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: "pilot reuse among d2d users in d2d underlaid massive mimo systems"
  Abstract: In a device-to-device (D2D) underlaid massive MIMO system, D2D transmitters reuse the uplink spectrum of cellular users (CUs), leading to cochannel interference. To decrease pilot overhead, we assume pilot reuse (PR) among D2D pairs. We first derive the minimum-mean-square-error (MMSE) estimation of all channels and give a lower bound on the ergodic achievable rate of both cellular and D2D links. To mitigate pilot contamination caused by PR, we then propose a pilot scheduling and pilot power control algorithm based on the criterion of minimizing the sum mean-square-error (MSE) of channel estimation of D2D links. We show that, with an appropriate PR ratio and a well designed pilot scheduling scheme, each D2D transmitter could transmit its pilot with maximum power. In addition, we also maximize the sum rate of all D2D links while guaranteeing the quality of service (QoS) of CUs, and develop an iterative algorithm to obtain a suboptimal solution. Simulation results show that the effect of pilot contamination can be greatly decreased by the proposed pilot scheduling algorithm, and the PR scheme provides significant performance gains over the conventional orthogonal training scheme in terms of system spectral efficiency.

Connected through hyperedge HE-1 (induced by source paper "optimized power control for massive mimo with underlaid d2d communications"):
  with members:
    - "power control for d2d underlay in multi cell massive mimo networks"
    - "spectral and energy efficiency of uplink d2d underlaid massive mimo cellular networks"
    - "joint pilot design and uplink power allocation in multi cell massive mimo systems"
    - "energy efficiency and sum rate tradeoffs for massive mimo systems with underlaid device to device communications"
    - "the interplay between massive mimo and underlaid d2d networking"
    - "a survey on device to device communication in cellular networks"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"

Connected through hyperedge HE-2 (induced by source paper "joint power and resource allocation of d2d communication with low resolution adc"):
  with members:
    - "throughput analysis of massive mimo uplink with low resolution adcs"
    - "energy efficiency and sum rate when massive mimo meets device to device communication"
    - "uplink achievable rate for massive mimo systems with low resolution adc"
    - "d2d based v2v communications with latency and reliability constraints"
    - "the interplay between massive mimo and underlaid d2d networking"

Connected through hyperedge HE-3 (induced by source paper "power control for d2d underlay in multi cell massive mimo networks"):
  with members:
    - "cell free massive mimo versus small cells"
    - "the interplay between massive mimo and underlaid d2d networking"
    - "a survey on device to device communication in cellular networks"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"

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)