fixedlatency

Fixed latency, also known as deterministic latency, is a property of a system in which the time from an input event to the corresponding output is guaranteed to stay within a fixed bound. The bound is typically independent of input value and system load, and the latency is predictable and repeatable. This is in contrast to systems with variable latency, where the delay can fluctuate and jitter can occur.

Fixed latency is a core requirement in hard real-time and safety-critical domains, such as industrial automation, aerospace, and medical devices, where missing a deadline can have serious consequences. It is also relevant in telecommunications and audio/video processing, where consistent end-to-end delay improves synchronization and user experience.

Achieving fixed latency typically involves deterministic design: time-triggered or fixed-priority scheduling, bounded processing times, fixed-size buffers, and avoiding competing resource contention. Real-time operating systems (RTOS), fixed-cycle architectures, and time-aware networking are common approaches. In networks, protocols and mechanisms such as time synchronization and bounded transmission times aim to provide end-to-end latency guarantees.

Validation relies on worst-case analysis and measurement of the latency bound (worst-case latency) and jitter. Techniques include worst-case execution time (WCET) analysis, schedulability tests, and network timing measurements. Tools may simulate workloads and monitor latency under peak conditions to confirm compliance with the specified bound.

Trade-offs include potential inefficiency under light loads, increased design complexity, and higher cost due to reserved resources. Fixed latency is not always necessary; in less time-sensitive applications, lower average latency may be preferred with flexible resource use.

See also deterministic systems, real-time scheduling, jitter, latency, time-triggered architecture, time-sensitive networking, RTOS, WCET.