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: "maximizing energy efficiency in multi relay ofdma cellular networks"
  Abstract: This contribution presents a method of obtaining the optimal power and subcarrier allocations that maximize the energy-efficiency (EE) of a multi-user, multi-relay, orthogonal frequency division multiple access (OFDMA) cellular network. Initially, the objective function (OF) is formulated as the ratio of the spectral-efficiency (SE) over the power consumption of the network. This OF is shown to be quasi-concave, thus Dinkelbach's method can be employed for solving it as a series of parameterized concave problems. We characterize the performance of the aforementioned method by comparing the optimal solutions obtained to those found using an exhaustive search. Additionally, we explore the relationship between the achievable SE and EE in the cellular network upon increasing the number of active users. In general, increasing the number of users supported by the system benefits both the SE and EE, and higher SE values may be obtained at the cost of EE, when an increased power may be allocated.

Connected through hyperedge HE-1 (induced by source paper "energy efficient resource allocation for time varying ofdma relay systems with hybrid energy supplies"):
  with members:
    - "cross layer scheduling for ofdma based cognitive radio systems with delay and security constraints"
    - "power allocation for conventional and buffer aided link adaptive relaying systems with energy harvesting nodes"
    - "energy efficient resource allocation in ofdma systems with hybrid energy harvesting base station"
    - "decentralized delay optimal control for interference networks with limited renewable energy storage"
    - "jointly optimal channel and power assignment for dual hop multi channel multi user relaying"
    - "a cross layer perspective on energy harvesting aided green communications over fading channels"
    - "adaptive power management for wireless base stations in a smart grid environment"
    - "wsr maximized resource allocation in multiple df relays aided ofdma downlink transmission"

Connected through hyperedge HE-2 (induced by source paper "distributed energy spectral efficiency optimization for partial full interference alignment in multi user multi relay multi cell mimo systems"):
  with members:
    - "limited feedback based interference alignment for interfering multi access channels"
    - "performance analysis and optimization for interference alignment over mimo interference channels with limited feedback"
    - "opportunistic downlink interference alignment"
    - "spectral and energy spectral efficiency optimization of joint transmit and receive beamforming based multi relay mimo ofdma cellular networks"
    - "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"
    - "a reconfigurable distributed algorithm for k user mimo interference networks"
    - "exploiting interference alignment in multi cell cooperative ofdma resource allocation"
    - "framework for link level energy efficiency optimization with informed transmitter"

Connected through hyperedge HE-3 (induced by source paper "energy efficient ofdma networks maintaining statistical qos guarantees for delay sensitive traffic"):
  with members:
    - "distributed energy spectral efficiency optimization for partial full interference alignment in multi user multi relay multi cell mimo systems"
    - "large scale mimo is capable of eliminating power thirsty channel coding for wireless transmission of hevc h 265 video"
    - "spectral and energy spectral efficiency optimization of joint transmit and receive beamforming based multi relay mimo ofdma cellular networks"
    - "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"
    - "qos aware base station selections for distributed mimo links in broadband wireless networks"
    - "statistical delay control and qos driven power allocation over two hop wireless relay links"
    - "the impact of qos constraints on the energy efficiency of fixed rate wireless transmissions"

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)