Four paradigms for spectrum sharing
Spectrum sharing looks beyond exclusive-license models for spectrum use
Spectrum is a finite resource, and regulators and the wireless industry are always looking for ways to open up additional bands for wireless service use in order to address capacity issues. However, the general consensus is that at this point the low-hanging fruit, as it were – the spectrum that had relatively few, relatively easy to move incumbents – has been picked. Carriers may well get more spectrum, but much of it may not be spectrum that they can purchase for exclusive use.
“I think this area is, almost inevitably, becoming very hot and interesting, because it is hard to imagine how, given all of the spectrum demands that are already in front of us, as well as those that we know are coming, how we manage to do that under the old, static model of spectrum management,” said Kalpak Gude, president of the Dynamic Spectrum Alliance.
Here are four paradigms for spectrum sharing:
Unlicensed spectrum. The sharing of spectrum resources isn’t a new concept: unlicensed spectrum, for instance, supports different technologies in the same band as a matter of course. The unlicensed spectrum concept will continue to be utilized, but it is also changing and becoming more important in wireless operators’ network plans — such as in the case of LTE operating in unlicensed spectrum at 5 GHz. The cellular and Wi-Fi industry spent more than a year debating acceptable coexistence mechanisms for the use of LTE in unlicensed, hashing out the differences between the listen-before-talk approach taken by Wi-Fi and LTE License-Assisted Access and a duty-cycling strategy taken by Qualcomm, Verizon and other backers of LTE-U. T-Mobile US and AT&T are both testing LAA, and T-Mobile US expects to eventually enable LAA in all new small cells.
User prioritization (and eventually preemption) within licensed bands. This paradigm is playing out in the case of the First Responders Network Authority: AT&T won the $6.5 billion contract to build out a national, public safety broadband network in Band 14 for the First Responders Network Authority. As part of that deal, AT&T can make use of the 20 megahertz of spectrum for secondary, commercial users – but it has to ensure that public safety users get priority and eventually, preemption of any commercial users in the band. Although some level of paid prioritization of public safety users has been available through the carriers, FirstNet aims to go beyond what has been available to users on purely commercial wireless networks to ensure that first responders have network access whenever they need it, even during congested emergency situations. AT&T has said that it expects prioritization of public safety users to be implemented on its network by the end of this year — across all of its bands, not just the Band 14 spectrum — and Verizon is working on that feature for public safety users as well.
Dynamic spectrum sharing as a licensing approach. Perhaps the most eagerly anticipated spectrum sharing arrangement is the one at 3.5 GHz, or the Citizens Broadband Radio Service band. The framework is a three-tiered system with varying levels of priority and both licensed and unlicensed access. Incumbent naval radar systems on ships that travel along the coasts and into port cities, wireless Internet service providers and fixed satellite providers must be protected as part of the sharing arrangement. This system is enabled via a combination of a database-centric Spectrum Access System and RF sensing, according to Lee Pucker, CEO of the Wireless Innovation Forum – one of the organizations that has been backing the development of an ecosystem at 3.5 GHz.
CBRS is seen as a major opportunity for IoT deployments and private LTE networks, and development is ramping up with various tests and trials ongoing from companies including Huawei and Comcast, Google and others.
Baked in to future “5G” systems. Multiple radio access technologies, or multi-RAT, is seen as one of the critical capabilities for next-generation, 5G systems. As a 2015 research paper on 5G architectures put it, “cellular-to-Wi-Fi offloading, the standard modus operandi of recent years, is … shifting towards a true integration of both technology families. Users in future 5G systems will thus likely be able to use 3GPP, IEEE, and other technologies simultaneously, so as to maximize their quality of experience.” That is expected to happen for internet of things devices as well, with network slicing supporting a multi-RAT radio access layer. 5G is envisioned as able to take advantage of whatever radio resources are most efficient to serve the needs of the user and/or device.
In 5G systems, spectrum sharing capabilities are being built in from the ground up, according to Dean Brenner, senior VP of government affairs for Qualcomm.
“We’re going to continue to get licensed spectrum, bring new licensed bands online where you have exclusive access and where these problems can be avoided. That always has been and always will be the industry’s top priority and the easiest paradigm to deal with,” said Brenner. “However, the world we live is in not one where that’s going to be the only paradigm, and you’ve got to be able to deal with the others.”