Android Game Additional Patch File

Hello I am planning to develop an android game. But I have a problem, how can I implement an Additional Patch when I already finished developing it without downloading the whole file. Like for example, those RPG games in google play store now, after downloading the game it will check if there is an additional patch from the server and it will download & update the game. It will be too hustle if I will download the whole apk file over and over again. Thank you in advance. Hope you can help me...