Re: Differential decoding block and PN15 code

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Hi Mason,

There is something odd about your flowgraph: the Constellation Modulator
expects the input to be packed as 8 bits/byte. On the other hand, the
Differential Encoder requires the data to be unpacked (1 bits/byte). You
don't say whether your new_prn15.bin file is packed or unpacked, but
since you say that things work without the Differential Encoder, then I
imagine that the file is packed. So it looks like your problem is that
you're missing to convert back and forth between packed and unpacked for
the Differential Encoder.

Best,
Daniel.

On 10/04/2025 19:12, Starr, Mason S wrote:
> Thank you, Marcus! Attached is the flowgraph. The top segment reads the
> file, which is confirmed to be a PN15 sequence. Well, 8 back-to-back
> PN15 sequences, as each is 4096*8-1 bits long and the file needs to be a
> whole number of bytes.
>
> When differential decoder and CC encoder are bypassed, everything works
> well. The receiver hooked up to the USRP tracks the PN15. As soon as I
> enable differential decoding, no luck. Perhaps I am misunderstanding how
> bytes move from block to block; my assumption has been that it is a
> continuous stream of bits. As far as I can tell, the differential
> decoder block is the same as an NRZ-L to NRZ-M conversion.
>
> Thank you,
>
> Mason
>
> ------------------------------------------------------------------------
> *From:* discuss-gnuradio-bounces+mstarr32=gatech.edu@gnu.org <discuss-
> gnuradio-bounces+mstarr32=gatech.edu@gnu.org> on behalf of Marcus Müller
> <mmueller@gnuradio.org>
> *Sent:* Thursday, April 10, 2025 12:44 PM
> *To:* discuss-gnuradio@gnu.org <discuss-gnuradio@gnu.org>
> *Subject:* Re: Differential decoding block and PN15 code
> [You don't often get email from mmueller@gnuradio.org. Learn why this is
> important at https://aka.ms/LearnAboutSenderIdentification <https://
> aka.ms/LearnAboutSenderIdentification> ]
>
> Hi Mason,
> yes, you can attach images and files! Keep it (solidly) under 4 MB, and
> when taking a
> screenshot, use your operating system's screenshot functionality, and
> not a camera :)
>
> Best,
> Marcus
>
> On 4/9/25 7:51 PM, Starr, Mason S wrote:
>> Hello all,
>>
>> I have a file source that loops through a file containing eight PN15 sequences, which then
>> goes into a differential decoder with M=2. PN15 has the property that after differential
>> decoding it should still be a PN15 sequence, but that is not what I'm seeing. I'm brand
>> new so I'm unclear on if I can attach images or files to this listserve, but if I can, I
>> will provide some supporting information. Has anyone faced a similar issue?
>>
>> Thank you,
>> Mason
>
>