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: "modulation in the air backscatter communication over ambient ofdm carrier"
  Abstract: Ambient backscatter communication (AmBC) enables radio-frequency (RF) powered backscatter devices (BDs) (e.g., sensors, tags) to modulate their information bits over ambient RF carriers in an over-the-air manner. This technology also called "modulation in the air", thus has emerged as a promising solution to achieve green communications for future Internet-of-Things. This paper studies an AmBC system by leveraging the ambient orthogonal frequency division multiplexing (OFDM) modulated signals in the air. We first model such AmBC system from a spread-spectrum communication perspective, upon which a novel joint design for BD waveform and receiver detector is proposed. The BD symbol period is designed to be in general an integer multiplication of the OFDM symbol period, and the waveform for BD bit `0' maintains the same state within a BD symbol period, while the waveform for BD bit `1' has a state transition in the middle of each OFDM symbol period within a BD symbol period. In the receiver detector design, we construct the test statistic that cancels out the direct-link interference by exploiting the repeating structure of the ambient OFDM signals due to the use of cyclic prefix. For the system with a single-antenna receiver, the maximum-likelihood detector is proposed to recover the BD bits, for which the optimal threshold is obtained in closed-form expression. For the system with a multi-antenna receiver, we propose a new test statistic, and derive the optimal detector. Moreover, practical timing synchronization algorithms are proposed, and we also analyze the effect of various system parameters on the system performance. Finally, extensive numerical results are provided to verify that the proposed transceiver design can improve the system bit-error-rate (BER) performance and the operating range significantly, and achieve much higher data rate, as compared to the conventional design.

Connected through hyperedge HE-1 (induced by source paper "a retrodirective wireless power transfer scheme for ambient backscatter systems"):
  with members:
    - "design of ambient backscatter training for retrodirective wireless power transfer"
    - "retrodirective large antenna energy beamforming in backscatter multi user networks"
    - "retrodirective multi user wireless power transfer with massive mimo"
    - "performance analysis of massive mimo for cell boundary users"
    - "joint wireless information and energy transfer with reduced feedback in mimo interference channels"
    - "energy beamforming with one bit feedback"
    - "joint beamforming design for multi user wireless information and power transfer"
    - "optimized training design for wireless energy transfer"

Connected through hyperedge HE-2 (induced by source paper "energy efficient uav backscatter communication with joint trajectory design and resource optimization"):
  with members:
    - "sum throughput maximization in multi tag backscattering to multiantenna reader"
    - "large intelligent surface antennas lisa making reflective radios smart"
    - "uav data collection over noma backscatter networks uav altitude and trajectory optimization"
    - "cooperative ambient backscatter communications for green internet of things"
    - "symbiotic radio a new communication paradigm for passive internet of things"
    - "energy minimization for wireless communication with rotary wing uav"
    - "spectrum sharing for internet of things a survey"
    - "throughput maximization for uav enabled wireless powered communication networks"

Connected through hyperedge HE-3 (induced by source paper "design of ambient backscatter training for retrodirective wireless power transfer"):
  with members:
    - "retrodirective large antenna energy beamforming in backscatter multi user networks"
    - "retrodirective multi user wireless power transfer with massive mimo"
    - "next generation backscatter communication systems techniques and applications"
    - "ambient backscatter communications a contemporary survey"
    - "inter technology backscatter towards internet connectivity for implanted devices"
    - "communications and signals design for wireless power transmission"
    - "wireless powered communication opportunities and challenges"
    - "performance analysis of massive mimo for cell boundary users"

Connected through hyperedge HE-4 (induced by source paper "intelligent reflecting surface assisted non orthogonal multiple access"):
  with members:
    - "large intelligent surface antennas lisa making reflective radios smart"
    - "a simple design of irs noma transmission"
    - "reliability analysis of large intelligent surfaces liss rate distribution and outage probability"
    - "cooperative ambient backscatter communications for green internet of things"
    - "achievable rate maximization by passive intelligent mirrors"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"
    - "joint pilot and payload power control for uplink mimo noma with mrc sic receivers"
    - "reconfigurable intelligent surfaces for energy efficiency in wireless communication"

Connected through hyperedge HE-5 (induced by source paper "large intelligent surface antennas lisa making reflective radios smart"):
  with members:
    - "miso wireless communication systems via intelligent reflecting surfaces"
    - "enabling large intelligent surfaces with compressive sensing and deep learning"
    - "cooperative ambient backscatter communications for green internet of things"
    - "achievable rate maximization by passive intelligent mirrors"
    - "intelligent reflecting surface enhanced wireless network via joint active and passive beamforming"
    - "symbiotic radio a new communication paradigm for passive internet of things"
    - "riding on the primary a new spectrum sharing paradigm for wireless powered iot devices"
    - "beamforming optimization for intelligent reflecting surface with discrete phase shifts"

Connected through hyperedge HE-6 (induced by source paper "non coherent detection and bit error rate for an ambient backscatter link in time selective fading"):
  with members:
    - "ambient backscatter systems exact average bit error rate under fading channels"
    - "semi coherent detection and performance analysis for ambient backscatter system"
    - "wide area wireless communication challenges for the internet of things"
    - "wireless backhaul networks capacity bound scalability analysis and design guidelines"
    - "massive mimo meets hetnet interference coordination through spatial blanking"
    - "joint spatial division and multiplexing for mm wave channels"

Connected through hyperedge HE-7 (induced by source paper "energy beamforming for wireless information and power transfer in backscatter multiuser networks"):
  with members:
    - "optimization of power transfer efficiency and energy efficiency for wireless powered systems with massive mimo"
    - "beamforming design for max min fair swipt in green cloud ran with wireless fronthaul"
    - "wirelessly powered backscatter communication networks modeling coverage and capacity"
    - "throughput optimization for massive mimo systems powered by wireless energy transfer"
    - "multi antenna wireless energy transfer for backscatter communication systems"
    - "mimo broadcasting for simultaneous wireless information and power transfer"

Connected through hyperedge HE-8 (induced by source paper "performance characterisation of relaying using backscatter devices"):
  with members:
    - "ambient backscatter systems exact average bit error rate under fading channels"
    - "fm backscatter enabling connected cities and smart fabrics"
    - "backscatter communications for the internet of things a stochastic geometry approach"
    - "wirelessly powered backscatter communication networks modeling coverage and capacity"
    - "semi coherent detection and performance analysis for ambient backscatter system"

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)