Communications Blockset

Speed of Baseband Versus Passband Models

The passband and baseband models produce error rates that differ from each other by less than 1%. However, the passband model takes a significantly longer time to process the same amount of data. Although the actual speed depends on your system, the relative times in the tables below can serve as a guide. Each table shows the approximate clock time that simulations take to run, expressed as a multiple of the clock time that the model bbmoddoc takes to run. Notice these general trends:

• Baseband simulation is considerably faster than passband simulation. The difference in speed is especially dramatic when the carrier frequency in the passband simulation is high.
• Baseband simulation using large frames is faster than baseband simulation that does not use frames.

To time simulations on your own computer, use the functions tic, toc, and sim.

Relative Clock Times Corresponding to 1 Second of Simulation Time

Simulation	Relative Time
bbmoddoc (baseband)	1
pbmoddoc (passband)	52
pbmoddoc (passband), after multiplying carrier frequency and modulated signal sample time by 10 and 1/10, respectively	916

Relative Clock Times Corresponding to 3 Seconds of Simulation Time

Simulation	Relative Time
bbmoddoc (baseband)	1
pbmoddoc (passband)	100
bbmoddoc (baseband), using frame-based processing with 512-sample frames	0.28

Relative Clock Times to Execute Code as in Generating Error Curves

Simulation	Relative Time
bbmoddoc (baseband)	1
pbmoddoc (passband)	100
bbmoddoc (baseband), using frame-based processing with 512-sample frames	.30

Generating Error Curves

Comparing Baseband and Passband Signals