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: "millimeter wave mimo channel tracking systems"
  Abstract: We consider channel/subspace tracking systems for temporally correlated millimeter wave (e.g., E-band) multiple-input multiple-output (MIMO) channels. Our focus is given to the tracking algorithm in the non-line-of-sight (NLoS) environment, where the transmitter and the receiver are equipped with hybrid analog/digital precoder and combiner, respectively. In the absence of straightforward time-correlated channel model in the millimeter wave MIMO literature, we present a temporal MIMO channel evolution model for NLoS millimeter wave scenarios. Considering that conventional MIMO channel tracking algorithms in microwave bands are not directly applicable, we propose a new channel tracking technique based on sequentially updating the precoder and combiner. Numerical results demonstrate the superior channel tracking ability of the proposed technique over independent sounding approach in the presented channel model and the spatial channel model (SCM) adopted in 3GPP specification.

Connected through hyperedge HE-1 (induced by source paper "optimal precoders for tracking the aod and aoa of a mmwave path"):
  with members:
    - "fast channel estimation for millimetre wave wireless systems using overlapped beam patterns"
    - "robust location aided beam alignment in millimeter wave massive mimo"
    - "modeling and analyzing millimeter wave cellular systems"
    - "error bounds for uplink and downlink 3d localization in 5g mmwave systems"
    - "transmitter beam selection in millimeter wave mimo with in band position aiding"
    - "hierarchical codebook design for beamforming training in millimeter wave communication"
    - "millimeter wave vehicular communication to support massive automotive sensing"
    - "channel estimation for hybrid architecture based wideband millimeter wave systems"

Connected through hyperedge HE-2 (induced by source paper "efficient beam training and channel estimation for millimeter wave communications under mobility"):
  with members:
    - "compressive channel estimation and tracking for large arrays in mm wave picocells"
    - "an overview of signal processing techniques for millimeter wave mimo systems"
    - "tracking mm wave channel dynamics fast beam training strategies under mobility"
    - "compressed sensing for wireless communications useful tips and tricks"
    - "tracking angles of departure and arrival in a mobile millimeter wave channel"
    - "a survey of millimeter wave mmwave communications for 5g opportunities and challenges"
    - "training beam sequence design for millimeter wave mimo systems a pomdp framework"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"

Connected through hyperedge HE-3 (induced by source paper "omnidirectional precoding and combining based synchronization for millimeter wave massive mimo systems"):
  with members:
    - "bdma for millimeter wave terahertz massive mimo transmission with per beam synchronization"
    - "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"

Connected through hyperedge HE-4 (induced by source paper "low complexity channel estimation for millimeter wave systems with hybrid a d antenna processing"):
  with members:
    - "compressive channel estimation and tracking for large arrays in mm wave picocells"
    - "low rank spatial channel estimation for millimeter wave cellular systems"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "what will 5g be"
    - "five disruptive technology directions for 5g"
    - "millimeter wave beamforming for wireless backhaul and access in small cell networks"
    - "iterative hard thresholding for compressed sensing"

Connected through hyperedge HE-5 (induced by source paper "tracking mm wave channel dynamics fast beam training strategies under mobility"):
  with members:
    - "comparative analysis of initial access techniques in 5g mmwave cellular networks"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "millimeter wave channel modeling and cellular capacity evaluation"

Connected through hyperedge HE-6 (induced by source paper "beampattern based tracking for millimeter wave communication systems"):
  with members:
    - "spatially sparse precoding in millimeter wave mimo systems"

Connected through hyperedge HE-7 (induced by source paper "millimeter wave cellular networks a mac layer perspective"):
  with members:
    - "stochastic geometry modeling and analysis of multi tier millimeter wave cellular networks"
    - "beam searching and transmission scheduling in millimeter wave communications"
    - "a survey of millimeter wave mmwave communications for 5g opportunities and challenges"
    - "subspace estimation and decomposition for hybrid analog digital millimetre wave mimo systems"
    - "design aspects of short range millimeter wave networks a mac layer perspective"
    - "on the joint impact of beamwidth and orientation error on throughput in directional wireless poisson networks"
    - "an overview of load balancing in hetnets old myths and open problems"
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"

Connected through hyperedge HE-8 (induced by source paper "pilot beam sequence design for channel estimation in millimeter wave mimo systems a pomdp framework"):
  with members:
    - "channel estimation and hybrid precoding for millimeter wave cellular systems"
    - "incremental pruning a simple fast exact method for partially observable markov decision processes"
    - "point based pomdp algorithms improved analysis and implementation"

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)