taxi: price: 15-20 €. Journey time: 10 min.
 train: see below

By train: RENFE. Phone: 902 24 02 02. Compatible with TMB transportation cards
  http://www.renfe.es

  Complete map of Central Integrated Railway Network:

  http://www.atmtransmet.org/pdfs_cat/A.3%20ATM%20Central.pdf

 Take "Rodalies Line 2 (C2 or R2)" to "Castelldefels", take the rail's subway path and go to "Campus UPC - Parc  Mediterrani de la Tecnologia"

 Approx. 25 min travel time; 10 to 20 minutes pass time.

 
By bus: Mohn Buses ("the yellow ones"). Phone: 902 023 393. Compatible with TMB Transportation Cards.
  http://www.emt-amb.cat/links/lineas/mohn/l95.htm

  http://www.emt-amb.cat/links/lineas/mohn/l96.htm

  http://www.emt-amb.cat/links/lineas/mohn/l97.htm
 

  L95: Barcelona-Rambla Catalunya/Balmes - Castelldefels: Av. Canal Olímpic
  L96: Sant Boi de LLobregat - Castelldefels
  L97: Zona Universitaria - Castelldefels
  N14: Night Bus; Plaza Catalunya - Castelldefels

  Approx. 45 min travel time from first bus stop; 20 to 30 minutes pass time.

By car: take the C32 (formerly A16) to Castelldefels-Sitges, Exit 46: "Castelldefels" (once on the "Av, Canal Olímpic" watch carefully for a small sign on the right pointing towards "UPC Campus").
 

C31 (formerly N246) take the "Canal Olimpic Exit" and once on the "Av, Canal Olímpic" watch carefully for an entrance to the left.
 

Approx. 25 min travel time from city centre; 10 from the airport.