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: "low complexity cfo estimation for multi user massive mimo systems"
  Abstract: Low-complexity carrier frequency offset (CFO) estimation and compensation in multi-user massive multiple-input multiple-output (MIMO) systems is a challenging problem. The existing CFO estimation algorithms incur tremendous increase in complexity with increasing number of base station (BS) antennas, $M$ and number of user terminals (UTs) $K$ (i.e. massive MIMO regime). In this paper, we address this problem by proposing a novel low-complexity algorithm for CFO estimation which uses the pilot signal received at the BS during special uplink slots. The total per-channel use complexity of the proposed algorithm increases only linearly with increasing $M$ and is independent of $K$. Analysis reveals that the CFO estimation accuracy can be considerably improved by increasing $M$ and $K$ (i.e. massive MIMO regime). For example, for a fixed $K$ and a fixed training length, the required per-user radiated power during uplink training decreases as $\frac{1}{\sqrt{M}}$ with increasing $M$.

Connected through hyperedge HE-1 (induced by source paper "frequency synchronization for uplink massive mimo systems"):
  with members:
    - "constant envelope pilot based low complexity cfo estimation in massive mu mimo systems"
    - "impact of cfo estimation on the performance of zf receiver in massive mu mimo systems"
    - "impact of frequency selectivity on the information rate performance of cfo impaired single carrier massive mu mimo uplink"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "massive mimo for next generation wireless systems"
    - "downlink training techniques for fdd massive mimo systems open loop and closed loop training with memory"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"

Connected through hyperedge HE-2 (induced by source paper "information theoretic performance of periodogram based cfo estimation in massive mu mimo systems"):
  with members:
    - "constant envelope pilot based low complexity cfo estimation in massive mu mimo systems"
    - "impact of cfo estimation on the performance of zf receiver in massive mu mimo systems"
    - "impact of frequency selectivity on the information rate performance of cfo impaired single carrier massive mu mimo uplink"
    - "uplink performance of time reversal mrc in massive mimo systems subject to phase noise"
    - "what will 5g be"
    - "five disruptive technology directions for 5g"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-3 (induced by source paper "impact of cfo estimation on the performance of zf receiver in massive mu mimo systems"):
  with members:
    - "uplink performance of time reversal mrc in massive mimo systems subject to phase noise"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"
    - "five disruptive technology directions for 5g"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "blind estimation of multiple carrier frequency offsets"

Connected through hyperedge HE-4 (induced by source paper "constant envelope pilot based low complexity cfo estimation in massive mu mimo systems"):
  with members:
    - "what will 5g be"
    - "five disruptive technology directions for 5g"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "blind estimation of multiple carrier frequency offsets"

Connected through hyperedge HE-5 (induced by source paper "impact of frequency selectivity on the information rate performance of cfo impaired single carrier massive mu mimo uplink"):
  with members:
    - "impact of cfo estimation on the performance of zf receiver in massive mu mimo systems"
    - "uplink performance of time reversal mrc in massive mimo systems subject to phase noise"
    - "what will 5g be"
    - "energy and spectral efficiency of very large multiuser 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)