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: "energy efficiency optimization of 5g radio frequency chain systems"
  Abstract: With the massive multi-input multi-output (MIMO) antennas technology adopted for the fifth generation (5G) wireless communication systems, a large number of radio frequency (RF) chains have to be employed for RF circuits. However, a large number of RF chains not only increase the cost of RF circuits but also consume additional energy in 5G wireless communication systems. In this paper we investigate energy and cost efficiency optimization solutions for 5G wireless communication systems with a large number of antennas and RF chains. An energy efficiency optimization problem is formulated for 5G wireless communication systems using massive MIMO antennas and millimeter wave technology. Considering the nonconcave feature of the objective function, a suboptimal iterative algorithm, i.e., the energy efficient hybrid precoding (EEHP) algorithm is developed for maximizing the energy efficiency of 5G wireless communication systems. To reduce the cost of RF circuits, the energy efficient hybrid precoding with the minimum number of RF chains (EEHP-MRFC) algorithm is also proposed. Moreover, the critical number of antennas searching (CNAS) and user equipment number optimization (UENO) algorithms are further developed to optimize the energy efficiency of 5G wireless communication systems by the number of transmit antennas and UEs. Compared with the maximum energy efficiency of conventional zero-forcing (ZF) precoding algorithm, numerical results indicate that the maximum energy efficiency of the proposed EEHP and EEHP-MRFC algorithms are improved by 220% and 171%, respectively.

Connected through hyperedge HE-1 (induced by source paper "energy efficient hybrid precoding design for integrated multicast unicast millimeter wave communications with swipt"):
  with members:
    - "hybrid precoding based millimeter wave massive mimo noma with simultaneous wireless information and power transfer"
    - "joint optimization of computation and communication power in multi user massive mimo systems"
    - "energy efficient transceiver design for hybrid sub array architecture mimo systems"
    - "energy efficient power allocation in millimeter wave massive mimo with non orthogonal multiple access"
    - "joint base station clustering and beamforming for non orthogonal multicast and unicast transmission with backhaul constraints"
    - "joint beamforming and broadcasting in massive mimo"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "on the spectral efficiency and security enhancements of noma assisted multicast unicast streaming"

Connected through hyperedge HE-2 (induced by source paper "principal component analysis based broadband hybrid precoding for millimeter wave massive mimo systems"):
  with members:
    - "closed loop sparse channel estimation for wideband millimeter wave full dimensional mimo systems"
    - "periodic analog channel estimation aided beamforming for massive mimo systems"
    - "device to device communications enabled energy efficient multicast scheduling in mmwave small cells"
    - "energy efficient multi user miso communication using low resolution large intelligent surfaces"
    - "wideband hybrid precoding for next generation backhaul fronthaul based on mmwave fd mimo"
    - "hybrid beamforming with selection for multiuser massive mimo systems"
    - "massive mimo channel estimation for millimeter wave systems via matrix completion"
    - "stochastic successive convex optimization for two timescale hybrid precoding in massive mimo"

Connected through hyperedge HE-3 (induced by source paper "neural networks in hybrid precoding for millimeter wave massive mimo systems"):
  with members:
    - "deep learning based channel estimation for beamspace mmwave massive mimo systems"
    - "energy efficiency of mmwave massive mimo precoding with low resolution dacs"
    - "an introduction to deep learning for the physical layer"
    - "energy efficiency challenges of 5g small cell networks"
    - "spatial spectrum and energy efficiency of random cellular networks"
    - "user mobility evaluation for 5g small cell networks based on individual mobility model"
    - "deep residual learning for image recognition"
    - "5g ultra dense cellular networks"

Connected through hyperedge HE-4 (induced by source paper "enabling security and high energy efficiency in the internet of things with massive mimo hybrid precoding"):
  with members:
    - "joint optimization of computation and communication power in multi user massive mimo systems"
    - "secure massive mimo systems with limited rf chains"
    - "physical layer security in heterogeneous cellular networks"
    - "large scale mimo relaying techniques for physical layer security af or df"
    - "jamming aided secure communication in massive mimo rician channels"
    - "on the secrecy outage capacity of physical layer security in large scale mimo relaying systems with imperfect csi"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "low complexity hybrid precoding in massive multiuser mimo systems"

Connected through hyperedge HE-5 (induced by source paper "performance analysis of urban mmwave multi hop v2v communications with shifted exponential distribution headway"):
  with members:
    - "5g software defined vehicular networks"
    - "energy efficiency challenges of 5g small cell networks"
    - "multi hop links quality analysis of 5g enabled vehicular networks"
    - "spatial spectrum and energy efficiency of random cellular networks"
    - "user mobility evaluation for 5g small cell networks based on individual mobility model"
    - "5g ultra dense cellular networks"
    - "5g wireless backhaul networks challenges and research advances"
    - "energy efficiency optimization for mimo ofdm mobile multimedia communication systems with qos constraints"

Connected through hyperedge HE-6 (induced by source paper "coverage and handoff analysis of 5g fractal small cell networks"):
  with members:
    - "modeling and analyzing millimeter wave cellular systems"
    - "a novel millimeter wave channel simulator and applications for 5g wireless communications"
    - "vehicular communications for 5g cooperative small cell networks"
    - "analysis of human body blockage in urban millimeter wave cellular communications"
    - "a dual directional path loss model in 5g wireless fractal small cell networks"
    - "wireless fractal cellular networks"
    - "fundamentals of the downlink green coverage and energy efficiency in heterogeneous networks"
    - "joint millimeter wave and microwave resources allocation in cellular networks with dual mode base stations"

Connected through hyperedge HE-7 (induced by source paper "optimal base station antenna downtilt in downlink cellular networks"):
  with members:
    - "performance analysis of ultra dense networks with elevated base stations"
    - "ultra dense networks is there a limit to spatial spectrum reuse"
    - "performance impact of base station antenna heights in dense cellular networks"
    - "joint tilt angle adaptation and beamforming in multicell multiuser cellular networks"
    - "please lower small cell antenna heights in 5g"
    - "performance impact of los and nlos transmissions in dense cellular networks"
    - "spatial spectrum and energy efficiency of random cellular networks"
    - "towards 1 gbps ue in cellular systems understanding ultra dense small cell deployments"

Connected through hyperedge HE-8 (induced by source paper "joint optimization of computation and communication power in multi user massive mimo systems"):
  with members:
    - "energy efficient transceiver design for hybrid sub array architecture mimo systems"
    - "energy efficiency challenges of 5g small cell networks"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "hybrid block diagonalization for massive multiuser mimo systems"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "impact of transceiver power consumption on the energy efficiency of zero forcing detector in massive mimo systems"

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.NI(Networking and Internet Architecture)