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: "performance of cell free massive mimo with rician fading and phase shifts"
  Abstract: In this paper, we study the uplink (UL) and downlink (DL) spectral efficiency (SE) of a cell-free massive multiple-input-multiple-output (MIMO) system with Rician fading channels. The phase of the line-of-sight (LoS) path is modeled as a uniformly distributed random variable to take the phase-shifts due to mobility and phase noise into account. Considering the availability of prior information at the access points (APs), the phase-aware minimum mean square error (MMSE), non-aware linear MMSE (LMMSE), and least-square (LS) estimators are derived. The MMSE estimator requires perfectly estimated phase knowledge whereas the LMMSE and LS are derived without it. #R##N#In the UL, a two-layer decoding method is investigated in order to mitigate both coherent and non-coherent interference. Closed-form UL SE expressions with phase-aware MMSE, LMMSE, and LS estimators are derived for maximum-ratio (MR) combining in the first layer and optimal large-scale fading decoding (LSFD) in the second layer. In the DL, two different transmission modes are studied: coherent and non-coherent. Closed-form DL SE expressions for both transmission modes with MR precoding are derived for the three estimators. Numerical results show that the LSFD improves the UL SE performance and coherent transmission mode performs much better than non-coherent transmission in the DL. Besides, the performance loss due to the lack of phase information depends on the pilot length and it is small when the pilot contamination is low.

Connected through hyperedge HE-1 (induced by source paper "joint power control and lsfd for wireless powered cell free massive mimo"):
  with members:
    - "max min fair wireless powered cell free massive mimo for uncorrelated rician fading channels"
    - "optimal downlink transmission for cell free swipt massive mimo systems with active eavesdropping"
    - "scalability aspects of cell free massive mimo"
    - "scalable cell free massive mimo systems"
    - "massive mimo with spatially correlated rician fading channels"
    - "multiple antenna technologies for beyond 5g"
    - "making cell free massive mimo competitive with mmse processing and centralized implementation"
    - "massive mimo has unlimited capacity"

Connected through hyperedge HE-2 (induced by source paper "max min fair wireless powered cell free massive mimo for uncorrelated rician fading channels"):
  with members:
    - "optimal downlink transmission for cell free swipt massive mimo systems with active eavesdropping"
    - "scalability aspects of cell free massive mimo"
    - "massive mimo with spatially correlated rician fading channels"
    - "multiple antenna technologies for beyond 5g"
    - "making cell free massive mimo competitive with mmse processing and centralized implementation"
    - "optimization of power transfer efficiency and energy efficiency for wireless powered systems with massive mimo"
    - "green cell less design for rf wireless power transfer networks"
    - "performance of cell free massive mimo systems with mmse and lsfd receivers"

Connected through hyperedge HE-3 (induced by source paper "large scale fading precoding for maximizing the product of sinrs"):
  with members:
    - "joint user selection power allocation and precoding design with imperfect csit for multi cell mu mimo downlink systems"
    - "scalability aspects of cell free massive mimo"
    - "massive mimo with spatially correlated rician fading channels"
    - "optimized power control for massive mimo with underlaid d2d communications"
    - "large scale fading decoding in cellular massive mimo systems with spatially correlated channels"
    - "uplink massive mimo for channels with spatial correlation"
    - "a bilinear equalizer for massive mimo systems"
    - "massive mimo has unlimited capacity"

Connected through hyperedge HE-4 (induced by source paper "multiple antenna technologies for beyond 5g"):
  with members:
    - "intelligent reflecting surface versus decode and forward how large surfaces are needed to beat relaying"
    - "robust trajectory and resource allocation design for secure uav aided communications"
    - "a new look at cell free massive mimo making it practical with dynamic cooperation"
    - "scalability aspects of cell free massive mimo"
    - "cascaded channel estimation for large intelligent metasurface assisted massive mimo"
    - "robust and secure wireless communications via intelligent reflecting surfaces"
    - "channel estimation for intelligent reflecting surface assisted multiuser communications framework algorithms and analysis"
    - "resource allocation for secure irs assisted multiuser miso 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)