Design and Implementation of a Feedback Control Approach for QoS-enhanced MAC in WSN

Ang Gao and Yansu Hu


FD-MAC, Feedback Control, CSMA/CA


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 pre-fixed 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 EEE 802.15.4 and IEEE 802.11a/b. Comparing with the standard SMA/CA, FD-MAC not only has a better verage delay, less jitter and osciliation´╝îas well as no throughput lost, but also has the advantage of QoS enhanced ability.

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