Channeling TV White Space (TVWS) and Spectrum Sharing —
During the COVID-19 pandemic, my family and I moved to a beautiful country town in the northeast of Colombia where my father has a small farm. It is a nice place to stay during the quarantine and we feel extremely lucky to be here. However, despite the lovely landscape, the fresh air, and the calm, broadband Internet access is a huge issue.
Fiber optic networks and microwave links are not an option here because the users in this region are farmers and countryside households that require an affordable price and not a business-oriented solution. For now, mobile coverage using 2G and 3G technologies is the only alternative; which, at best, is enough to receive WhatsApp messages and check some emails. But it cannot sustain video calls or common telework platforms like GoToMeeting, Microsoft Teams, Zoom, etc., making working from home a big challenge.
This has been an interesting experience, and I have learned a lot about local companies who are trying to provide a better Internet service in rural regions like this one. Having spoken to multiple Internet Service Providers (ISPs), I have discovered many small, but very active, companies working to provide Internet to local households.
However, when I asked these ISPs about the TV White Space (TVWS) technology, they had not heard about it — despite TVWS regulations being in place in Colombia since 2017.
Currently, most of these ISPs connect urban users via a fiber node that spans throughout the town. Beyond that, they use unlicensed frequencies in the 5 GHz band to reach the surrounding farms and rural houses. Unfortunately, this band is limited to locations with line of sight (LOS), which does not allow the service to be offered to all potential users in the area.
When I described the capabilities of the TVWS technology, it opened their eyes! Such technology would finally allow them to reach people that are currently unserved because the links they use in the 5 GHz band simply don’t reach those places.
Questions About the TVWS Ecosystem
In this article, we cover the situation that we — among millions — are facing, as well as answering some of the most frequently asked questions among regulators regarding the TVWS ecosystem:
• How vast is it?
• How popular is the technology?
• What developments are being made?
A Growing Lineup
TVWS works on the VHF and UHF television bands — although most of the equipment is primarily developed for the UHF band (470 to 690 MHz). These frequency bands are especially good for rural areas with low to medium population densities as larger areas can be covered with less links (compared to other deployments on higher unlicensed bands like 3.x and 5.x GHz), which significantly reduces the deployment costs. TVWS links are usually optimal up to a 10km radius, but they can reach larger distances when deployed in clean radio frequency (RF) environments.
It’s hard to believe that just a couple of years ago, the maximum throughput of a TVWS link was about 30 Mbps; now, some TVWS radios can reach up to 186 Mbps. This evolution is due to the dedication and effort that TVWS equipment manufacturers have put into this technology, and it is driven by an ecosystem of customers and suppliers that keeps growing.
Currently, there are at least 10 TVWS equipment manufacturers who are fully committed to the technology. It is these equipment suppliers, along with the increasing number of countries adopting regulations for TVWS, that are causing the ecosystem to grow at an accelerated pace.
The evolution of TVWS has been made possible by the implementation of technological enhancements that were initially envisioned for other technologies like Wi-Fi and LTE. Three of them are highlighted here:
The creation of bigger bandwidth channels through channel bonding, which allows multiple contiguous TVWS channels to work as a single channel. Most manufacturers allow four 6MHz channels to be bonded for a total of 24MHz bandwidth. Some manufacturers are also working on channel aggregation capabilities, which allow non-contiguous channels to operate also as a single larger bandwidth channel.
The enhancement of these radios to work on higher modulation and coding schemes, with some of the newer radios reaching up to 256QAM.
The implementation of MIMO capabilities using multiple transmission and reception streams has been another key factor to increase capacity. Some of the existing radios allow 2×2 MIMO, and future versions are expected to include 4×4 MIMO capabilities.
In the future, we expect other technological enhancements like beamforming and massive MIMO to be implemented on TVWS, which will result in even more robust radios with higher throughputs.
The FCC in the United States oversees the deployment, fair use and maintenance of safe and reputable technology. The FCC certification is required before any TVWS device enters in circulation in the US and is widely recognized in other countries that have adopted TVWS regulations. Further afield, other governing bodies, such as ETSI, operate in different regions to continue the adoption of such standards and ensure the full-coverage protection of incumbents all over the world. The compliance with these regulations is best practice for all solutions providers to ensure the avoidance of electromagnetic interference between transmission signals.
Traditionally, there have been only 2 approaches to spectrum management:
Approach #1. Licensed usage requires every user to have a license for a particular frequency band or geographic area, including satellite and public safety communications, as well as mobile operators delivering cellular networks.
