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.zubi1...@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
