human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "mimo channel hardening a physical model based analysis"):
  Abstract: In a multiple-input-multiple-output (MIMO) communication system, the multipath fading is averaged#R##N#over radio links. This well-known channel hardening phenomenon plays a central role in#R##N#the design of massive MIMO systems. The aim of this paper is to study channel hardening using a#R##N#physical channel model in which the influences of propagation rays and antenna array topologies#R##N#are highlighted. A measure of channel hardening is derived through the coefficient of variation#R##N#of the channel gain.  Our analyses and closed form results based on the used physical#R##N#model are consistent with those of the literature relying on more abstract Rayleigh fading#R##N#models, but offer further insights on the relationship with channel characteristics.

Includes members:
  Member "parametric channel estimation for massive mimo":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "wideband massive mimo channel estimation via sequential atomic norm minimization")
  Member "no downlink pilots are needed in tdd massive mimo":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "massive mimo asymptotics for ray based propagation channels")

Question: Please tell me which class the source paper 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.NI(Networking and Internet Architecture)