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: "cell free massive mimo uniformly great service for everyone"
  Abstract: We consider the downlink of Cell-Free Massive MIMO systems, where a very large number of distributed access points (APs) simultaneously serve a much smaller number of users. Each AP uses local channel estimates obtained from received uplink pilots and applies conjugate beamforming to transmit data to the users. We derive a closed-form expression for the achievable rate. This expression enables us to design an optimal max-min power control scheme that gives equal quality of service to all users. #R##N#We further compare the performance of the Cell-Free Massive MIMO system to that of a conventional small-cell network and show that the throughput of the Cell-Free system is much more concentrated around its median compared to that of the small-cell system. The Cell-Free Massive MIMO system can provide an almost $20-$fold increase in 95%-likely per-user throughput, compared with the small-cell system. Furthermore, Cell-Free systems are more robust to shadow fading correlation than small-cell systems.

Connected through hyperedge HE-1 (induced by source paper "analysis of uav communications in cell free massive mimo systems"):
  with members:
    - "scalability aspects of cell free massive mimo"
    - "max min rate of cell free massive mimo uplink with optimal uniform quantization"
    - "ubiquitous cell free massive mimo communications"
    - "cellular uav to uav communications"
    - "making cell free massive mimo competitive with mmse processing and centralized implementation"
    - "understanding uav cellular communications from existing networks to massive mimo"
    - "tutorial on uav a blue sky view on wireless communication"
    - "cellular connected uav uplink association power control and interference coordination"

Connected through hyperedge HE-2 (induced by source paper "enabling uav communications with cell free massive mimo"):
  with members:
    - "ubiquitous cell free massive mimo communications"
    - "making cell free massive mimo competitive with mmse processing and centralized implementation"
    - "understanding uav cellular communications from existing networks to massive mimo"
    - "supporting uav cellular communications through massive mimo"
    - "the essential guide to realizing 5g connected uavs with massive mimo"
    - "the sky is not the limit lte for unmanned aerial vehicles"
    - "downlink performance of uplink fractional power control in 5g massive mimo systems"
    - "a tutorial on uavs for wireless networks applications challenges and open problems"

Connected through hyperedge HE-3 (induced by source paper "edge computing enabled cell free massive mimo systems"):
  with members:
    - "mobile edge computing enabled heterogeneous networks"
    - "fog massive mimo a user centric seamless hot spot architecture"
    - "joint energy minimization and resource allocation in c ran with mobile cloud"
    - "a survey on mobile edge computing the communication perspective"
    - "channel hardening and favorable propagation in cell free massive mimo with stochastic geometry"
    - "energy efficient resource allocation for mobile edge computation offloading"
    - "collaborative mobile edge computing in 5g networks new paradigms scenarios and challenges"
    - "power delay tradeoff in multi user mobile edge computing systems"

Connected through hyperedge HE-4 (induced by source paper "performance of network assisted full duplex for cell free massive mimo"):
  with members:
    - "on the feasibility of full duplex large scale mimo cellular systems"
    - "cell free massive mimo versus small cells"
    - "full duplex emulation via spatial separation of half duplex nodes in a planar cellular network"
    - "why to decouple the uplink and downlink in cellular networks and how to do it"
    - "interference management in 5g reverse tdd hetnets with wireless backhaul a large system analysis"
    - "compflex comp for in band wireless full duplex"
    - "in band alpha duplex scheme for cellular networks a stochastic geometry approach"
    - "multipair full duplex relaying with massive arrays and linear processing"

Connected through hyperedge HE-5 (induced by source paper "cell free massive mimo networks optimal power control against active eavesdropping"):
  with members:
    - "on the total energy efficiency of cell free massive mimo"
    - "mimo beamforming for secure and energy efficient wireless communication"
    - "energy efficiency in cell free massive mimo with zero forcing precoding design"
    - "mimo secret communications against an active eavesdropper"
    - "cell free massive mimo versus small cells"
    - "secure massive mimo transmission with an active eavesdropper"
    - "secret key agreement with large antenna arrays under the pilot contamination attack"
    - "physical layer security for massive mimo an overview on passive eavesdropping and active attacks"

Connected through hyperedge HE-6 (induced by source paper "a bilinear equalizer for massive mimo systems"):
  with members:
    - "massive mimo has unlimited capacity"
    - "uplink interference reduction in large scale antenna systems"
    - "massive mimo with imperfect channel covariance information"
    - "robust pilot decontamination based on joint angle and power domain discrimination"
    - "cell free massive mimo versus small cells"
    - "low complexity polynomial channel estimation in large scale mimo with arbitrary statistics"
    - "massive mimo for maximal spectral efficiency how many users and pilots should be allocated"
    - "scaling up mimo opportunities and challenges with very large arrays"

Connected through hyperedge HE-7 (induced by source paper "learning the mmse channel estimator"):
  with members:
    - "investigation of prediction accuracy sensitivity and parameter stability of large scale propagation path loss models for 5g wireless communications"
    - "cell free massive mimo versus small cells"
    - "massive mimo in real propagation environments do all antennas contribute equally"
    - "adam a method for stochastic optimization"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "distributed compressive csit estimation and feedback for fdd multi user massive mimo systems"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"

Connected through hyperedge HE-8 (induced by source paper "user centric 5g cellular networks resource allocation and comparison with the cell free massive mimo approach"):
  with members:
    - "cell free massive mimo with limited backhaul"
    - "cell free and user centric massive mimo at millimeter wave frequencies"
    - "downlink power control in user centric and cell free massive mimo wireless networks"
    - "cell free massive mimo versus small cells"
    - "how much do downlink pilots improve cell free massive mimo"
    - "compute and forward in cell free massive mimo great performance with low backhaul load"
    - "what will 5g be"

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)