This chapter shows possibilities to upgrade to follow-up kernel versions without having to download a new kernel archive in it's entirety.
Upgrading is done utilizing the small program patch, originally developed by Larry Wall.
You will just have to download a rather small file (called "patch") that contains the differences between the two kernel versions. You can get it, for instance, from kernel.org.
The following lines show how to backup your current kernel tree and how to apply the patch.