具有通信时延的AQM控制算法的稳定性

Stability of an AQM Control Algorithm with Communication Delays

具有通信时延的AQM控制算法是一个复杂的动态非线性反馈系统.为了调查通信时延对Internet服务质量的影响,借助广义Nyquist判据研究了具有通信时延的AQM策略的稳定性.通过对网络系统的传递函数的分析,得到了各通信回路时延相同和时延不同条件下网络系统在平衡点的稳定性判据.这些结论表明,影响Internet性能的关键因素之一的通信时延在Internet通信过程中起着重要的作用.最后仿真验证了该判据的有效性.

An AQM (active queue management) control algorithm is a complicated dynamical nonlinear feedback system, which is applied at the link node to control the congestion rates based on the network loadings from the source nodes. In order to investigate the influence of the communication delays on the quality of service (QoS) of the Internet, the stability of an AQM algorithm with communication delays is studied by applying the general Nyquist criterion. The stability criteria of the AQM scheme with the homogeneous delays and heterogeneous delays are obtained by analyzing the frequency function of the network system. These results exhibit that the communication delay is one of the key factors to affect the Internet capability and plays an important role in communicating process of the Internet. A computer simulation supports the validity of these stability criteria on the AQM congestion control algorithm.