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: "electromagnetic lens focusing antenna enabled massive mimo performance improvement and cost reduction"
  Abstract: Massive multiple-input multiple-output (MIMO) techniques have been recently advanced to tremendously improve the performance of wireless communication networks. However, the use of very large antenna arrays at the base stations (BSs) brings new issues, such as the significantly increased hardware and signal processing costs. In order to reap the enormous gain of massive MIMO and yet reduce its cost to an affordable level, this paper proposes a novel system design by integrating an electromagnetic (EM) lens with the large antenna array, termed the EM-lens enabled MIMO. The EM lens has the capability of focusing the power of an incident wave to a small area of the antenna array, while the location of the focal area varies with the angle of arrival (AoA) of the wave. Therefore, in practical scenarios where the arriving signals from geographically separated users have different AoAs, the EM-lens enabled system provides two new benefits, namely energy focusing and spatial interference rejection. By taking into account the effects of imperfect channel estimation via pilot-assisted training, in this paper we analytically show that the average received signal-to-noise ratio (SNR) in both the single-user and multiuser uplink transmissions can be strictly improved by the EM-lens enabled system. Furthermore, we demonstrate that the proposed design makes it possible to considerably reduce the hardware and signal processing costs with only slight degradations in performance. To this end, two complexity/cost reduction schemes are proposed, which are small-MIMO processing with parallel receiver filtering applied over subgroups of antennas to reduce the computational complexity, and channel covariance based antenna selection to reduce the required number of radio frequency (RF) chains. Numerical results are provided to corroborate our analysis.

Connected through hyperedge HE-1 (induced by source paper "majorization minimization aided hybrid transceivers for mimo interference channels"):
  with members:
    - "a framework on hybrid mimo transceiver design based on matrix monotonic optimization"
    - "hybrid analog and digital beamforming for mmwave ofdm large scale antenna arrays"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "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"
    - "near optimal hybrid processing for massive mimo systems via matrix decomposition"

Connected through hyperedge HE-2 (induced by source paper "hybrid beamforming with selection for multiuser massive mimo systems"):
  with members:
    - "stationarity region of mm wave channel based on outdoor microcellular measurements at 28 ghz"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "5g 3gpp like channel models for outdoor urban microcellular and macrocellular environments"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "massive mimo combining with switches"
    - "hybrid beamforming for massive mimo a survey"
    - "analysis of the local quasi stationarity of measured dual polarized mimo channels"

Connected through hyperedge HE-3 (induced by source paper "tracking position and orientation through millimeter wave lens mimo in 5g systems"):
  with members:
    - "optimal precoders for tracking the aod and aoa of a mmwave path"
    - "direct localization for massive mimo"
    - "error bounds for uplink and downlink 3d localization in 5g mmwave systems"
    - "multi user millimeter wave mimo with full dimensional lens antenna array"
    - "compressive channel estimation and tracking for large arrays in mm wave picocells"
    - "joint device positioning and clock synchronization in 5g ultra dense networks"
    - "frequency selective hybrid precoding for limited feedback millimeter wave systems"
    - "tracking angles of departure and arrival in a mobile millimeter wave channel"

Connected through hyperedge HE-4 (induced by source paper "uplink channel estimation and data transmission in millimeter wave cran with lens antenna arrays"):
  with members:
    - "fronthaul limited uplink ofdma in ultra dense cran with hybrid decoding"
    - "joint millimeter wave fronthaul and ofdma resource allocation in ultra dense cran"
    - "multi user millimeter wave mimo with full dimensional lens antenna array"
    - "rf lens embedded massive mimo systems fabrication issues and codebook design"
    - "channel estimation for hybrid architecture based wideband millimeter wave systems"
    - "cost effective millimeter wave communications with lens antenna array"
    - "millimeter wave mimo with lens antenna array a new path division multiplexing paradigm"
    - "optimized uplink transmission in multi antenna c ran with spatial compression and forward"

Connected through hyperedge HE-5 (induced by source paper "beyond massive mimo the potential of data transmission with large intelligent surfaces"):
  with members:
    - "the potential of using large antenna arrays on intelligent surfaces"
    - "a generalized zero forcing precoder with successive dirty paper coding in miso broadcast channels"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"
    - "a low complexity channel shortening receiver with diversity support for evolved 2g device"
    - "massive mimo performance evaluation based on measured propagation data"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"
    - "millimeter wave cellular wireless networks potentials and challenges"

Connected through hyperedge HE-6 (induced by source paper "codebook design for channel feedback in lens based millimeter wave massive mimo systems"):
  with members:
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "millimeter wave mimo with lens antenna array a new path division multiplexing paradigm"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"

Connected through hyperedge HE-7 (induced by source paper "multi user millimeter wave mimo with full dimensional lens antenna array"):
  with members:
    - "beamspace channel estimation for millimeter wave massive mimo systems with lens antenna array"
    - "rf lens embedded massive mimo systems fabrication issues and codebook design"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "low rf complexity technologies to enable millimeter wave mimo with large antenna array for 5g wireless communications"
    - "cost effective millimeter wave communications with lens antenna array"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "frequency selective hybrid precoding for limited feedback millimeter wave systems"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"

Connected through hyperedge HE-8 (induced by source paper "rf lens embedded massive mimo systems fabrication issues and codebook design"):
  with members:
    - "performance analysis of massive mimo for cell boundary users"
    - "compressed channel feedback for correlated massive mimo systems"
    - "millimeter wave mimo with lens antenna array a new path division multiplexing paradigm"
    - "achievable rates of fdd massive mimo systems with spatial channel correlation"
    - "what will 5g be"
    - "downlink training techniques for fdd massive mimo systems open loop and closed loop training with memory"
    - "noncoherent trellis coded quantization a practical limited feedback technique for massive mimo systems"
    - "five disruptive technology directions for 5g"

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)