The telecoms industry is gearing up for the rollout of 5G in the next couple of years, which is expected to provide Internet connections 40 times faster and with at least four times more coverage worldwide than current 4G connectivity. Delivering on these expectations requires a cost-effective and reliable means of providing connectivity on a massive scale, and Internet service providers (ISPs) across the globe are weighing their options for deploying 5G as quickly and efficiently as possible.
Where 4G was a pure mobile play, it seems increasingly likely that 5G will be initially introduced over fixed wireless. This is because fixed wireless currently offers the greatest commercial value for 5G technology, providing reliable, high-performance connectivity that can be established with relative ease and at a low price point in densely populated areas.
Verizon has voiced its goal of being the first U.S. company to roll out 5G technology and, earlier this year, CEO Lowell McAdam stressed that the company’s focus is on fixed wireless rather than mobile, as it offers “the return on capital you need.” This logic has also resulted in U.S. Cellular and Nokia testing 5G technologies together over fixed wireless, as the companies look to play a key role in the introduction of the technology across North America.
5G on trial
However, given the scarcity and cost of the precious cellular frequencies, carriers are looking to increase capacity for 5G over fixed wireless by hunting for alternative spectrum. The critical dialog now is about which bands will be a good match technically for these types of fixed applications, and of course, which is the most cost effective.
A number of interested parties have pushed the FCC to progress its plan to open up additional high-frequency, mmWave spectrum for 5G. The commission first allocated high-frequency spectrum for 5G earlier this year, and last month it announced a Further Notice of Proposed Rulemaking that would open an additional 17.7GHz of spectrum for licensed fixed and mobile use.
In October 2016, U.S. Cellular and Nokia completed tests on 28GHz spectrum in both an outdoor setting and indoors in a lab. The outdoor trial involved a point-to-point, clear line-of-sight scenario between a base station and user equipment, with ‘real world environment’ impairments such as dry wall, windows and metal panels introduced. However, it is unlikely this same success could be replicated in a densely populated urban setting, where manmade infrastructure and foliage are more widespread and impair high frequency mmWave signals. Furthermore, in higher frequency bands, it is more likely that weather will negatively impact signal propagation. As a result, using the mmWave spectrum, homes and businesses could experience limited connectivity.
At longer distances, without being able to penetrate barriers like foliage, and with limited ability to generate multi-path, line-of-sight becomes a virtual necessity with mmWave band connectivity. The only viable solution is to shorten links to overcome environmental challenges, resulting in a much denser constellation of base stations, closer to households. This in turn will significantly increase the cost of covering an area. Furthermore, the current cost of the equipment in the 28GHz spectrum is over $700 per subscriber due to expensive high frequency RF components and requires professional installation. This begs the questions of whether the mmWave bands are appropriate for delivering 5G.
The sub-6GHz spectrum solution
Fortunately there is an alternative. Rather than using mmWave channels that are not proven in dense urban areas, ISPs should switch their focus to reusing a small amount of spectrum in the 6GHz spectrum, used by Wi-Fi. Over 14,000 wireless ISPs globally have quietly proven in rural areas where the sub-6 GHz bands are extremely effective at delivering fixed wireless services at long distances.
The 5Ghz spectrum has traditionally been subject to potential interference from Wi-Fi operators in the same frequency bands. However, by using GPS+GLONASS to synchronize transmissions across the network, a single channel can be reused in a given geography. This means it will not suffer from the self-interference typically seen in Wi-Fi and FDD microwave deployments as more radios are added to increase network capacity.
MIMO (multiple input, multiple output) technology can also help solve the problem of interference by using a large number of antennae at the base station, allowing it to serve many users in densely populated urban areas while staying in the confines of the radio spectrum. This approach results in improved signal propagation and near-line-of sight performance, as well as considerable cost savings; the current cost of the subscriber equipment in 28GHz is more than seven times that of sub-6GHz equipment.
There is also potential to utilize the 3.55-3.70GHz in the deployment of 5G services, leaving as much spectrum available to Wi-Fi as possible. The FCC has already established regulations for the 3.5GHz band (the Citizens Broadband Radio Service band), which will make 150MHz of spectrum available for ISPs. Google is actively conducting experiments in the 3.5GHz band in up to 24 areas in the U.S., and preparing for the new SAS spectrum sharing database to go live in early 2017. With new innovations in fixed wireless spectrum re-use, using the 3.5GHz band could further extend the value of the sub-6GHz spectrum and raises geocapacity to unprecedented levels.
5G adoption will be vital in order to support the increasing demand for data and connectivity, particularly in light of the expanding IoT. Despite ongoing debate, it is likely that fixed wireless for 5G within the sub-6GHz spectrum will offer the best commercial model for operators. Unlike mmWave spectrum, advances in technology mean 5G can be reliably delivered in built up urban areas, and the costs of equipment and deployment are considerably lower than those incurred deploying 5G in mmWave spectrum. Capacity is a major challenge for wireless networks, and a solution will only come about with continued trialling of technologies and methods, ultimately creating an efficient 5G infrastructure which will serve all environments on a global scale.
About the Author
As Co-founder and Chief Product Officer of Mimosa, Jaime is driving a disruptive wireless alternative solution for gigabit fixed Internet and Wi-Fi applications. With his prior experience as CTO of 2Wire (acquired by Pace), Jaime pioneered delivering IP services to the home over Fiber and xDSL.
At Mimosa, he now aims to surpass the capacities of legacy wireline technology and deliver multi-gigabit wireless access solutions at a fraction of the cost. Previously, he headed Product Management at Polycom, and Zhone Technologies. Jaime holds a BSCE from the University of California, Irvine, USA.
Edited by Alicia Young