Proceed to Tower Rooftop
You'll see allied soldier after reaching the third tower (if you need to recover health and armor, do it now - there's the medic and the engineer). Move ahead, open the door and use the elevator. You'll meet next humans (#201). After a while, four teleportation balls summoning enemies will appear under the ceiling. Destroy them as fast as you can, or you'll have to face many opponents.
Walk trough only unlocked door and activate the bridge (#202). It'll help you to get on the other side. Call for the elevator (#203) in the next hall. You'll run into Gunner and in all four corners of the room the next teleportation balls will appear. Kill enemies and travel up. Walk straight ahead, successively eliminating enemies and next teleportation balls.
The huge hall is located at the end of the track. You can found teleport in the center (#204). This time you must use it.