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: "training optimization for energy harvesting communication systems"
  Abstract: Energy harvesting (EH) has recently emerged as an effective way to solve the lifetime challenge of wireless sensor networks, as it can continuously harvest energy from the environment. Unfortunately, it is challenging to guarantee a satisfactory short-term performance in EH communication systems because the harvested energy is sporadic. In this paper, we consider the channel training optimization problem in EH communication systems, i.e., how to obtain accurate channel state information to improve the communication performance. In contrast to conventional communication systems, the optimization of the training power and training period in EH communication systems is a coupled problem, which makes such optimization very challenging. We shall formulate the optimal training design problem for EH communication systems, and propose two solutions that adaptively adjust the training period and power based on either the instantaneous energy profile or the average energy harvesting rate. Numerical and simulation results will show that training optimization is important in EH communication systems. In particular, it will be shown that for short block lengths, training optimization is critical. In contrast, for long block lengths, the optimal training period is not too sensitive to the value of the block length nor to the energy profile. Therefore, a properly selected fixed training period value can be used.

Connected through hyperedge HE-1 (induced by source paper "layered coding for energy harvesting communication without csit"):
  with members:
    - "non asymptotic achievable rates for energy harvesting channels using save and transmit"
    - "energy harvesting wireless communications a review of recent advances"
    - "outage minimization for a fading wireless link with energy harvesting transmitter and receiver"
    - "outage probability of energy harvesting relay aided cooperative networks over rayleigh fading channel"
    - "broadcasting with an energy harvesting rechargeable transmitter"
    - "transmission with energy harvesting nodes in fading wireless channels optimal policies"
    - "optimal packet scheduling in an energy harvesting communication system"
    - "distortion minimization in gaussian layered broadcast coding with successive refinement"

Connected through hyperedge HE-2 (induced by source paper "grid energy consumption and qos tradeoff in hybrid energy supply wireless networks"):
  with members:
    - "transmit power minimization for wireless networks with energy harvesting relays"
    - "energy harvesting wireless communications a review of recent advances"
    - "comp meets smart grid a new communication and energy cooperation paradigm"
    - "energy harvesting small cell networks feasibility deployment and operation"
    - "a lyapunov optimization approach for green cellular networks with hybrid energy supplies"
    - "cost minimization for fading channels with energy harvesting and conventional energy"
    - "power allocation for conventional and buffer aided link adaptive relaying systems with energy harvesting nodes"
    - "multiuser joint energy bandwidth allocation with energy harvesting part i optimum algorithm multiple point to point channels"

Connected through hyperedge HE-3 (induced by source paper "transmit power minimization for wireless networks with energy harvesting relays"):
  with members:
    - "energy harvesting wireless communications a review of recent advances"
    - "energy harvesting small cell networks feasibility deployment and operation"
    - "a lyapunov optimization approach for green cellular networks with hybrid energy supplies"
    - "power allocation for conventional and buffer aided link adaptive relaying systems with energy harvesting nodes"
    - "throughput maximization for the gaussian relay channel with energy harvesting constraints"
    - "optimal scheduling and power allocation for two hop energy harvesting communication systems"
    - "optimal transmission policies for energy harvesting two hop networks"
    - "sum rate optimal power policies for energy harvesting transmitters in an interference channel"

Connected through hyperedge HE-4 (induced by source paper "energy harvesting wireless communications a review of recent advances"):
  with members:
    - "renewable powered cellular networks energy field modeling and network coverage"
    - "dynamic compression transmission for energy harvesting multihop networks with correlated sources"
    - "constrained codes for joint energy and information transfer"
    - "energy harvesting broadband communication systems with processing energy cost"
    - "spatial throughput of mobile ad hoc networks powered by energy harvesting"
    - "energy cooperation in energy harvesting communications"
    - "interactive joint transfer of energy and information"
    - "opportunistic wireless energy harvesting in cognitive radio networks"

Connected through hyperedge HE-5 (induced by source paper "optimal policies for wireless networks with energy harvesting transmitters and receivers effects of decoding costs"):
  with members:
    - "iterative dynamic water filling for fading multiple access channels with energy harvesting"
    - "convex separable problems with linear constraints in signal processing and communications"
    - "energy harvesting broadband communication systems with processing energy cost"
    - "energy cooperation in energy harvesting communications"
    - "throughput maximization for the gaussian relay channel with energy harvesting constraints"
    - "optimal scheduling and power allocation for two hop energy harvesting communication systems"
    - "throughput optimal policies for energy harvesting wireless transmitters with non ideal circuit power"
    - "throughput maximization for an energy harvesting communication system with processing cost"

Connected through hyperedge HE-6 (induced by source paper "optimal scheduling and power allocation for two hop energy harvesting communication systems"):
  with members:
    - "throughput maximization for the gaussian relay channel with energy harvesting constraints"
    - "throughput optimal policies for energy harvesting wireless transmitters with non ideal circuit power"
    - "optimal power allocation for outage minimization in fading channels with energy harvesting constraints"
    - "optimal transmission policies for energy harvesting two hop networks"
    - "broadcasting with an energy harvesting rechargeable transmitter"
    - "sum rate optimal power policies for energy harvesting transmitters in an interference channel"
    - "two hop communication with energy harvesting"
    - "capacity of fading gaussian channel with an energy harvesting sensor node"

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)