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: "downlink precoding with mixed statistical and imperfect instantaneous csi for massive mimo systems"
  Abstract: In this paper, the feasibility of a new downlink transmission mode in massive multi-input multi-output (MIMO) systems is investigated with two types of users, i.e., the users with only statistical channel state information (CSI) and the users with imperfect instantaneous CSI. The problem of downlink precoding design with mixed utilization of statistical and imperfect instantaneous CSI is addressed. We first theoretically analyze the impact of the mutual interference between the two types of users on their achievable rate. Then, considering the mutual interference suppression, we propose an extended zero forcing and an extended maximum ratio transmission precoding methods to minimize the total transmit power of base station and to maximize the received signal power of users, respectively. Thanks to the exploitation of statistical CSI, pilot-based channel estimation is avoided enabling more active users, higher system sum rate, and shorter transmission delay. Finally, simulations are performed to validate the accuracy of the theoretical analysis and the advantages of the proposed precoding methods.

Connected through hyperedge HE-1 (induced by source paper "spectral efficiency analysis of cell free massive mimo systems with zero forcing detector"):
  with members:
    - "enhanced max min sinr for uplink cell free massive mimo systems"
    - "on the total energy efficiency of cell free massive mimo"
    - "performance analysis for massive mimo downlink with low complexity approximate zero forcing precoding"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "energy efficient downlink transmission for multicell massive das with pilot contamination"
    - "energy efficiency in cell free massive mimo with zero forcing precoding design"
    - "cell free massive mimo versus small cells"
    - "how much do downlink pilots improve cell free massive mimo"

Connected through hyperedge HE-2 (induced by source paper "ieee 802 15 4 e tsch based scheduling for throughput optimization a combinatorial multi armed bandit approach"):
  with members:
    - "online learning for combinatorial network optimization with restless markovian rewards"

Connected through hyperedge HE-3 (induced by source paper "a covariance based hybrid channel feedback in fdd massive mimo systems"):
  with members:
    - "fdd massive mimo via ul dl channel covariance extrapolation and active channel sparsification"
    - "channel feedback based on aod adaptive subspace codebook in fdd massive mimo systems"
    - "enabling covariance based feedback in massive mimo a user classification approach"
    - "channel estimation for tdd fdd massive mimo systems with channel covariance computing"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "spatially common sparsity based adaptive channel estimation and feedback for fdd massive mimo"
    - "antenna grouping based feedback compression for fdd based massive mimo systems"
    - "dealing with interference in distributed large scale mimo systems a statistical approach"

Connected through hyperedge HE-4 (induced by source paper "non uniform quantization codebook based hybrid precoding to reduce feedback overhead in millimeter wave mimo systems"):
  with members:
    - "channel feedback based on aod adaptive subspace codebook in fdd massive mimo systems"
    - "spectral and energy efficiency of multi pair massive mimo relay network with hybrid processing"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "structured compressive sensing based spatio temporal joint channel estimation for fdd massive mimo"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "dynamic subarrays for hybrid precoding in wideband mmwave mimo systems"
    - "mixed adc massive mimo detectors performance analysis and design optimization"

Connected through hyperedge HE-5 (induced by source paper "millimeter wave massive mimo systems relying on generalized sub array connected hybrid precoding"):
  with members:
    - "spatial lobes division based low complexity hybrid precoding and diversity combining for mmwave iot systems"
    - "non uniform quantization codebook based hybrid precoding to reduce feedback overhead in millimeter wave mimo systems"
    - "on the energy efficiency of mimo hybrid beamforming for millimeter wave systems with nonlinear power amplifiers"
    - "stepwise transmit antenna selection in downlink massive multiuser mimo"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "codebook based hybrid precoding for millimeter wave multiuser systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"

Connected through hyperedge HE-6 (induced by source paper "spatial lobes division based low complexity hybrid precoding and diversity combining for mmwave iot systems"):
  with members:
    - "beam tracking for uav mounted satcom on the move with massive antenna array"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "cost effective millimeter wave communications with lens antenna array"
    - "dynamic subarrays for hybrid precoding in wideband mmwave mimo systems"
    - "mixed adc massive mimo detectors performance analysis and design optimization"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "turbo like beamforming based on tabu search algorithm for millimeter wave massive mimo systems"

Connected through hyperedge HE-7 (induced by source paper "energy efficient extended sub connected architecture for hybrid precoding in millimeter wave massive mimo systems"):
  with members:
    - "spatial lobes division based low complexity hybrid precoding and diversity combining for mmwave iot systems"
    - "non uniform quantization codebook based hybrid precoding to reduce feedback overhead in millimeter wave mimo systems"
    - "stepwise transmit antenna selection in downlink massive multiuser mimo"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "low rf complexity technologies to enable millimeter wave mimo with large antenna array for 5g wireless communications"
    - "dynamic subarrays for hybrid precoding in wideband mmwave mimo systems"

Connected through hyperedge HE-8 (induced by source paper "enabling covariance based feedback in massive mimo a user classification approach"):
  with members:
    - "spatially common sparsity based adaptive channel estimation and feedback for fdd massive mimo"
    - "trellis extended codebooks and successive phase adjustment a path from lte advanced to fdd massive mimo systems"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"
    - "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)