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: "directional beamforming for millimeter wave mimo systems"
  Abstract: The focus of this paper is on beamforming in a millimeter-wave (mmW) multi-input multi-output (MIMO) setup that has gained increasing traction in meeting the high data-rate requirements of next-generation wireless systems. For a given MIMO channel matrix, the optimality of beamforming with the dominant right-singular vector (RSV) at the transmit end and with the matched filter to the RSV at the receive end has been well-understood. When the channel matrix can be accurately captured by a physical (geometric) scattering model across multiple clusters/paths as is the case in mmW MIMO systems, we provide a physical interpretation for this optimal structure: beam steering across the different paths with appropriate power allocation and phase compensation. While such an explicit physical interpretation has not been provided hitherto, practical implementation of such a structure in a mmW system is fraught with considerable difficulties (complexity as well as cost) as it requires the use of per-antenna gain and phase control. This paper characterizes the loss in received SNR with an alternate low-complexity beamforming solution that needs only per-antenna phase control and corresponds to steering the beam to the dominant path at the transmit and receive ends. While the loss in received SNR can be arbitrarily large (theoretically), this loss is minimal in a large fraction of the channel realizations reinforcing the utility of directional beamforming as a good candidate solution for mmW MIMO systems.

Connected through hyperedge HE-1 (induced by source paper "hand and body blockage measurements with form factor user equipment at 28 ghz"):
  with members:
    - "statistical blockage modeling and robustness of beamforming in millimeter wave systems"
    - "millimeter wave mimo prototype measurements and experimental results"
    - "small scale local area and transitional millimeter wave propagation for 5g communications"
    - "rapid fading due to human blockage in pedestrian crowds at 5g millimeter wave frequencies"
    - "millimeter wave human blockage at 73 ghz with a simple double knife edge diffraction model and extension for directional antennas"
    - "beamforming tradeoffs for initial ue discovery in millimeter wave mimo systems"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "millimeter wave beamforming for wireless backhaul and access in small cell networks"

Connected through hyperedge HE-2 (induced by source paper "evolution of physical layer communications research in the post 5g era"):
  with members:
    - "statistical blockage modeling and robustness of beamforming in millimeter wave systems"
    - "deep learning coordinated beamforming for highly mobile millimeter wave systems"
    - "channel reconstruction based hybrid precoding for millimeter wave multi user mimo systems"
    - "millimeter wave mimo prototype measurements and experimental results"
    - "beamforming tradeoffs for initial ue discovery in millimeter wave mimo systems"

Connected through hyperedge HE-3 (induced by source paper "channel reconstruction based hybrid precoding for millimeter wave multi user mimo systems"):
  with members:
    - "millimeter wave mimo prototype measurements and experimental results"
    - "common codebook millimeter wave beam design designing beams for both sounding and communication with uniform planar arrays"
    - "investigation of prediction accuracy sensitivity and parameter stability of large scale propagation path loss models for 5g wireless communications"
    - "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"
    - "beamforming tradeoffs for initial ue discovery in millimeter wave mimo systems"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"

Connected through hyperedge HE-4 (induced by source paper "millimeter wave channel measurements and implications for phy layer design"):
  with members:
    - "millimeter wave mimo prototype measurements and experimental results"
    - "millimeter wave human blockage at 73 ghz with a simple double knife edge diffraction model and extension for directional antennas"
    - "investigation of prediction accuracy sensitivity and parameter stability of large scale propagation path loss models for 5g wireless communications"
    - "beamforming tradeoffs for initial ue discovery in millimeter wave mimo systems"
    - "millimeter wave cellular networks a mac layer perspective"
    - "directional cell discovery in millimeter wave cellular networks"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "five disruptive technology directions for 5g"

Connected through hyperedge HE-5 (induced by source paper "multi user millimeter wave channel estimation using generalized block omp algorithm"):
  with members:
    - "subspace estimation and decomposition for large millimeter wave mimo systems"
    - "compressed sensing based multi user millimeter wave systems how many measurements are needed"
    - "millimeter wave cellular wireless networks potentials and challenges"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "block sparse signals uncertainty relations and efficient recovery"

Connected through hyperedge HE-6 (induced by source paper "directivity beamwidth tradeoff of massive mimo uplink beamforming for high speed train communication"):
  with members:
    - "turbo like beamforming based on tabu search algorithm for millimeter wave massive mimo systems"
    - "what will 5g be"
    - "five disruptive technology directions for 5g"

Connected through hyperedge HE-7 (induced by source paper "massive mimo beam forming for high speed train communication directivity vs beamwidth"):
  with members:
    - "what will 5g be"
    - "five disruptive technology directions for 5g"

Connected through hyperedge HE-8 (induced by source paper "beamforming tradeoffs for initial ue discovery in millimeter wave mimo systems"):
  with members:
    - "millimeter wave cellular networks a mac layer perspective"
    - "directional cell discovery in millimeter wave cellular networks"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "millimeter wave cellular wireless networks potentials and challenges"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "millimeter wave channel modeling and cellular capacity evaluation"
    - "statistical beamforming on the grassmann manifold for the two user broadcast channel"
    - "five disruptive technology directions for 5g"

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)