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: "power allocation for multi pair massive mimo two way af relaying with linear processing"
  Abstract: In this paper, we consider a multi-pair two-way amplify-and-forward relaying system where multiple sources exchange information via a relay node equipped with large-scale antenna arrays. Given that channel estimation is non-ideal, and that the relay employs either maximum-ratio combining/maximum-ratio transmission (MRC/MRT) or zero-forcing reception/zero-forcing transmission (ZFR/ZFT) beamforming, we derive two corresponding closed-form lower bound expressions for the ergodic achievable rate of each pair sources. The closed-form expressions enable us to design an optimal power allocation (OPA) scheme that maximizes the sum spectral efficiency under certain practical constraints. As the antenna array size tends to infinity and the signal to noise ratios become very large, asymptotically optimal power allocation schemes in simple closed-form are derived. The capacity lower bounds are verified to be accurate predictors of the system performance by simulations, and the proposed OPA outperforms equal power allocation (EPA). It is also found that in the asymptotic regime, when MRC/MRT is used at the relay and the link end-to-end large-scale fading factors among all pairs are equal, the optimal power allocated to a user is inverse to the large-scale fading factor of the channel from the user to the relay, while OPA approaches EPA when ZFR/ZFT is adopted.

Connected through hyperedge HE-1 (induced by source paper "impact of relay cooperation on the performance of large scale multipair two way relay networks"):
  with members:
    - "reciprocity calibration for massive mimo proposal modeling and validation"
    - "massive mimo for next generation wireless systems"
    - "scalable synchronization and reciprocity calibration for distributed multiuser mimo"

Connected through hyperedge HE-2 (induced by source paper "framework of channel estimation for hybrid analog and digital processing enabled massive mimo communications"):
  with members:
    - "multipair massive mimo relaying with pilot data transmission overlay"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "on the number of rf chains and phase shifters and scheduling design with hybrid analog digital beamforming"
    - "frequency selective hybrid precoding for limited feedback millimeter wave systems"
    - "hybrid beamforming for massive mimo a survey"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "two stage subspace constrained precoding in massive mimo cellular systems"
    - "compressed sensing based multi user millimeter wave systems how many measurements are needed"

Connected through hyperedge HE-3 (induced by source paper "energy efficient multi pair two way af full duplex massive mimo relaying"):
  with members:
    - "a survey of multi objective optimization in wireless sensor networks metrics algorithms and open problems"
    - "joint beamforming optimization and power control for full duplex mimo two way relay channel"
    - "multipair full duplex relaying with massive arrays and linear processing"
    - "energy efficiency optimization in relay assisted mimo systems with perfect and statistical csi"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "in band full duplex wireless challenges and opportunities"
    - "green cellular networks a survey some research issues and challenges"
    - "energy and spectral efficiency of very large multiuser mimo systems"

Connected through hyperedge HE-4 (induced by source paper "multi pair two way af full duplex massive mimo relaying with zfr zft processing"):
  with members:
    - "multipair full duplex relaying with massive arrays and linear processing"
    - "in band full duplex wireless challenges and opportunities"
    - "a tutorial on the optimization of amplify and forward mimo relay systems"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "pilot contamination and precoding in multi cell tdd systems"

Connected through hyperedge HE-5 (induced by source paper "multipair massive mimo relaying with pilot data transmission overlay"):
  with members:
    - "energy efficient power control a look at 5g wireless technologies"
    - "massive mimo ten myths and one critical question"
    - "full duplex relaying in mimo ofdm frequency selective channels with optimal adaptive filtering"
    - "massive mimo full duplex relaying with optimal power allocation for independent multipairs"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "multipair full duplex relaying with massive arrays and linear processing"
    - "massive mimo for next generation wireless systems"
    - "emerging technologies and research challenges for 5g 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)