Real-time LANs in combat vehicles: feasibility criteria for non-preemptive messages and multiple message streams originating from individual nodes

A significant trend in mission critical systems (MCS) such as combat vehicles is the migration towards LAN based computer architectures. This paper presents a method for determining the feasibility of message sets for the real-time LAN (RT-LAN) in combat vehicles. Several methods have been established to determine the feasibility of message sets in RT-LANs that assume preemptable messages and a single message stream originating from each node. In combat vehicles, the lengths of device control messages and the disparity in the inter-arrival times of messages necessitates the consideration of non-preemptive single frame messages and multiple message streams originating from each node. The approach we propose considers the message set, the system requirement for continuous operations under fault conditions, and bandwidth utilization efficiency. Our method uses a non-preemptive scheduling policy in conjunction with a token-based priority driven protocol (PDP) and is suitable for RT-LANs with limited geographic spans. In order to clarify our reasoning for selecting PDP media arbitration, we compare the PDP approach against the time division multiplexed (TDM) approach from the perspective of combat vehicle LANs.