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: "wireless power transfer in massive mimo aided hetnets with user association"
  Abstract: This paper explores the potential of wireless power transfer (WPT) in massive multiple-input multiple-output (MIMO)-aided heterogeneous networks (HetNets), where massive MIMO is applied in the macrocells, and users aim to harvest as much energy as possible and reduce the uplink path loss for enhancing their information transfer. By addressing the impact of massive MIMO on the user association, we compare and analyze user association schemes: 1) downlink received signal power (DRSP)-based approach for maximizing the harvested energy and 2) uplink received signal power (URSP)-based approach for minimizing the uplink path loss. We adopt the linear maximal-ratio transmission beamforming for massive MIMO power transfer to recharge users. By deriving new statistical properties, we obtain the exact and asymptotic expressions for the average harvested energy. Then, we derive the average uplink achievable rate under the harvested energy constraint. Numerical results demonstrate that the use of massive MIMO antennas can improve both the users’ harvested energy and uplink achievable rate in the HetNets; however, it has negligible effect on the ambient RF energy harvesting. Serving more users in the massive MIMO macrocells will deteriorate the uplink information transfer because of less harvested energy and more uplink interference. Moreover, although DRSP-based user association harvests more energy to provide larger uplink transmit power than the URSP-based one in the massive MIMO HetNets, URSP-based user association could achieve better performance in the uplink information transmission.

Connected through hyperedge HE-1 (induced by source paper "optimal downlink transmission for cell free swipt massive mimo systems with active eavesdropping"):
  with members:
    - "ubiquitous cell free massive mimo communications"
    - "cell free massive mimo networks optimal power control against active eavesdropping"
    - "spectral and energy efficiency of cell free massive mimo systems with hardware impairments"
    - "on the total energy efficiency of cell free massive mimo"
    - "energy efficiency in cell free massive mimo with zero forcing precoding design"
    - "secrecy and energy efficiency in massive mimo aided heterogeneous c ran a new look at interference"
    - "cell free massive mimo versus small cells"
    - "how much do downlink pilots improve cell free massive mimo"

Connected through hyperedge HE-2 (induced by source paper "multi antenna aided secrecy beamforming optimization for wirelessly powered hetnets"):
  with members:
    - "optimal beamforming and time allocation for partially wireless powered sensor networks with downlink swipt"
    - "energy efficient user association and power allocation in millimeter wave based ultra dense networks with energy harvesting base stations"
    - "secrecy transmit beamforming for heterogeneous networks"
    - "evolution toward 5g multi tier cellular wireless networks an interference management perspective"
    - "five disruptive technology directions for 5g"
    - "outage constrained robust secure transmission for miso wiretap channels"
    - "heterogeneous cellular networks with flexible cell association a comprehensive downlink sinr analysis"
    - "optimal and robust transmit designs for miso channel secrecy by semidefinite programming"

Connected through hyperedge HE-3 (induced by source paper "content placement in cache enabled sub 6 ghz and millimeter wave multi antenna dense small cell networks"):
  with members:
    - "random caching based cooperative transmission in heterogeneous wireless networks"
    - "modeling and analyzing millimeter wave cellular systems"
    - "caching meets millimeter wave communications for enhanced mobility management in 5g networks"
    - "caching policy toward maximal success probability and area spectral efficiency of cache enabled hetnets"
    - "a tractable framework for performance analysis of dense multi antenna networks"
    - "a new look at physical layer security caching and wireless energy harvesting for heterogeneous ultra dense networks"
    - "antenna count for massive mimo 1 9 ghz versus 60 ghz"
    - "on optimal geographical caching in heterogeneous cellular networks"

Connected through hyperedge HE-4 (induced by source paper "fundamentals of simultaneous wireless information and power transmission in heterogeneous networks a cell load perspective"):
  with members:
    - "modeling and analysis of cellular networks using stochastic geometry a tutorial"
    - "fundamentals of the downlink green coverage and energy efficiency in heterogeneous networks"
    - "traffic management for heterogeneous networks with opportunistic unlicensed spectrum sharing"
    - "on the limits of coexisting coverage and capacity in multi rat heterogeneous networks"
    - "random cell association and void probability in poisson distributed cellular networks"
    - "optimal cell load and throughput in green small cell networks with generalized cell association"
    - "wireless networks with rf energy harvesting a contemporary survey"
    - "simultaneous information and energy transfer in large scale networks with without relaying"

Connected through hyperedge HE-5 (induced by source paper "user association and load balancing for massive mimo through deep learning"):
  with members:
    - "massive mimo has unlimited capacity"
    - "joint power allocation and user association optimization for massive mimo systems"
    - "massive mimo with multi cell mmse processing exploiting all pilots for interference suppression"
    - "user association and interference management in massive mimo hetnets"
    - "adam a method for stochastic optimization"
    - "optimal user cell association for massive mimo wireless networks"

Connected through hyperedge HE-6 (induced by source paper "wireless powered dense cellular networks how many small cells do we need"):
  with members:
    - "user association in 5g networks a survey and an outlook"
    - "tractable resource management with uplink decoupled millimeter wave overlay in ultra dense cellular networks"
    - "millimeter wave energy harvesting"
    - "performance analysis of ambient rf energy harvesting with repulsive point process modeling"
    - "millimeter wave power transfer and information transmission"
    - "deploying dense networks for maximal energy efficiency small cells meet massive mimo"
    - "5g ultra dense cellular networks"
    - "throughput optimization for massive mimo systems powered by wireless energy transfer"

Connected through hyperedge HE-7 (induced by source paper "wireless powered cooperative jamming for secure ofdm system"):
  with members:
    - "waveform optimization for radio frequency wireless power transfer"
    - "waveform design for wireless power transfer"
    - "secrecy wireless information and power transfer in fading wiretap channel"
    - "a general design framework for mimo wireless energy transfer with limited feedback"
    - "accumulate and jam towards secure communication via a wireless powered full duplex jammer"
    - "communications and signals design for wireless power transmission"
    - "to harvest and jam a paradigm of self sustaining friendly jammers for secure af relaying"
    - "wireless powered communication opportunities and challenges"

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)