in nokia equipment there are 2 types of links to BS: LADP and O&M links, LAPD link for GSM signallink only, I mean layer 3 signallink, O&M link used for all other purposes like alarms, remote connection to BS, lock/unlock BS commands etc…
about LAPD and LAPDm, in GSM it’s the same, if they say LAPD they mean LAPDm, LAPD is in ISDN specification…
Alex
http://www.dx200.biz