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: "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"
  Abstract: In this paper, the joint power and subcarrier allocation problem is solved in the context of maximizing the energy-efficiency (EE) of a multi-user, multi-relay orthogonal frequency division multiple access (OFDMA) cellular network, where the objective function is formulated as the ratio of the spectral-efficiency (SE) over the total power dissipation. It is proven that the fractional programming problem considered is quasi-concave so that Dinkelbach's method may be employed for finding the optimal solution at a low complexity. This method solves the above-mentioned master problem by solving a series of parameterized concave secondary problems. These secondary problems are solved using a dual decomposition approach, where each secondary problem is further decomposed into a number of similar subproblems. The impact of various system parameters on the attainable EE and SE of the system employing both EE maximization (EEM) and SE maximization (SEM) algorithms is characterized. In particular, it is observed that increasing the number of relays for a range of cell sizes, although marginally increases the attainable SE, reduces the EE significantly. It is noted that the highest SE and EE are achieved, when the relays are placed closer to the BS to take advantage of the resultant line-of-sight link. Furthermore, increasing both the number of available subcarriers and the number of active user equipment (UE) increases both the EE and the total SE of the system as a benefit of the increased frequency and multi-user diversity, respectively. Finally, it is demonstrated that as expected, increasing the available power tends to improve the SE, when using the SEM algorithm. By contrast, given a sufficiently high available power, the EEM algorithm attains the maximum achievable EE and a suboptimal SE.

Connected through hyperedge HE-1 (induced by source paper "twin timescale radio resource management for ultra reliable and low latency vehicular networks"):
  with members:
    - "on low resolution adcs in practical 5g millimeter wave massive mimo systems"
    - "fractional programming for communication systems part i power control and beamforming"
    - "physical layer authentication in mission critical mtc networks a security and delay performance analysis"
    - "a two stage allocation scheme for delay sensitive services in dense vehicular networks"
    - "cross layer optimization for ultra reliable and low latency radio access networks"
    - "low latency millimeter wave communications traffic dispersion or network densification"
    - "on the feasibility of wireless energy transfer using massive antenna arrays"
    - "blocklength limited performance of relaying under quasi static rayleigh channels"

Connected through hyperedge HE-2 (induced by source paper "energy efficiency of opportunistic device to device relaying under lognormal shadowing"):
  with members:
    - "dore an experimental framework to enable outband d2d relay in cellular networks"
    - "a stochastic geometric analysis of device to device communications operating over generalized fading channels"
    - "device relaying in cellular d2d networks a fairness perspective"
    - "effects of relay selection strategies on the spectral efficiency of wireless systems with half and full duplex nodes"
    - "a survey on device to device communication in cellular networks"
    - "energy efficiency optimization in relay assisted mimo systems with perfect and statistical csi"
    - "what will 5g be"
    - "fully distributed optimal channel assignment for open spectrum access"

Connected through hyperedge HE-3 (induced by source paper "fractional programming for communication systems part i power control and beamforming"):
  with members:
    - "fractional programming for communication systems part ii uplink scheduling via matching"
    - "energy efficient power control a look at 5g wireless technologies"
    - "framework for link level energy efficiency optimization with informed transmitter"

Connected through hyperedge HE-4 (induced by source paper "a survey of multi objective optimization in wireless sensor networks metrics algorithms and open problems"):
  with members:
    - "distributed energy spectral efficiency optimization for partial full interference alignment in multi user multi relay multi cell mimo systems"
    - "energy efficient ofdma networks maintaining statistical qos guarantees for delay sensitive traffic"
    - "wireless sensor network virtualization a survey"
    - "markov decision processes with applications in wireless sensor networks a survey"
    - "accuracy of homology based coverage hole detection for wireless sensor networks on sphere"
    - "end to end reliability aware scheduling for wireless sensor networks"
    - "multiband spectrum access great promises for future cognitive radio networks"
    - "spectral and energy spectral efficiency optimization of joint transmit and receive beamforming based multi relay mimo ofdma cellular networks"

Connected through hyperedge HE-5 (induced by source paper "energy efficient resource allocation for hybrid bursty services in multi relay ofdm networks"):
  with members:
    - "spectral and energy spectral efficiency optimization of joint transmit and receive beamforming based multi relay mimo ofdma cellular networks"
    - "relay selection with network coding in two way relay channels"
    - "physical network coding in two way wireless relay channels"

Connected through hyperedge HE-6 (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"
    - "maximizing energy efficiency in multi relay ofdma cellular networks"
    - "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-7 (induced by source paper "energy efficient small cell with spectrum power trading"):
  with members:
    - "fundamental green tradeoffs progresses challenges and impacts on 5g networks"
    - "an overview of sustainable green 5g networks"
    - "energy efficient resource allocation for wireless powered communication networks"
    - "a traffic load balancing framework for software defined radio access networks powered by hybrid energy sources"
    - "quantifying potential energy efficiency gain in green cellular wireless networks"
    - "joint energy and spectrum cooperation for cellular communication systems"
    - "energy efficiency optimization for mimo ofdm mobile multimedia communication systems with qos constraints"
    - "energy efficient resource allocation in ofdma systems with hybrid energy harvesting base station"

Connected through hyperedge HE-8 (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"
    - "maximizing energy efficiency in multi relay ofdma cellular networks"
    - "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)