Alcatel BTS are not “smart”, so they do not manage handovers. All the processing is performed by the BSC.
An ABIS nibble is always using 1/4 of a timeslot, you cannot change that.
1 Abis TS = 64kbps
1 Abis nibble = 16kbps
In the OMCR you can only allocate a full Abis TS, either for CS or for PS, but you can’t allocate just an abis nibble.
A TRX carrying voice = 2 Abis nibble
For signaling, you need to add additional dedicated Abis TS (usually one per 4 TRX)
For Packet, you can add as much as you want. It depends on how many PDCH you expect in your BTS at a certain instant. If you don’t put enough Abis TS for PS, subscribers can still access GPRS/EDGE, but not at full speed.