CSSR Decrease in our network

In december 2008 CSSR [call setup success ratio] in our network is going to decrease to 85% [threshold 95%] its mean that a lot of call being rejected. after get some reason why a lot of call rejected and collect all support data that we get conclussion how to solve this problem.
its a simple way to analyze the problem
if there are normal in Traffic Channel Element than please check in Walsh Code Occupancy [CDMA and WCDMA]..if occupanciest of walscode is upto 98% its mean we need to upgrade from lower WC to greater WC, the impact is a lot user can access the network and make the resources is used up. in CDMA and WCDMA system, user to access the network is limited by power, WalshCode, and Traffic Channel element.
After already checked all supported document and bts reason etc, the main problem in the network is forward power is limited, and after we checked in SHO statistic its show a lot of user is mobile in that BTSes, we cannot limited and user to access the resources, cause if the user get dominant Ec/Io and can be a main pilot, user will used that resources., so the way that we can do is give more forward power that can boost the user and give a space for user to used the resources, and decrease overhead message to give a lot space for traffic power.