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: "enhanced max min sinr for uplink cell free massive mimo systems"
  Abstract: In this paper, we consider the max-min signal-to-interference plus noise ratio (SINR) problem for the uplink transmission of a cell-free Massive multiple-input multiple-output (MIMO) system. Assuming that the central processing unit (CPU) and the users exploit only the knowledge of the channel statistics, we first derive a closed-form expression for uplink rate. In particular, we enhance (or maximize) user fairness by solving the max-min optimization problem for user rate, by power allocation and choice of receiver coefficients, where the minimum uplink rate of the users is maximized with available transmit power at the particular user. Based on the derived closed-form expression for the uplink rate, we formulate the original user max-min problem to design the optimal receiver coefficients and user power allocations. However, this max-min SINR problem is not jointly convex in terms of design variables and therefore we decompose this original problem into two sub-problems, namely, receiver coefficient design and user power allocation. By iteratively solving these sub-problems, we develop an iterative algorithm to obtain the optimal receiver coefficient and user power allocations. In particular, the receiver coefficients design for a fixed user power allocation is formulated as generalized eigenvalue problem whereas a geometric programming (GP) approach is utilized to solve the power allocation problem for a given set of receiver coefficients. Numerical results confirm a three-fold increase in system rate over existing schemes in the literature.

Connected through hyperedge HE-1 (induced by source paper "spectral efficiency analysis of cell free massive mimo systems with zero forcing detector"):
  with members:
    - "downlink precoding with mixed statistical and imperfect instantaneous csi for massive mimo systems"
    - "on the total energy efficiency of cell free massive mimo"
    - "performance analysis for massive mimo downlink with low complexity approximate zero forcing precoding"
    - "pilot power allocation through user grouping in multi cell massive mimo systems"
    - "energy efficient downlink transmission for multicell massive das with pilot contamination"
    - "energy efficiency in cell free massive mimo with zero forcing precoding design"
    - "cell free massive mimo versus small cells"
    - "how much do downlink pilots improve cell free massive mimo"

Connected through hyperedge HE-2 (induced by source paper "max min rate of cell free massive mimo uplink with optimal uniform quantization"):
  with members:
    - "on the uplink throughput of zero forcing in cell free massive mimo with coarse quantization"
    - "ubiquitous cell free massive mimo communications"
    - "on the energy efficiency of limited backhaul cell free massive mimo"
    - "cell free massive mimo with limited backhaul"
    - "on the performance of backhaul constrained cell free massive mimo with linear receivers"
    - "cooperative access networks optimum fronthaul quantization in distributed massive mimo and cloud ran"
    - "network deployment for maximal energy efficiency in uplink with multislope path loss"
    - "performance of cell free massive mimo systems with mmse and lsfd receivers"

Connected through hyperedge HE-3 (induced by source paper "optimal design of energy efficient cell free massive mimo joint power allocation and load balancing"):
  with members:
    - "ubiquitous cell free massive mimo communications"
    - "making cell free massive mimo competitive with mmse processing and centralized implementation"
    - "downlink spectral efficiency of cell free massive mimo with full pilot zero forcing"
    - "performance of cell free massive mimo systems with mmse and lsfd receivers"
    - "on the total energy efficiency of cell free massive mimo"
    - "energy efficiency in cell free massive mimo with zero forcing precoding design"
    - "joint power allocation and user association optimization for massive mimo systems"
    - "cell free massive mimo versus small cells"

Connected through hyperedge HE-4 (induced by source paper "on the energy efficiency of limited backhaul cell free massive mimo"):
  with members:
    - "on the uplink throughput of zero forcing in cell free massive mimo with coarse quantization"
    - "on the performance of backhaul constrained cell free massive mimo with linear receivers"
    - "cooperative access networks optimum fronthaul quantization in distributed massive mimo and cloud ran"
    - "on the total energy efficiency of cell free massive mimo"
    - "robust geometry based user scheduling for large mimo systems under realistic channel conditions"
    - "cell free massive mimo versus small cells"
    - "optimal design of energy efficient multi user mimo systems is massive mimo the answer"

Connected through hyperedge HE-5 (induced by source paper "few bit csi acquisition for centralized cell free massive mimo with spatial correlation"):
  with members:
    - "on the uplink throughput of zero forcing in cell free massive mimo with coarse quantization"
    - "channel estimation for one bit massive mimo systems exploiting spatio temporal correlations"
    - "cell free massive mimo with limited backhaul"
    - "recent advances in cloud radio access networks system architectures key techniques and open issues"
    - "cell free massive mimo versus small cells"

Connected through hyperedge HE-6 (induced by source paper "on max min sinr with mmse processing for uplink cell free massive mimo"):
  with members:
    - "ubiquitous cell free massive mimo communications"
    - "making cell free massive mimo competitive with mmse processing and centralized implementation"
    - "cell free massive mimo versus small cells"

Connected through hyperedge HE-7 (induced by source paper "cell free massive mimo with limited backhaul"):
  with members:
    - "cooperative access networks optimum fronthaul quantization in distributed massive mimo and cloud ran"
    - "energy efficient power control a look at 5g wireless technologies"
    - "cell free massive mimo versus small cells"
    - "multiobjective signal processing optimization the way to balance conflicting metrics in 5g systems"

Connected through hyperedge HE-8 (induced by source paper "on the performance of backhaul constrained cell free massive mimo with linear receivers"):
  with members:
    - "cooperative access networks optimum fronthaul quantization in distributed massive mimo and cloud ran"
    - "cell free massive mimo versus small cells"

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)