Re: Detected an invalid packet at item

[Johannes Demel]

Hi Hamed,





You already mentioned a few channel effects that influence your reception:
- multipath
- interference
I'd like to stress that:
- noise
- hardware imperfections
- any unfortunate condition in your receiver chain
may also affect your reception.

The questions that arise are:
- What do you want to fix here?
- Did you observe anything that you didn't expect?

Cheers
Johannes

On 14.05.23 05:33, Hamed Al-Zubi wrote:

you mentioned that increasing the TX and RX gain reduced the number of invalid packets. Still, as long as you transmit over an imperfect channel, there will be reception errors. The reports you receive stem from the logging system. They are tagged ":info:" because this might be an interesting information in some cases. However, this is not a software system error. This is a reception error and should be treated as such.

Ed,



Thanks!
HZ





@(^.^)@ Ed
Sent from my iPhone

I tried the NLOS scenario to avoid distortion, but still the same error occurs. On Saturday, May 13, 2023 at 11:07:22 AM CDT, Ed Criscuolo <e...@chessie.com> wrote: 2 meters seems like an incredibly short distance unless you have an attenuator in series with the Tx antenna. You may be overdriving the receiver and causing distortion errors.

On May 12, 2023, at 8:10 PM, Hamed Al-Zubi <hamed.zubi1...@yahoo.com> wrote:


Hello,



*packet_headerparser_b :info: Detected an invalid packet at item 167472*
*header_payload_demux :info: Parser returned #f*





When I used a channel model instead of USRPs, the error did not occur.
I am still uncertain about the exact cause of the error I am experiencing.


Thanks,
HZ

I am utilizing two USRPs, specifically the X300 models, along with GNURadio for the purpose of transmitting and receiving OFDM signals. I have implemented the OFDM flowgraphs available on Github for this purpose. The transmission and reception setup involves LOS (Line-of-Sight) configuration, where the transmit and receive antennas are positioned with a separation distance of 2 meters. To minimize the impact of multipath interference, the antennas are surrounded by absorption boards. Although the transmission and reception process itself is functioning without issues, I have encountered a problem when displaying the channel state information. In particular, there are instances where invalid packets are detected, as evidenced by the following occurrences. I have searched the possible causes of the error I'm encountering, and there are a few factors that have been suggested: 1- Interference--> I used different frequencies and ensured they are not in use. 2- Multipath --> absorption boards were used to minimize the impact of multipath. 3- Some people suggested to change  the FFT length and CRC length as a potential solution, however, modifying these papermeters did not resolve the issue.

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