LTE-Advanced and the Evolution to 4G Cellular Systems
In the last two decades, the relevance of cellular systems in our society has grown extremely fast, a fact that is reflected by the high speed at which their supporting technologies have been developed. The Third Generation Partnership Project (3GPP) assumed the task of studying and choosing candidate technologies for Universal Mobile Telephone Systems (UMTS), which is probably now the most representative technology of “third generation” (3G) wireless networks. Early packet-based 3G systems did not immediately meet the original data rate targets defined in the International Mobile Telecommunications 2000 project (IMT-2000) by the Universal Telecommunications Union Radiocommunications Sector (ITU-R), so a series of improvements were introduced to the basic UMTS systems. These improvements led to the High Speed Packet Access (HSPA) standard that completed the work towards what is known as 3.5G.
The necessity for a major evolution of UMTS became evident with the emergence of the IEEE 802.16e standard (Mobile WiMAX). The 3GPP group initiated the development of Long Term Evolution (LTE) by setting its requirements in 2005, which mainly included reduced bit cost, increased peak data rates and spectral efficiency, scalable bandwidth and low latency. Work began both on the radio access and core network: a new air interface based on Orthogonal Frequency Division Multiplexing (OFDM) and multiple antenna techniques was envisioned and it was combined with a flat all-IP packet core essential for the delivery of higher throughputs. Since the ITU-R had not yet formally defined the 4G framework, these technologies are usually referred to as 3.9G and their commercial deployment is aimed for 2010 and 2011.
In early 2008, the ITU-R had already translated the vision of 4G systems into a set of requirements that defined the IMT-Advanced project by which technologies and systems could be considered as 4G. Important novelties in this set of requirements were the inclusion of explicit targets for average and cell edge throughput, not reflected in IMT-2000. An open call for candidate technologies was held during the following two years and no fewer than six technologies were submitted seeking for approval. LTE-Advanced, a further evolution of modern cellular systems based on LTE, is the candidate technology submitted by 3GPP with several solution proposals that address each of the IMT-Advanced requirements.
This project is focused on the technologies, research areas and challenges regarding LTE-Advanced and other next generation cellular systems that will enable the 4G and beyond family of standards.