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: "e 2 mac energy efficient medium access for massive m2m communications"
  Abstract: In this paper, we investigate energy-efficient clustering and medium access control (MAC) for cellular-based M2M networks to minimize device energy consumption and prolong network battery lifetime. First, we present an accurate energy consumption model that considers both static and dynamic energy consumptions, and utilize this model to derive the network lifetime. Second, we find the cluster size to maximize the network lifetime and develop an energy-efficient cluster-head selection scheme. Furthermore, we find feasible regions where clustering is beneficial in enhancing network lifetime. We further investigate communications protocols for both intra- and inter-cluster communications. While inter-cluster communications use conventional cellular access schemes, we develop an energy-efficient and load-adaptive multiple access scheme, called n-phase CSMA/CA, which provides a tunable tradeoff between energy efficiency, delay, and spectral efficiency of the network. The simulation results show that the proposed clustering, cluster-head selection, and communications protocol design outperform the others in energy saving and significantly prolong the lifetimes of both individual nodes and the whole M2M network.

Connected through hyperedge HE-1 (induced by source paper "performance evaluation and optimization of lpwa iot networks a stochastic geometry approach"):
  with members:
    - "optimized resource provisioning and operation control for low power wide area iot networks"
    - "grant free radio access for short packet communications over 5g networks"
    - "poisson cluster process bridging the gap between ppp and 3gpp hetnet models"
    - "grant free radio access iot networks scalability analysis in coexistence scenarios"
    - "network lifetime maximization for cellular based m2m networks"
    - "non orthogonal multiple access noma in cellular uplink and downlink challenges and enabling techniques"
    - "2d time frequency interference modelling using stochastic geometry for performance evaluation in low power wide area networks"
    - "interference and outage in clustered wireless ad hoc networks"

Connected through hyperedge HE-2 (induced by source paper "grant free radio access iot networks scalability analysis in coexistence scenarios"):
  with members:
    - "grant free radio access for short packet communications over 5g networks"
    - "on lorawan scalability empirical evaluation of susceptibility to inter network interference"
    - "lorawan in the wild measurements from the things network"
    - "low power wide area network analysis can lora scale"
    - "understanding the limits of lorawan"
    - "2d time frequency interference modelling using stochastic geometry for performance evaluation in low power wide area networks"
    - "long range communications in unlicensed bands the rising stars in the iot and smart city scenarios"

Connected through hyperedge HE-3 (induced by source paper "network lifetime maximization for cellular based m2m networks"):
  with members:
    - "energy efficient scheduling and grouping for machine type communications over cellular networks"
    - "design of a scalable hybrid mac protocol for heterogeneous m2m networks"
    - "power efficient system design for cellular based machine to machine communications"
    - "a quantitative measure of fairness and discrimination for resource allocation in shared computer systems"

Connected through hyperedge HE-4 (induced by source paper "grant free radio access for short packet communications over 5g networks"):
  with members:
    - "enhancing contention resolution aloha using combining techniques"
    - "exploiting combination techniques in random access mac protocols enhanced contention resolution aloha"
    - "2d time frequency interference modelling using stochastic geometry for performance evaluation in low power wide area networks"

Connected through hyperedge HE-5 (induced by source paper "massive machine type communication with data aggregation and resource scheduling"):
  with members:
    - "massive multiple access based on superposition raptor codes for cellular m2m communications"
    - "massive non orthogonal multiple access for cellular iot potentials and limitations"
    - "spatiotemporal stochastic modeling of iot enabled cellular networks scalability and stability analysis"
    - "energy efficient scheduling and grouping for machine type communications over cellular networks"
    - "a delay optimal mac and packet scheduler for heterogeneous m2m uplink"
    - "massive machine type communications in 5g physical and mac layer solutions"
    - "random cell association and void probability in poisson distributed cellular networks"
    - "aggregation and trunking of m2m traffic via d2d connections"

Connected through hyperedge HE-6 (induced by source paper "energy efficient scheduling and grouping for machine type communications over cellular networks"):
  with members:
    - "understanding the iot connectivity landscape a contemporary m2m radio technology roadmap"
    - "aggregation and trunking of m2m traffic via d2d connections"
    - "a survey on device to device communication in cellular networks"
    - "zero outage cellular downlink with fixed rate d2d underlay"
    - "reliable reporting for massive m2m communications with periodic resource pooling"
    - "power efficient system design for cellular based machine to machine communications"

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)