This paper is concerned with the design of improved AQM control scheme to cope with unwanted variations of characteristic parameters such as the average round-trip time, the load and link capacity without the necessity of its measurements. An appropriate robust H1 controller for timedelay systems is proposed and hence used to design a suitable AQM control scheme. A robust observer is used to estimate online the transmission window resulting in a novel output feedback stabilization scheme for AQM. The resulting control law is validated, tested and compared with other classical AQM schemes firstly through numerical NS-2 simulations and then experimentally.