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: "increasing opportunistic gain in small cells through energy aware user cooperation"
  Abstract: To meet the increasing demand for wireless capacity, future networks are likely to consist of dense layouts of small cells. The number of users in each cell is thus reduced which results in diminished gains from opportunistic scheduling, particularly under dynamic traffic loads. We propose an user-initiated base station (BS)-transparent traffic spreading approach that leverages user-user communication to increase BS scheduling flexibility. The proposed scheme can increase opportunistic gain and improve user performance. For a specified tradeoff between performance and power expenditure, we characterize the optimal policy by modeling the system as a Markov decision process and also present a heuristic algorithm that yields significant performance gains. Our simulations show that, in the performance-centric case, average file transfer delays are lowered by up to 20% even in homogeneous scenarios, and up to 50% with heterogeneous users. Further, we show that the bulk of the performance improvement can be achieved with a small increase in power expenditure, e.g., in an energy-sensitive case, up to 78% of the performance improvement can be typically achieved at only 20% of the power expenditure of the performance-centric case.

Connected through hyperedge HE-1 (induced by source paper "fundamental green tradeoffs progresses challenges and impacts on 5g networks"):
  with members:
    - "spectrum power trading for energy efficient small cell"
    - "power efficient resource allocation for full duplex radio distributed antenna networks"
    - "energy recycling full duplex radios for next generation networks"
    - "energy efficient resource allocation for wireless powered communication networks"
    - "multi objective optimization for robust power efficient and secure full duplex wireless communication systems"
    - "hybrid millimeter wave systems a novel paradigm for hetnets"
    - "coexistence of wi fi and heterogeneous small cell networks sharing unlicensed spectrum"
    - "on the spectral efficiency of full duplex small cell wireless systems"

Connected through hyperedge HE-2 (induced by source paper "a survey on device to device communication in cellular networks"):
  with members:
    - "wireless device to device caching networks basic principles and system performance"
    - "spectrum sharing for device to device communication in cellular networks"
    - "low rate machine type communication via wireless device to device d2d links"
    - "spectrum sharing scheme between cellular users and ad hoc device to device users"
    - "base station assisted device to device communications for high throughput wireless video networks"
    - "fundamental limits of caching"

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.NI(Networking and Internet Architecture)