i have windows 8.1 and recently i tried to share my 3G connection with my smartphone but i found that i don’t have ad-hoc in my system
i don’t know if only my version don’t have this option or all the other version anyway i found this great tool to create a wifi hotspot
it call Virtual Router Plus you can download it from here.
after you install it you can share your connection
if you get an error make sure to Allow the share option
there are also another way from the Command you can see it in this article.