human: Given a node-centered hypergraph: <hypergraph>, where nodes represent authors and hyperedges represent groups of authors who co-authored the same paper.

Details of the hypergraph:
Center node: "MIMO Downlink Scheduling with Non-Perfect Channel State Knowledge"
  Abstract: Downlink scheduling schemes are well-known and widely investigated under the assumption that the channel state is perfectly known to the scheduler. In the multiuser MIMO (broadcast) case, downlink scheduling in the presence of non-perfect channel state information (CSI) is only scantly treated. In this paper we provide a general framework that addresses the problem systematically. Also, we illuminate the key role played by the channel state prediction error: our scheme treats in a fundamentally different way users with small channel prediction error ("predictable" users) and users with large channel prediction error ("non-predictable" users), and can be interpreted as a near-optimal opportunistic time-sharing strategy between MIMO downlink beamforming to predictable users and space-time coding to non-predictable users. Our results, based on a realistic MIMO channel model used in 3GPP standardization, show that the proposed algorithms can significantly outperform a conventional "mismatched" scheduling scheme that treats the available CSI as if it was perfect.

Connected through hyperedge HE-1 (induced by source paper "Fairness and optimal stochastic control for heterogeneous networks"):
  with members:
    - "Scheduling for end-to-end deadline-constrained traffic with reliability requirements in multihop networks"
    - "Resource allocation and cross-layer control in wireless networks"

Connected through hyperedge HE-2 (induced by source paper "Resource allocation and cross-layer control in wireless networks"):
  with members:
    - "Fairness and optimal stochastic control for heterogeneous networks"

Connected through hyperedge HE-3 (induced by source paper "Achieving "Massive MIMO" Spectral Efficiency with a Not-so-Large Number of Antennas"):
  with members:
    - "On Superimposed Pilot for Channel Estimation in Multicell Multiuser MIMO Uplink: Large System Analysis"

Question: Please tell me which research area the center author belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Computer science