Abstract: The method to reduce the bandwidth necessary for the renewal of subscription message is achieved using group messages in which each member of the group is associated with a bit of a bitmap. In order to have the maximum members in a group, the size dedicated for the bitmap is determined first by calculating the size remaining after putting the command and other necessary data into the message, and using an iterative process to determine whether the bitmap, once compressed, will fit this remaining size. The iterative process adds a new member into the group, thus increasing the bitmap size, then compresses the resulting bitmap and checks if the compressed bitmap will fit into the remaining size.

Abstract: A method to reduce the bandwidth for the renewal of subscriptions includes: A) defining a maximum length for a message, B) defining a command for security modules, C) forming a message comprising the command, D) filling the message with a starting address and a range E) determining a remaining length in the message, F) defining a bitmap of variable length, G) starting at identification address equal to the starting address and initializing an index value and the bitmap length, H) updating the bitmap bit for the security module pertaining to the identification address to activate/deactivate the command, I) compressing the bitmap, J) when the compressed bitmap length is smaller than the remaining size in the message, updating the index value, the bitmap length and the identification address and re-executing the steps H to J, K) updating the range with the index value and filling the message with the bitmap.