There are several links where you can book a hotel in Berlin
with different price ranges.
Berlin Tourismus (BTM):
Here you can book a selection of reasonably-priced hotels which have the most
direct public transport connection to the conference site in the Arnimallee. 12.
The cheapest rooms are found in the first hotel of this list: Aletto Jugendhotel Schönebergs
with Bed-and-Breakfast price of 23 €!
Hotel.de / Expedia.de/.com:
These links offer all hotels in Berlin sortet by price,
irrespective of their connections to the conference site!
This link offers numerous hostels in Berlin at various locations
indicated on a map!
At Hotel Ansbach, you can get a double-room for 20 € per bed.
Location of various hotels with respect to conference Site: