The first channels to relocate will not do so for another 18 months, according to the FCC. And TV stations that are changing channels or will go off the air

The first channels to relocate will not do so for another 18 months, according to the FCC. And TV stations that are changing channels or will go off the air will be expected to notify their viewers ahead of time with on-screen banners and other guides. I thought digital over the air TV had some sort of channel-mapping that decoupled broadcast frequency from the programming channels the viewer sees, and the relationship between the two post-transition was just a historical artifact. (hence the decimal fraction broadcast channels and occasional need to convince your DTV/adapter to re-scan for metadata) Can't these moving stations just change their frequency and keep their numbers?