A Direct Adaptive Controller for ATM ABR Congestion Control

One of the more challenging and yet unresolved issues which is paramount to the success of ATM networks is that of congestion control for Available Bit Rate (ABR) traffic. Unlike other ATM service categories, ABR provides a feedback mechanism, allowing interior nodes to dictate source rates. Previous work has demonstrated how linear control theory can be utilized to create a stable and efficient control system for the purposes of ATM ABR congestion control. This paper extends our previous contribution that assumed a minimum-phase plant, an assumption that is likely violated in practice. Presented here is a direct adaptive controller that uses a finite impulse response (FIR) filter to approximately invert the FIR plant. This controller is well suited for the ATM ABR non-minimum-phase plant. Other control architectures, which motivate the final proposed controller, are also discussed.