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: "bi directional multi antenna relay communications with wireless network coding"
  Abstract: In this paper, we consider a two-way or bidirectional communications system with a relay equipped with multiple antennas. We show that when the downlink channel state information is not known at the relay, the benefit of having additional antennas at the relay can only be obtained by using decode and forward (DF) but not amplify and forward (AF). The gain becomes significant when we employ transmit diversity together with wireless network coding. We also demonstrate how the performance of such system can be improved by performing antenna selection at the relay. Our results show that if downlink channel state information is known at the relay, network coding may not provide additional gain than simple antenna selection scheme.

Connected through hyperedge HE-1 (induced by source paper "performance analysis of two step bi directional relaying with multiple antennas"):
  with members:
    - "physical layer network coding"
    - "a simple cooperative diversity method based on network path selection"

Connected through hyperedge HE-2 (induced by source paper "a distributed differential space time coding scheme with analog network coding in two way relay networks"):
  with members:
    - "relay selection for two way relaying with amplify and forward protocols"

Connected through hyperedge HE-3 (induced by source paper "joint relay selection and analog network coding using differential modulation in two way relay channels"):
  with members:
    - "optimal beamforming for two way multi antenna relay channel with analogue network coding"

Connected through hyperedge HE-4 (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"

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)