How do I differentiate between a field engineer and a RF network engineer?

I am working with a company that from time to time needs people to help it with mobile device testing. Tools used would be things like QXDM Pro and TEMS.

Both types of professionals do drive testing, but one tests networks while the other tests how well specific devices perform on networks.

My question is whether there's an easy way to differentiate one from the other... A skill that a field engineer would have, for instance, that a RF network engineer likely wouldn't.

Thanks in advance.

Tim