Achievable QoS and scheduling policies for integrated services wireless networks

Abstract

In Integrated Services Wireless Networks transmission resources are shared among geographically disperse applications with diverse Quality of Service (QoS) requirements and traffic characteristics. To provide QoS guarantees and use the bandwidth efficiently, call admission and scheduling functions are necessary. These functions should ensure the delivery of the target QoS to the supported applications while achieving statistical multiplexing gains, without explicit and continuous exchange of information between sources and scheduler. In this dissertation, call admission and transmission scheduling policies are studied for a TDMA system. Variable bit rate (VBR) applications with distinct QoS requirements and traffic characteristics are considered. In this environment, packets which cannot be transmitted over the frame following their arrival may be dropped (due to delay violations) or may be delayed to compete for service in the next frame, depending on the QoS requirements. The focus of the research is to determine the region of achievable multi-dimensional (non-degenerate) QoS vectors for heterogeneous VBR applications in this shared resource environment. Determining the region of achievable QoS is central to the admission control problem. For example, if with the addition of the new source, the new multi-dimensional target QoS vector is in the region of achievable QoS, then the call can be admitted. The problem of determining the region of achievable QoS vectors is formulated in a manner that makes it possible to investigate by employing polytope/convex space and game theory. As a result, the region of achievable QoS for heterogeneous applications in a interference/resource-limited wireless network is precisely described. In addition, it is possible to identify simple policies which deliver any given QoS vector within the region, by proving properties associated with the extreme points of the region. Together, call admission and scheduling are shown to ensure that the target QoS is delivered to each application. Finally, the impact that channel quality has on the region of achievable QoS is studied. In a wireless environment, packets are dropped not only due to the competition for the transmission resources, but also due to channel induced errors (interference). Thus, the physical channel can affect the region of achievable QoS as well. As a consequence, the region of achievable QoS vectors is shaped by the packet discarding process at both the transmitter and the receiver due to resource and interference limitations, respectively.