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: "reduced rank doa estimation based on joint iterative subspace optimization and grid search"
  Abstract: In this paper, we propose a novel reduced-rank algorithm for direction of arrival (DOA) estimation based on the minimum variance (MV) power spectral evaluation. It is suitable to DOA estimation with large arrays and can be applied to arbitrary array geometries. The proposed DOA estimation algorithm is formulated as a joint optimization of a subspace projection matrix and an auxiliary reduced-rank parameter vector with respect to the MV and grid search. A constrained least squares method is employed to solve this joint optimization problem for the output power over the grid. The proposed algorithm is described for problems of large number of users' direction finding with or without exact information of the number of sources, and does not require the singular value decomposition (SVD). The spatial smoothing (SS) technique is also employed in the proposed algorithm for dealing with correlated sources problem. Simulations are conducted with comparisons against existent algorithms to show the improved performance of the proposed algorithm in different scenarios.

Connected through hyperedge HE-1 (induced by source paper "multi user flexible coordinated beamforming using lattice reduction for massive mimo systems"):
  with members:
    - "robust adaptive beamforming using a low complexity shrinkage based mismatch estimation algorithm"
    - "multi branch tomlinson harashima precoding design for mu mimo systems theory and algorithms"
    - "generalized design of low complexity block diagonalization type precoding algorithms for multiuser mimo systems"
    - "blind adaptive interference suppression based on set membership constrained constant modulus algorithms with dynamic bounds"
    - "massive mimo systems signal processing challenges and research trends"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "adaptive distributed space time coding based on adjustable code matrices for cooperative mimo relaying systems"
    - "adaptive reduced rank lcmv beamforming algorithms based on joint iterative optimization of filters design and analysis"

Connected through hyperedge HE-2 (induced by source paper "coordinate tomlinson harashima precoding design for overloaded multi user mimo systems"):
  with members:
    - "robust adaptive beamforming using a low complexity shrinkage based mismatch estimation algorithm"
    - "multi branch tomlinson harashima precoding design for mu mimo systems theory and algorithms"
    - "generalized design of low complexity block diagonalization type precoding algorithms for multiuser mimo systems"
    - "blind adaptive interference suppression based on set membership constrained constant modulus algorithms with dynamic bounds"
    - "adaptive distributed space time coding based on adjustable code matrices for cooperative mimo relaying systems"
    - "adaptive reduced rank lcmv beamforming algorithms based on joint iterative optimization of filters design and analysis"
    - "lll reduction achieves the receive diversity in mimo decoding"

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)