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: "broadbeam for massive mimo systems"
  Abstract: Massive MIMO has been identified as one of the promising disruptive air interface techniques to address the huge capacity requirement of 5G wireless communications. For practical deployment of such systems, the control message needs to be broadcast to all users reliably in the cell using broadbeam. A perfect broadbeam is expected to have the same radiated power in all directions to cover users in any place in a cell. In this paper, we will show that there is no non-trivial solution for perfect broadbeam. Therefore, we develop a method for generating broadbeam that can allow tiny fluctuation in radiated power. Overall, this can serve as an ingredient for practical deployment of the massive MIMO systems.

Connected through hyperedge HE-1 (induced by source paper "performance of in band transmission of system information in massive mimo systems"):
  with members:
    - "optimal pilot and payload power control in single cell massive mimo systems"
    - "joint beamforming and broadcasting in massive mimo"
    - "omnidirectional space time block coding for common information broadcasting in massive mimo systems"
    - "massive mimo ten myths and one critical question"
    - "hybrid beamforming for massive mimo a survey"
    - "massive mimo performance evaluation based on measured propagation data"
    - "massive mimo multicasting in noncooperative cellular networks"

Connected through hyperedge HE-2 (induced by source paper "energy efficient beamforming for massive mimo public channel"):
  with members:
    - "performance analysis of mixed adc massive mimo systems over rician fading channels"
    - "joint beamforming and broadcasting in massive mimo"
    - "on the spectral efficiency of massive mimo systems with low resolution adcs"
    - "omnidirectional space time block coding for common information broadcasting in massive mimo systems"
    - "transmit radiation pattern invariance in mimo radar with application to doa estimation"
    - "spatially sparse precoding in millimeter wave mimo systems"

Connected through hyperedge HE-3 (induced by source paper "power efficient hybrid beamforming for massive mimo public channel"):
  with members:
    - "performance analysis of mixed adc massive mimo systems over rician fading channels"
    - "joint beamforming and broadcasting in massive mimo"
    - "omnidirectional space time block coding for common information broadcasting in massive mimo systems"
    - "transmit radiation pattern invariance in mimo radar with application to doa estimation"
    - "spatially sparse precoding in 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)