As technology advances in electronics, systems with higher complexity, interconnectedness and heterogeneity can be developed. Being constituted by several control units and communication buses, the development of such systems can only be done concurrently by teams of specialists. At the same time as many as possible design steps have to be automated to accelerate the design process itself. Typically, in current design processes, systems are described using manually written specifications or non-executable, model-based specifications. However, such specifications cannot be executed and therefore cannot be validated, evaluated, and optimized prior to the availability of hardware. This results in a design process exhibiting high uncertainty in the early design stages and thus, high development risks and costs .This paper demonstrates why current design processes cause critical design errors and how system- level design automation technologies can be used to increase the specification quality and accelerate the design process itself to increase competitive advantage. In the paper, a simulation-driven design process is introduced, based on holistic executable specifications including functional, architectural and environment components. This design process is self-executing and thus enabling the automation of design steps such as system validation and optimization . In the example used in the paper, the process is applied to architecture optimization for an avionic application, where cable length is reduced by two-thirds and system availability is improved. However, we believe the process is general enough to be applied to the automotive segment as well without significant penalties and loss of optimality.