Robust EKF-Based Wireless Congestion Control

Many of the recently proposed high performance congestion control protocols rely on an estimation of the available link bandwidths. Specially, XCP and VCP need an explicit knowledge of the link bandwidth. However, wireless networks are characterized by bandwidth variations due to the openness of air links. Experiments have clearly shown that operating over variable bandwidth wireless links can lead to a significant performance degradation of congestion control protocols. Such degradation is typically measured in terms of oscillatory behavior. In this paper, we propose the use of an Extended Kalman Filter (EKF) to filter out the impact of bandwidth variations from the operation of wireless congestion control protocols. Our EKF-based Bandwidth Estimation (EBE) scheme can predict link capacity by monitoring the persistent queue size of a wireless link thereby eliminating the need for direct measuring of the real-time bandwidth. We implement EBE in NS-2 and integrate it with XCP and VCP protocols. Through extensive simulation studies, we demonstrate significant performance improvements of both protocols as the result of using EBE.