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: "achievable rate regions for bi directional relaying"
  Abstract: In a bi-directional relay channel, two nodes wish to exchange independent messages over a shared wireless half-duplex channel with the help of a relay. In this paper, we derive achievable rate regions for four new half-duplex protocols and compare these to four existing half-duplex protocols and outer bounds. In time, our protocols consist of either two or three phases. In the two phase protocols, both users simultaneously transmit during the first phase and the relay alone transmits during the second phase, while in the three phase protocol the two users sequentially transmit followed by a transmission from the relay. The relay may forward information in one of four manners; we outline existing Amplify and Forward (AF), Decode and Forward (DF) and Compress and Forward (CF) relaying schemes and introduce the novel Mixed Forward scheme. The latter is a combination of CF in one direction and DF in the other. We derive achievable rate regions for the CF and Mixed relaying schemes for the two and three phase protocols. In the last part of this work we provide a comprehensive treatment of 8 possible half-duplex bi-directional relaying protocols in Gaussian noise, obtaining their respective achievable rate regions, outer bounds, and their relative performance under different SNR and relay geometries.

Connected through hyperedge HE-1 (induced by source paper "resource allocation and outage analysis for an adaptive cognitive two way relay network"):
  with members:
    - "optimal relay selection for physical layer security in cooperative wireless networks"
    - "relay selection and resource allocation for two way df af cognitive radio networks"

Connected through hyperedge HE-2 (induced by source paper "pairwise check decoding for ldpc coded two way relay block fading channels"):
  with members:
    - "joint source and relay precoding designs for mimo two way relaying based on mse criterion"
    - "channel coding and decoding in a relay system operated with physical layer network coding"
    - "broadcast capacity region of two phase bidirectional relaying"
    - "joint physical layer coding and network coding for bi directional relaying"
    - "physical network coding in two way wireless relay channels"
    - "physical layer network coding"
    - "performance bounds for bi directional coded cooperation protocols"

Connected through hyperedge HE-3 (induced by source paper "a tutorial on the optimization of amplify and forward mimo relay systems"):
  with members:
    - "power allocation in two hop amplify and forward mimo relay systems with qos requirements"
    - "asymptotic capacity and optimal precoding in mimo multi hop relay networks"
    - "transceiver design for dual hop nonregenerative mimo ofdm relay systems under channel uncertainties"
    - "diversity of mimo multihop relay channels"
    - "optimal space time codes for the mimo amplify and forward cooperative channel"

Connected through hyperedge HE-4 (induced by source paper "physical layer network coding tutorial survey and beyond"):
  with members:
    - "an algebraic approach to physical layer network coding"
    - "eigen direction alignment based physical layer network coding for mimo two way relay channels"
    - "asynchronous physical layer network coding"
    - "optimal decoding algorithm for asynchronous physical layer network coding"
    - "non memoryless analog network coding in two way relay channel"
    - "reliable physical layer network coding"
    - "blind known interference cancellation"
    - "wireless mimo switching with zero forcing relaying and network coded relaying"

Connected through hyperedge HE-5 (induced by source paper "alternative awaiting and broadcast for two way relay fading channels"):
  with members:
    - "on achievable rate regions of the asymmetric awgn two way relay channel"
    - "broadcast capacity region of two phase bidirectional relaying"
    - "physical network coding in two way wireless relay channels"
    - "performance bounds for bi directional coded cooperation protocols"

Connected through hyperedge HE-6 (induced by source paper "achievable rate regions and outer bounds for a multi pair bi directional relay network"):
  with members:
    - "the multi way relay channel"
    - "capacity of the gaussian two way relay channel to within 1 2 bit"
    - "the mimo wireless switch relaying can increase the multiplexing gain"
    - "capacity region of the deterministic multi pair bi directional relay network"
    - "bits through relay cascades with half duplex constraint"
    - "broadcast capacity region of two phase bidirectional relaying"
    - "to code or not to code in multi hop relay channels"
    - "on the capacity and diversity multiplexing tradeoff of the two way relay channel"

Connected through hyperedge HE-7 (induced by source paper "power allocation strategies and lattice based coding schemes for bi directional relaying"):
  with members:
    - "joint physical layer coding and network coding for bi directional relaying"

Connected through hyperedge HE-8 (induced by source paper "on the capacity and diversity multiplexing tradeoff of the two way relay channel"):
  with members:
    - "approximate capacity of the two way relay channel a deterministic approach"
    - "optimal beamforming for two way multi antenna relay channel with analogue network coding"
    - "joint physical layer coding and network coding for bi directional relaying"
    - "the capacity of two way relay channel"
    - "physical network coding in two way wireless relay channels"
    - "performance bounds for bi directional coded cooperation protocols"
    - "optimal space time codes for the mimo amplify and forward cooperative channel"
    - "approximately universal optimality over several dynamic and non dynamic cooperative diversity schemes for wireless networks"

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)