ower commisioner uses E1 config(2.5), so for each TRX they put 2.5 Ts on A-bis…(2Ts for traffic & 0.5 Ts for signaling bcch,sdcch,…).
this is OK for BCCH TRX, But for another non BCCH TRX what is the useful of 0.5 Ts/A-bis.
more over what is the signaling moved on the extra 2Ts on 32Ts/E1.is it LAPDm.
thanks in advance.
1)In A-bis (BTS/BSC commands, Alarms, call control). is this right they transsimited in one link (not separated).
2)furthermore what is the functional different between LAPD & LAPDm.
thanks in advance
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…
As i know the LAPDm on Um is modified LAPD in A-bis.
BUT the function of error detection & correction are removed from LAPDm to layer1 on Um, and the message frmes on LAPD can be much longer than frames on LAPDm which must be fit in to the bursts on Um interface.