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: "on the optimum energy efficiency for flat fading channels with rate dependent circuit power"
  Abstract: This paper investigates the optimum energy efficiency (EE) and the corresponding spectral efficiency (SE) for a communication link operating over a flat-fading channel. The EE is evaluated by the total energy consumption for transmitting per message bit. Three channel cases are considered, namely static channel with channel state information available at transmitter (CSIT), fast-varying (FV) channel with channel distribution information available at transmitter (CDIT), and FV channel with CSIT. A general circuit power model is considered. For all the three channel cases, the tradeoff between the EE and SE is studied. It is shown that the EE improves strictly as the SE increases from 0 to the optimum SE, and then strictly degrades as the SE increases beyond the optimum SE. The impact of {\kappa}, {\rho} and other system parameters on the optimum EE and corresponding SE is investigated to obtain insight.Some of the important and interesting results for all the channel cases include: (1) when {\kappa} increases the SE corresponding to the optimum EE should keep unchanged if {\phi}(R) = R, but reduced if {\phi}(R) is strictly convex of R; (2) when the rate-independent circuit power {\rho} increases, the SE corresponding to the optimum EE has to be increased. A polynomial-complexity algorithm is developed with the bisection method to find the optimum SE. The insight is corroborated and the optimum EE for the three cases are compared by simulation results.

Connected through hyperedge HE-1 (induced by source paper "energy efficiency maximization for c rans discrete monotonic optimization penalty and ell _ 0 approximation methods"):
  with members:
    - "globally optimal beamforming design for downlink comp transmission with limited backhaul capacity"
    - "elastic net boosting energy efficiency and resource utilization in 5g c rans"
    - "understanding the computational requirements of virtualized baseband units using a programmable cloud radio access network testbed"
    - "recent advances in cloud radio access networks system architectures key techniques and open issues"
    - "energy efficiency of downlink transmission strategies for cloud radio access networks"
    - "fronthaul constrained cloud radio access networks insights and challenges"
    - "backhaul limited asymmetric cooperation for mimo cellular networks via semidefinite relaxation"
    - "sparse beamforming and user centric clustering for downlink cloud radio access network"

Connected through hyperedge HE-2 (induced by source paper "energy efficient beam coordination strategies with rate dependent processing power"):
  with members:
    - "comparison of polar decoders with existing low density parity check and turbo decoders"
    - "optimal policies for wireless networks with energy harvesting transmitters and receivers effects of decoding costs"
    - "energy efficient precoder design for mimo ofdm with rate dependent circuit power"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "energy efficient scheduling and power allocation in downlink ofdma networks with base station coordination"
    - "optimal design of energy efficient multi user mimo systems is massive mimo the answer"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"
    - "fast converging algorithm for weighted sum rate maximization in multicell miso downlink"

Connected through hyperedge HE-3 (induced by source paper "energy efficient transmission strategies for comp downlink overview extension and numerical comparison"):
  with members:
    - "energy efficient coordinated multi cell multi group multicast beamforming with antenna selection"
    - "energy efficient beam coordination strategies with rate dependent processing power"
    - "energy efficient scheduling and power allocation in downlink ofdma networks with base station coordination"
    - "max min energy efficient beamforming for multicell multiuser joint transmission systems"
    - "framework for link level energy efficiency optimization with informed transmitter"
    - "a quantitative measure of fairness and discrimination for resource allocation in shared computer systems"

Connected through hyperedge HE-4 (induced by source paper "energy efficient precoder design for mimo ofdm with rate dependent circuit power"):
  with members:
    - "framework for link level energy efficiency optimization with informed transmitter"
    - "energy efficient precoding for multiple antenna terminals"

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.OH(Other Computer Science)