This one is a bit difficult and easy to miss. You have to survive all five waves. If you 'die' you get knocked out and move on to the next part of the story, thus missing the trophy.
I've never used this, but there's a console on the right up the stairs that has some glass around it that's good to hide behind. But that's not the strategy I employ here.
When the battle first starts, I book it over to the top left hand corner. There's an 'L' shaped desk. That's where I hide.
Weapons don't really matter as long as you have weapons that have lots of ammo, or have ammo extending armor equipped. If you're playing as an Engineer, having a Drone helps a ton.
I advise saving your heavy weapons for the YMIR mech and the guys who have flame throwers equipped. I recommended the 'Collector Particle Beam', though shotguns do a good amount of damage.