for mmwave communications"):
  with members:
    - "a new reconfigurable antenna mimo architecture for mmwave communication"
    - "reconfigurable antenna multiple access for 5g mmwave systems"
    - "a multi beam noma framework for hybrid mmwave systems"
    - "non orthogonal multiple access based on hybrid beamforming for mmwave systems"
    - "exploiting multiple antenna techniques for non orthogonal multiple access"
    - "modeling and analyzing millimeter wave cellular systems"
    - "energy efficient power allocation in millimeter wave massive mimo with non orthogonal multiple access"
    - "joint power allocation and beamforming for non orthogonal multiple access noma in 5g millimeter wave communications"

Connected through hyperedge HE-4 (induced by source paper "a high diversity transceiver design for k user miso broadcast channels"):
  with members:
    - "beam design and user scheduling for nonorthogonal multiple access with multiple antennas based on pareto optimality"
    - "rate splitting multiple access for downlink communication systems bridging generalizing and outperforming sdma and noma"
    - "a generalized zero forcing precoder with successive dirty paper coding in miso broadcast channels"
    - "a minorization maximization method for optimizing sum rate in the downlink of non orthogonal multiple access systems"
    - "non orthogonal multiple access noma for downlink multiuser mimo systems user clustering beamforming and power allocation"
    - "the application of mimo to non orthogonal multiple access"
    - "transmit optimization with improper gaussian signaling for interference channels"
    - "network mimo with linear zero forcing beamforming large system analysis impact of channel estimation and reduced complexity scheduling"

Connected through hyperedge HE-5 (induced by source paper "an overview on resource allocation techniques for multi user mimo systems"):
  with members:
    - "low complexity downlink user selection for massive mimo systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "user association in 5g networks a survey and an outlook"
    - "cell free massive mimo versus small cells"
    - "mu mimo mac protocols for wireless local area networks a survey"
    - "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"

Connected through hyperedge HE-6 (induced by source paper "robust geometry based user scheduling for large mimo systems under realistic channel conditions"):
  with members:
    - "cell free massive mimo with limited backhaul"
    - "enhanced max min sinr for uplink cell free massive mimo systems"
    - "cell free massive mimo versus small cells"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-7 (induced by source paper "two stage beamformer design for massive mimo downlink by trace quotient formulation"):
  with members:
    - "pilot signal design for massive mimo systems a received signal to noise ratio based approach"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "training sequence design for feedback assisted hybrid beamforming in massive mimo systems"
    - "two tier precoding for fdd multi cell massive mimo time varying interference networks"
    - "downlink training techniques for fdd massive mimo systems open loop and closed loop training with memory"
    - "coordinated beamforming with relaxed zero forcing the sequential orthogonal projection combining method and rate control"
    - "scaling up mimo opportunities and challenges with very large arrays"

Connected through hyperedge HE-8 (induced by source paper "training sequence design for feedback assisted hybrid beamforming in massive mimo systems"):
  with members:
    - "pilot signal design for massive mimo systems a received signal to noise ratio based approach"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "distributed compressive csit estimation and feedback for fdd multi user massive mimo systems"
    - "downlink training techniques for fdd massive mimo systems open loop and closed loop training with memory"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "noncoherent trellis coded quantization a practical limited feedback technique for massive mimo systems"
    - "joint spatial division and multiplexing opportunistic beamforming and user grouping"
    - "scaling up mimo opportunities and challenges with very large arrays"

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)