This paper proposes a new persistent contention-based real-time Ethernet MAC protocol that provides a predictable upper bound for the delivery delay of real-time frames.Under the new protocol

if a collision occurs

the real-time station keeps on sending a contention signal instead of stopping transmissions.Through this persistent transmission mechanism the protocol informs non real-time and low-priority real-time stations to stop transmissions and leaves the bandwidth to high-priority stations.Moreover

this protocol is compatible with Ethernet MAC protocol and thus real-time stations can coexist with standard Ethernet stations in the same system.The paper describes the protocol in detail and analyses the delivery delay for real-time traffic.The analysis and the simulation results demonstrate the method is correct and efficient.