human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "a retrodirective wireless power transfer scheme for ambient backscatter systems"):
  Abstract: One of the key challenges of the Internet of Things (IoT) is to sustainably power the large number of IoT devices in real-time. In this paper, we consider a wireless power transfer (WPT) scenario between an energy transmitter (ET) capable of retrodirective WPT and an energy receiver (ER) capable of ambient backscatter in the presence of an ambient source (AS). The ER requests WPT by backscattering signals from an AS towards the ET, which then retrodirectively beamforms an energy signal towards the ER. To remove the inherent direct-link ambient interference, we propose a scheme of ambient backscatter training. Specifically, the ER varies the reflection coefficient multiple times while backscattering each ambient symbol according to a certain pattern called the training sequence, whose design criterion we also present. To evaluate the system performance, we derive an analytical expression for the average harvested power at the ER. Our numerical results show that with the proposed scheme, the ER harvests tens of $\mu$W of power, without any CSI estimation or active transmission from the ER, which is a significant improvement for low-power and low-cost ambient backscatter devices.

Includes members:
  Member "design of ambient backscatter training for retrodirective wireless power transfer":
    also connected through other hyperedges:
      (none)
  Member "retrodirective large antenna energy beamforming in backscatter multi user networks":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "design of ambient backscatter training for retrodirective wireless power transfer")
  Member "retrodirective multi user wireless power transfer with massive mimo":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "design of ambient backscatter training for retrodirective wireless power transfer")
  Member "modulation in the air backscatter communication over ambient ofdm carrier":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "energy efficient uav backscatter communication with joint trajectory design and resource optimization")
  Member "performance analysis of massive mimo for cell boundary users":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "design of ambient backscatter training for retrodirective wireless power transfer")
  Member "joint wireless information and energy transfer with reduced feedback in mimo interference channels":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "design of ambient backscatter training for retrodirective wireless power transfer")
  Member "energy beamforming with one bit feedback":
    also connected through other hyperedges:
      - Hyperedge HE-6 (induced by source paper "wirelessly powered sensor networks power allocation for channel estimation and energy beamforming")
  Member "joint beamforming design for multi user wireless information and power transfer":
    also connected through other hyperedges:
      - Hyperedge HE-7 (induced by source paper "design of ambient backscatter training for retrodirective wireless power transfer")

Question: Please tell me which class the source paper 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)