Jacek Góra, Krystian Safjan, Jarosław Lachowski, Agnieszka Szufarska, Stanisław Strzyż, Szymon Stefański, Damian Kolmas, Jyrki T. J. Penttinen, Francesco D. Calabrese, Guillaume Monghal, Mohammad Anas, Luis Maestro, Juha Kallio and Olli Ramula
Long Term Evolution (LTE) and System Architecture Evolution (SAE) are the next, evolutionary steps in the development of mobile communication systems for both radio access (LTE) and core network (SAE). They are often commonly referred to as the “4th generation” systems (4G) though such terminology is over-simplified as within LTE itself one can distinguish a number of releases with gradually more advanced features and better performance.
The work on 4G mobile communication systems began in 2004 when there was already a mature concept for evolving WCDMA in a more mature state – HSPA. It was clear that the 3rd generation (3G) systems might still be competitive and guarantee bit rates required by end-users for the next few years – yet 3GPP decided to go for resource-consuming development of the 4G system with an entirely new air interface as well as significant changes in system architecture.
The motivation and requirements can be found in the publicly available 3GPP specification  – one of opening sentences there reads: “(…) to ensure competitiveness in an even longer time frame, that is, for the next 10 years and beyond, a long-term evolution of the 3GPP radio-access ...