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Re: [Discuss-gnuradio] Meaning of header_payload_demux0 - Parser returne


From: Michael Dickens
Subject: Re: [Discuss-gnuradio] Meaning of header_payload_demux0 - Parser returned #f
Date: Tue, 27 Mar 2018 19:37:25 -0400

Hi Alex - The OFDM "#f" printouts means that the header didn't decode 
correctly, which in turn means its Rx-computed CRC8 didn't equal the embedded 
CRC8 from the header generation. This in turn generally means that OFDM sync 
has been lost, which in turn generally means that the Rx "SNR" isn't high 
enough ("SNR" here being the average power in the OFDM band divided by the 
average power outside the OFDM band but still within the sampling frequency 
range). I can't say specifically for the example you cite what's going on, but 
maybe the above helps? - MLD

On Tue, Mar 27, 2018, at 6:54 PM, Roberts, Alex S. wrote:
> I'm playing around with some of the packet and ofdm examples with the 
> eventual goal of streaming udp packets generated by gsrteamer encoding a 
> webcamera. Unfortunately, I've been having some difficulty with the examples 
> that I can't understand. For example, running the packet_loopback_hier 
> example, it will run fine for some period of time (seems to be different 
> amount each run) then it stops printing message debugs and spams the console 
> with
> 
>  header_payload_demux0 - Parser returned #f
>  
> Occasionally, the flowchart will crash and stop running.
>  
> In the current run I have open, the correlation plot looks good, the transmit 
> Time Freq and Constellation Plots are active, and the receive plots are no 
> longer updated (probably because nothing is being decoded?)
> 
> I've tried looking a the archives to see what causes this problem, but have 
> not found a good answer.



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