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: "user association and resource allocation in unified non orthogonal multiple access enabled heterogeneous ultra dense networks"
  Abstract: Heterogeneous ultra dense networks (HUDNs) and non-orthogonal multiple access (NOMA) have been identified as two proposing techniques for 5G mobile communication systems due to their great capabilities to enhance spectrum efficiency. This article investigates the application of NOMA techniques in HUDNs to support massive connectivity in 5G systems. In particular, a unified NOMA framework is proposed, including power-domain NOMA and code-domain NOMA, which can be configured flexibly to serve different application scenarios. As a further advance, unified NOMA framework enabled HUDNs are further investigated, with particular focus on user association and resource allocation. Two case studies are provided for demonstrating the effectiveness of unified NOMA enabled HUDNs. Finally, some main challenges and promising research directions in NOMA enabled HUDNs are identified.

Connected through hyperedge HE-1 (induced by source paper "noma enhanced terrestrial and aerial iot networks with partial csi"):
  with members:
    - "beyond 5g with uavs foundations of a 3d wireless cellular network"
    - "spectral and energy efficient wireless powered iot networks noma or tdma"
    - "multiple antenna aided noma in uav networks a stochastic geometry approach"
    - "multidimensional constellations for uplink scma systems a comparative study"
    - "mobile unmanned aerial vehicles uavs for energy efficient internet of things communications"
    - "modulation and multiple access for 5g networks"
    - "throughput of cognitive radio systems with finite blocklength codes"

Connected through hyperedge HE-2 (induced by source paper "exploiting noma for uav communications in large scale cellular networks"):
  with members:
    - "downlink non orthogonal multiple access noma in poisson networks"
    - "exploiting noma for multi beam uav communication in cellular uplink"
    - "connectivity and blockage effects in millimeter wave air to everything networks"
    - "uav aided offloading for cellular hotspot"
    - "modeling and analysis of two way relay non orthogonal multiple access systems"
    - "energy minimization for wireless communication with rotary wing uav"
    - "cellular enabled uav communication a connectivity constrained trajectory optimization perspective"
    - "multiple antenna aided noma in uav networks a stochastic geometry approach"

Connected through hyperedge HE-3 (induced by source paper "non orthogonal multiple access in uav to everything u2x networks"):
  with members:
    - "exploiting noma oma for multi uav communications in large scale networks"
    - "exploiting noma for multi beam uav communication in cellular uplink"
    - "connectivity and blockage effects in millimeter wave air to everything networks"
    - "energy minimization for wireless communication with rotary wing uav"
    - "cellular enabled uav communication a connectivity constrained trajectory optimization perspective"
    - "multiple antenna aided noma in uav networks a stochastic geometry approach"
    - "modeling and analysis of d2d millimeter wave networks with poisson cluster processes"
    - "uplink cooperative noma for cellular connected uav"

Connected through hyperedge HE-4 (induced by source paper "multiple antenna aided noma in uav networks a stochastic geometry approach"):
  with members:
    - "multiple antenna assisted non orthogonal multiple access"
    - "toward cross layer design for non orthogonal multiple access a quality of experience perspective"
    - "resource allocation for downlink noma systems key techniques and open issues"
    - "modulation and multiple access for 5g networks"
    - "capacity comparison between mimo noma and mimo oma with multiple users in a cluster"
    - "efficient deployment of multiple unmanned aerial vehicles for optimal wireless coverage"
    - "enabling uav cellular with millimeter wave communication potentials and approaches"
    - "enhancing the physical layer security of non orthogonal multiple access in large scale networks"

Connected through hyperedge HE-5 (induced by source paper "robust physical layer security for power domain non orthogonal multiple access based hetnets and hudns sic avoidance at eavesdroppers"):
  with members:
    - "massive connectivity with massive mimo part i device activity detection and channel estimation"
    - "joint power allocation and beamforming for non orthogonal multiple access noma in 5g millimeter wave communications"
    - "secrecy sum rate maximization in non orthogonal multiple access"
    - "on the spectral efficiency and security enhancements of noma assisted multicast unicast streaming"
    - "optimal joint power and subcarrier allocation for full duplex multicarrier non orthogonal multiple access systems"
    - "enhancing the physical layer security of non orthogonal multiple access in large scale networks"
    - "fairness for non orthogonal multiple access in 5g systems"
    - "a general mimo framework for noma downlink and uplink transmission based on signal alignment"

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)