It depend on hove many TRX’s do you have in a cell. If You have two then it is recomended to create 2 TS in a cell, but also you have to have on TRX0 TS0 BCCH whole for him self ( not combined with SDCCH, because of AGCH, PCH and RACH ). Be careful not to take TS if you need it for speech or data.