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: "scma for downlink multiple access of 5g wireless networks"
  Abstract: Sparse code multiple access (SCMA) is a new frequency domain non-orthogonal multiple-access technique which can improve spectral efficiency of wireless radio access. With SCMA, different incoming data streams are directly mapped to codewords of different multi-dimensional cookbooks, where each codeword represents a spread transmission layer. Multiple SCMA layers share the same time-frequency resources of OFDMA. The sparsity of codewords makes the near-optimal detection feasible through iterative message passing algorithm (MPA). Such low complexity of multi-layer detection allows excessive codeword overloading in which the dimension of multiplexed layers exceeds the dimension of codewords. Optimization of overloading factor along with modulation-coding levels of layers provides a more flexible and efficient link-adaptation mechanism. On the other hand, the signal spreading feature of SCMA can improve link-adaptation as a result of less colored interference. In this paper a technique is developed to enable multi-user SCMA (MU-SCMA) for downlink wireless access. User pairing, power sharing, rate adjustment, and scheduling algorithms are designed to improve the downlink throughput of a heavily loaded network. The advantage of SCMA spreading for lightly loaded networks is also evaluated.

Connected through hyperedge HE-1 (induced by source paper "secure communications in a unified non orthogonal multiple access framework"):
  with members:
    - "exploiting full half duplex user relaying in noma systems"
    - "user association and resource allocation in unified noma enabled heterogeneous ultra dense networks"
    - "securing downlink non orthogonal multiple access systems by trusted relays"
    - "a unified framework for non orthogonal multiple access"
    - "edge computing aware noma for 5g networks"
    - "impact of non orthogonal multiple access on the offloading of mobile edge computing"
    - "secure communications in noma system subcarrier assignment and power allocation"
    - "performance analysis of noma with fixed gain relaying over nakagami m fading channels"

Connected through hyperedge HE-2 (induced by source paper "two layer coded channel access with collision resolution design and analysis"):
  with members:
    - "coded random access applying codes on graphs to design random access protocols"
    - "probabilistic rateless multiple access for machine to machine communication"
    - "near capacity adaptive analog fountain codes for wireless channels"
    - "aloha random access that operates as a rateless code"
    - "graph based random access for the collision channel without feedback capacity bound"
    - "high throughput random access via codes on graphs coded slotted aloha"

Connected through hyperedge HE-3 (induced by source paper "robust radio resource allocation in miso scma assisted c ran in 5g networks"):
  with members:
    - "a survey on non orthogonal multiple access for 5g networks research challenges and future trends"
    - "iterative receivers for downlink mimo scma message passing and distributed cooperative detection"
    - "a minorization maximization method for optimizing sum rate in the downlink of non orthogonal multiple access systems"
    - "mechanism design for base station association and resource allocation in downlink ofdma network"
    - "robust monotonic optimization framework for multicell miso systems"

Connected through hyperedge HE-4 (induced by source paper "a unified framework for non orthogonal multiple access"):
  with members:
    - "exploiting full half duplex user relaying in noma systems"
    - "user association and resource allocation in unified noma enabled heterogeneous ultra dense networks"
    - "performance analysis of noma with fixed gain relaying over nakagami m fading channels"
    - "power domain non orthogonal multiple access noma in 5g systems potentials and challenges"
    - "modulation and multiple access for 5g networks"
    - "fundamentals of modeling finite wireless networks using binomial point process"
    - "on the spectral efficiency and security enhancements of noma assisted multicast unicast streaming"
    - "enhancing the physical layer security of non orthogonal multiple access in large scale networks"

Connected through hyperedge HE-5 (induced by source paper "fairness and sum rate maximization via joint channel and power allocation in uplink scma networks"):
  with members:
    - "single or multiple frames content delivery for next generation networks"
    - "a survey on non orthogonal multiple access for 5g networks research challenges and future trends"
    - "fundamental limits of low density spreading noma with fading"
    - "modeling and analysis of scma enhanced d2d and cellular hybrid network"
    - "joint downlink base station association and power control for max min fairness computation and complexity"
    - "distributed pricing based user association for downlink heterogeneous cellular networks"
    - "uplink contention based scma for 5g radio access"
    - "scma codebook design"

Connected through hyperedge HE-6 (induced by source paper "efficient sparse code multiple access decoder based on deterministic message passing algorithm"):
  with members:
    - "non orthogonal multiple access in multi cell networks theory performance and practical challenges"

Connected through hyperedge HE-7 (induced by source paper "on user pairing in noma uplink"):
  with members:
    - "an optimization perspective of the superiority of noma compared to conventional oma"
    - "non orthogonal multiple access noma in cellular uplink and downlink challenges and enabling techniques"
    - "design of massive mimo noma with limited feedback"
    - "optimal joint power and subcarrier allocation for mc noma systems"
    - "a survey of downlink non orthogonal multiple access for 5g wireless communication networks"
    - "the application of mimo to non orthogonal multiple access"
    - "fairness for non orthogonal multiple access in 5g systems"
    - "a general mimo framework for noma downlink and uplink transmission based on signal alignment"

Connected through hyperedge HE-8 (induced by source paper "power domain non orthogonal multiple access noma in 5g systems potentials and challenges"):
  with members:
    - "non orthogonal multiple access for visible light communications"
    - "the application of mimo to non orthogonal multiple access"
    - "fairness for non orthogonal multiple access in 5g systems"
    - "a hybrid tim noma scheme for the siso broadcast channel"
    - "uplink non orthogonal multiple access for 5g wireless networks"
    - "millimeter wave cellular wireless networks potentials and challenges"
    - "on the performance of non orthogonal multiple access in 5g systems with randomly deployed users"

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)