I'm trying to find a sci fi book (or possibly) series that I read in either late 1990s or early 2000s. I think it was on Earth, but most of civilisation was gone (like rediscovered eden type sci-fi), and the protagonists find bits of old technology like mobile phones (possibly they called them pearls?) that don't work very well. They might have been nomadic tribes are there weren't any cities left?

I'm trying to find a sci-fi book (or possibly series) that I read in either the late 1990s or early 2000s. I think it was on Earth, but most civilisation was gone (rediscovered Eden type sci-fi). The protagonists find bits of old technology like mobile phones (possibly they called them pearls?) that don't work very well. They might have been nomadic tribes and there weren't any cities left?.