A Distributed QoS Control Mechanism for Soft-QoS Provisioning in UMTS Multitier Systems

This paper investigates the topic of QoS provisioning both at the application and network level in an evolutionary scenario consisting of a UMTS multi-tier platform enhanced by a satellite coverage level and suitably thought for supporting multimedia traffic. In this “next-generation” scenario the main objective is the introduction of a distributed QoS control mechanism, with Middleware functionality, into the system and the evaluation of its effectiveness in achieving the major goal which it has been designed for: accomplishing a soft QOS paradigm which dynamically maximises the perceived QoS provided to the end user according to his/her needs. The highlighted objective has to be achieved by always coping with the highly variable constraints characterising the mobile environment under study. The foremost intended contribution of this paper is represented by the design of such a novel distributed mechanism exploiting algorithms able to accomplish a twofold functionality: dynamically optimising the QoS perceived by the user while always maximising the system efficiency. The assessment study presented in this paper testifies to the flexibility of the proposed algorithms and to their effectiveness in achieving the highlighted goals. To this aim suitable metrics are defined at different protocol levels and their output values are evaluated during a comprehensive simulation campaign under different conditions of load, traffic distribution and resource availability.