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: "subspace estimation and decomposition for hybrid analog digital millimetre wave mimo systems"
  Abstract: In this work, we address the problem of channel estimation and precoding / combining for the so-called hybrid millimeter wave (mmWave) MIMO architecture. Our proposed channel estimation scheme exploits channel reciprocity in TDD MIMO systems, by using echoing, thereby allowing us to implement Krylov subspace methods in a fully distributed way. The latter results in estimating the right (resp. left) singular subspace of the channel at the transmitter (resp. receiver). Moreover, we also tackle the problem of subspace decomposition whereby the estimated right (resp. left) singular subspaces are approximated by a cascade of analog and digital precoder (resp. combiner), using an iterative method. Finally we compare our scheme with an equivalent fully digital case and conclude that a relatively similar performance can be achieved, however, with a drastically reduced number of RF chains - 4 ∼ 8 times less (i.e., massive savings in cost and power consumption).

Connected through hyperedge HE-1 (induced by source paper "energy efficiency and asymptotic performance evaluation of beamforming structures in doubly massive mimo mmwave systems"):
  with members:
    - "doubly massive mmwave mimo systems using very large antenna arrays at both transmitter and receiver"
    - "multi user massive mimo communication systems based on irregular antenna arrays"
    - "enhancing the estimation of mm wave large array channels by exploiting spatio temporal correlation and sparse scattering"
    - "energy efficiency optimization of 5g radio frequency chain systems"
    - "on clustered statistical mimo millimeter wave channel simulation"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"
    - "massive mimo combining with switches"

Connected through hyperedge HE-2 (induced by source paper "doubly massive mmwave mimo systems using very large antenna arrays at both transmitter and receiver"):
  with members:
    - "enhancing the estimation of mm wave large array channels by exploiting spatio temporal correlation and sparse scattering"
    - "spectral efficiency of mimo millimeter wave links with single carrier modulation for 5g networks"
    - "on clustered statistical mimo millimeter wave channel simulation"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "massive antenna arrays with low front end hardware complexity an enabling technology for the emerging small cell and distributed network architectures"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"

Connected through hyperedge HE-3 (induced by source paper "are mmwave low complexity beamforming structures energy efficient analysis of the downlink mu mimo"):
  with members:
    - "on clustered statistical mimo millimeter wave channel simulation"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"
    - "massive mimo combining with switches"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "what will 5g be"

Connected through hyperedge HE-4 (induced by source paper "channel estimation for millimeter wave massive mimo with hybrid precoding over frequency selective fading channels"):
  with members:
    - "frequency selective hybrid precoding for limited feedback millimeter wave systems"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "millimeter wave mimo with lens antenna array a new path division multiplexing paradigm"
    - "mmwave massive mimo based wireless backhaul for the 5g ultra dense network"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"

Connected through hyperedge HE-5 (induced by source paper "subspace estimation and decomposition for large millimeter wave mimo systems"):
  with members:
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "millimeter wave beamforming for wireless backhaul and access in small cell networks"
    - "coding the beams improving beamforming training in mmwave communication system"
    - "information theoretic analysis of mimo channel sounding"

Connected through hyperedge HE-6 (induced by source paper "millimeter wave cellular networks a mac layer perspective"):
  with members:
    - "stochastic geometry modeling and analysis of multi tier millimeter wave cellular networks"
    - "beam searching and transmission scheduling in millimeter wave communications"
    - "a survey of millimeter wave mmwave communications for 5g opportunities and challenges"
    - "design aspects of short range millimeter wave networks a mac layer perspective"
    - "on the joint impact of beamwidth and orientation error on throughput in directional wireless poisson networks"
    - "an overview of load balancing in hetnets old myths and open problems"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-7 (induced by source paper "near optimal hybrid processing for massive mimo systems via matrix decomposition"):
  with members:
    - "low power analog to digital conversion in millimeter wave systems impact of resolution and bandwidth on performance"
    - "spatially common sparsity based adaptive channel estimation and feedback for fdd massive mimo"
    - "hybrid block diagonalization for massive multiuser mimo systems"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "mmwave massive mimo based wireless backhaul for the 5g ultra dense network"
    - "on the convergence of massive mimo systems"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "massive mimo for next generation wireless 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)