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: "bdma for millimeter wave terahertz massive mimo transmission with per beam synchronization"
  Abstract: We propose beam division multiple access (BDMA) with per-beam synchronization (PBS) in time and frequency for wideband massive multiple-input multiple-output (MIMO) transmission over millimeter-wave (mmW)/Terahertz (THz) bands. We first introduce a physically motivated beam domain channel model for massive MIMO and demonstrate that the envelopes of the beam domain channel elements tend to be independent of time and frequency when both the numbers of antennas at base station and user terminals (UTs) tend to infinity. Motivated by the derived beam domain channel properties, we then propose PBS for mmW/THz massive MIMO. We show that both the effective delay and Doppler frequency spreads of wideband massive MIMO channels with PBS are reduced by a factor of the number of UT antennas compared with the conventional synchronization approaches. Subsequently, we apply PBS to BDMA, investigate beam scheduling to maximize the achievable ergodic rates for both uplink and downlink BDMA, and develop a greedy beam scheduling algorithm. Simulation results verify the effectiveness of BDMA with PBS for mmW/THz wideband massive MIMO systems in typical mobility scenarios.

Connected through hyperedge HE-1 (induced by source paper "energy efficiency optimization for downlink massive mimo with statistical csit"):
  with members:
    - "beam domain secure transmission for massive mimo communications"
    - "fractional programming for communication systems part i power control and beamforming"
    - "energy efficient multicell multigroup multicasting with joint beamforming and antenna selection"
    - "fdd massive mimo via ul dl channel covariance extrapolation and active channel sparsification"
    - "network deployment for maximal energy efficiency in uplink with multislope path loss"
    - "energy efficient beam coordination strategies with rate dependent processing power"
    - "free deterministic equivalents for the analysis of mimo multiple access channel"
    - "channel acquisition for massive mimo ofdm with adjustable phase shift pilots"

Connected through hyperedge HE-2 (induced by source paper "performance of high mobility mimo communications with doppler diversity"):
  with members:
    - "channel acquisition for massive mimo ofdm with adjustable phase shift pilots"
    - "an overview of transmission theory and techniques of large scale antenna systems for 5g wireless communications"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"

Connected through hyperedge HE-3 (induced by source paper "high mobility wideband massive mimo communications doppler compensation analysis and scaling law"):
  with members:
    - "a new view of multi user hybrid massive mimo non orthogonal angle division multiple access"
    - "frequency synchronization for uplink massive mimo systems"
    - "high mobility ofdm downlink transmission with large scale antenna array"
    - "angle domain doppler pre compensation for high mobility ofdm uplink with a massive ula"
    - "directivity beamwidth tradeoff of massive mimo uplink beamforming for high speed train communication"

Connected through hyperedge HE-4 (induced by source paper "joint user scheduling and beam selection optimization for beam based massive mimo downlinks"):
  with members:
    - "a real time millimeter wave phased array mimo channel sounder"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "hybrid beamforming for massive mimo a survey"
    - "achievable rates of fdd massive mimo systems with spatial channel correlation"
    - "dynamic channel acquisition in mu mimo"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "massive mimo for next generation wireless systems"
    - "spatially sparse precoding in millimeter wave mimo systems"

Connected through hyperedge HE-5 (induced by source paper "omnidirectional precoding and combining based synchronization for millimeter wave massive mimo systems"):
  with members:
    - "low complexity channel estimation for millimeter wave systems with hybrid a d antenna processing"
    - "omnidirectional space time block coding for common information broadcasting in massive mimo systems"
    - "beamforming tradeoffs for initial ue discovery in millimeter wave mimo systems"
    - "directional cell discovery in millimeter wave cellular networks"
    - "coverage and rate analysis for millimeter wave cellular networks"
    - "downlink training techniques for fdd massive mimo systems open loop and closed loop training with memory"
    - "spatially sparse precoding in millimeter wave mimo systems"
    - "millimeter wave mimo channel tracking 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)