13 LTE and SAE: Introduction and design targets In Chapters 8­12, HSPA and the evolution thereof were described. As explained in these chapters, HSPA is an evolution of WCDMA, building upon the basic WCDMA structure and with a strong requirement on backwards compatibility to leverage on already deployed networks. In parallel to evolving HSPA, 3GPP has specified a new radio access technology, known as Long-Term Evolution (LTE). As described in Chapter 2, LTE targets more complex spectrum situa- tions and has fewer restrictions on backwards compatibility. Thus, 3G evolution consists of two parallel tracks, both having their respective merits, for the radio