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: "optimization framework and graph based approach for relay assisted bidirectional ofdma cellular networks"
  Abstract: This paper considers a relay-assisted bidirectional cellular network where the base station (BS) communicates with each mobile station (MS) using OFDMA for both uplink and downlink. The goal is to improve the overall system performance by exploring the full potential of the network in various dimensions including user, subcarrier, relay, and bidirectional traffic. In this work, we first introduce a novel three-time-slot time-division duplexing (TDD) transmission protocol. This protocol unifies direct transmission, one-way relaying and network-coded two-way relaying between the BS and each MS. Using the proposed three-time-slot TDD protocol, we then propose an optimization framework for resource allocation to achieve the following gains: cooperative diversity (via relay selection), network coding gain (via bidirectional transmission mode selection), and multiuser diversity (via subcarrier assignment). We formulate the problem as a combinatorial optimization problem, which is NP-complete. To make it more tractable, we adopt a graph-based approach. We first establish the equivalence between the original problem and a maximum weighted clique problem in graph theory. A metaheuristic algorithm based on any colony optimization (ACO) is then employed to find the solution in polynomial time. Simulation results demonstrate that the proposed protocol together with the ACO algorithm significantly enhances the system total throughput.

Connected through hyperedge HE-1 (induced by source paper "joint uplink and downlink transmissions in user centric ofdma cloud ran"):
  with members:
    - "joint precoding and rrh selection for user centric green mimo c ran"
    - "fronthaul limited uplink ofdma in ultra dense cran with hybrid decoding"
    - "joint millimeter wave fronthaul and ofdma resource allocation in ultra dense cran"
    - "green ofdma resource allocation in cache enabled cran"
    - "why to decouple the uplink and downlink in cellular networks and how to do it"
    - "fronthaul constrained cloud radio access networks insights and challenges"
    - "coordinated scheduling for the downlink of cloud radio access networks"
    - "what will 5g be"

Connected through hyperedge HE-2 (induced by source paper "information and energy cooperation in ofdm relaying protocols and optimization"):
  with members:
    - "secrecy wireless information and power transfer in ofdma systems"
    - "wireless information and energy transfer for two hop non regenerative mimo ofdm relay networks"
    - "secure and green swipt in distributed antenna networks with limited backhaul capacity"
    - "power allocation strategies in energy harvesting wireless cooperative networks"
    - "wireless information and power transfer with full duplex relaying"
    - "energy cooperation in energy harvesting communications"
    - "simultaneous information and power transfer for broadband wireless systems"
    - "wireless information and power transfer in multiuser ofdm systems"

Connected through hyperedge HE-3 (induced by source paper "energy harvesting for physical layer security in ofdma networks"):
  with members:
    - "secrecy wireless information and power transfer in fading wiretap channel"
    - "information and energy cooperation in ofdm relaying protocols and optimization"
    - "robust beamforming for secure communication in systems with wireless information and power transfer"
    - "secrecy wireless information and power transfer with miso beamforming"
    - "spatially selective artificial noise aided transmit optimization for miso multi eves secrecy rate maximization"
    - "simultaneous information and power transfer for broadband wireless systems"
    - "wireless information and power transfer in multiuser ofdm systems"
    - "wireless information and power transfer a dynamic power splitting approach"

Connected through hyperedge HE-4 (induced by source paper "energy harvesting for secure ofdma systems"):
  with members:
    - "simultaneous information and power transfer for broadband wireless systems"
    - "wireless information and power transfer in multiuser ofdm systems"
    - "wireless information and power transfer energy efficiency optimization in ofdma systems"
    - "wireless information and power transfer a dynamic power splitting approach"
    - "qos aware transmission policies for ofdm bidirectional decode and forward relaying"
    - "wireless information transfer with opportunistic energy harvesting"
    - "on the transfer of information and energy in multi user systems"
    - "resource allocation with subcarrier pairing in ofdma two way relay networks"

Connected through hyperedge HE-5 (induced by source paper "capacity region bounds and resource allocation for two way ofdm relay channels"):
  with members:
    - "outer bounds for the capacity region of a gaussian two way relay channel"
    - "optimal power allocation for two way decode and forward ofdm relay networks"
    - "a tutorial on the optimization of amplify and forward mimo relay systems"
    - "optimal real time spectrum sharing between cooperative relay and ad hoc networks"
    - "broadcast capacity region of two phase bidirectional relaying"
    - "on the capacity and diversity multiplexing tradeoff of the two way relay channel"
    - "mimo two way relay channel diversity multiplexing tradeoff analysis"

Connected through hyperedge HE-6 (induced by source paper "weighted sum rate maximization for downlink ofdma with subcarrier pair based opportunistic df relaying"):
  with members:
    - "power minimization for ofdm transmission with subcarrier pair based opportunistic df relaying"
    - "on the scale algorithm for multiuser multicarrier power spectrum management"
    - "wsr maximized resource allocation in multiple df relays aided ofdma downlink transmission"
    - "joint subcarrier pairing and power allocation for ofdm transmission with decode and forward relaying"
    - "sum rate maximized resource allocation in multiple df relays aided ofdm transmission"

Connected through hyperedge HE-7 (induced by source paper "optimal linear transceiver designs for cognitive two way relay networks"):
  with members:
    - "joint source and relay precoding designs for mimo two way relaying based on mse criterion"
    - "blind spectrum sensing by information theoretic criteria for cognitive radios"
    - "broadcast capacity region of two phase bidirectional relaying"
    - "optimal beamforming for two way multi antenna relay channel with analogue network coding"

Connected through hyperedge HE-8 (induced by source paper "relay selection for bidirectional af relay network with outdated csi"):
  with members:
    - "capacity analysis of bidirectional af relay selection with imperfect channel state information"
    - "relay selection for two way relaying with amplify and forward protocols"
    - "channel coding and decoding in a relay system operated with physical layer network coding"
    - "a simple cooperative diversity method based on network path selection"

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)