Stephen M. Blust, Chairman, ITU-R Working Party 5D (IMT Systems)
ITU started the development of radio interface standards for mobile communications on the eve of the initial deployments of the first digital cellular systems (known as 2G). This effort, led by governments and industry, gave birth to the framework of standards known as IMT – for international mobile telecommunications – which also includes the identification of radio frequency spectrum and band arrangements. The IMT scope encompasses the well-established IMT-2000 and the newly developed IMT-Advanced.
Since 2000, the world has seen the introduction of the first family of standards derived from the IMT concept – IMT-2000 (commonly referred to as 3G). 3G is now widely deployed and being rapidly enhanced. IMT-2000 is the foundation for the personal mobile communications industry and is present in the pocket of almost everyone in the world.
Pursuing its initiative to lead international efforts to produce global standards for mobile communications, ITU’s Radiocommunication Sector (ITU-R) completed in 2011 the assessment of candidate submissions for the next generation global mobile broadband technology, otherwise known as IMT-Advanced. Harmonization among these proposals has resulted in the choice of two technologies, LTE-Advanced and WirelessMAN-Advanced. These radio interface technology standards have been submitted to the Radiocommunication Assembly 2012, held in Geneva on 16-20 January, for final endorsement by the ITU Member States and have been agreed
ITU-R has also commenced the process of developing an ITU-R Recommendation for the satellite component of the IMT-Advanced radio interfaces, having recently invited the submission of proposals for candidate radio interface technologies.
IMT-Advanced brings major improvements, including increased spectrum efficiency – more users at higher data rates per radio channel and fully packet-based architecture – reduced costs, comprehensive support for broadband wireless data, lower latency – more responsive Internet and multimedia applications, and improved radio resource management and control – enhanced quality of service, and new capabilities for the physical layer of the radio interface – including wideband radio channels, multiple-input and multiple-output (MIMO) smart antennas and flexible deployment options.
Among the critical technical features of IMT-Advanced technologies, the requirements for working in IMT frequency bands (see Table 1) is particularly important, as is interoperability with IMT-2000 to facilitate global roaming. To the extent possible, ITU has sought to harmonize the use of these IMT bands on a global basis, although in some of these bands and in some parts of the world such harmonization has not been able to be achieved because of the conflicting requirements of other radio services.
While voice traffic on mobile networks is growing at a relatively constant rate, there has in the past few years been a very rapid increase in the volume of data traffic. This increase is being further accelerated by the introduction of a growing array of advanced multimedia devices, including smartphones and tablets and their related applications. Comparisons of traffic demand estimates prepared in 2005 in Report ITU-R M.2072 with current assessments for 2020 from recently concluded ITU studies (see Figure 1) indicate that the earlier projections significantly understated the current and future levels of data carried on broadband mobile systems. Actual data traffic in 2010 was more than 5 times greater than some of the estimates prepared for Report ITU-R M.2072. Not only that, but in 2011 some operators even experienced a higher level of actual traffic than Report ITU-R M.2072 forecast for 2020.
Even with the significant leap in spectrum efficiency available in IMT-Advanced, it is apparent that the overall amount of spectrum currently identified for IMT might not be sufficient for the future. A number of ITU Member States are now considering proposals for WRC-12 to add an item to the WRC-15 agenda to address future spectrum requirements for IMT mobile broadband.
Figure 1 – Assessment of the global mobile broadband deployments and forecasts for IMT