using DSP resources

[garcarulo]

Hello everyone!

I have just a question, I'm installing a Voice Gateway in a branch office that will be receiving inbound calls through PSTN (E1 and T1) and routing these calls to the HQ office, using G.729 as codec.

I need to know if I need to transcode these calls coming from the E1 or T1, using the DSP allocated in my VG to do it, or it is not needed and what I'll be doing is just MTP these calls or packetizing these calls and then send them over the WAN.

Any help will be really appreciated

Leo

[yahsiel2004]

I believe the DSP resources would be used for MTP but if the branch phones are doing G.729 and the HQ phones are doing G.711 then I would configure the VG to provide Transcoding resources for the branch phones.

Regards,

Yosh

[Aaron Harrison · Accepted solution]

Hi

The calls don't need transcoding as such. They will simply go from the PSTN to IP and be encoded once into G729.

The phones support G729, so when they terminate the call no transcoding is needed at that end.

If you call Unity Connection, then that will support G729, so again no transcoding.

If you call UCCX, and that is configured for G711, then it will need transcoders installed at the site that has UCCX, as the G729 call will need transcoding to G711 so UCCX can understand it.

So - for your gateway all you need to do is ensure that you overprovision the DSPs. A single channel of DSP can do one PSTN call at G711, but requires more for G729. e.g. in the UK a PVDM-32 will cater for a 30-channel E1,but if running G729 you might provision a PVDM-64.

There is a calculator available for DSP provisioning:

http://www.cisco.com/web/applicat/dsprecal/dsp_calc.html

Aaron

[garcarulo]

Thank you Guys for your help  !