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: "optimal multiuser transmit beamforming a difficult problem with a simple solution structure"
  Abstract: Transmit beamforming is a versatile technique for signal transmission from an array of $N$ antennas to one or multiple users [1]. In wireless communications, the goal is to increase the signal power at the intended user and reduce interference to non-intended users. A high signal power is achieved by transmitting the same data signal from all antennas, but with different amplitudes and phases, such that the signal components add coherently at the user. Low interference is accomplished by making the signal components add destructively at non-intended users. This corresponds mathematically to designing beamforming vectors (that describe the amplitudes and phases) to have large inner products with the vectors describing the intended channels and small inner products with non-intended user channels. #R##N#While it is fairly easy to design a beamforming vector that maximizes the signal power at the intended user, it is difficult to strike a perfect balance between maximizing the signal power and minimizing the interference leakage. In fact, the optimization of multiuser transmit beamforming is generally a nondeterministic polynomial-time (NP) hard problem [2]. Nevertheless, this lecture shows that the optimal transmit beamforming has a simple structure with very intuitive properties and interpretations. This structure provides a theoretical foundation for practical low-complexity beamforming schemes. #R##N#(See this lecture note for the complete abstract/introduction)

Connected through hyperedge HE-1 (induced by source paper "massive mimo has unlimited capacity"):
  with members:
    - "massive mimo pilot decontamination and channel interpolation via wideband sparse channel estimation"
    - "massive mimo with imperfect channel covariance information"
    - "robust pilot decontamination based on joint angle and power domain discrimination"
    - "pilot contamination is not a fundamental asymptotic limitation in massive mimo"
    - "massive mimo with multi cell mmse processing exploiting all pilots for interference suppression"
    - "massive mimo in real propagation environments do all antennas contribute equally"
    - "massive mimo performance evaluation based on measured propagation data"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"

Connected through hyperedge HE-2 (induced by source paper "capacity analysis for full duplex self backhauled small cells"):
  with members:
    - "exploiting full half duplex user relaying in noma systems"
    - "scheduling and power allocation in self backhauled full duplex small cells"
    - "full duplex multi antenna relay assisted cooperative non orthogonal multiple access"
    - "joint beamforming design and power allocation for full duplex noma cognitive relay systems"
    - "joint backhaul access analysis of full duplex self backhauling heterogeneous networks"
    - "sum rate analysis and optimization of self backhauling based full duplex radio access system"
    - "analysis of massive mimo enabled downlink wireless backhauling for full duplex small cells"
    - "what will 5g be"

Connected through hyperedge HE-3 (induced by source paper "an overview on resource allocation techniques for multi user mimo systems"):
  with members:
    - "low complexity downlink user selection for massive mimo systems"
    - "alternating minimization algorithms for hybrid precoding in millimeter wave mimo systems"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "user association in 5g networks a survey and an outlook"
    - "cell free massive mimo versus small cells"
    - "mu mimo mac protocols for wireless local area networks a survey"
    - "on the number of rf chains and phase shifters and scheduling design with hybrid analog digital beamforming"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"

Connected through hyperedge HE-4 (induced by source paper "1 bit massive mu mimo precoding in vlsi"):
  with members:
    - "decentralized baseband processing for massive mu mimo systems"
    - "channel estimation and performance analysis of one bit massive mimo systems"
    - "uplink performance of wideband massive mimo with one bit adcs"
    - "massive mu mimo ofdm downlink with one bit dacs and linear precoding"
    - "nonlinear 1 bit precoding for massive mu mimo with higher order modulation"
    - "minimum ber precoding in 1 bit massive mimo systems"
    - "data detection in large multi antenna wireless systems via approximate semidefinite relaxation"
    - "performance of the wideband massive uplink mimo with one bit adcs"

Connected through hyperedge HE-5 (induced by source paper "max min sinr in large scale single cell mu mimo asymptotic analysis and low complexity transceivers"):
  with members:
    - "large system analysis of the energy consumption distribution in multi user mimo systems with mobility"
    - "large system analysis of base station cooperation for power minimization"
    - "linear precoding based on polynomial expansion large scale multi cell mimo systems"
    - "massive mimo for next generation wireless systems"
    - "joint beamforming and power control in coordinated multicell max min duality effective network and large system transition"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"
    - "robust monotonic optimization framework for multicell miso systems"

Connected through hyperedge HE-6 (induced by source paper "reel bf design achieving the sdp bound for downlink beamforming with arbitrary shaping constraints"):
  with members:
    - "rank two beamforming and power allocation in multicasting relay networks"
    - "general rank multiuser downlink beamforming with shaping constraints using real valued ostbc"
    - "multiuser miso beamforming for simultaneous wireless information and power transfer"
    - "physical layer multicasting by stochastic transmit beamforming and alamouti space time coding"
    - "spatially selective artificial noise aided transmit optimization for miso multi eves secrecy rate maximization"
    - "throughput maximization for the gaussian relay channel with energy harvesting constraints"
    - "outage constrained robust transmit optimization for multiuser miso downlinks tractable approximations by conic optimization"
    - "secure transmission with artificial noise over fading channels achievable rate and optimal power allocation"

Connected through hyperedge HE-7 (induced by source paper "robust transceiver design based on interference alignment for multi user multi cell mimo networks with channel uncertainty"):
  with members:
    - "two stage beamformer design for massive mimo downlink by trace quotient formulation"
    - "exploiting known interference as green signal power for downlink beamforming optimization"
    - "rethinking the role of interference in wireless networks"
    - "two tier precoding for fdd multi cell massive mimo time varying interference networks"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "grouping based interference alignment with ia cell assignment in multi cell mimo mac under limited feedback"
    - "multi cell random beamforming achievable rate and degrees of freedom region"
    - "outage probability and outage based robust beamforming for mimo interference channels with imperfect channel state information"

Connected through hyperedge HE-8 (induced by source paper "unraveling the rank one solution mystery of robust miso downlink transmit optimization a verifiable sufficient condition via a new duality result"):
  with members:
    - "coordinate update algorithms for robust power loading for the mu miso downlink with outage constraints"
    - "a parallel decomposition method for nonconvex stochastic multi agent optimization problems"
    - "a stochastic beamformed amplify and forward scheme in a multigroup multicast mimo relay network with per antenna power constraints"
    - "physical layer multicasting by stochastic transmit beamforming and alamouti space time coding"
    - "distributed robust multicell coordinated beamforming with imperfect csi an admm approach"
    - "worst case robust multiuser transmit beamforming using semidefinite relaxation duality and implications"
    - "robust linear precoder design for multi cell downlink transmission"
    - "outage constrained robust transmit optimization for multiuser miso downlinks tractable approximations by conic optimization"

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)