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Designing a multiplex network configuration for vehicles using a J-1850 compatible network can be a difficult and time consuming task. Parameters such as network bus rates, module transmit queues, module transmit message rates, and other message characteristics all have an effect on the latency of messages transmitted on the network. These parameters can also effect the control strategy used within network modules. This paper will discuss the use of network traffic simulation and evaluation in a systems engineering approach to the design of vehicle multiplex systems.

Design and testing of J-1850 multiplex communications networks requires a range of support tools which facilitate the process from initial concept, thru bench development and vehicle implementation. In the early stages of design, vehicle features, I/O, and functionality of the various option mixes must be mapped into modules, and communications requirements and message strategy between modules defined and simulated. When modules become available, a means of emulating network traffic on the bus is required in order to evaluate actual module responses. Network monitoring and diagnostic tools are also necessary at both low and high detail levels. This discussion will cover several multiplex design and analysis tools which are under development at Ford.

The continued increase in complexity of automotive electronics has further necessitated for systems to be designed for optimal testing and servicing in the field. Locating failures within complex, interactive electronic systems can create conditions of both high warranty costs and customer dissatisfaction. Decisions about levels of system integration and diagnostics early in the design phases are fundamental parts of these considerations and are addressed in this paper. The approach focuses on projecting field repair rates and maintenance costs using a Monte Carlo computer simulation method given various component parameters such as part costs, reliability, labor time, and field diagnostic strategies. Results of the projection technique were shown to be quite accurate in projecting field warranty costs of a complex electronic system.