In Chapters 8–12, 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 situations and has fewer restrictions on backwards compatibility. Thus, 3G evolution consists of two parallel tracks, both having their respective merits, for the radio access evolution. Figure 13.1 illustrates the relation between HSPA and LTE.