  Wireless sensor networks (WSNs) became one of the high technology domains
during the last ten years. Real-time applications for them make it necessary to
provide the guaranteed Quality of Service (QoS). The main contributions of this
paper are a system skeleton and a guaranteed QoS model that are suitable for
the WSNs. To do it, we develop a sensor node model based on virtual buffer
sharing and present a two-layer scheduling model using the network calculus.
With the system skeleton, we develop a guaranteed QoS model, such as the upper
bounds on buffer queue length/delay/effective bandwidth, and single-hop/
multi-hops delay/jitter/effective bandwidth. Numerical results show the system
skeleton and the guaranteed QoS model are scalable for different types of
flows, including the self-similar traffic flows, and the parameters of flow
regulators and service curves of sensor nodes affect them. Our proposal leads
to buffer dimensioning, guaranteed QoS support and control in the WSNs.
