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 precoding and rrh selection for user centric green mimo c ran"
  Abstract: This paper jointly optimizes the precoding matrices and the set of active remote radio heads (RRHs) to minimize the network power consumption (NPC) for a user-centric cloud radio access network (C-RAN), where both the RRHs and users have multiple antennas and each user is served by its nearby RRHs. Both users' rate requirements and per-RRH power constraints are considered. Due to these conflicting constraints, this optimization problem may be infeasible. In this paper, we propose to solve this problem in two stages. In Stage I, a low-complexity user selection algorithm is proposed to find the largest subset of feasible users. In Stage II, a low-complexity algorithm is proposed to solve the optimization problem with the users selected from Stage I. Specifically, the re-weighted $l_1$-norm minimization method is used to transform the original problem with non-smooth objective function into a series of weighted power minimization (WPM) problems, each of which can be solved by the weighted minimum mean square error (WMMSE) method. The solution obtained by the WMMSE method is proved to satisfy the Karush-Kuhn-Tucker (KKT) conditions of the WPM problem. Moreover, a low-complexity algorithm based on Newton's method and the gradient descent method is developed to update the precoder matrices in each iteration of the WMMSE method. Simulation results demonstrate the rapid convergence of the proposed algorithms and the benefits of equipping multiple antennas at the user side. Moreover, the proposed algorithm is shown to achieve near-optimal performance in terms of NPC.

Connected through hyperedge HE-1 (induced by source paper "hybrid precoder design for cache enabled millimeter wave radio access networks"):
  with members:
    - "hybrid beamforming based on implicit channel state information for millimeter wave links"
    - "two level transmission scheme for cache enabled fog radio access networks"
    - "optimized base station cache allocation for cloud radio access network with multicast backhaul"
    - "spatial and frequency wideband effects in millimeter wave massive mimo systems"
    - "energy efficient transceiver design for hybrid sub array architecture mimo systems"
    - "joint design of digital and analog processing for downlink c ran with large scale antenna arrays"
    - "codebook based hybrid precoding for millimeter wave multiuser systems"
    - "joint optimization of user association data delivery rate and precoding for cache enabled f rans"

Connected through hyperedge HE-2 (induced by source paper "joint uplink and downlink transmissions in user centric ofdma cloud ran"):
  with members:
    - "fronthaul limited uplink ofdma in ultra dense cran with hybrid decoding"
    - "joint millimeter wave fronthaul and ofdma resource allocation in ultra dense cran"
    - "green ofdma resource allocation in cache enabled cran"
    - "why to decouple the uplink and downlink in cellular networks and how to do it"
    - "fronthaul constrained cloud radio access networks insights and challenges"
    - "coordinated scheduling for the downlink of cloud radio access networks"
    - "what will 5g be"
    - "sparse beamforming and user centric clustering for downlink cloud radio access network"

Connected through hyperedge HE-3 (induced by source paper "robust beamforming with pilot reuse scheduling in a heterogeneous cloud radio access network"):
  with members:
    - "joint user selection and energy minimization for ultra dense multi channel c ran with incomplete csi"
    - "energy efficient resource allocation optimization for multimedia heterogeneous cloud radio access networks"
    - "robust pilot decontamination based on joint angle and power domain discrimination"
    - "energy efficient joint congestion control and resource optimization in heterogeneous cloud radio access networks"
    - "energy efficiency of downlink transmission strategies for cloud radio access networks"
    - "contract based interference coordination in heterogeneous cloud radio access networks"
    - "coordinated shared spectrum precoding with distributed csit"
    - "energy efficient resource assignment and power allocation in heterogeneous cloud radio access networks"

Connected through hyperedge HE-4 (induced by source paper "power minimization based joint task scheduling and resource allocation in downlink c ran"):
  with members:
    - "joint energy minimization and resource allocation in c ran with mobile cloud"
    - "energy efficiency of downlink transmission strategies for cloud radio access networks"
    - "joint multiuser downlink beamforming and admission control for green cloud rans with limited fronthaul based on mixed integer semi definite program"
    - "decentralized computation offloading game for mobile cloud computing"
    - "fronthaul constrained cloud radio access networks insights and challenges"
    - "heterogeneous cloud radio access networks a new perspective for enhancing spectral and energy efficiencies"
    - "distributed pricing based user association for downlink heterogeneous cellular networks"
    - "optimized backhaul compression for uplink cloud radio access network"

Connected through hyperedge HE-5 (induced by source paper "boosting fronthaul capacity global optimization of power sharing for centralized radio access network"):
  with members:
    - "differential evolution algorithm aided turbo channel estimation and multi user detection for g fast systems in the presence of fext"
    - "regularized zero forcing precoding aided adaptive coding and modulation for large scale antenna array based air to air communications"
    - "joint user selection and energy minimization for ultra dense multi channel c ran with incomplete csi"
    - "overview of millimeter wave communications for fifth generation 5g wireless networks with a focus on propagation models"
    - "adaptive coding and modulation for large scale antenna array based aeronautical communications in the presence of co channel interference"
    - "multivariate fronthaul quantization for downlink c ran"
    - "fronthauling for 5g lte u ultra dense cloud small cell networks"
    - "cluster content caching an energy efficient approach to improve quality of service in cloud radio access networks"

Connected through hyperedge HE-6 (induced by source paper "group sparse precoding for cloud ran with multiple user antennas"):
  with members:
    - "energy efficiency of downlink transmission strategies for cloud radio access networks"
    - "a survey of sparse representation algorithms and applications"
    - "robust group sparse beamforming for multicast green cloud ran with imperfect csi"
    - "large scale convex optimization for ultra dense cloud ran"
    - "a comparative study of downlink mimo cellular networks with co located and distributed base station antennas"
    - "sparse beamforming and user centric clustering for downlink cloud radio access network"
    - "group sparse beamforming for green cloud ran"
    - "asymptotic rate analysis of downlink multi user systems with co located and distributed antennas"

Connected through hyperedge HE-7 (induced by source paper "joint user selection and energy minimization for ultra dense multi channel c ran with incomplete csi"):
  with members:
    - "tradeoff caching strategy of outage probability and fronthaul usage in cloud ran"
    - "energy efficiency of downlink transmission strategies for cloud radio access networks"
    - "power efficient resource allocation for full duplex radio distributed antenna networks"
    - "5g ultra dense cellular networks"
    - "heterogeneous cloud radio access networks a new perspective for enhancing spectral and energy efficiencies"
    - "secure and green swipt in distributed antenna networks with limited backhaul capacity"
    - "what will 5g be"
    - "ergodic capacity analysis of remote radio head associations in cloud radio access networks"

Connected through hyperedge HE-8 (induced by source paper "user centric performance optimization with remote radio head cooperation in c ran"):
  with members:
    - "load balancing via joint transmission in heterogeneous lte modeling and computation"
    - "joint comp cell selection and resource allocation with fronthaul constrained c ran"
    - "load optimization with user association in cooperative and load coupled lte networks"
    - "dynamic joint uplink and downlink optimization for uplink and downlink decoupling enabled 5g heterogeneous networks"
    - "green ofdma resource allocation in cache enabled cran"
    - "cooperative interference mitigation and handover management for heterogeneous cloud small cell networks"
    - "system architecture and key technologies for 5g heterogeneous cloud radio access networks"
    - "analysis of cell load coupling for lte network planning and 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)