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: "multi user linear precoding for multi polarized massive mimo system under imperfect csit"
  Abstract: The space limitation and the channel acquisition prevent Massive MIMO from being easily deployed in a practical setup. Motivated by current deployments of LTE-Advanced, the use of multi-polarized antennas can be an efficient solution to address the space constraint. Furthermore, the dual-structured precoding, in which a preprocessing based on the spatial correlation and a subsequent linear precoding based on the short-term channel state information at the transmitter (CSIT) are concatenated, can reduce the feedback overhead efficiently. By grouping and preprocessing spatially correlated mobile stations (MSs), the dimension of the precoding signal space is reduced and the corresponding short-term CSIT dimension is reduced. In this paper, to reduce the feedback overhead further, we propose a dual-structured multi-user linear precoding, in which the subgrouping method based on co-polarization is additionally applied to the spatially grouped MSs in the preprocessing stage. Furthermore, under imperfect CSIT, the proposed scheme is asymptotically analyzed based on random matrix theory. By investigating the behavior of the asymptotic performance, we also propose a new dual-structured precoding in which the precoding mode is switched between two dual-structured precoding strategies with 1) the preprocessing based only on the spatial correlation and 2) the preprocessing based on both the spatial correlation and polarization. Finally, we extend it to 3D dual-structured precoding.

Connected through hyperedge HE-1 (induced by source paper "two dimensional aod and aoa acquisition for wideband millimeter wave systems with dual polarized mimo"):
  with members:
    - "channel estimation for millimeter wave massive mimo with hybrid precoding over frequency selective fading channels"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "channel estimation for hybrid architecture based wideband millimeter wave systems"
    - "auxiliary beam pair enabled aod and aoa estimation in closed loop large scale mmwave mimo systems"
    - "low rank tensor decomposition aided channel estimation for millimeter wave mimo ofdm systems"
    - "frequency selective hybrid precoding for limited feedback millimeter wave systems"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"

Connected through hyperedge HE-2 (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"
    - "free deterministic equivalents for the analysis of mimo multiple access channel"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "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-3 (induced by source paper "a rate splitting strategy for massive mimo with imperfect csit"):
  with members:
    - "a hierarchical rate splitting strategy for fdd massive mimo under imperfect csit"
    - "two stage beamformer design for massive mimo downlink by trace quotient formulation"
    - "sum rate maximization for mu miso with partial csit using joint multicasting and broadcasting"
    - "rate analysis of two receiver miso broadcast channel with finite rate feedback a rate splitting approach"
    - "optimal multiuser transmit beamforming a difficult problem with a simple solution structure"
    - "massive mimo multicasting in noncooperative cellular networks"
    - "massive mimo for next generation wireless systems"
    - "two tier precoding for fdd multi cell massive mimo time varying interference networks"

Connected through hyperedge HE-4 (induced by source paper "inter tier interference suppression in heterogeneous cloud radio access networks"):
  with members:
    - "fronthaul constrained cloud radio access networks insights and challenges"
    - "system architecture and key technologies for 5g heterogeneous cloud radio access networks"
    - "comp meets smart grid a new communication and energy cooperation paradigm"
    - "joint power and antenna selection optimization in large cloud radio access networks"
    - "heterogeneous cloud radio access networks a new perspective for enhancing spectral and energy efficiencies"
    - "ergodic capacity analysis of remote radio head associations in cloud radio access networks"
    - "sparse beamforming and user centric clustering for downlink cloud radio access network"
    - "group sparse beamforming for green cloud ran"

Connected through hyperedge HE-5 (induced by source paper "a hierarchical rate splitting strategy for fdd massive mimo under imperfect csit"):
  with members:
    - "a rate splitting strategy for massive mimo with imperfect csit"
    - "two stage beamformer design for massive mimo downlink by trace quotient formulation"
    - "sum rate maximization for mu miso with partial csit using joint multicasting and broadcasting"
    - "rate analysis of two receiver miso broadcast channel with finite rate feedback a rate splitting approach"
    - "two tier precoding for fdd multi cell massive mimo time varying interference networks"
    - "degrees of freedom of time correlated miso broadcast channel with delayed csit"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"

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)