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: "channel estimation and linear precoding in multiuser multiple antenna tdd systems"
  Abstract: Traditional approaches in the analysis of downlink systems decouple the precoding and the channel estimation problems. However, in cellular systems with mobile users, these two problems are, in fact, tightly coupled. In this paper, this coupling is explicitly studied by accounting for the channel training overhead and estimation error while determining the overall system throughput. This paper studies the problem of utilizing imperfect channel estimates for efficient linear precoding and user selection. It presents precoding methods that take into account the degree of channel estimation error. Information-theoretic lower and upper bounds are derived to evaluate the performance of these precoding methods. In typical scenarios, these bounds are close.

Connected through hyperedge HE-1 (induced by source paper "joint beamforming and power allocation in downlink noma multiuser mimo networks"):
  with members:
    - "joint beamforming and power splitting control in downlink cooperative swipt noma systems"
    - "noma in 5g systems exciting possibilities for enhancing spectral efficiency"
    - "capacity comparison between mimo noma and mimo oma with multiple users in a cluster"
    - "robust resource allocation for mimo wireless powered communication networks based on a non linear eh model"
    - "design of massive mimo noma with limited feedback"
    - "on the spectral efficiency and security enhancements of noma assisted multicast unicast streaming"
    - "a minorization maximization method for optimizing sum rate in the downlink of non orthogonal multiple access systems"
    - "non orthogonal multiple access noma for downlink multiuser mimo systems user clustering beamforming and power allocation"

Connected through hyperedge HE-2 (induced by source paper "performance analysis of multi user massive mimo downlink under channel non reciprocity and imperfect csi"):
  with members:
    - "a novel hybrid beamforming algorithm with unified analog beamforming by subspace construction based on partial csi for massive mimo ofdm systems"
    - "analysis of massive mimo with hardware impairments and different channel models"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"
    - "massive mimo for maximal spectral efficiency how many users and pilots should be allocated"
    - "scalable synchronization and reciprocity calibration for distributed multiuser mimo"
    - "five disruptive technology directions for 5g"
    - "massive mu mimo downlink tdd systems with linear precoding and downlink pilots"

Connected through hyperedge HE-3 (induced by source paper "estimation and mitigation of channel non reciprocity in massive mimo"):
  with members:
    - "performance analysis of multi user massive mimo downlink under channel non reciprocity and imperfect csi"
    - "joint beamforming and broadcasting in massive mimo"
    - "analysis of massive mimo with hardware impairments and different channel models"
    - "massive mimo for next generation wireless systems"
    - "scalable synchronization and reciprocity calibration for distributed multiuser mimo"
    - "five disruptive technology directions for 5g"
    - "massive mu mimo downlink tdd systems with linear precoding and downlink pilots"
    - "pilot contamination and precoding in multi cell tdd systems"

Connected through hyperedge HE-4 (induced by source paper "a survey on legacy and emerging technologies for public safety communications"):
  with members:
    - "survey of important issues in uav communication networks"
    - "28 ghz and 73 ghz millimeter wave indoor propagation measurements and path loss models"
    - "massive mimo for next generation wireless systems"
    - "cognitive and energy harvesting based d2d communication in cellular networks stochastic geometry modeling and analysis"
    - "what will 5g be"
    - "incentivizing spectrum sharing via subsidy regulations"
    - "millimeter wave channel modeling and cellular capacity evaluation"
    - "internet of things iot a vision architectural elements and future directions"

Connected through hyperedge HE-5 (induced by source paper "secret key agreement with large antenna arrays under the pilot contamination attack"):
  with members:
    - "the sender excited secret key agreement model capacity reliability and secrecy exponents"
    - "secure transmission in multi cell massive mimo systems"
    - "secrecy sum rates for multi user mimo regularized channel inversion precoding"
    - "exploiting channel diversity in secret key generation from multipath fading randomness"
    - "secret sharing ldpc codes for the bpsk constrained gaussian wiretap channel"
    - "achieving the secrecy capacity of wiretap channels using polar codes"
    - "polar coding for secure transmission and key agreement"
    - "nested polar codes for wiretap and relay channels"

Connected through hyperedge HE-6 (induced by source paper "codebook based opportunistic interference alignment"):
  with members:
    - "on the achievable dof and user scaling law of opportunistic interference alignment in 3 transmitter mimo interference channels"
    - "opportunistic interference alignment for mimo interfering multiple access channels"
    - "multi cell random beamforming achievable rate and degrees of freedom region"
    - "opportunistic interference mitigation achieves optimal degrees of freedom in wireless multi cell uplink networks"
    - "interference alignment under limited feedback for mimo interference channels"
    - "interference alignment with limited feedback"
    - "pilot contamination and precoding in multi cell tdd systems"
    - "mimo broadcast channels with finite rate feedback"

Connected through hyperedge HE-7 (induced by source paper "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"):
  with members:
    - "mimo interference alignment over correlated channels with imperfect csi"
    - "massive mimo how many antennas do we need"
    - "a deterministic equivalent for the analysis of correlated mimo multiple access channels"
    - "base station cooperation on the downlink large system analysis"
    - "optimized training and feedback for mimo downlink channels"
    - "what is the value of joint processing of pilots and data in block fading channels"
    - "multiuser mimo achievable rates with downlink training and channel state feedback"
    - "mimo broadcast channels with finite rate feedback"

Connected through hyperedge HE-8 (induced by source paper "airsync enabling distributed multiuser mimo with full spatial multiplexing"):
  with members:
    - "experiment driven characterization of full duplex wireless systems"
    - "the degrees of freedom regions of mimo broadcast interference and cognitive radio channels with no csit"
    - "multiuser mimo achievable rates with downlink training and channel state feedback"
    - "on the capacity of fading mimo broadcast channels with imperfect transmitter side information"

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)