DSP Blockset

Computational Delay

The computational delay of a block or subsystem is related to the number of operations involved in executing that component. For example, an FFT block operating on a 256-sample input requires Simulink to perform a certain number of multiplications for each input frame. The actual amount of time that these operations consume (as measured in a benchmark test, for example) depends heavily on the performance of both the computer hardware and underlying software layers, such as MATLAB and the operating system. Computational delay for a particular model therefore typically varies from one computer platform to another.

The simulation time represented on a model's status bar (which can be accessed via the Simulink Digital Clock block) does not provide any information about computational delay. For example, according to the Simulink timer, the FFT mentioned above executes instantaneously, with no delay whatsoever. An input to the FFT block at simulation time t=25.0 is processed and output at time t=25.0, regardless of the number of operations performed by the FFT algorithm. The Simulink timer reflects only algorithmic delay (described below), not computational delay.

The next section discussed methods of reducing computational delay.

Delay and Latency

Reducing Computational Delay