Hi
We also recently shifted to CBCCH and found that call drop rate is increasing post CBCCH implementation. Presently we are verifying the physical antenna specification for 1800 and 900 bts so that rf enviroment should be similar to both layers. We have observed that after CBCCH traffic is shifted to GSM layer to DCS layer. As we had better RF enviroment for DCS than GSM this can be one of the reason. Though we are also in process of anaysis of core reason of CDR increase