EA/DICE will be launching Star Wars: Battlefront Beta in October and it will include the earlier seen Battle of Hoth with Walker Assault mode.
According to EA's devblog update, Star Wars: Battlefront will enter its beta phase in "early October" and it will be available for PC, Playstation 4 and Xbox One. The beta will include the Battle of Hoth with 20 vs. 20 Assault Walker Mode. It will also have a few more modes including Drop Zone mode which will be revealed soon as well as the earlier seen co-op survival mission on Tatooine.
Unfortunately, sign-up for the beta phase have not been yet opened and there is still no information on how to be a part of it. We guess that those who pre-order the game will be able to get it first but hopefully there will be some other way to be a part of it.