Real-time communication

Real-time communication systems are generally understood as one of two types: hard real-time (HRT) and soft real-time (SRT). The difference between a hard and soft real-time communication system is the consequences of incorrect operation. Safety-critical systems capable of causing catastrophic consequences upon a fault, such as aircraft fly-by-wire systems, are designated as hard real-time, whereas non-critical but ideally real-time systems, such as hotel reservation systems, are designated as soft real-time. The designation of a real-time communication system as hard or soft has significant influence on its design.

Hard real-time systems

Hard real-time communication systems are frequently electromechanically linked to a physical mechanism, often one that interfaces directly with people or property, which often contributes to or defines the potential danger of a fault. Due to their safety-critical nature, the communication protocols defined in a hard real-time system generally must be deterministic. Hard real-time communication systems are particularly common in the transportation, industrial, and medical sectors. Common applications include control systems, automotive controllers, medical devices, and critical safety systems such as airbag firing computers.

Examples

• The spacecraft communication network SpaceWire supports real-time communication.
• Time-Triggered Ethernet supports real-time synchronous communication in complex multi-hop Ethernet networks.