Verification of Timeliness QoS Properties in Multimedia Systems

Abstract

Abstract.One of the main challenges of the design of object-based Distributed Multimedia Systems is to address the performance related issues such as the Quality of Service (QoS). The specification of QoS is a crucial part of architectural object-based methods such as Open Distributed Processing (ODP). In the ODP, a QoS property assigned to an object is modelled via two clauses of required and provided QoS statements, which specify the level of QoS required/provided by an object from/to its environment, respectively. An over-demanding QoS statement can be beyond the physical limitation of the system and might result in inconsistencies. In particular, to produce a correct design, it is crucial to study the effect of QoS statements of components on the overall behaviour of the system in earlier stages of the design. This paper develops a theory for the verification of Timeliness QoS properties such as Jitter, Throughput and Latency. The approach adopted is based on the idea of Test Automata. We shall present a formal definition of Timeliness QoS properties, which is used for the creation of Test Automata. Such Test Automata, which we shall refer to as QoS Timed Automata, can be used to verify the corresponding QoS Timeliness property. The method is illustrated by the verification of Throughput in a Video Player systems via the model checker UPPAAL.

An Architecture for Automated QoS Resolution in Wireless Systems

“…For example, [15] presents an attempt to standardise such views and create a UML profile, a dialect of UML, for the specification of QoS. Since the focus of this paper is on Timeliness properties in multimedia systems [4][5] such as Throughput, Latency and Jitter, it is necessary to define these terms. Throughput is the total number of signals per second.…”

“…Jitter, also known as non-anchored jitter, is the variation of nominal latency suffered by the successive occurrence of the same signal. A formal definition of the Timeliness QoS properties is given in [4][5].…”

“…The network of Timed Automata in Figure 4 gives a high level view of the behaviour of the system presented in . QoS specification: The specification of QoS aspects of system has received considerable attention For example, [4] presents a method of verification of Timeliness QoS properties such as jitter, throughput and latency, which draws on the idea of Test Automata [1] [9]. Assume that A is a network of Timed Automata representing the behaviour of the system.…”

“…[4] • models of communication protocol [3] • QoS Timed Automata for various types of QoS such as Jitter, Throughput etc [4]. The above items are parametric representations and by instantiation (assigning value to parameters) it is possible to generate potentially an infinite number of combinations of behavioural models.…”

“…More specifically, the use of UPPAAL is computationally demanding. For example, verification of a system consisting of 7 components takes around 600 sec CPU time [4]. This is due to the stateexplosion problem.…”