Hierarchical Programming Language for Modal Multi-rate Real-Time Stream Processing Applications

Modal multi-rate stream processing applications with real-time constraints which are executed on multi-core embedded systems often cannot be conveniently specified using current programming languages. An important issue is that sequential programming languages do not allow for convenient programming of multi-rate behavior, whereas parallel programming languages are insufficiently analyzable such that deadlock-freedom and a sufficient throughput cannot be guaranteed. In this paper a programming language is proposed by which a sequential specification of the behavior of an application can be nested in a concurrent specification. Multi-rate behavior can be conveniently expressed using concurrent modules which have well-defined, but restricted interfaces. Complex control behavior can be expressed in the sequential specification of the body of a module. The language is not Turing complete such that a Compositional Temporal Analysis (CTA) model can be derived. It is shown that the CTA model can be used despite the presence of control statements and that the composition of black-box components is possible. Algorithms with a polynomial time complexity can be used to verify whether throughput and latency constraints are met and to determine sufficient buffer capacities. A Phase Alternating Line (PAL) video decoder application is used to demonstrate the applicability of the presented language and analysis approach.