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: "energy efficiency optimization in relay assisted mimo systems with perfect and statistical csi"
  Abstract: A framework for energy-efficient resource allocation in a single-user, amplify-and-forward (AF), relay-assisted, multiple-input-multiple-output (MIMO) system is devised in this paper. Previous results in this area have focused on rate maximization or sum power minimization problems, whereas fewer results are available when bits/Joule energy efficiency (EE) optimization is the goal. Here, the performance metric to optimize is the ratio between the system's achievable rate and the total consumed power. The optimization is carried out with respect to the source and relay precoding matrices, subject to quality-of-service (QoS) and power constraints. Such a challenging non-convex optimization problem is tackled by means of fractional programming and alternating maximization algorithms, for various channel state information (CSI) assumptions at the source and relay. In particular the scenarios of perfect CSI and those of statistical CSI for either the source-relay or the relay-destination channel are addressed. Moreover, sufficient conditions for beamforming optimality are derived, which is useful in simplifying the system design. Numerical results are provided to corroborate the validity of the theoretical findings.

Connected through hyperedge HE-1 (induced by source paper "energy efficiency fairness for multi pair wireless powered relaying systems"):
  with members:
    - "joint power allocation and beamforming for energy efficient two way multi relay communications"
    - "energy efficiency maximization of full duplex two way relay with non ideal power amplifiers and non negligible circuit power"
    - "energy efficient beam coordination strategies with rate dependent processing power"
    - "relaying strategies for wireless powered mimo relay networks"
    - "wireless powered relays in cooperative communications time switching relaying protocols and throughput analysis"
    - "practical non linear energy harvesting model and resource allocation for swipt systems"
    - "wireless networks with rf energy harvesting a contemporary survey"
    - "power allocation strategies in energy harvesting wireless cooperative networks"

Connected through hyperedge HE-2 (induced by source paper "reconfigurable intelligent surfaces for energy efficiency in wireless communication"):
  with members:
    - "energy efficient multi user miso communication using low resolution large intelligent surfaces"
    - "achievable rate maximization by passive intelligent mirrors"
    - "using any surface to realize a new paradigm for wireless communications"
    - "energy efficiency of mmwave massive mimo precoding with low resolution dacs"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"
    - "deep learning coordinated beamforming for highly mobile millimeter wave systems"
    - "capacity degradation with modeling hardware impairment in large intelligent surface"
    - "asymptotically optimal estimation algorithm for the sparse signal with arbitrary distributions"

Connected through hyperedge HE-3 (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"
    - "what will 5g be"
    - "fully distributed optimal channel assignment for open spectrum access"
    - "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"

Connected through hyperedge HE-4 (induced by source paper "wireless powered dual hop multi antenna relaying systems impact of csi and antenna correlation"):
  with members:
    - "on the performance of multi antenna wireless powered communications with energy beamforming"
    - "an overview of sustainable green 5g networks"
    - "training based swipt optimal power splitting at the receiver"
    - "joint wireless information and power transfer for an autonomous multiple antenna relay system"
    - "wireless powered communications performance analysis and optimization"
    - "energy efficient resource allocation for wireless powered communication networks"
    - "wireless information and power transfer in relay systems with multiple antennas and interference"
    - "harvest then cooperate wireless powered cooperative communications"

Connected through hyperedge HE-5 (induced by source paper "energy efficient multi pair two way af full duplex massive mimo relaying"):
  with members:
    - "a survey of multi objective optimization in wireless sensor networks metrics algorithms and open problems"
    - "power allocation for multi pair massive mimo two way af relaying with linear processing"
    - "joint beamforming optimization and power control for full duplex mimo two way relay channel"
    - "multipair full duplex relaying with massive arrays and linear processing"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "in band full duplex wireless challenges and opportunities"
    - "green cellular networks a survey some research issues and challenges"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-6 (induced by source paper "energy efficient precoding design for swipt in mimo two way relay networks"):
  with members:
    - "energy efficient power control a look at 5g wireless technologies"
    - "distributed power splitting for swipt in relay interference channels using game theory"
    - "application of smart antenna technologies in simultaneous wireless information and power transfer"

Connected through hyperedge HE-7 (induced by source paper "joint transmit and receive beamforming for multi relay mimo ofdma cellular networks"):
  with members:
    - "spectral and energy spectral efficiency optimization of joint transmit and receive beamforming based multi relay mimo ofdma cellular networks"

Connected through hyperedge HE-8 (induced by source paper "energy efficiency optimization for mimo distributed antenna systems"):
  with members:
    - "totally distributed energy efficient transmission in mimo interference channels"
    - "what will 5g be"
    - "energy efficiency optimization for mimo ofdm mobile multimedia communication systems with qos constraints"
    - "energy efficiency optimization for mimo broadcast channels"
    - "transmission schemes based on sum rate analysis in distributed antenna systems"
    - "framework for link level energy efficiency optimization with informed transmitter"
    - "miso capacity with per antenna power constraint"
    - "cooperative interference management with miso beamforming"

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)