Additional spectrum was identified for IMT-2000 at later World Radio communication
conferences. WRC-2000 identified the existing 2G bands at 800/900 MHz and 1800/1900 MHz,
plus an additional 190 MHz of spectrum at 2.6 GHz, all for IMT-2000. As additional spectrum for
IMT-2000, WRC’07 identified a band at 450 MHz, the so-called “digital dividend” at 698–806
MHz, plus an additional 300 MHz of spectrum at higher frequencies. The applicability of these
new bands varies on a regional and national basis. WRC’12 did not identify any additional
spectrum allocations for IMT, but the issue was put on the agenda for WRC’15. It was also
determined to study the use of the band 694-790 MHz for mobile services in Region 1 (Europe,
Middle East, and Africa).
The worldwide frequency arrangements for IMT are outlined in ITU-R recommendation
M.1036 [8], which is presently being updated with the arrangements for the most recent
frequency bands added. The recommendation outlines the regional variations in how the
bands are implemented and also identifies which parts of the spectrum are paired and which
are unpaired. For the paired spectrum, the bands for uplink (mobile transmit) and downlink
(base-station transmit) are identified for Frequency-Division Duplex (FDD) operation. The
unpaired bands can, for example, be used for Time-Division Duplex (TDD) operation. Note
that the band that is most globally deployed for 3G is still 2 GHz.
The same bands that were originally defined for IMT-2000 and used for 3G deployment
are also being used for 4G, including LTE-Advanced deployment. The latest version of
the ITU-R spectrum recommendation M.1036 [8] is renamed with a more generic title having
the identifier “IMT” instead of “IMT-2000” and is now applicable for both LTE and
LTE-Advanced deployments. Some regions and countries have issued licenses for new
spectrum identified at WRC-2000 and WRC’07 with the intention of allowing 4G
deployments, but in most cases new spectrum is licensed on a technology-neutral basis. Many
new deployments are either 4G or 3G, but some are also a mix of 4G and 3G, sometimes also
together with significant parts of the spectrum still used for 2G.
1.4 Drivers for LTE and LTE-Advanced
The evolution of 3G systems into 4G is driven by the creation and development of new
services for mobile devices, and is enabled by advancement of the technology available for
mobile systems. There has also been an evolution of the environment in which mobile
systems are deployed and operated, in terms of competition between mobile operators,
challenges from other mobile technologies, and new regulation of spectrum use and market
aspects of mobile systems.
The rapid evolution of the technology used in telecommunication systems, consumer
electronics, and specifically mobile devices has been remarkable in the last 20 years. Moore’s
law illustrates this and indicates a continuing evolution of processor performance and
increased memory size, often combined with reduced size, power consumption, and cost for
devices. Combined with a high-speed internet backbone often based on optical fiber
8 CHAPTER 1 Background of LTE