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: "joint pilot design and uplink power allocation in multi cell massive mimo systems"
  Abstract: This paper considers pilot design to mitigate pilot contamination and provide good service for everyone in multi-cell Massive multiple input multiple output (MIMO) systems. Instead of modeling the pilot design as a combinatorial assignment problem, as in prior works, we express the pilot signals using a pilot basis and treat the associated power coefficients as continuous optimization variables. We compute a lower bound on the uplink capacity for Rayleigh fading channels with maximum ratio detection that applies with arbitrary pilot signals. We further formulate the max-min fairness problem under power budget constraints, with the pilot signals and data powers as optimization variables. Because this optimization problem is non-deterministic polynomial-time hard due to signomial constraints, we then propose an algorithm to obtain a local optimum with polynomial complexity. Our framework serves as a benchmark for pilot design in scenarios with either ideal or non-ideal hardware. Numerical results manifest that the proposed optimization algorithms are close to the optimal solution obtained by exhaustive search for different pilot assignments and the new pilot structure and optimization bring large gains over the state-of-the-art suboptimal pilot design.

Connected through hyperedge HE-1 (induced by source paper "average sep optimal precoding for correlated massive mimo with zf detection an asymptotic analysis"):
  with members:
    - "large scale fading decoding in cellular massive mimo systems with spatially correlated channels"
    - "massive mimo has unlimited capacity"
    - "performance analysis for massive mimo downlink with low complexity approximate zero forcing precoding"
    - "the world s first real time testbed for massive mimo design implementation and validation"
    - "power scaling of uplink massive mimo systems with arbitrary rank channel means"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "massive mimo systems with non ideal hardware energy efficiency estimation and capacity limits"
    - "massive mimo for next generation wireless systems"

Connected through hyperedge HE-2 (induced by source paper "enhanced channel estimation in massive mimo via coordinated pilot design"):
  with members:
    - "pilot contamination mitigation with reduced rf chains"
    - "fractional programming for communication systems part i power control and beamforming"
    - "optimization of mimo device to device networks via matrix fractional programming a minorization maximization approach"
    - "a successive optimization approach to pilot design for multi cell massive mimo systems"
    - "smart pilot assignment for massive mimo"
    - "pilot beam pattern design for channel estimation in massive mimo systems"
    - "massive mimo for next generation wireless systems"
    - "blind pilot decontamination"

Connected through hyperedge HE-3 (induced by source paper "optimized power control for massive mimo with underlaid d2d communications"):
  with members:
    - "power control for d2d underlay in multi cell massive mimo networks"
    - "spectral and energy efficiency of uplink d2d underlaid massive mimo cellular networks"
    - "pilot reuse among d2d users in d2d underlaid massive mimo systems"
    - "energy efficiency and sum rate tradeoffs for massive mimo systems with underlaid device to device communications"
    - "the interplay between massive mimo and underlaid d2d networking"
    - "a survey on device to device communication in cellular networks"
    - "massive mimo for next generation wireless systems"
    - "what will 5g be"

Connected through hyperedge HE-4 (induced by source paper "power control for massive mimo systems with nonorthogonal pilots"):
  with members:
    - "large scale fading decoding in cellular massive mimo systems with spatially correlated channels"
    - "pilot contamination mitigation with reduced rf chains"
    - "massive mimo has unlimited capacity"
    - "optimal pilot and payload power control in single cell massive mimo systems"
    - "a parallel decomposition method for nonconvex stochastic multi agent optimization problems"
    - "distributed massive mimo in cellular networks impact of imperfect hardware and number of oscillators"

Connected through hyperedge HE-5 (induced by source paper "distributed power control in downlink cellular massive mimo systems"):
  with members:
    - "uplink interference reduction in large scale antenna systems"
    - "robust chance constrained optimization for power efficient and secure swipt systems"
    - "joint power allocation and user association optimization for massive mimo systems"
    - "cell free massive mimo uniformly great service for everyone"
    - "outage constrained robust transmit optimization for multiuser miso downlinks tractable approximations by conic optimization"

Connected through hyperedge HE-6 (induced by source paper "downlink performance of uplink fractional power control in 5g massive mimo systems"):
  with members:
    - "uplink sounding reference signal coordination to combat pilot contamination in 5g massive mimo"
    - "massive mimo ten myths and one critical question"
    - "massive mimo for next generation wireless systems"
    - "five disruptive technology directions for 5g"

Connected through hyperedge HE-7 (induced by source paper "a successive optimization approach to pilot design for multi cell massive mimo systems"):
  with members:
    - "massive mimo ten myths and one critical question"
    - "pilot reuse for massive mimo transmission over spatially correlated rayleigh fading channels"
    - "smart pilot assignment for massive mimo"
    - "outage constrained robust transmit optimization for multiuser miso downlinks tractable approximations by conic optimization"

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)