Predictibility of inter-component latency in a software communications architecture operating environment

This paper presents an in-depth analysis of the behavior of a SCA component-based waveform application in terms of ¿inter-component¿ communication latency. The main limitation with SCA, in the context of embedded systems, is the additional cost introduced by the use of CORBA. Previous studies have already defined the major metrics of interest regarding this issue, these are CPU cost, memory requirements and ¿inter-component¿ latency. Real-time systems can not afford high latency, in consequence, this paper focuses on this metric. The starting point of this paper is the desire of knowing if the SCA CF does not also bring an overhead. Measurements have been realized with OmniORB as CORBA distribution and OSSIE for SCA implementation. In order to perform these measurements, a SCA waveform composed of several ¿empty-components¿ have been created. ¿Empty-components¿ are software components compliant to SCA without any signal processing part. The study only focuses on communications between components. The same kind of ¿inter-component¿ link has been measured between two components using CORBA without SCA. It is possible to compare the latency values between the two measurements and to show as a result that they are approximately the same. The CORBA bus is really the part which brings an overhead to the system. The final part of this paper introduces a statistical estimation of the latency distributions. It results from measurements performed with various data packet sizes and uses a fitting method based on a combination of Gaussian functions.