If you do this:
[rate] = rate(device,BandWidth,Tx,Power1,fading1,No_power);
Then rate is now a variable (the output from the function rate()). And the rate() function can no longer be called by saying rate(whatever). 'whatever' is treated like indexes into the variable rate rather than like inputs to the function rate(). So you may get an error the next time you use rate.
Changing the output variable to rate1 fixes it because the function rate() is not replaced in the workspace by the variable rate.
