Why am I unable to find the delay in my model with the Find Delay block in the Communications Blockset 2.5 (R13)?

I am using the Find Delay block to find the delay in my model. However, when I place this block in my model and make the appropriate connections, I cannot find the delay. The delay value varies, and never settles to a final value.

Answer 1

[MathWorks Support Team]

This problem occurs when a delay-inducing block (for example, the CPM decoder) is concatenated with a multi-rate block, such as the Viterbi decoder.

The delay induced by all the blocks preceding the Viterbi decoder must be a multiple of N, where the Viterbi decoder is operating on a rate K/N code. If this is not done, then when the Viterbi decoder presents its output, the delay will include a fractional sample, and the bit error rate results will be incorrect.