How far should we spread using DS-CDMA in time and frequency selective fading channels?

Changqing Zheng, Muriel Médard. How far should we spread using DS-CDMA in time and frequency selective fading channels?. In Proceedings of the Global Telecommunications Conference, 2003. GLOBECOM '03, San Francisco, CA, USA, 1-5 December 2003. pages 1563-1567, IEEE, 2003. [doi]