A simple approach for minimal jitter in Ethernet for real-time control communication

The aim of this paper is to develop an approach for cheap and deterministic control communication using Ethernet. A half-duplex Ethernet network populated with a small/medium number of Media Access Controllers (MACs) is used for timed real-time communication. Data packages are sent at well defined times to avoid collisions. Collisions mainly occur due to jitter of the transmitter system, so that arbitration (similar to CANopen) is necessary. The Binary Exponential Backoff (BEB) scheme is used. This paper analyzes and investigates how the backoff time affects the performance of the Carrier Sense Multiple Access protocol with Collision Detection (CSMA/CD) in a basic Media Access Controller (MAC), in terms of data arrival characteristics, i.e jitter and delay. We propose to assign different minimal backoff times for each of the CSMA/CD controller units to minimize packet collisions. Simulated tests show the advantage of our approach over a standard CSMA/CD setting.