Frequency hopping during FCC Testing

[tmeizeli]

I am going through FCC Testing for a BLE device, and among other things, they are asking for the ability to be able to turn frequency hopping on and off. It is my understanding that frequency hopping is not really a specific standard when it comes to BLE meaning different vendors have different implementations. I could be wrong though. I have looked through some of the radio test examples, and I haven't found an example that shows how to do hopping. I was thinking of just transmitting at a pseudo-random sequence of channels, but I don't know if there is any standard to conform to.

So TL;DR: is there a standard for frequency hopping on Bluetooth? If so, what is that standard? If not, are there any guidelines for testing the frequency hopping aspect of Bluetooth? In either case, is there an example project that sends a test 'frequency hopping signal" that can be used for FCC testing?

[ketiljo]

BLE is not defied as FHSS as it uses only 3 channels in advertisement mode, which is less than the minimum number of channels for FHSS. Hence there's no need to demonstrate FHSS. You will test it under FCC 14.247 (a)(2) https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15/subpart-C/subject-group-ECFR2f2e5828339709e/section-15.247, systems using digital modulation. 

BLE isn't using any particular standard for FHSS but in normal operation, it will use all 37 secondary channels in an uniform way. The only way to observe this will to to setup the device in connected mode. 

[tmeizeli]

That is what i guessed based on the looking around I did. It seems that my best bet is something I saw in another post which is to work closely with the test facility.

[ketiljo]

You should be good by using the "radio test" from the SDK here. No need to demonstrate FHSS.  This is stated in the DTS measurement guideline from FCC https://apps.fcc.gov/kdb/GetAttachment.html?id=tylb5MMggvhIlVMK75RrRQ%3D%3D

FAQ section: 

"Question 7: Can Bluetooth Low Energy (BLE) mode (V4.0, etc.) devices be approved under the FHSS rules (equipment class DSS)?
Answer 7: Advertising mode operation uses only three channels, and regular connections can drop to only two channels, therefore BLE mode does not meet the FHSS minimum number of channels requirement. Compliance must be addressed under Section 15.247 DTS requirements or using Section 15.249 for qualifying devices."

Radio test: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/peripheral/radio_test/README.html