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Standardizing M17 BER Testing
#1
It would be useful to have interoperable BER testing between conforming implementations, so that a transmitters, receivers, and test equipment from different vendors could be used for M17 equipment testing.  This would be useful for end users -- especially ham operators -- in tuning their equipment.

As a strawman, I propose using the reserved sync word (now BER SYNC WORD) for this purpose, along with a custom frame type which uses the P2 puncture matrix.  The frame would be 197 bits long (24 bytes + 5 bits).  The first two bytes would be a frame number and would seed a LFSR PRNG.  If we want to use more than one LFSR, we could use some of the reserved bits in the frame type word for this.

The LSF would be sent as-is, with the frame type set as STREAM and the stream type set to the reserved type "00".  This would be followed by BER frames using the BER SYNC WORD, containing a 16-bit frame number and 181 bits of pseudo-random data encoded similarly to the stream payload audio data (i.e. using the same puncture matrix).

197 bits gets extended to 201 bits with 4 bits of 0 used to flush the convolutional encoder.  This is encoded into 402 bits.  This is then punctured to 368 bits, which is a full frame.

Frame numbers would start at 1 in order to have at least on bit set in the LFSR.

Seeding the LFSR with a frame number allows for synchronization and recovery of the BER test.

We would use a 16-bit LFSR with the polynomial [img]data:image/png;base64,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[/img]

https://en.wikipedia.org/wiki/Linear-fee...imal_LFSRs

The least significant 8 bits would be used, then shifted 8 bits, then the next 8 bits extracted and so on.  On the final byte, only the most-significant 5 bits will be used.
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Messages In This Thread
Standardizing M17 BER Testing - by WX9O - 07-26-2021, 03:52 AM
RE: Standardizing M17 BER Testing - by G4KLX - 07-30-2021, 12:00 AM
RE: Standardizing M17 BER Testing - by WX9O - 07-31-2021, 04:36 AM
RE: Standardizing M17 BER Testing - by G4KLX - 07-31-2021, 09:38 AM
RE: Standardizing M17 BER Testing - by WX9O - 07-31-2021, 05:09 PM
RE: Standardizing M17 BER Testing - by David.cureton@dcureton.com - 09-23-2021, 12:10 AM

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