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.

摘要

弹性数据包环 (RPR) 由 IEEE 802.17 定义，以实现公平性和高带宽利用率。公平在 RPR 中很重要，其中公平算法有两种类型的操作，激进和保守。目前的算法很简单；但是，如果流量不平衡导致资源丢失，它就会变得不稳定。在本文中，通过设计一个PID控制器来应用控制理论来计算公平率。控制器在解决公平问题方面运行良好，但如果系统延迟很大，则变得不稳定。因此，研究了延迟对稳定性的影响。此外，建议使用 Smith 预测器来补偿延迟。增强型控制器保证了环的利用率和稳定性。