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: "RMAC: A Routing-Enhanced Duty-Cycle MAC Protocol for Wireless Sensor Networks"
  Abstract: Duty-cycle MAC protocols have been proposed to meet the demanding energy requirements of wireless sensor networks. Although existing duty-cycle MAC protocols such as S-MAC are power efficient, they introduce significant end-to-end delivery latency and provide poor traffic contention handling. In this paper, we present a new duty-cycle MAC protocol, called RMAC (the routing enhanced MAC protocol), that exploits cross-layer routing information in order to avoid these problems without sacrificing energy efficiency. In RMAC, a setup control frame can travel across multiple hops and schedule the upcoming data packet delivery along that route. Each intermediate relaying node for the data packet along these hops sleeps and intelligently wakes up at a scheduled time, so that its upstream node can send the data packet to it and it can immediately forward the data packet to its downstream node. When wireless medium contention occurs, RMAC moves contention traffic away from the busy area by delivering data packets over multiple hops in a single cycle, helping to reduce the contention in the area quickly. Our simulation results in ns-2 show that RMAC achieves significant improvement in end-to-end delivery latency over S-MAC and can handle traffic contention much more efficiently than S-MAC, without sacrificing energy efficiency or network throughput.

Connected through hyperedge HE-1 (induced by source paper "Fine-grained network time synchronization using reference broadcasts"):
  with members:
    - "Stitching: pen gestures that span multiple displays"
    - "Sensor networks for medical care"
    - "A wireless sensor network For structural monitoring"
    - "Locating tiny sensors in time and space: a case study"
    - "TOSSIM: accurate and scalable simulation of entire TinyOS applications"
    - "PSKA: Usable and Secure Key Agreement Scheme for Body Area Networks"

Connected through hyperedge HE-2 (induced by source paper "Terminal Design without Using Receiver Circuits for Wireless Sensor Networks"):
  with members:
    (none)

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