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: "joint power allocation and beamforming for energy efficient two way multi relay communications"
  Abstract: This paper considers the joint design of user power allocation and relay beamforming in relaying communications, in which multiple pairs of single-antenna users exchange information with each other via multiple-antenna relays in two time slots. All users transmit their signals to the relays in the first time slot while the relays broadcast the beamformed signals to all users in the second time slot. The aim is to maximize the system's energy efficiency (EE) subject to quality-of-service (QoS) constraints in terms of exchange throughput requirements. The QoS constraints are nonconvex with many nonlinear cross-terms, so finding a feasible point is already computationally challenging. The sum throughput appears in the numerator while the total consumption power appears in the denominator of the EE objective function. The former is a nonconcave function and the latter is a nonconvex function, making fractional programming useless for EE optimization. Nevertheless, efficient iterations of low complexity to obtain its optimized solutions are developed. The performances of the multiple-user and multiple-relay networks under various scenarios are evaluated to show the merit of the paper development.

Connected through hyperedge HE-1 (induced by source paper "energy efficiency fairness for multi pair wireless powered relaying systems"):
  with members:
    - "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"
    - "energy efficiency optimization in relay assisted mimo systems with perfect and statistical csi"
    - "power allocation strategies in energy harvesting wireless cooperative networks"

Connected through hyperedge HE-2 (induced by source paper "charge then forward wireless powered communication for multiuser relay networks"):
  with members:
    - "power allocation for secure swipt systems with wireless powered cooperative jamming"
    - "capacity of the two hop relay channel with wireless energy transfer from relay to source and energy transmission cost"
    - "multipair two way relay network with harvest then transmit users resolving pairwise uplink downlink coupling"
    - "artificial noise aided secrecy information and power transfer in ofdma systems"
    - "wireless powered communication opportunities and challenges"
    - "wireless powered relays in cooperative communications time switching relaying protocols and throughput analysis"
    - "harvest then cooperate wireless powered cooperative communications"
    - "wireless powered cooperative communications via a hybrid relay"

Connected through hyperedge HE-3 (induced by source paper "low latency multiuser two way wireless relaying for spectral and energy efficiencies"):
  with members:
    - "overview of full dimension mimo in lte advanced pro"
    - "energy efficient power control a look at 5g wireless technologies"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"
    - "passive self interference suppression for full duplex infrastructure nodes"
    - "analysis of oscillator phase noise effects on self interference cancellation in full duplex ofdm radio transceivers"
    - "on design of collaborative beamforming for two way relay networks"
    - "optimal beamforming for two way multi antenna relay channel with analogue network coding"

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)