I’m sorry Abdel, I forgot, which vendor are you working with ?
Pros of concentric dualband cells :
– less cells in the network
– less adjacencies to define
– only one BCCH planning to perform
– 1800 BCCH TS is replaced by a TCH (+ 1 TS gain)
– easier parameters settings
– monoband 1800 MS cannot access these cells
– GPRS *might* be allowed only on the 900 TRX (vendor dependent, i suppose).
– parameters are possibly less flexible, but more complex.
I designed concentric cells in malaysia, country wide, the results were great (alcatel systems). I would recommend this to anyone who
1. doesn’t care putting all the GPRS on the 900 band.
2. have a good overlap between 1800 cells
3. doesn’t mind learning about concentric parameters