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: "relay selection for two way relaying with amplify and forward protocols"
  Abstract: In this paper, we propose a relay selection amplify-and-forward (RS-AF) protocol in general bidirectional relay networks with two sources and N relays. In the proposed scheme, the two sources first simultaneously transmit to all the relays, and then, a single relay with a minimum sum symbol error rate (SER) will be selected to broadcast the received signals back to both sources. To facilitate the selection process, we propose a simple suboptimal min-max criterion for relay selection, where a single relay that minimizes the maximum SER of two source nodes will be selected. Simulation results show that the proposed min-max selection has almost the same performance as the optimal selection with lower complexity. We also present a simple asymptotic SER expression and make a comparison with the conventional all-participate AF relaying scheme. The analytical results are verified through simulations. To improve the system performance, optimal power allocation (OPA) between the sources and the relay is determined based on the asymptotic SER. Simulation results indicate that the proposed RS-AF scheme with OPA yields considerable performance improvement over an equal-power-allocation scheme, particularly with a large number of relay nodes.

Connected through hyperedge HE-1 (induced by source paper "hybrid beamforming for reconfigurable intelligent surface based multi user communications achievable rates with limited discrete phase shifts"):
  with members:
    - "beamforming optimization for intelligent reflecting surface with discrete phase shifts"
    - "large intelligent surface assisted wireless communication exploiting statistical csi"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "massive mimo for next generation wireless systems"
    - "scaling up mimo opportunities and challenges with very large arrays"

Connected through hyperedge HE-2 (induced by source paper "phase rotation aided relay selection in two way decode and forward relay networks"):
  with members:
    - "performance analysis of two step bi directional relaying with multiple antennas"
    - "a simple cooperative diversity method based on network path selection"

Connected through hyperedge HE-3 (induced by source paper "a buffer aided successive opportunistic relay selection scheme with power adaptation and inter relay interference cancellation for cooperative diversity systems"):
  with members:
    - "buffer aided relaying with adaptive link selection"
    - "opportunistic buffered decode wait and forward obdwf protocol for mobile wireless relay networks"
    - "splitting algorithms for fast relay selection generalizations analysis and a unified view"
    - "superposition coded concurrent decode and forward relaying"
    - "recovering multiplexing loss through successive relaying using repetition coding"
    - "a simple cooperative diversity method based on network path selection"

Connected through hyperedge HE-4 (induced by source paper "energy harvesting cooperative networks is the max min criterion still diversity optimal"):
  with members:
    - "power allocation strategies in energy harvesting wireless cooperative networks"
    - "throughput maximization in wireless powered communication networks"
    - "cooperative energy harvesting networks with spatially random users"
    - "opportunistic wireless energy harvesting in cognitive radio networks"
    - "simultaneous information and power transfer for broadband wireless systems"
    - "relaying protocols for wireless energy harvesting and information processing"
    - "multi antenna wireless powered communication with energy beamforming"
    - "relay selection for simultaneous information transmission and wireless energy transfer a tradeoff perspective"

Connected through hyperedge HE-5 (induced by source paper "a semiblind two way training method for discriminatory channel estimation in mimo systems"):
  with members:
    - "on the secrecy outage capacity of physical layer security in large scale mimo relaying systems with imperfect csi"
    - "two way training for discriminatory channel estimation in wireless mimo systems"
    - "on the design of artificial noise aided secure multi antenna transmission in slow fading channels"
    - "robust beamforming for security in mimo wiretap channels with imperfect csi"
    - "secure transmission with artificial noise over fading channels achievable rate and optimal power allocation"

Connected through hyperedge HE-6 (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"
    - "optimization framework and graph based approach for relay assisted bidirectional ofdma cellular networks"
    - "channel coding and decoding in a relay system operated with physical layer network coding"
    - "a simple cooperative diversity method based on network path selection"

Connected through hyperedge HE-7 (induced by source paper "error performance analysis of df and af multi way relay networks with bpsk modulation"):
  with members:
    - "multi way relay networks orthogonal uplink source channel separation and code design"
    - "asynchronous physical layer network coding"
    - "an optimal coding strategy for the binary multi way relay channel"

Connected through hyperedge HE-8 (induced by source paper "performance of opportunistic fixed gain bidirectional relaying with outdated csi"):
  with members:
    - "relay selection with network coding in two way relay channels"
    - "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)