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: "matrix monotonic optimization for mimo systems"
  Abstract: For MIMO systems, due to the deployment of multiple antennas at both the transmitter and the receiver, the design variables e.g., precoders, equalizers, training sequences, etc. are usually matrices. It is well known that matrix operations are usually more complicated compared to their vector counterparts. In order to overcome the high complexity resulting from matrix variables, in this paper we investigate a class of elegant multi-objective optimization problems, namely matrix-monotonic optimization problems (MMOPs). In our work, various representative MIMO optimization problems are unified into a framework of matrix-monotonic optimization, which includes linear transceiver design, nonlinear transceiver design, training sequence design, radar waveform optimization, the corresponding robust design and so on as its special cases. Then exploiting the framework of matrix-monotonic optimization the optimal structures of the considered matrix variables can be derived first. Based on the optimal structure, the matrix-variate optimization problems can be greatly simplified into the ones with only vector variables. In particular, the dimension of the new vector variable is equal to the minimum number of columns and rows of the original matrix variable. Finally, we also extend our work to some more general cases with multiple matrix variables.

Connected through hyperedge HE-1 (induced by source paper "hybrid transceiver optimization for multi hop communications"):
  with members:
    - "hybrid beamforming for millimeter wave systems using the mmse criterion"
    - "majorization minimization aided hybrid transceivers for mimo interference channels"
    - "hybrid precoding architecture for massive multiuser mimo with dissipation sub connected or fully connected structures"
    - "hybrid beamforming with selection for multiuser massive mimo systems"
    - "spectral efficiency optimization for millimeter wave multiuser mimo systems"
    - "spectral and energy efficiency of multi pair massive mimo relay network with hybrid processing"
    - "multi user precoding and channel estimation for hybrid millimeter wave systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"

Connected through hyperedge HE-2 (induced by source paper "a framework on hybrid mimo transceiver design based on matrix monotonic optimization"):
  with members:
    - "hybrid beamforming via the kronecker decomposition for the millimeter wave massive mimo systems"
    - "spectral and energy efficiency of multi pair massive mimo relay network with hybrid processing"
    - "a new view of multi user hybrid massive mimo non orthogonal angle division multiple access"
    - "hybrid analog digital beamforming for massive mimo systems"
    - "hybrid analog and digital beamforming for mmwave ofdm large scale antenna arrays"
    - "codebook based hybrid precoding for millimeter wave multiuser systems"
    - "a novel hybrid beamforming algorithm with unified analog beamforming by subspace construction based on partial csi for massive mimo ofdm systems"
    - "hybrid beamforming for large antenna arrays with phase shifter selection"

Connected through hyperedge HE-3 (induced by source paper "unified overview of matrix monotonic optimization for mimo transceivers"):
  with members:
    - "a framework for joint design of pilot sequence and linear precoder"
    - "on weighted mse model for mimo transceiver optimization"
    - "a framework for transceiver designs for multi hop communications with covariance shaping constraints"
    - "fifty years of mimo detection the road to large scale mimos"
    - "convex separable problems with linear constraints in signal processing and communications"
    - "robust transceiver with tomlinson harashima precoding for amplify and forward mimo relaying systems"
    - "miso capacity with per antenna power constraint"

Connected through hyperedge HE-4 (induced by source paper "new viewpoint and algorithms for water filling solutions in wireless communications"):
  with members:
    - "a framework for transceiver designs for multi hop communications with covariance shaping constraints"
    - "transceiver designs with matrix version water filling architecture under mixed power constraints"
    - "convex separable problems with linear constraints in signal processing and communications"

Connected through hyperedge HE-5 (induced by source paper "on weighted mse model for mimo transceiver optimization"):
  with members:
    - "a framework for transceiver designs for multi hop communications with covariance shaping constraints"
    - "a general robust linear transceiver design for multi hop amplify and forward mimo relaying systems"
    - "transceiver design for dual hop nonregenerative mimo ofdm relay systems under channel uncertainties"

Connected through hyperedge HE-6 (induced by source paper "energy harvesting noncoherent cooperative communications"):
  with members:
    - "wireless networks with rf energy harvesting a contemporary survey"
    - "power allocation strategies in energy harvesting wireless cooperative networks"
    - "simultaneous information and energy transfer in large scale networks with without relaying"
    - "throughput maximization in wireless powered communication networks"
    - "a general robust linear transceiver design for multi hop amplify and forward mimo relaying systems"
    - "cooperative energy harvesting networks with spatially random users"
    - "simultaneous information and power transfer for broadband wireless systems"
    - "relaying protocols for wireless energy harvesting and information processing"

Connected through hyperedge HE-7 (induced by source paper "a framework for transceiver designs for multi hop communications with covariance shaping constraints"):
  with members:
    - "evolution toward 5g multi tier cellular wireless networks an interference management perspective"
    - "beamforming for miso interference channels with qos and rf energy transfer"
    - "a general robust linear transceiver design for multi hop amplify and forward mimo relaying systems"
    - "robust transceiver with tomlinson harashima precoding for amplify and forward mimo relaying systems"
    - "a tutorial on the optimization of amplify and forward mimo relay systems"
    - "transceiver design for dual hop nonregenerative mimo ofdm relay systems under channel uncertainties"
    - "ergodic capacity analysis of amplify and forward mimo dual hop 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)