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: "graph coloring based pilot allocation to mitigate pilot contamination for multi cell massive mimo systems"
  Abstract: A massive multiple-input multiple-output (MIMO) system, which utilizes a large number of base station (BS) antennas to serve a set of users, suffers from pilot contamination due to the inter-cell interference (ICI). In this letter, a graph coloring based pilot allocation (GC-PA) scheme is proposed to mitigate pilot contamination for multi-cell massive MIMO systems. Specifically, by exploiting the large-scale characteristics of fading channels, an interference graph is firstly constructed to describe the potential ICI relationship of all users. Then, with the limited pilot resource, the proposed GC-PA scheme aims to mitigate the potential ICI by efficiently allocating pilots among users in the interference graph. The performance gain of the proposed scheme is verified by simulations.

Connected through hyperedge HE-1 (induced by source paper "joint pilot design and uplink power allocation in multi cell massive mimo systems"):
  with members:
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "optimal pilot and payload power control in single cell massive mimo systems"
    - "joint power allocation and user association optimization for massive mimo systems"
    - "robust pilot decontamination based on joint angle and power domain discrimination"
    - "channel acquisition for massive mimo ofdm with adjustable phase shift pilots"
    - "massive mimo ten myths and one critical question"
    - "massive mimo with multi cell mmse processing exploiting all pilots for interference suppression"
    - "massive mimo performance evaluation based on measured propagation data"

Connected through hyperedge HE-2 (induced by source paper "pilot reuse among d2d users in d2d underlaid massive mimo systems"):
  with members:
    - "energy efficient joint resource allocation and power control for d2d communications"
    - "energy efficient resource allocation for device to device underlay communication"
    - "an uplink interference analysis for massive mimo systems with mrc and zf receivers"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "the interplay between massive mimo and underlaid d2d networking"
    - "a survey on device to device communication in cellular networks"
    - "asymptotic coverage probability and rate in massive mimo networks"
    - "a coordinated approach to channel estimation in large scale multiple antenna systems"

Connected through hyperedge HE-3 (induced by source paper "joint pilot sequence design and power control for max min fairness in uplink massive mimo"):
  with members:
    - "uplink pilot and data power control for single cell massive mimo systems with mrc"
    - "smart pilot assignment for massive mimo"
    - "aspects of favorable propagation in massive mimo"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"
    - "massive mimo for maximal spectral efficiency how many users and pilots should be allocated"
    - "energy and spectral efficiency of very large multiuser mimo systems"
    - "pilot contamination and precoding in multi cell tdd systems"

Connected through hyperedge HE-4 (induced by source paper "joint power allocation and user association optimization for massive mimo systems"):
  with members:
    - "downlink power control for massive mimo cellular systems with optimal user association"
    - "massive mimo ten myths and one critical question"
    - "joint downlink base station association and power control for max min fairness computation and complexity"
    - "uplink pilot and data power control for single cell massive mimo systems with mrc"
    - "massive mimo performance evaluation based on measured propagation data"
    - "smart pilot assignment for massive mimo"
    - "optimal user cell association for massive mimo wireless networks"
    - "aspects of favorable propagation in massive mimo"

Connected through hyperedge HE-5 (induced by source paper "multi cell multiuser massive mimo networks user capacity analysis and pilot design"):
  with members:
    - "user load analysis and pilot sequence design for multi cell massive mimo networks"
    - "performance analysis and location optimization for massive mimo systems with circularly distributed antennas"
    - "power allocation schemes for multicell massive mimo systems"
    - "fundamental limits of training based multiuser mimo systems"
    - "pilot signal design for massive mimo systems a received signal to noise ratio based approach"
    - "massive mimo performance evaluation based on measured propagation data"
    - "smart pilot assignment for massive mimo"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-6 (induced by source paper "user capacity analysis and pilot design for multi cell multiuser massive mimo networks"):
  with members:
    - "user load analysis and pilot sequence design for multi cell massive mimo networks"
    - "performance analysis and location optimization for massive mimo systems with circularly distributed antennas"
    - "power allocation schemes for multicell massive mimo systems"
    - "pilot signal design for massive mimo systems a received signal to noise ratio based approach"
    - "massive mimo performance evaluation based on measured propagation data"
    - "smart pilot assignment for massive mimo"
    - "massive mimo for next generation wireless systems"
    - "blind pilot decontamination"

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)