Spectrum is the life-blood of wireless networks. In the quest to solve the 1000x mobile data challenge, spectrum is an important building block. We have introduced innovations to better utilize existing spectrum and access to new spectrum.
Given that spectrum is a finite resource, the industry is hard at work to utilize the available spectrum better and to identify opportunities to access more spectrum. There are primarily three approaches to make new spectrum available:
Higher bands is one of the options for new spectrum, and 3.5 GHz band is a prudent initial candidate. Because of its smaller coverage, this band is also emerging as a global choice for small cells. Parts of this band may be traditionally licensed and other parts through LSA.
Thanks to the industry’s relentless efforts, wireless technologies have been continuously evolving, offering ever higher efficiencies for the existing spectrum. Continuing on this path is the most obvious first step toward the 1000x goal. This means evolving HSPA+, LTE Advanced, DO Advanced, 1x Advanced, WCDMA+, and Wi-Fi to 802.11ac. These upgrades significantly improve capacity, data rates and user experience.
Small cells are essential to increase the utilization of existing spectrum since they enable much greater reuse of the same spectrum also used by the macro network. Thanks to the advanced interference management and techniques, the overall capacity increase enabled by small cells grows as the densification of the small cell deployment increases.
Although traditional licensing is the main solution, it may not always be feasible. Some spectrum holders, such as government users, may not be using the entire allocated spectrum in every part of their geographic boundaries on a 24x7 basis. For example spectrum for military radar may have been allocated countrywide , but the radar operations may only be at certain places such as coastline. In such cases, Licensed Shared Access (LSA) is an ideal approach for 3G/4G operators to access the underutilized spectrum in a mutually beneficial way. It proposes a new regulatory framework to share the spectrum in terms of time or location on an exclusive basis, without interfering with the incumbent’s operations.
Everybody wins with ASA—Incumbent spectrum holders can monetize their underutilized spectrum, 3G/4G operators can get new spectrum for exclusive use, ensuring reliability, and predictability for long time investments.
For operators solving the 1000x challenge, licensed spectrum is the foundation. Equally important is leveraging all of the available spectrum, including unlicensed. The best way to make use of unlicensed spectrum is to aggregate it with a licensed LTE anchor.
There are two solutions for aggregation: LTE – Wi-Fi link aggregation, for existing and new carrier Wi-Fi utilizing both 2.4 GHz and 5 GHz; and LTE in unlicensed (LTE-U) for new small cells utilizing 5GHz. Many operators will do both.
Mobile wireless has spanned across many technologies (3G/4G/Wi-Fi), across several bands, and across different licensing models (licensed, unlicensed, and LSA). Aggregating all the available spectrum resources enables operators to increase overall network capacity and to provide best possible mobile broadband experience to users.
Carrier aggregations defined in EV-DO, HSPA+, LTE allows combining different bands of the same technology, as well as across licensed and unlicensed spectrum (for LTE Advanced). Supplemental Downlink (SDL) is a special case of carrier aggregation enabled by HSPA+ and LTE Advanced. It aggregates unpaired spectrum with the downlink of paired spectrum substantially increasing downlink capacity. SDL is on track to be commercially deployed globally (e.g. L-band/1400 MHz in Europe & 700MHz band in the US).