nRF24L01+ communication is interfered by WiFi

[harryAI]

In our project, two RF modules (with nRF24L01+ IC) are used in communicating data. If there is no WiFi around, the two RF modules can communicate very well without packet lost. However, if cell phone or laptop is used in browsing web pages or listening youtube music via WiFi, RF module will lose some packets.

My question is how to avoid WiFi signal to affect RF communication? If it can not avoid, how to mitigate this problem?

[Håkon Alseth]

Hi,

 

Which channels do you communicate on?

As the nRF24L01+ does not have a proper RSSI (1 bit "RPD" is available, detects if power in channel is above or below -64 dBm), I would recommend that you communicate on RF channels that are in between normally used wifi channels. Here's a picture that shows where wifi-channels operate:

https://www.allaboutcircuits.com/uploads/articles/Bluetooth_and_WLAN_frequencies.jpg

 

Choosing channels between 2420 - 2427 MHz, 2445 - 2454 MHz, or 2472 - 2480 MHz can be a good option to avoid the frequently used wifi channels 1/6/11.

 

Best regards,

Håkon

 

[harryAI]

Thank your useful recommendation about the channel selection. I tested RF channel 37 (2437 MHz), 38 (2438 MHz) and 108 (2508 MHz). All are interfered by WiFi. RF channel 37 and 38 overlaps with WiFi channel 6, so this makes sense that it is interfered.

Two more questions:

1. In my test, when I use channel 108 (2508 MHz), RF is still interfered by WiFi? In theory, WiFi should not use the frequency of 2508 MHz (https://en.wikipedia.org/wiki/List_of_WLAN_channels). Do you have any idea why?

2. In addition, nRF24L01+ supports frequency from 2.4 GHz to 2.525 GHz. The world wide ISM frequency band is at 2.400 - 2.4835GHz. From the regulation, do you know is it legitimate to use the frequency above 2.4835GHz in RF in north America area (USA and Canada)? If it is legitimate, perhaps we can also use this frequency to avoid interference with WiFi.

[Håkon Alseth]

Hi,

 

There are restricted bands outside the ISM band, so you might be sampling that one in our area.

Going outside the ISM band (>2.4835 GHz) is not permitted. Note that this is a hard limit, meaning that I would recommend that you use up to 2480 MHz, leaving 3.5MHz "safety space" for any bleeding in the outer edges of the band.

Best regards,

Håkon