Re: Detected an invalid packet at item

[Hamed Al-Zubi]

Ed, 

I tried the NLOS scenario to avoid distortion, but still the same error occurs. 

Thanks!

HZ 

On Saturday, May 13, 2023 at 11:07:22 AM CDT, Ed Criscuolo <ed@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. 

@(^.^)@ Ed

Sent from my iPhone

On May 12, 2023, at 8:10 PM, Hamed Al-Zubi <hamed.zubi1980@yahoo.com> wrote:



Hello, 

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.

packet_headerparser_b :info: Detected an invalid packet at item 167472

header_payload_demux :info: Parser returned #f

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. 

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