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: "free deterministic equivalents for the analysis of mimo multiple access channel"
  Abstract: In this paper, a free deterministic equivalent is proposed for the capacity analysis of the multi-input multi-output (MIMO) multiple access channel (MAC) with a more general channel model compared to previous works. In particular, a MIMO MAC with one base station (BS) equipped with several distributed antenna sets is considered. Each link between a user and a BS antenna set forms a jointly correlated Rician fading channel. The analysis is based on operator-valued free probability theory, which broadens the range of applicability of free probability techniques tremendously. By replacing independent Gaussian random matrices with operator-valued random variables satisfying certain operator-valued freeness relations, the free deterministic equivalent of the considered channel Gram matrix is obtained. The Shannon transform of the free deterministic equivalent is derived, which provides an approximate expression for the ergodic input-output mutual information of the channel. The sum-rate capacity achieving input covariance matrices are also derived based on the approximate ergodic input-output mutual information. The free deterministic equivalent results are easy to compute, and simulation results show that these approximations are numerically accurate and computationally efficient.

Connected through hyperedge HE-1 (induced by source paper "energy efficiency optimization for downlink massive mimo with statistical csit"):
  with members:
    - "beam domain secure transmission for massive mimo communications"
    - "fractional programming for communication systems part i power control and beamforming"
    - "energy efficient multicell multigroup multicasting with joint beamforming and antenna selection"
    - "fdd massive mimo via ul dl channel covariance extrapolation and active channel sparsification"
    - "network deployment for maximal energy efficiency in uplink with multislope path loss"
    - "energy efficient beam coordination strategies with rate dependent processing power"
    - "bdma for millimeter wave terahertz massive mimo transmission with per beam synchronization"
    - "channel acquisition for massive mimo ofdm with adjustable phase shift pilots"

Connected through hyperedge HE-2 (induced by source paper "beam domain secure transmission for massive mimo communications"):
  with members:
    - "linear precoding of data and artificial noise in secure massive mimo systems"
    - "massive mimo ten myths and one critical question"
    - "secure communications in millimeter wave ad hoc networks"
    - "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"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "on capacity of large scale mimo multiple access channels with distributed sets of correlated antennas"

Connected through hyperedge HE-3 (induced by source paper "robust transmission for massive mimo downlink with imperfect csi"):
  with members:
    - "performance analysis of multi user massive mimo downlink under channel non reciprocity and imperfect csi"
    - "on optimizing feedback interval for temporally correlated mimo channels with transmit beamforming and finite rate feedback"
    - "analysis and augmented spatial processing for uplink ofdma mu mimo receiver with transceiver i q imbalance and external interference"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "multi user linear precoding for multi polarized massive mimo system under imperfect csit"
    - "asymptotic rate analysis of downlink multi user systems with co located and distributed antennas"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "statistical eigenmode transmission over jointly correlated mimo channels"

Connected through hyperedge HE-4 (induced by source paper "omnidirectional space time block coding for common information broadcasting in massive mimo systems"):
  with members:
    - "channel acquisition for massive mimo ofdm with adjustable phase shift pilots"
    - "secure massive mimo transmission with an active eavesdropper"
    - "physical layer security for massive mimo an overview on passive eavesdropping and active attacks"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "massive mimo multicasting in noncooperative cellular networks"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"

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)