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: "equalized time reversal beamforming for indoor wireless communications"
  Abstract: One of the technologies with potential to provide advanced beamforming capabilities for future indoor wireless communications is time-reversal (TR). By using the channel impulse response as a pre-filter at the transmitter, TR provides automatic spatial focusing of the signal at the receiver. In this paper we present two contributions on single-user indoor wideband TR systems. First, we provide a novel analysis of a baseband time-reversal (TR) beamforming system using two propagation models commonly used in indoor wireless communications. We derive a new closed-form approximation for the inter-symbol interference (ISI) power in such scenarios, which leads to a more accurate estimation of the probability of bit error compared to previous works. We define performance parameters for the spatial focusing and time compression properties of TR beamforming and find closed-form approximations for them. We use this parameters to compare TR performance under different propagation conditions and channel models. Second, we propose an Equalized TR (ETR) technique that mitigates the ISI of conventional TR. ETR uses a zero-forcing pre-equalizer at the transmitter in cascade configuration with the TR pre-filter. We derive theoretical performance bounds for ETR and show that it greatly enhances the BER performance of conventional TR with minimal impact to its beamforming capability. By means of numerical simulations, we verify our closed-form approximations and show that the proposed ETR technique outperforms conventional TR with respect to the BER under any SNR.

Connected through hyperedge HE-1 (induced by source paper "ofdm without cp in massive mimo"):
  with members:
    - "time reversal with post equalization for ofdm without cp in massive mimo"
    - "massive mimo in real propagation environments do all antennas contribute equally"
    - "uplink performance of time reversal mrc in massive mimo systems subject to phase noise"
    - "massive mimo with non ideal arbitrary arrays hardware scaling laws and circuit aware design"
    - "filter bank multicarrier for massive mimo"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"
    - "scaling up mimo opportunities and challenges with very large arrays"

Connected through hyperedge HE-2 (induced by source paper "interference nulling time reversal beamforming for mm wave massive mimo in multi user frequency selective indoor channels"):
  with members:
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "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"
    - "millimeter wave channel modeling and cellular capacity evaluation"
    - "five disruptive technology directions for 5g"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "joint spatial division and multiplexing for mm wave channels"

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.NI(Networking and Internet Architecture)