Error Correction for Unit/Source ID in LCW

[robotastic]

Is the Unit ID / Source ID covered by any error correction or detection? I am getting some really weird values for Source. I have been logging them, and I am getting a bunch of Source IDs that are high and only show up in a single LCW message.

Is there another P25 Message that also contains Source ID and is covered by error correction or detection?

[EdFuentetaja]

Yes, the whole LCW is protected by Hamming and Reed-Solomon codes. If no error is detected the source ID is likely correct.

LCW shows up in "LDU1" (voice) and "TDU with link control info" units.

Not sure which field to refer by "Unit ID," if you mean the "data unit ID" on the network identifier (NI), yes, it's also error protected.

Kind regards,

Ed

[robotastic]

That is great! I was just referring to the Source ID, I had also seen it
called Unit ID other places, the radio id of the unit that is transmitting.

I am capturing the Source that is generated at line 149 of p25_lcw.c . If I
pass in irrecoverable_errors, will that tell me if there was a bad enough
error that I should probably ignore the Source ID from this message?

Thanks again for adding in all the error correction!

On Sun, Jun 8, 2014 at 11:41 PM, EdFuentetaja notifications@github.com
wrote:

Yes, the whole LCW is protected by Hamming and Reed-Solomon codes. If no
error is detected the source ID is likely correct.

LCW shows up in "LDU1" (voice) and "TDU with link control info" units.

Not sure which field to refer by "Unit ID," if you mean the "data unit ID"
on the network identifier (NI), yes, it's also error protected.

Kind regards,

Ed

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[robotastic]

To answer my own question - it looks like you can use irrecoverable_error to determine whether the Source ID is good or not.