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 real time millimeter wave phased array mimo channel sounder"
  Abstract: In this paper, we present a novel real-time MIMO channel sounder for 28 GHz. Until now, the common practice to investigate the directional characteristics of millimeter-wave channels has been using a rotating horn antenna. The sounder presented here is capable of performing horizontal and vertical beam steering with the help of phased arrays. Thanks to fast beam-switching capability, the proposed sounder can perform measurements that are directionally resolved both at the transmitter (TX) and receiver (RX) as fast as 1.44 milliseconds compared to the minutes or even hours required for rotating horn antenna sounders. This does not only enable us to measure more points for better statistical inference but also allows to perform directional analysis in dynamic environments. Equally importantly, the short measurement time combined with the high phase stability of our setup limits the phase drift between TX and RX, enabling phase-coherent sounding of all beam pairs even when TX and RX are physically separated and have no cabled connection for synchronization. This ensures that the measurement data is suitable for high-resolution parameter extraction algorithms. Along with the system design and specifications, this paper also discusses the measurements performed for verification of the sounder. Furthermore, we present sample measurements from a channel sounding campaign performed on a residential street.

Connected through hyperedge HE-1 (induced by source paper "enable super resolution parameter estimation for mm wave channel sounding"):
  with members:
    - "on channel sounding with switched arrays in fast time varying channels"
    - "what will 5g be"
    - "millimeter wave channel modeling and cellular capacity evaluation"

Connected through hyperedge HE-2 (induced by source paper "optimal discrete spatial compression for beamspace massive mimo signals"):
  with members:
    - "branch and bound precoding for multiuser mimo systems with 1 bit quantization"
    - "spatio temporal waveform design for multiuser massive mimo downlink with 1 bit receivers"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "cost effective millimeter wave communications with lens antenna array"
    - "fronthaul compression and transmit beamforming optimization for multi antenna uplink c ran"
    - "quantized precoding for massive mu mimo"
    - "hybrid beamforming for massive mimo a survey"
    - "capacity analysis of one bit quantized mimo systems with transmitter channel state information"

Connected through hyperedge HE-3 (induced by source paper "joint user scheduling and beam selection optimization for beam based massive mimo downlinks"):
  with members:
    - "bdma for millimeter wave terahertz massive mimo transmission with per beam synchronization"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "hybrid beamforming for massive mimo a survey"
    - "achievable rates of fdd massive mimo systems with spatial channel correlation"
    - "dynamic channel acquisition in mu mimo"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "massive mimo for next generation wireless systems"
    - "spatially sparse precoding in millimeter wave mimo systems"

Connected through hyperedge HE-4 (induced by source paper "28 ghz microcell measurement campaign for residential environment"):
  with members:
    - "what will 5g be"
    - "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)