– First of all, you need a third antenna for TX in the first sector where you will upgrade from 4 to 6 TRU’s.
– Secondly, you need 2 Master cabinets and 1 extension cabinet: cell A will be connected to 1 master cabinet with its TG and cells B and C will be connected to master and extension cabinets with another TG. If you are using LAPD-CON with a factor of 4, the 2 TG’s will be connected in cascade, with 18 RBLT devices allocated to 8 TRU’s (cells B and C) and 13 RBLT devices allocated to 6 TRU’s (cell A).
NOTE: normally, in this case, for 6 TRU’s, 14 RBLT devices are required, but in order to still use one single E1, you will just define 4 Radio TS on the 6th TRU.
I hope this will help.