Jitter Requirements

Definition

A jitter requirement is a performance requirement that specifies a maximum amount of the performance quality subfactor jitter.

Objectives

The typical objectives of a jitter requirement are to:

• Ensure (for all practical purposes) that:
  • An individual event happens when it should.
  • Periodic events happen when they should.
• Jitter does not grow large enough to cause failures.

Measurements

Jitter requirements are typically specified in terms of the following measurements:

• The maximum acceptable time interval.
• The maximum acceptable standard deviation in the time distribution.
• The maximum acceptable variability in time.

Examples

The following are typical examples of jitter requirements:

• “The application shall display temperature sensor readings every 5 seconds plus or minus 1 second.”
• “The application shall read the pressure sensor every 100 miliseconds with a standard deviation of 30 miliseconds.”

Guidelines

The following guidelines have been found to be useful when producing jitter requirements:

• The scope of a jitter requirement is typically:
  • An application
  • A component
  but may also include:
  • A business enterprise
  • A center
• Jitter is an error in time when one or more events occur due to varying time delays. Jitter can be important because the existance of jitter means that events that should happen at an exact time do not and that events that should be periodic do not occur on exactly regular intervals. If jitter becomes too large, then failures can occur.
• Jitter requirements are typically only required for real-time systems.
• Jitter requirements are different from and not to be confused with the architectural mechanisms that may be used to implement them:
  • TBD