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: "mmwave massive mimo based wireless backhaul for the 5g ultra dense network"
  Abstract: The ultra-dense network (UDN) has been considered as a promising candidate for future 5G networks to meet the explosive data demand. To realize UDN, a reliable, gigahertz bandwidth, and cost-effective backhaul connecting ultradense small-cell BSs and macrocell BS are prerequisite. Millimeter-wave can provide the potential gigabit-per-second traffic for wireless backhaul. Moreover, mmWave can easily be integrated with massive MIMO for improved link reliability. In this article, we discuss the feasibility of mmWave massive-MIMO-based wireless backhaul for 5G UDN, and the benefits and challenges are also addressed. In particular, we propose a digitally controlled phase shifter network (DPSN)-based hybrid precoding/combining scheme for mmWave massive MIMO, whereby the low-rank property of the mmWave massive MIMO channel matrix is leveraged to reduce the required cost and complexity of a transceiver with a negligible performance loss. One key feature of the proposed scheme is that the macrocell BS can simultaneously support multiple small-cell BSs with multiple streams for each small-cell BS, which is essentially different from conventional hybrid precoding/combining schemes, typically limited to single-user MIMO with multiple streams or multi-user MIMO with single stream for each user. Based on the proposed scheme, we further explore the fundamental issues of developing mmWave massive MIMO for wireless backhaul, and the associated challenges, insight, and prospects to enable mmWave massive-MIMO-based wireless backhaul for 5G UDN are discussed.

Connected through hyperedge HE-1 (induced by source paper "ultra low latency ull networks the ieee tsn and ietf detnet standards and related 5g ull research"):
  with members:
    - "a basic result on the superposition of arrival processes in deterministic networks"
    - "end to end simulation of 5g mmwave networks"
    - "information and communications technologies for sustainable development goals state of the art needs and perspectives"
    - "5g fronthaul latency and jitter studies of cpri over ethernet"
    - "r fft function split at ifft fft in unified lte cran and cable access network"
    - "towards 5g enabled tactile robotic telesurgery"
    - "fog aided wireless networks for content delivery fundamental latency tradeoffs"
    - "formal scheduling constraints for time sensitive networks"

Connected through hyperedge HE-2 (induced by source paper "non uniform quantization codebook based hybrid precoding to reduce feedback overhead in millimeter wave mimo systems"):
  with members:
    - "downlink precoding with mixed statistical and imperfect instantaneous csi for massive mimo systems"
    - "channel feedback based on aod adaptive subspace codebook in fdd massive mimo systems"
    - "spectral and energy efficiency of multi pair massive mimo relay network with hybrid processing"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "structured compressive sensing based spatio temporal joint channel estimation for fdd massive mimo"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "dynamic subarrays for hybrid precoding in wideband mmwave mimo systems"

Connected through hyperedge HE-3 (induced by source paper "security of 5g mobile backhaul networks a survey"):
  with members:
    - "bandwidth partitioning and downlink analysis in mmwave integrated access and backhaul for 5g"
    - "cross layer authentication protocol design for ultra dense 5g hetnets"
    - "formal analysis of 5g authentication"
    - "massive multiple input massive multiple output for 5g wireless backhauling"
    - "a survey of physical layer security techniques for 5g wireless networks and challenges ahead"
    - "the 5g cellular backhaul management dilemma to cache or to serve"
    - "optimal joint routing and scheduling in millimeter wave cellular networks"
    - "a survey on low latency towards 5g ran core network and caching solutions"

Connected through hyperedge HE-4 (induced by source paper "spectral efficiency optimization for millimeter wave multiuser mimo systems"):
  with members:
    - "hybrid beamforming via the kronecker decomposition for the millimeter wave massive mimo systems"
    - "penalty dual decomposition method for nonsmooth nonconvex optimization"
    - "joint source relay design for full duplex mimo af relay systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "near optimal hybrid processing for massive mimo systems via matrix decomposition"
    - "hybrid block diagonalization for massive multiuser mimo systems"

Connected through hyperedge HE-5 (induced by source paper "machine learning based hybrid precoding for mmwave mimo ofdm with dynamic subarray"):
  with members:
    - "energy efficient transceiver design for hybrid sub array architecture mimo systems"
    - "compressive sensing techniques for next generation wireless communications"
    - "codebook based hybrid precoding for millimeter wave multiuser systems"
    - "2d unitary esprit based super resolution channel estimation for millimeter wave massive mimo with hybrid precoding"
    - "codebook design for millimeter wave channel estimation with hybrid precoding structure"
    - "dynamic subarrays for hybrid precoding in wideband mmwave mimo systems"
    - "frequency selective hybrid precoding for limited feedback millimeter wave systems"
    - "hybrid mimo architectures for millimeter wave communications phase shifters or switches"

Connected through hyperedge HE-6 (induced by source paper "wideband hybrid precoding for next generation backhaul fronthaul based on mmwave fd mimo"):
  with members:
    - "energy efficient transceiver design for hybrid sub array architecture mimo systems"
    - "compressive sensing techniques for next generation wireless communications"
    - "codebook based hybrid precoding for millimeter wave multiuser systems"
    - "channel estimation for millimeter wave massive mimo with hybrid precoding over frequency selective fading channels"
    - "dynamic subarrays for hybrid precoding in wideband mmwave mimo systems"
    - "frequency selective hybrid precoding for limited feedback millimeter wave systems"
    - "spatially sparse precoding in millimeter wave mimo systems"

Connected through hyperedge HE-7 (induced by source paper "over sampling codebook based hybrid minimum sum mean square error precoding for millimeter wave 3d mimo"):
  with members:
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "hybrid block diagonalization for massive multiuser mimo systems"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "low complexity hybrid precoding in massive multiuser mimo systems"

Connected through hyperedge HE-8 (induced by source paper "routing protocols performance in mobile ad hoc networks using millimeter wave"):
  with members:
    - "end to end simulation of 5g mmwave networks"
    - "study on 3gpp rural macrocell path loss models for millimeter wave wireless communications"
    - "5g cellular user equipment from theory to practical hardware design"
    - "parallel routing in mobile ad hoc networks"

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)