Effects of control loop delay on the stability of a rate control algorithm

This paper presents exact stability analysis of a rate control algorithm described in Perform. Eval. 2001; 43(2-3):63-94; Int. J. Commun. Systems 2001; 14(6):593-618. The stability regions of the rate control process in the presence of control loop delay are analysed. The rate control process is represented by delay-difference equation and the criteria for asymptotic stability are derived in terms of the control parameters and control loop delay. The analysis shows that the approximate upper bound of the control gain derived in Aweya et al. is very close to the exact bound developed here. Using theoretical calculations performed in the discrete-time domain, we show that as the feedback time delay d increases, the intensity of control (i.e. the control gain a) must decrease in order for the system to remain stable.