There's an excellent guide to DMR technology by Andrew Barron (ZL3DW) and brief overview by Motorola Solutions, one of the major suppliers of commercial DMR [1],[2].

[1] Work the world with DMR: Digital Mobile Radio (2022):

https://www.hamradio.com/detail.cfm?pid=H0-019172

[2] WHAT IS DMR?

https://www.motorolasolutions.com/en_xp/solutions/what-is-dm...