How to scan the OFDM Beacons of WiFi working in 2.4GHz with MATLAB and USRP devices?

Recently, we try to use the example from MATLAB, which is called "OFDM Beacon Receiver Using Software-Defined Radio", to detect the Beacon frames from wireless access points(WAP) and thus monitoring the status of wireless channels. The USRP we use is B210 from Ettus Research.

The link of this example: https://ww2.mathworks.cn/help/wlan/ug/ofdm-beacon-receiver-using-software-defined-radio.html

This example is declared as "retrieving information about WiFi networks on the 5 GHz band", and it work well on 5 GHz band. However, we when change related configurations to make it scan on 2.4GHz band, only few beacons can be successfully detected by this program.

We now hope to modify the program to make it adapt to the WIFI beacon scanning on 2.4GHz band. Could someone with knowledge and experiences about it give us some suggestion about how to modify this program?

Answer 1

[Simar]

Hi Yintian,

It appears you are seeking assistance to enhance the "OFDM Beacon Receiver Using Software-Defined Radio" MATLAB example, aiming to improve beacon detection within the 2.4 GHz frequency band using a B210 USRP.

Adapting the MATLAB example to work with the 2.4 GHz band involves several changes due to differences in frequency characteristics and regulations between the 2.4 GHz and 5 GHz bands. Here are some specific steps and considerations for modifying the program:

1. Center Frequency: Change the centre frequency parameter to match one of the 2.4 GHz Wi-Fi channels. For example, the centre frequency for channel 1 is 2.412 GHz.
2. Channel Bandwidth: Ensure channel bandwidth is set to 20 MHz, which is the typical bandwidth for Wi-Fi channels in the 2.4 GHz band.
3. Sampling Rate: Adjust the sampling rate to accommodate the 20 MHz channel bandwidth. The sampling rate must be high enough to capture the full bandwidth of the channel.
4. Filter Design: Update any filters used in the receiver chain to match the 2.4 GHz band characteristics. This includes low-pass filters, band-pass filters, and any other signal conditioning elements.
5. Antenna Selection: The Ettus B210 SDR has two RF chains. Make sure to use the RF chain that is optimized for the 2.4 GHz band and select the appropriate antenna port.
6. Receiver Gain: Experiment with the receiver gain settings. The optimal gain for the 2.4 GHz band may differ from that of the 5 GHz band due to different signal propagation characteristics and levels of interference.

By carefully adjusting these parameters and considering the environmental factors, one should be able to modify the MATLAB example to effectively scan for Wi-Fi beacons in the 2.4 GHz band. Keep in mind that it might take some trial and error to optimize the receiver performance due to the congested nature of the 2.4 GHz spectrum.

Hope it helps !

Best Regards,

Simar

[Jay]

Did you ever get the correct parameters/characteristics to work I am still having no results