human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "optimal user association for massive mimo empowered ultra dense wireless networks"):
  Abstract: Ultra network densification and Massive MIMO are considered major 5G enablers since they promise huge capacity gains by exploiting proximity, spectral and spatial reuse benefits. Both approaches rely on increasing the number of access elements per user, either through deploying more access nodes over an area or increasing the number of antenna elements per access node. At the network-level, optimal user-association for a densely and randomly deployed network of Massive MIMO empowered access nodes must account for both channel and load conditions. In this paper we formulate this complex problem, report its computationally intractability and reformulate it to a plausible form, amenable to acquire a global optimal solution with reasonable complexity. We apply the proposed optimization model to typical ultra-dense outdoor small-cell setups and demonstrate: (i) the significant impact of optimal user-association to the achieved rate levels compared to a baseline strategy, and (ii) the optimality of alternative network access element deployment strategies.

Includes members:
  Member "delay minimizing user association in cellular networks via hierarchically well separated trees":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "utility maximization for single station user association in downlink cellular networks")
  Member "large scale mimo versus network mimo for multicell interference mitigation":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "multi cell sparse activity detection for massive random access massive mimo versus cooperative mimo")
  Member "massive mimo for next generation wireless systems":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "joint power control and lsfd for wireless powered cell free massive mimo")
  Member "what will 5g be":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "5g network slicing using sdn and nfv a survey of taxonomy architectures and future challenges")
  Member "evolution toward 5g multi tier cellular wireless networks an interference management perspective":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "a survey on the security and the evolution of osmotic and catalytic computing for 5g networks")

Question: Please tell me which class the source paper 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.NI(Networking and Internet Architecture)