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: "massive mimo and small cells improving energy efficiency by optimal soft cell coordination"
  Abstract: To improve the cellular energy efficiency, without sacrificing quality-of-service (QoS) at the users, the network topology must be densified to enable higher spatial reuse. We analyze a combination of two densification approaches, namely “massive” multiple-input multiple-output (MIMO) base stations and small-cell access points. If the latter are operator-deployed, a spatial soft-cell approach can be taken where the multiple transmitters serve the users by joint non-coherent multiflow beamforming. We minimize the total power consumption (both dynamic emitted power and static hardware power) while satisfying QoS constraints. This problem is proved to have a hidden convexity that enables efficient solution algorithms. Interestingly, the optimal solution promotes exclusive assignment of users to transmitters. Furthermore, we provide promising simulation results showing how the total power consumption can be greatly improved by combining massive MIMO and small cells; this is possible with both optimal and low-complexity beamforming.

Connected through hyperedge HE-1 (induced by source paper "a data aided channel estimation scheme for decoupled systems in heterogeneous networks"):
  with members:
    - "performance impact of los and nlos transmissions in dense cellular networks"
    - "why to decouple the uplink and downlink in cellular networks and how to do it"
    - "analysis of the decoupled access for downlink and uplink in wireless heterogeneous networks"
    - "joint rate and sinr coverage analysis for decoupled uplink downlink biased cell associations in hetnets"
    - "what will 5g be"
    - "massive mimo meets hetnet interference coordination through spatial blanking"
    - "downlink and uplink decoupling a disruptive architectural design for 5g networks"
    - "load backhaul aware decoupled downlink uplink access in 5g systems"

Connected through hyperedge HE-2 (induced by source paper "toward intelligent network optimization in wireless networking an auto learning framework"):
  with members:
    - "cognitive lpwan towards intelligent wireless services in hybrid low power wide area networks"
    - "machine learning for networking workflow advances and opportunities"
    - "coalitional game theory for communication networks a tutorial"

Connected through hyperedge HE-3 (induced by source paper "heterogeneous cellular networks with los and nlos transmissions the role of massive mimo and small cells"):
  with members:
    - "modeling and analyzing millimeter wave cellular systems"
    - "downlink cellular network analysis with los nlos propagation and elevated base stations"
    - "performance impact of los and nlos transmissions in dense cellular networks"
    - "power allocation schemes for multicell massive mimo systems"
    - "massive mimo versus small cell systems spectral and energy efficiency comparison"
    - "energy efficient design of mimo heterogeneous networks with wireless backhaul"
    - "analyzing uplink sinr and rate in massive mimo systems using stochastic geometry"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"

Connected through hyperedge HE-4 (induced by source paper "user association in massive mimo hetnets"):
  with members:
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"
    - "joint spatial division and multiplexing opportunistic beamforming and user grouping"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "downlink multi antenna heterogeneous cellular network with load balancing"
    - "user association for load balancing in heterogeneous cellular networks"

Connected through hyperedge HE-5 (induced by source paper "energy efficiency and sum rate tradeoffs for massive mimo systems with underlaid device to device communications"):
  with members:
    - "massive mimo ten myths and one critical question"
    - "energy efficiency and sum rate when massive mimo meets device to device communication"
    - "an analytical framework for device to device communication in cellular networks"
    - "energy efficient resource allocation for device to device underlay communication"
    - "design aspects of short range millimeter wave networks a mac layer perspective"
    - "the interplay between massive mimo and underlaid d2d networking"
    - "optimal multiuser transmit beamforming a difficult problem with a simple solution structure"
    - "spectrum sharing for device to device communication in cellular networks"

Connected through hyperedge HE-6 (induced by source paper "wireless power transfer in massive mimo aided hetnets with user association"):
  with members:
    - "user association in massive mimo hetnets"
    - "user association in 5g networks a survey and an outlook"
    - "joint downlink cell association and bandwidth allocation for wireless backhauling in two tier hetnets with large scale antenna arrays"
    - "millimeter wave energy harvesting"
    - "performance analysis of simultaneous wireless information and power transfer with ambient rf energy harvesting"
    - "why to decouple the uplink and downlink in cellular networks and how to do it"
    - "5g cellular key enabling technologies and research challenges"
    - "millimeter wave power transfer and information transmission"

Connected through hyperedge HE-7 (induced by source paper "joint power allocation and user association optimization for massive mimo systems"):
  with members:
    - "downlink power control for massive mimo cellular systems with optimal user association"
    - "massive mimo ten myths and one critical question"
    - "graph coloring based pilot allocation to mitigate pilot contamination for multi cell massive mimo systems"
    - "joint downlink base station association and power control for max min fairness computation and complexity"
    - "uplink pilot and data power control for single cell massive mimo systems with mrc"
    - "massive mimo performance evaluation based on measured propagation data"
    - "smart pilot assignment for massive mimo"
    - "optimal user cell association for massive mimo wireless networks"

Connected through hyperedge HE-8 (induced by source paper "efficient optimal joint channel estimation and data detection for massive mimo systems"):
  with members:
    - "optimality of large mimo detection via approximate message passing"
    - "joint channel and data estimation for large mimo systems with low precision adcs"
    - "massive mimo for next generation wireless systems"
    - "optimal non coherent data detection for massive simo wireless systems a polynomial complexity solution"
    - "blind pilot decontamination"
    - "massive mu mimo downlink tdd systems with linear precoding and downlink pilots"
    - "massive mimo how many antennas do we need"
    - "glrt optimal noncoherent lattice decoding"

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)