I have the same problem. I am using different channel models for

simulation and some samples either disappear or are incorrect. In your

answer, group delay = (N-1)/2, I assume that N is the number of taps of

the filter. So, how can I compensate this delay to obtain the correct

samples at the receiver?

Thanks so much

Hector

Tom R. wrote in post #1115636:

On Wed, Jul 10, 2013 at 8:42 AM, Gregory W. [email protected] wrote:

calculating BER), it is necessary to account for the 3-sample offset.

documentation except to say that you need to calculate the total group

delay of your system if you want to align the data.

Thanks Tom,

Is there a straightforward way to calculate group delay for a flow graph?

Alternatively, would it be straightforward to create a block that annotates the

data stream with a time index and another block that uses this

information to

align streams?

-Greg

Greg,

Symmetric FIR filters have a known group delay of (N-1)/2. So what you

need to do is a) make sure all of your filters are symmetric FIRs (and

they probably are; firdes and optfir produce these types of filters)

and b) know all of the filters in the path, which includes the

transmit and receive pulse shaping filters and any filter in the

channel model (used to simulate multipath). You should be able to add

up the group delays of all filters to get your answer.

Tom