A control-engineering approach to integrated congestion control and scheduling in wireless local area networks

Abstract

The paper deals with the problem of guaranteeing a target quality of service (QoS) to connections set-up over wireless internet protocol (IP) networks, while efficiently exploiting the air interface. In the literature, this problem is coped with congestion control and traffic scheduling algorithms: congestion control deals with the problem of computing the traffic relevant to in progress connections which can be admitted into the wireless network without causing the infringing of the QoS, while the scheduling deals with the problem of deciding the priorities for the transmission of the admitted traffic over the air interface. The paper presents the original and simple architecture and procedures of a Traffic Control Module aiming at solving the above-mentioned problem following a control-based approach. The Traffic Control Module includes some buffers storing the IP datagrams waiting for being transmitted over the air interface and a controller which controls both the admission of the offered IP datagrams into these buffers and the retrieval of the IP datagrams from these buffers for transmission over the air interface. The purpose of the above-mentioned controller is to steer the overall system towards an ideal equilibrium at which desirable performance is achieved. The controller is also in charge of periodically updating this ideal equilibrium, which is a function of the IP traffic presently offered to the wireless network. The adopted control based approach deals with congestion control and scheduling problems in a fully integrated way and in a feedback fashion, so as to take the present wireless network load into account. This paper has been partly sponsored by the European Union (EU) in the framework of the wireless networks (WINE) project belonging to the Information Society and Technology (IST) programme (fifth framework programme 2000–2003). 1 1 The underlying concepts are going to be further developed even in the EU sixth framework programme (2003–2006), e.g. in the Daidalos (Designing Advanced Interfaces for the Delivery and Administration of Location independent Optimised personal Services) and in the EuQoS (End-to-end Quality of Service support over heterogeneous networks) projects.