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: "multi user massive mimo communication systems based on irregular antenna arrays"
  Abstract: In practical mobile communication engineering applications, surfaces of antenna array deployment regions are usually uneven. Therefore, massive multi-input-multi-output (MIMO) communication systems usually transmit wireless signals by irregular antenna arrays. To evaluate the performance of irregular antenna arrays, the matrix correlation coefficient and ergodic received gain are defined for massive MIMO communication systems with mutual coupling effects. Furthermore, the lower bound of the ergodic achievable rate, symbol error rate (SER) and average outage probability are firstly derived for multi-user massive MIMO communication systems using irregular antenna arrays. Asymptotic results are also derived when the number of antennas approaches infinity. Numerical results indicate that there exists a maximum achievable rate when the number of antennas keeps increasing in massive MIMO communication systems using irregular antenna arrays. Moreover, the irregular antenna array outperforms the regular antenna array in the achievable rate of massive MIMO communication systems when the number of antennas is larger than or equal to a given threshold.

Connected through hyperedge HE-1 (induced by source paper "power consumption outage challenge in next generation cellular networks"):
  with members:
    - "spatial spectrum and energy efficiency of random cellular networks"
    - "5g ultra dense cellular networks"
    - "energy efficiency evaluation of cellular networks based on spatial distributions of traffic load and power consumption"

Connected through hyperedge HE-2 (induced by source paper "energy efficiency and asymptotic performance evaluation of beamforming structures in doubly massive mimo mmwave systems"):
  with members:
    - "doubly massive mmwave mimo systems using very large antenna arrays at both transmitter and receiver"
    - "enhancing the estimation of mm wave large array channels by exploiting spatio temporal correlation and sparse scattering"
    - "energy efficiency optimization of 5g radio frequency chain systems"
    - "on clustered statistical mimo millimeter wave channel simulation"
    - "hybrid digital and analog beamforming design for large scale antenna arrays"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"
    - "massive mimo combining with switches"
    - "limited feedback hybrid precoding for multi user millimeter wave systems"

Connected through hyperedge HE-3 (induced by source paper "uplink analysis of large mu mimo systems with space constrained arrays in ricean fading"):
  with members:
    - "on the role of transmit correlation diversity in multiuser mimo systems"
    - "on the spectral efficiency of space constrained massive mimo with linear receivers"
    - "space constrained massive mimo hitting the wall of favorable propagation"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "massive mimo for next generation wireless systems"
    - "millimeter wave channel modeling and cellular capacity evaluation"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "performance analysis of macrodiversity mimo systems with mmse and zf receivers in flat rayleigh fading"

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)