The evolution of the 3G systems to the fourth generation is motivated by the creation and development of new services for mobile devices, and this is possible thanks to the new available technologies for mobile telecommunications.
During the last few years, the evolution of technologies in the telecommunication systems, consume electronics and mobile devices has been enlarged. The increase of bandwidth consumption in each mobile due to the new and many devices available, and the high capacity of the Internet core networks push the creation of a new standard for operators of mobile technology.
The services based on the Internet have been transferred to the mobile telephones, creating the service called Mobile Broadband. To be able to support the same services which are obtained in computers, based on IP, in a mobile phone is what pushes the development and evolution towards Long Term Evolution (LTE). Since the 2.5 and 3G systems were not specifically designed for IP services (although 3G is close to this requisite), it is necessary to create a new standard to evolve towards the Mobile Broadband model completely.
The motivation behind LTE can be summarized in the following bullet points:
- The need of more bandwidth for the users and more spectral efficiency.
- The evolution towards an optimized packet switching system.
- The need to improve the quality of service (Round trip delay, latency, broadcasting mechanisms, etc.).
- Simpler infrastructure, with less quantity of nodes and, thus, more economical.
- The coexistence with legacy standads.
LTE is the last standard in mobile networks technologies, proposed by the 3GPP group (see point 3GPP). The development of the LTE standard started in 2004, in charge of the 3GPP group. At the beginning, the goal of the analysis was based on the optimization of the radio interface and the access architecture. For this purpose, a work group was created: Technical Specification Group – Radio Access Networks (3GPP TSG RAN). This group was in charge of the development of a new radio interface, which was presented as standard in the year 2008 as "Release 8 3GPP".
The Release 8, closed in December 2008, was the first version available of the new radio interface E-UTRAN and it allows quadrupling the spectral efficiency and to increment the quantity of the users supported in the same cell significantly. This is the first version of LTE.
In December 2009, it was completed and presented as Release 9, which included minor changes. To this point, LTE was considered a 3.9G technology, not following the IMT-Advance standard (See “About IMT norms”).
From the Release 10, closed in March 2011, the name of the project changed to LTE Advanced. Since this Release, the standard was accepted under the family of norms IMT-Advanced, and, thus, is considered a 4G technology.
As main improvements in LTE, there are new transmission frequencies, the power comsuption of the terminals was improved, there is a plane architecture, eliminating the 3G RNC equipment (the radio control functionality is deployed in the eNodeB), the quality of the end-to-end services, the system is improved being based on packet switching schemes only and acquisition costs (CAPEX) and operation costs (OPEX) are reduced. What is more, many techniques and improvements are added such as: MBMS (Multimedia Broadcast Multicast Service), MIMO (Multiple Input, Multiple Output) and ICIC (Inter Cell Interference Coordination). As regards the architecture, the functionalities of the network are gathered and a plane topology of few nodes, based on IP, is achieved.
The evolution of the packet switched backbone was worked under the name System Architecture Evolution (SAE), but its formal name is Evolved Packet Core (EPC). The term SAE is usually used as a synonym for EPC. The combination of the access network (E-UTRAN) and the core network (EPC) is what makes up the new network and receives the name of Evolved Packet System (EPS).
The LTE system provides compatibility with the GERAN (GSM EDGE Radio Access Network) and UTRAN (UMTS Terrestrial Radio Access Network) access networks, allowing to interconnect the GERAN, UTRAN and E-UTRAN networks through the same core.
About the IMT norms
The International Telecommunication Union (ITU) is the international authority which establishes the criteria of the Wireless technologies generations. These criteria dictate the requirements to consider a technology inside a generation. The IMT-2000 criteria for 3G were defined and then, for 4G, the criteria under IMT-Advanced were defined. The ITU has analyzed several technologies for their inclusion in the IMT-Advanced family. In January 2012, the ITU defined that the LTE-Advanced had reached the requirements to be considered as an alternative of forth generation. The inclusion of the standard WirelessMAN Advanced (based on IEEE 802.16m) was also approved. LTE and LTE Advanced are the same technology. The name Advanced is applied for the relationship between the Release 10 3GPP with ITU-IMT Advanced. LTE Advanced (Release 10 3GPP) is not a new technology but the evolution of LTE.
The Third Generation Partnership Project, known as 3GPP, is an agreement of collaboration between different standardization organisms for the development and evolution of technical specifications of mobile standards.
This forum was constructed in December 1998, and it originates as the meeting point between the different entities and standardization organisms which had presented a similar proposal based on Wideband Code Division Multiple Access (WCDMA) technologies, during the process of selection of the IMT-2000 standards (by the ITU). After some time, several tasks were added: The development and maintenance of GSM/GPRS/EDGE standards and radio access technologies; the evolution of the mobile system (Core and Access); and the development of an IMS technology (IP Multimedia Subsystem) independent of the access technology
In practice, the 3GPP recommendations are usually adopted and considered by most operators and mobile manufacturers.