Delivering Diverse Delay/dropping Qos Requirements in a Tdma Environment

In Wireless ATM networks transmission resources are shared among geographically disperse applications with diverse Quality of Service (QoS) requirements and traac characteristics. To provide QoS guarantees and use the bandwidth eeciently, 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 paper the problem of sharing resources (slots of an up-link TDMA frame) among heterogeneous Variable Bit Rate (VBR) applications with diverse QoS requirements is addressed. The QoS requirements for each application is deened in terms of a maximum tolerable packet delay and dropping probability; a packet is dropped if it experiences excess delay. The region of achievable QoS vectors is established for policies that are work-conserving and satisfy the earliest due date (EDD) service criterion (WC-EDD policies); such policies are known to optimize the overall system performance. In addition to the determination of the region of achievable QoS vectors, this study leads also to the construction of scheduling policies which deliver any performance in the region established for WC-EDD policies. Finally, an upper bound on the region of QoS vectors that can be achieved under any policy (not limited to the WC-EDD policies) is determined.