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: "energy efficient multi pair two way af full duplex massive mimo relaying"
  Abstract: We consider multi-pair two-way amplify and forward (AF) relaying, where multiple full-duplex source-node pairs exchange information via a shared full-duplex massive multiple-input multiple-output (MIMO) relay. Most of the previous massive MIMO relay works maximize spectral efficiency (SE). We maximize global energy efficiency (GEE) with quality-of-service (QoS) constraints that are expressed as the rate required by source nodes. The problem is non-convex and is solved by approximating it as a pseudo-concave problem, which is then solved using the Dinkelbach method. We also consider the max-min EE problem which maximizes the EE of the worst energy efficient user. For solving the EE optimization, we derive approximate closed-form lower bounds for the ergodic achievable rate for maximal-ratio and zero-forcing processing at the relay by using minimum mean squared error channel estimation. We numerically show the accuracy of the derived lower bounds and the improved GEE with optimal power allocation, with and without QoS constraints.

Connected through hyperedge HE-1 (induced by source paper "spectral efficiency of multipair massive mimo two way relaying with hardware impairments"):
  with members:
    - "performance analysis of mixed adc massive mimo systems over rician fading channels"
    - "on the spectral efficiency of massive mimo systems with low resolution adcs"
    - "achievable rate of rician large scale mimo channels with transceiver hardware impairments"
    - "massive mimo performance evaluation based on measured propagation data"
    - "massive mimo with non ideal arbitrary arrays hardware scaling laws and circuit aware design"
    - "multipair full duplex relaying with massive arrays and linear processing"
    - "energy and spectral efficiency of very large multiuser mimo systems"

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)