[EAS] Part 11 / Local CAP Relay Networks

[Harold Price]

When discussing alternative CAP networks, keep the following in mind:

CAP messages containing audio have that audio compressed at 
64kbits/sec, per the IPAWS recommendation.  If you want your message 
to keep up with realtime, and it contains embedded audio, you'll need 
to have a link that takes this into account.  You can simply not 
include the compressed audio, and let the text to speech at the 
broadcaster generate audio.  Even a 4800bps link is adequate for that.

If, however, this is a full Internet replacement, and the only way to 
get audio to the stations is via the alternate path, then it must be 
suitable for use with the President's message, the EAN.  EAN audio 
will be sent in an audio stream.  The current standard for that is 
again 64kbps compressed with MP3, so your alternate system must be 
able to handle that.  To allow for overhead, you'll need a little 
more than a 64kbps data rate.

This could be reduced if IPAWS drops to 24kbps MP3 audio, which is 
very intelligible for mono voice.

Harold

At 01:53 PM 5/20/2011, David Ostmo wrote:
>Hi Richard,
>
>It appears that we are thinking the exact same way.  I would like to 
>see a secure microwave / radio link from the EOC to a couple of 
>local DTV stations that would serve as the local CAP relay 
>network.  The configuration would provide the local community the 
>CAP payload.  The arrangement is safe, secure and robust.