[drats_users] ERROR Correction in slow speed data

[Matthew Pitts]

Joel,

Conventional VoIP probably doesn't, but D-Star and other similar systems don't follow those rules; the FEC is actually handled by the AMBE Vocoder chips through firmware programming.

Matthew Pitts
N8OHU




________________________________
 From: Joel Black <w4jbb at charter.net>
To: Discussion of D-RATS <drats_users at intrepid.danplanet.com> 
Sent: Friday, September 20, 2013 6:23 PM
Subject: Re: [drats_users] ERROR Correction in slow speed data
 


Okay, this goes against what little I have learned about VoIP traffic.

I didn't think there was any FEC with voice.  That's why voice has
    priority on data networks that use VoIP.  Otherwise, if a data
    packet has priority, it would bump a voice packet.  When a voice
    packet is bumped, you lose bits of it resulting in choppy audio.

I have experienced this when some of our first quasi VoIP locations
    came online.  Voice is live traffic.  Once it is said, it goes. 
    There's nothing to re-transmit.

Without getting into the engineering (which will leave me drooling
    and nodding off to sleep), how does D-STAR use FEC on voice?

73,
Joel - W4JBB


On 9/20/13 3:57 PM, John Davis wrote:

 
>That is true. The FEC is on the voice with 2400 bits for voice and 1200 for FEC.
> 
>John WB4QDX
> 
>From:drats_users-bounces at intrepid.danplanet.com [mailto:drats_users-bounces at intrepid.danplanet.com] On Behalf Of Daniel Metcalf
>Sent: Friday, September 20, 2013 4:55 PM
>To: Discussion of D-RATS
>Subject: Re: [drats_users] ERROR Correction in slow speed data
> 
>Agreed. From what I have read d-star is a lot like the UDP network protocol where it is transmit and forget there is no handshaking / error correction built in. It is up to the application developer to handle error correction and the d-rats package does perform some level of error correction.
>Dan Metcalf - KB3UUN.
>On Sep 20, 2013 3:54 PM, "John Davis" <jdavis at gtworks.com> wrote:
>My understanding is that the low speed data channel does NOT have error correction, however, D-RATS offers Error correction in Message and File Transfer modes where it is most important.
>> 
>>John WB4QDX
>> 
>>From:drats_users-bounces at intrepid.danplanet.com [mailto:drats_users-bounces at intrepid.danplanet.com] On Behalf Of Dave Welker
>>Sent: Friday, September 20, 2013 3:19 PM
>>To: D-Rats Mailing List
>>Subject: [drats_users] ERROR Correction in slow speed data
>> 
>>Hello all,
>>Can anyone confirm if the D-RATS slow speed data has FEC (Forward Error Correction) built in now or not?
>>I understand that D-STAR voice does have error correction built in.  I've checked on the D-RATS home page/documentation
>>which is a August 2009 reference.
>> 
>>This is what I found in this document Under users manual/files:  Is this still current information?
>> 
>>Unlike the D-STAR DV Voice Channel, which has error correction built into the protocol, the Data Sub-channel has no error correction. 
>> 
>>This makes the transfer of data across D-STAR a lot more dependant on a good radio path being established between the two locations wishing to 
>> 
>>exchange data.  D-RATS includes the ability to test connectivity between two locations.
>> 
>>Thanks in advance
>>regards
>>Dave
>>W2SRP
>> 
>> 
>>Goals are where we want to be;
>>Objectives are the steps to get there.
>> 
>>There are 2 rules to success in life:
>>1. Don't tell people everything you know.
>>
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>
>
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