Approach #2. Unlicensed usage where an entire frequency band is reserved exclusively for unlicensed operations. For example, the 2.4 and 5 GHz bands where Wi-Fi, Bluetooth, and other unlicensed devices operate stand as an existing example of unlicensed usage.
Today, there are several approaches to spectrum management that include sharing between different types of services, blurring the line between the 2 traditional methods.
While it is still desirable to have bands dedicated to unlicensed access, and some applications and use cases require exclusive or priority access to spectrum, it is difficult to find sufficient spectrum to support this. This is due to the vast number of users currently operating across all frequencies, and the complex and onerous process of clearing or relocating users. Spectrum sharing technology can be used to combat this challenge, enabling spectrum to be shared efficiently among users while simultaneously protecting incumbents.
New spectrum access options must be considered for Wireless Internet Service Providers (WISPs) that are offering rural broadband connectivity. Such WISPs are dependent on having sufficient access to spectrum, as well as to well-developed equipment ecosystems.
New LTE and 5G networks can also benefit from the use of spectrum sharing technology, which helps to increase access to spectrum for existing Mobile Network Operators, and to support new business cases that have previously had limited spectrum access options.
By building the right regulatory framework for spectrum sharing and creating good operating conditions for incumbents without interference, more users are able to benefit from spectrum access. Applicable to both residential and enterprise use cases, this allows different providers and companies to contribute to the network, connecting more people in different environments, and facilitating the expansion of a richer spectrum ecosystem.
Our society is now so dependent on wireless technology that we must act to adapt it to our ever-evolving lifestyles. The DSA advocates for a range of different options to do that very thing.
A New Age of TV
Today, dynamic spectrum sharing offers far more efficient options for providing opportunities to access frequency bands. In the CBRS framework, the dynamic aspect refers to the nature of the incumbent use, which changes depending on time and location, requiring new users to adapt to fluctuating conditions and to access the spectrum under an opportunistic scheme. Dynamic users are harder to protect than static users, requiring different techniques to effectively protect them while still allowing new users in the same band.
One such technique involves the detection of incumbents through the use of sensors. Once incumbent use is detected, spectrum sharing systems can instruct new users to relocate to a different part of the band on a temporary basis to avoid interference with incumbents.
New entrants can also benefit from dynamic sharing of spectrum. At times and in locations where incumbents are not using spectrum, spectrum sharing systems can assign it to others. Thus, the dynamic aspect of spectrum sharing not only protects incumbents, but also allows new entrants access when and where they need it, making far more efficient use of spectrum and eliminating waste.
Unlicensed technologies, such as Wi-Fi and TVWS, are mature and continue to support vast numbers of users on an affordable basis. However, there are other types of spectrum sharing that enable new opportunities. Regional context is important for judging which is most appropriate for a particular country or frequency band.
For example, frequency bands which are heavily occupied in the US, such as the television broadcast bands, might host only a few national broadcasters in other countries. While many bands are being used extensively in big cities, that same spectrum might be readily available in rural or isolated regions. So long as the incumbent users are protected, spectrum sharing technologies can open large amounts of spectrum to new users.
Regulatory frameworks that involve spectrum sharing must be flexible and adaptable for future changes of both incumbent and new users. As the influx of data and cutting-edge devices is projected to boost traffic being carried by Wi-Fi from 50% to 70%, we risk facing a shortage or bottleneck of spectrum. At the same time, in order to achieve the low latency, high power capabilities that are being imagined for the 5G era, access to spectrum in the entire 6 GHz band will be urgently needed. Shared spectrum solutions are available today that can help meet these challenges.
The DSA is thrilled to see the movement towards far-reaching deployment realized as more companies become recognized and dynamic spectrum access technology is driven into the mainstream. We congratulate members and non-members alike for contributing to this breakthrough journey, and we look forward to seeing spectrum made more accessible as regulations progress as a result of their help in facilitating its implementation and adoption.
By Martha Suárez and Hender Jimenez
Hender Jimenez has over 20 years of experience in wireless telecommunications, having held planning, design, research and project management positions at companies such as Ericsson, T-Mobile, Sprint, and Claro. He is currently a Technical Program Manager at the Microsoft Airband Initiative where he researches new technologies aimed to reduce the digital divide, and provides technical support to Internet service providers and regulators around the world regarding hybrid wireless networks. His research efforts also focus on digital transformation and data analytics with an emphasis on business intelligence and geospatial applications.