It is simple to add the SDCCH ,
But we need to find the reason for the congestion is it due to more calls or location updates.
If it is due to calls then SDCCH has to be added or the dynamic SDCCH can be configured in the network.
If due to location updates then we need to see the Location area dimensioning and planning.
be carefull before u add the SDCCH as it has to be planned