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: "constant envelope precoding with time variation constraint on the transmitted phase angles"
  Abstract: We consider downlink precoding in a frequency-selective multi-user massive MIMO system with highly efficient but non-linear power amplifiers at the base station (BS). A low-complexity precoding algorithm is proposed, which generates constant-envelope (CE) transmit signals for each BS antenna. To avoid large variations in the phase angle transmitted from each antenna, the difference of the phase angles transmitted in consecutive channel uses is limited to    $[-\alpha\pi,\ \alpha\pi]$   for a fixed    $0  . With independent Rayleigh distributed channel gains, numerical studies reveal that the extra total transmit power required under the time variation constraint when compared to the case of no time variation constraint (i.e.,    $\alpha=1$  ), is   small   (    $   dB) for many practical values of    $\alpha$  . Further, irrespective of the value of    $\alpha$  , the required total transmit power to achieve a fixed per-user information rate decreases by roughly 3 dB with every doubling in the number of BS antennas.

Connected through hyperedge HE-1 (induced by source paper "symbol level and multicast precoding for multiuser multiantenna downlink a survey classification and challenges"):
  with members:
    - "channel estimation and performance analysis of one bit massive mimo systems"
    - "an overview on resource allocation techniques for multi user mimo systems"
    - "spatio temporal waveform design for multiuser massive mimo downlink with 1 bit receivers"
    - "joint beamforming and broadcasting in massive mimo"
    - "coordinate update algorithms for robust power loading for the mu miso downlink with outage constraints"
    - "energy efficient symbol level precoding in multiuser miso based on relaxed detection region"
    - "robust transmission in downlink multiuser miso systems a rate splitting approach"
    - "adaptive pilot clustering in heterogeneous massive mimo networks"

Connected through hyperedge HE-2 (induced by source paper "constant envelope precoding for mimo systems"):
  with members:
    - "constant envelope precoding with adaptive receiver constellation in miso fading channel"
    - "designing unimodular codes via quadratic optimization"
    - "constant envelope multi user precoding for frequency selective massive mimo systems"
    - "per antenna constant envelope precoding for large multi user mimo systems"
    - "single user beamforming in large scale miso systems with per antenna constant envelope constraints the doughnut channel"
    - "cooperative multi cell block diagonalization with per base station power constraints"
    - "on gaussian mimo bc mac duality with multiple transmit covariance constraints"

Connected through hyperedge HE-3 (induced by source paper "constant envelope precoding with adaptive receiver constellation in miso fading channel"):
  with members:
    - "constant envelope multi user precoding for frequency selective massive mimo systems"
    - "per antenna constant envelope precoding for large multi user mimo systems"
    - "single user beamforming in large scale miso systems with per antenna constant envelope constraints the doughnut channel"
    - "cooperative multi cell block diagonalization with per base station power constraints"
    - "on gaussian mimo bc mac duality with multiple transmit covariance constraints"

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)