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: "performance analysis of optimum zero forcing beamforming with greedy user selection"
  Abstract: In this letter, an exact performance analysis is presented on the sum rate of zero-forcing beamforming with a greedy user selection algorithm in a downlink system. Adopting water-filling power allocation, we derive a compact form for the joint probability density function of the scheduled users' squared subchannel gains when a transmitter with multiple antennas sends information to at most two scheduled users with each having a single antenna. The analysis is verified by numerical results.

Connected through hyperedge HE-1 (induced by source paper "optimizing user selection schemes in vector broadcast channels"):
  with members:
    - "optimal selective feedback policies for opportunistic beamforming"
    - "eigen based transceivers for the mimo broadcast channel with semi orthogonal user selection"

Connected through hyperedge HE-2 (induced by source paper "optimal power allocation and user loading for multiuser miso channels with regularized channel inversion"):
  with members:
    - "network mimo with linear zero forcing beamforming large system analysis impact of channel estimation and reduced complexity scheduling"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"
    - "base station cooperation with feedback optimization a large system analysis"
    - "multi mode transmission for the mimo broadcast channel with imperfect channel state information"
    - "achievable throughput of multi mode multiuser mimo with imperfect csi constraints"
    - "estimation diversity and energy efficiency in distributed sensing"

Connected through hyperedge HE-3 (induced by source paper "exact joint distribution analysis of zero forcing v blast gains with greedy ordering"):
  with members:
    - "unified performance analysis of orthogonal transmit beamforming methods with user selection"
    - "on outage and error rate analysis of the ordered v blast"

Connected through hyperedge HE-4 (induced by source paper "unified performance analysis of orthogonal transmit beamforming methods with user selection"):
  with members:
    - "performance of orthogonal beamforming for sdma with limited feedback"

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)