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: "open vs closed access femtocells in the uplink"
  Abstract: Femtocells are assuming an increasingly important role in the coverage and capacity of cellular networks. In contrast to existing cellular systems, femtocells are end-user deployed and controlled, randomly located, and rely on third party backhaul (e.g. DSL or cable modem). Femtocells can be configured to be either open access or closed access. Open access allows an arbitrary nearby cellular user to use the femtocell, whereas closed access restricts the use of the femtocell to users explicitly approved by the owner. Seemingly, the network operator would prefer an open access deployment since this provides an inexpensive way to expand their network capabilities, whereas the femtocell owner would prefer closed access, in order to keep the femtocell's capacity and backhaul to himself. We show mathematically and through simulations that the reality is more complicated for both parties, and that the best approach depends heavily on whether the multiple access scheme is orthogonal (TDMA or OFDMA, per subband) or non-orthogonal (CDMA). In a TDMA/OFDMA network, closed-access is typically preferable at high user densities, whereas in CDMA, open access can provide gains of more than 300% for the home user by reducing the near-far problem experienced by the femtocell. The results of this paper suggest that the interests of the femtocell owner and the network operator are more compatible than typically believed, and that CDMA femtocells should be configured for open access whereas OFDMA or TDMA femtocells should adapt to the cellular user density.

Connected through hyperedge HE-1 (induced by source paper "a game theoretical approach for qos provisioning in heterogeneous networks"):
  with members:
    - "call admission control based on adaptive bandwidth allocation for wireless networks"
    - "cost effective frequency planning for capacity enhancement of femtocellular networks"
    - "power control in two tier femtocell networks"
    - "uplink capacity and interference avoidance for two tier femtocell networks"

Connected through hyperedge HE-2 (induced by source paper "physical layer security in heterogeneous cellular networks"):
  with members:
    - "optimal power allocation for artificial noise under imperfect csi against spatially random eavesdroppers"
    - "secrecy transmit beamforming for heterogeneous networks"
    - "physical layer security in downlink multi antenna cellular networks"
    - "principles of physical layer security in multiuser wireless networks a survey"
    - "throughput and energy efficiency analysis of small cell networks with multi antenna base stations"
    - "enhancing secrecy with multi antenna transmission in wireless ad hoc networks"
    - "physical layer security in cellular networks a stochastic geometry approach"
    - "on the design of artificial noise aided secure multi antenna transmission in slow fading channels"

Connected through hyperedge HE-3 (induced by source paper "multi antenna transmission in downlink heterogeneous cellular networks under a threshold based mobile association policy"):
  with members:
    - "optimal power allocation for artificial noise under imperfect csi against spatially random eavesdroppers"
    - "success probability and area spectral efficiency in multiuser mimo hetnets"
    - "optimal cell load and throughput in green small cell networks with generalized cell association"
    - "what will 5g be"
    - "massive mimo meets hetnet interference coordination through spatial blanking"
    - "throughput and energy efficiency analysis of small cell networks with multi antenna base stations"
    - "downlink mimo hetnets modeling ordering results and performance analysis"
    - "offloading in heterogeneous networks modeling analysis and design insights"

Connected through hyperedge HE-4 (induced by source paper "transmit power minimization in small cell networks under time average qos constraints"):
  with members:
    - "dynamic resource allocation in cognitive radio networks"
    - "femto macro cellular interference control with subband scheduling and interference cancelation"
    - "stability and delay of zero forcing sdma with limited feedback"
    - "training and feedback optimization for multiuser mimo downlink"
    - "delay optimal power and precoder adaptation for multi stream mimo systems"
    - "on peak versus average interference power constraints for protecting primary users in cognitive radio networks"

Connected through hyperedge HE-5 (induced by source paper "opportunistic multi channel access in heterogeneous networks with renewable energy supplies"):
  with members:
    - "optimal adaptive random multiaccess in energy harvesting wireless sensor networks"
    - "energy harvesting wireless communications a review of recent advances"
    - "throughput maximization for the gaussian relay channel with energy harvesting constraints"
    - "medium access control protocols for wireless sensor networks with energy harvesting"
    - "optimal save then transmit protocol for energy harvesting wireless transmitters"
    - "enhanced intercell interference coordination challenges in heterogeneous networks"
    - "optimal energy allocation for wireless communications with energy harvesting constraints"
    - "transmission with energy harvesting nodes in fading wireless channels optimal policies"

Connected through hyperedge HE-6 (induced by source paper "downlink cellular network analysis with multi slope path loss models"):
  with members:
    - "tractable model for rate in self backhauled millimeter wave cellular networks"
    - "coverage and rate analysis for millimeter wave cellular networks"
    - "millimeter wave cellular wireless networks potentials and challenges"
    - "a stochastic geometry analysis of inter cell interference coordination and intra cell diversity"
    - "analysis of blockage effects on urban cellular networks"
    - "modeling heterogeneous network interference using poisson point processes"
    - "modeling and analysis of k tier downlink heterogeneous cellular networks"
    - "mean interference in hard core wireless networks"

Connected through hyperedge HE-7 (induced by source paper "interference statistics and capacity analysis for uplink transmission in two tier small cell networks a geometric probability approach"):
  with members:
    - "on stochastic geometry modeling of cellular uplink transmission with truncated channel inversion power control"
    - "analytical modeling of uplink cellular networks"
    - "load aware modeling and analysis of heterogeneous cellular networks"
    - "heterogeneous cellular networks with flexible cell association a comprehensive downlink sinr analysis"
    - "modeling heterogeneous network interference using poisson point processes"
    - "modeling and analysis of k tier downlink heterogeneous cellular networks"
    - "a tractable approach to coverage and rate in cellular networks"
    - "coverage in multi antenna two tier networks"

Connected through hyperedge HE-8 (induced by source paper "spectrum and energy efficiency evaluation of two tier femtocell networks with partially open channels"):
  with members:
    - "spectrum leasing as an incentive towards uplink macrocell and femtocell cooperation"
    - "capacity analysis of a multi cell multi antenna cooperative cellular network with co channel interference"
    - "green cellular networks a survey some research issues and challenges"
    - "power control in two tier femtocell networks"
    - "interference mitigation using uplink power control for two tier femtocell networks"
    - "femtocell networks a survey"
    - "uplink capacity and interference avoidance for two tier femtocell networks"

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)