Re: Differential decoding block and PN15 code

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

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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

 

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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