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 efficient user association and power allocation in millimeter wave based ultra dense networks with energy harvesting base stations"
  Abstract: Millimeter wave (mmWave) communication technologies have recently emerged as an attractive solution to meet the exponentially increasing demand on mobile data traffic. Moreover, ultra dense networks (UDNs) combined with mmWave technology are expected to increase both energy efficiency and spectral efficiency. In this paper, user association and power allocation in mmWave based UDNs is considered with attention to load balance constraints, energy harvesting by base stations, user quality of service requirements, energy efficiency, and cross-tier interference limits. The joint user association and power optimization problem is modeled as a mixed-integer programming problem, which is then transformed into a convex optimization problem by relaxing the user association indicator and solved by Lagrangian dual decomposition. An iterative gradient user association and power allocation algorithm is proposed and shown to converge rapidly to an optimal point. The complexity of the proposed algorithm is analyzed and the effectiveness of the proposed scheme compared with existing methods is verified by simulations.

Connected through hyperedge HE-1 (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"
    - "wireless power transfer in massive mimo aided hetnets with user association"
    - "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-2 (induced by source paper "user association in dense mmwave networks based on rate requirements"):
  with members:
    - "time fractional user association in millimeter wave mimo networks"
    - "maximum throughput scheduling for multi connectivity in millimeter wave networks"
    - "optimal user cell association for massive mimo wireless networks"
    - "what will 5g be"
    - "user association for load balancing in heterogeneous cellular networks"

Connected through hyperedge HE-3 (induced by source paper "joint user association and resource allocation in the uplink of heterogeneous networks"):
  with members:
    - "multiple antenna technologies for beyond 5g"
    - "user transmit power minimization through uplink resource allocation and user association in hetnets"
    - "power efficient resource allocation for full duplex radio distributed antenna networks"

Connected through hyperedge HE-4 (induced by source paper "distributed uplink power control in an ultra dense millimeter wave network a mean field game approach"):
  with members:
    - "caching meets millimeter wave communications for enhanced mobility management in 5g networks"
    - "cognitive hierarchy theory for distributed resource allocation in the internet of things"
    - "millimeter wave cellular wireless networks potentials and challenges"

Connected through hyperedge HE-5 (induced by source paper "energy and delay optimization for cache enabled dense small cell networks"):
  with members:
    - "caching policy optimization for d2d communications by learning user preference"
    - "caching at the wireless edge design aspects challenges and future directions"
    - "a learning based approach to caching in heterogenous small cell networks"
    - "content centric sparse multicast beamforming for cache enabled cloud ran"
    - "power efficient resource allocation for full duplex radio distributed antenna networks"
    - "learning based optimization of cache content in a small cell base station"
    - "living on the edge the role of proactive caching in 5g wireless networks"
    - "mixed timescale precoding and cache control in cached mimo interference network"

Connected through hyperedge HE-6 (induced by source paper "device to device communications enabled multicast scheduling with the multi level codebook in mmwave small cells"):
  with members:
    - "joint power allocation and beamforming for non orthogonal multiple access noma in 5g millimeter wave communications"
    - "hierarchical codebook design for beamforming training in millimeter wave communication"
    - "millimeter wave vehicular communication to support massive automotive sensing"
    - "exploiting device to device communications to enhance spatial reuse for popular content downloading in directional mmwave small cells"
    - "enabling uav cellular with millimeter wave communication potentials and approaches"
    - "exploiting device to device communications in joint scheduling of access and backhaul for mmwave small cells"
    - "femtocell networks a survey"

Connected through hyperedge HE-7 (induced by source paper "user association and resource allocation in unified non orthogonal multiple access enabled heterogeneous ultra dense networks"):
  with members:
    - "non orthogonal multiple access in large scale heterogeneous networks"
    - "modulation and multiple access for 5g networks"
    - "fronthauling for 5g lte u ultra dense cloud small cell networks"
    - "optimal joint power and subcarrier allocation for full duplex multicarrier non orthogonal multiple access systems"
    - "5g ultra dense cellular networks"
    - "a quantitative measure of fairness and discrimination for resource allocation in shared computer systems"

Connected through hyperedge HE-8 (induced by source paper "user association and resource allocation in unified noma enabled heterogeneous ultra dense networks"):
  with members:
    - "non orthogonal multiple access in large scale heterogeneous networks"
    - "modulation and multiple access for 5g networks"
    - "fronthauling for 5g lte u ultra dense cloud small cell networks"
    - "optimal joint power and subcarrier allocation for full duplex multicarrier non orthogonal multiple access systems"
    - "5g ultra dense cellular 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)