Spectrum Developments 4G LTE

Spectrum continues to challenge the industry. Given this limited resource, the industry is:

q  Deploying technologies that have higher spectral efficiency.

q  Adapting specifications to enable operation of UMTS-HSPA and LTE in all available bands.

q  Designing both FDD and TDD versions of technology to take advantage of both paired and unpaired bands.

q  Designing carrier aggregation techniques in HSPA+ and LTE-Advanced that bond together multiple radio channels (both intra- and inter-frequency bands) to improve peak data rates and efficiency.

q  Deploying as many new cells (large and small) as is economically feasible.

Although all of these industry initiatives greatly expand capacity, they do not obviate the need for additional spectrum.

The FCC released a report in October 2010 that projected U.S. spectrum requirements19 and concluded that 275 MHz of additional spectrum would be needed within five years and 500 MHz of additional spectrum within 10 years. This forecast assumes ongoing increases in spectral efficiency from improving technologies.

An important aspect of UMTS-HSPA and LTE deployment is for infrastructure and mobile devices to accommodate the expanding number of available radio bands. The fundamental system design and networking protocols remain the same for each band; only the frequency- dependent portions of the radios must change. As other frequency bands become available for deployment, standards bodies adapt UMTS-HSPA and LTE for these bands as well.

The 1710-1770 uplink was matched with the 2110-2170 downlink to allow for additional global harmonization of the 1.7/2.1 GHz band. These new spectrum bands were reserved or allocated harmoniously across North, Central, and South America. The Advanced Wireless Services (AWS) band, at 1710-1755 MHz (uplink) with 2110-2155 MHz (downlink) in the United States, is affording operators additional deployment options and could eventually provide a means for LTE roaming in the Americas. Multiple U.S. operators are deploying LTE in 1.7 GHz, as is Rogers in Canada. In addition, many countries in Latin America have allocated this band for mobile broadband.

In 2012, the FCC changed the rules on the Wireless Communications Service (WCS) band, which constitutes 30 MHz of spectrum at 2.3 GHz, making 20 MHz available for mobile broadband.20

The forthcoming 2.6 GHz frequency band in Europe, Asia, Latin America, and other parts of the world will also be a common band for LTE deployment. Unfortunately, different band plans in different parts of the world will complicate roaming on this band. Globally, operators are also refarming spectrum by limiting the spectrum used for 2G (cellular and Personal Communications Service [PCS] bands) to create space for 3G and 4G deployments.

Recently, the FCC repurposed 40 MHz of Mobile Satellite Services (MSS) spectrum for terrestrial use in what it termed the “AWS-4 band.”

Unfortunately, the process of identifying new spectrum and making it available for the industry is a lengthy one, as shown in Figure 1.

Figure 1: Spectrum Acquisition Time

The biggest opportunity areas for new spectrum in the United States currently are incentive auctions of TV-broadcasting spectrum at 600 MHz, government spectrum from 1755 to 1850 MHz and 1695 to 1710 MHz managed by the National Telecommunications and Information Administration (NTIA) to be auctioned as part of AWS-3, and the proposed “small-cell” band from 3550 to 3650 MHz and its possible extension to 3700 MHz.

In June 2013, the Obama Administration announced new Administration spectrum initiatives, including directing Federal agencies to enhance the efficiency of their spectrum use, making greater capacity available for commercial networks, and funding research into spectrum sharing.

Table 1: United States Current and Future Spectrum Allocations

Frequency Band	Amount of Spectrum	Comments
700 MHz	70 MHz	Ultra-High Frequency (UHF)
850 MHz	64 MHz	Cellular and Specialized Mobile Radio
1.7/2.1 GHz	90 MHz	Advanced Wireless Services (AWS)-1
1.9 GHz	140 MHz	Personal Communications Service (PCS)
2000 to 2020, 2180 to 2200 MHz	40 MHz	AWS-4 (Previously Mobile Satellite Service)
2.3 GHz	20 MHz	Wireless Communications Service (WCS)
2.5 GHz	194 MHz	Broadband Radio Service (Closer to 160 MHz deployable.)
	FUTURE
600 MHz	Up to 120 MHz	Incentive auctions
1695-1710 and 1755 to 1780 MHz.	65 MHz	AWS-3. 1755 to 1780 MHz to be combined with  2155 to 2180 MHz. Spectrum sharing.
3.55 to 3.70 GHz	100 or 150 MHz	Small-cell band with spectrum sharing
Above 5 GHz	Multi GHz	Anticipated for 5G systems in 2020 or later timeframe