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: "linear precoding based on polynomial expansion reducing complexity in massive mimo"
  Abstract: Large-scale multi-user multiple-input multiple-output (MIMO) techniques have the potential to bring tremendous improvements for future communication systems. Counter-intuitively, the practical issues of having uncertain channel knowledge, high propagation losses, and implementing optimal non-linear precoding are solved more-or-less automatically by enlarging system dimensions. However, the computational precoding complexity grows with the system dimensions. For example, the close-to-optimal regularized zero-forcing (RZF) precoding is very complicated to implement in practice, since it requires fast inversions of large matrices in every coherence period. Motivated by the high performance of RZF, we propose to replace the matrix inversion by a truncated polynomial expansion (TPE), thereby obtaining the new TPE precoding scheme which is more suitable for real-time hardware implementation. The degree of the matrix polynomial can be adapted to the available hardware resources and enables smooth transition between simple maximum ratio transmission (MRT) and more advanced RZF. #R##N#By deriving new random matrix results, we obtain a deterministic expression for the asymptotic signal-to-interference-and-noise ratio (SINR) achieved by TPE precoding in large-scale MIMO systems. Furthermore, we provide a closed-form expression for the polynomial coefficients that maximizes this SINR. To maintain a fixed per-user rate loss as compared to RZF, the polynomial degree does not need to scale with the system, but it should be increased with the quality of the channel knowledge and the signal-to-noise ratio (SNR).

Connected through hyperedge HE-1 (induced by source paper "robust regularized zf in cooperative broadcast channel under distributed csit"):
  with members:
    - "on the optimal fronthaul compression and decoding strategies for uplink cloud radio access networks"
    - "network mimo transmitters with no csi can still be very useful"
    - "regularized zf in cooperative broadcast channels under distributed csit a large system analysis"
    - "drone small cells in the clouds design deployment and performance analysis"
    - "multihop backhaul compression for the uplink of cloud radio access networks"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"
    - "completely stale transmitter channel state information is still very useful"
    - "a scalable limited feedback design for network mimo using per cell product codebook"

Connected through hyperedge HE-2 (induced by source paper "linear precoding of data and artificial noise in secure massive mimo systems"):
  with members:
    - "physical layer cryptography through massive mimo"
    - "large scale mimo relaying techniques for physical layer security af or df"
    - "physical layer security for massive mimo an overview on passive eavesdropping and active attacks"
    - "secure massive mimo transmission in the presence of an active eavesdropper"
    - "securing massive mimo at the physical layer"
    - "linear precoding based on polynomial expansion large scale multi cell mimo systems"
    - "physical layer security in downlink multi antenna cellular networks"
    - "principles of physical layer security in multiuser wireless networks a survey"

Connected through hyperedge HE-3 (induced by source paper "sum rate and power scaling of massive mimo systems with channel aging"):
  with members:
    - "performance analysis of massive mimo for cell boundary users"
    - "uplink performance of time reversal mrc in massive mimo systems subject to phase noise"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"
    - "massive mimo for next generation wireless systems"
    - "energy efficiency optimization in hardware constrained large scale mimo systems"
    - "what will 5g be"

Connected through hyperedge HE-4 (induced by source paper "linear massive mimo precoders in the presence of phase noise a large scale analysis"):
  with members:
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "on the impact of oscillator phase noise on the uplink performance in a massive mimo ofdm system"
    - "soft metrics and their performance analysis for optimal data detection in the presence of strong oscillator phase noise"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "effects of channel aging in massive mimo systems"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"
    - "mimo interference alignment over correlated channels with imperfect csi"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-5 (induced by source paper "coordinated multi cell beamforming for massive mimo a random matrix approach"):
  with members:
    - "massive mimo for next generation wireless systems"
    - "hierarchical interference mitigation for massive mimo cellular networks"
    - "designing multi user mimo for energy efficiency when is massive mimo the answer"
    - "network mimo with linear zero forcing beamforming large system analysis impact of channel estimation and reduced complexity scheduling"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "base station cooperation on the downlink large system analysis"
    - "pilot contamination and precoding in multi cell tdd systems"
    - "eigenvalue distributions of sums and products of large random matrices via incremental matrix expansions"

Connected through hyperedge HE-6 (induced by source paper "regularized zf in cooperative broadcast channels under distributed csit a large system analysis"):
  with members:
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"
    - "completely stale transmitter channel state information is still very useful"
    - "mimo broadcast channels with finite rate feedback"

Connected through hyperedge HE-7 (induced by source paper "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"):
  with members:
    - "uplink performance of time reversal mrc in massive mimo systems subject to phase noise"
    - "robust estimates of covariance matrices in the large dimensional regime"
    - "low complexity polynomial channel estimation in large scale mimo with arbitrary statistics"
    - "blind pilot decontamination"
    - "massive mimo and small cells improving energy efficiency by optimal soft cell coordination"
    - "capacity limits and multiplexing gains of mimo channels with transceiver impairments"
    - "hardware impairments in large scale miso systems energy efficiency estimation and capacity limits"
    - "receive combining vs multi stream multiplexing in downlink systems with multi antenna users"

Connected through hyperedge HE-8 (induced by source paper "linear precoding based on polynomial expansion large scale multi cell mimo systems"):
  with members:
    - "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "pareto characterization of the multicell mimo performance region with simple receivers"
    - "joint spatial division and multiplexing"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"
    - "asymptotic moments for interference mitigation in correlated fading channels"
    - "pilot contamination and precoding in multi cell tdd systems"
    - "a central limit theorem for the sinr at the lmmse estimator output for large dimensional signals"

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)