Hello Rocel,
Please use the search function, you will find other topics related to UL and OL (i don’t know anything about that, i don’t work with it…)
2/ concentric cells are used in multiband networks, so that outer zone is 900, inner zone is 1800. Goal is to simplify settings (intracell HO), gain 1 TS for TCH, instead of using if for the 1800BCCH), reduce the nulber of neighbours declared in OMCR, etc.
Cheers
pix