Abstract
Resilient Packet Ring (RPR) is defined by IEEE 802.17 to achieve fairness and high bandwidth utilization. Fairness is important in RPR where fairness algorithm has two types of operation, aggressive and conservative. The current algorithm is simple; however, it becomes unstable, if the traffic is unbalanced which cause resources loss. In this paper, the control theory is applied by designing a PID controller to calculate the fair rate. The controller operates well in resolving the fairness issue, but becomes unstable if the system's delay is huge. Therefore, the delay influence on the stability is studied. Furthermore, a Smith predictor is suggested to compensate the delay. The enhanced controller reassures ring utilization and stability.