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: "blind estimation of effective downlink channel gains in massive mimo"
  Abstract: We consider the massive MIMO downlink with time-division duplex (TDD) operation and conjugate beamforming transmission. To reliably decode the desired signals, the users need to know the effective channel gain. In this paper, we propose a blind channel estimation method which can be applied at the users and which does not require any downlink pilots. We show that our proposed scheme can substantially outperform the case where each user has only statistical channel knowledge, and that the difference in performance is particularly large in certain types of channel, most notably keyhole channels. Compared to schemes that rely on downlink pilots, our proposed scheme yields more accurate channel estimates for a wide range of signal-to-noise ratios and avoid spending time-frequency resources on pilots.

Connected through hyperedge HE-1 (induced by source paper "joint beamforming and broadcasting in massive mimo"):
  with members:
    - "linear precoding of data and artificial noise in secure massive mimo systems"
    - "sum rate maximization for mu miso with partial csit using joint multicasting and broadcasting"
    - "multicast multigroup beamforming for per antenna power constrained large scale arrays"
    - "weighted fair multicast multigroup beamforming under per antenna power constraints"
    - "massive mimo for maximal spectral efficiency how many users and pilots should be allocated"
    - "physical layer multicasting by stochastic transmit beamforming and alamouti space time coding"
    - "massive mu mimo downlink tdd systems with linear precoding and downlink pilots"
    - "per antenna constant envelope precoding for large multi user mimo systems"

Connected through hyperedge HE-2 (induced by source paper "no downlink pilots are needed in tdd massive mimo"):
  with members:
    - "massive mimo ten myths and one critical question"
    - "performance analysis of massive mimo for cell boundary users"
    - "massive mimo performance evaluation based on measured propagation data"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "aspects of favorable propagation in massive mimo"
    - "massive mimo for next generation wireless systems"
    - "massive mu mimo downlink tdd systems with linear precoding and downlink pilots"
    - "from multi keyholes to measure of correlation and power imbalance in mimo channels outage capacity analysis"

Connected through hyperedge HE-3 (induced by source paper "user selection and minimum probability of error multiuser transmit beamforming"):
  with members:
    - "cell free massive mimo uniformly great service for everyone"
    - "gaussian interference channel capacity to within one bit"

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)