DESIGN AND IMPLEMENTATION OF A FEEDBACK CONTROL APPROACH FOR QOS-ENHANCED MAC IN WSN

摘要

This paper addresses the problem of quality of service (QoS) support in Wireless Sensor Network (WSN) from a renewed view of control theory and proposes a Feedback-based Diff-MAC (FD-MAC) architecture. By means of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), FD-MAC dynamically adjusts contention widow size according to the MAC frames' priorities and their actual QoS metrics. This architecture can be modeled as a linear time-invariant system by system identification, so Least-Beat controller can be designed to drive the system output to the desired value, which means the ratio of actual QoS metrics can be controlled to a prefixed value. The higher priorities enjoy the comparatively lower node-to-node delay while the lower priorities can still operate without over-sacrificed.The hardware experiments and simulations demonstrate FD-MAC operates effectively in providing proportional delay differentiation in IEEE 802.15.4 and IEEE 802.11a/b. Comparing with the standard CSMA/CA, FDMAC not only has a better average delay, less jitter and oscillations well as no throughput lost, but also has the advantage of QoS enhanced ability.