Can 5G Technology Affect Airplanes and Flights?

Another issue rumbling through the US is the upgrade of mobile networks to 5G and how the airline industry is worried about its potential interference on flights. Professor Henning Schulzrinne breaks down the debate and how the different business and government groups can work through the situation.


Currently, almost 42 million 5G mobile phones are used, and it is expected that over 100 million will be in the hands of Americans this year. What is 5G technology? Why should people care about it?

5G technology is the emerging fifth generation of cellular technology, now found on many smartphones and offered by all the major carriers. The wireless communications industry labels technical advances and changes by generation, from first-generation systems (1G) developed in the 1980s to the current fifth generation. Compared to the previous generation of technology, 5G can offer faster speeds to individual users and higher capacity overall for the wireless service providers. In the long term, it also has the capability to support specialized industrial applications. 5G also introduces some internal changes, not visible to customers, that make networks easier to operate.


What is the status of 5G in the US? Why isn’t it as widespread as it should be?

The big three service providers, AT&T, T-Mobile, and Verizon, have been upgrading their wireless networks for a few years, but it takes time and money to upgrade the tens of thousands of cell sites. Also, many smartphones are not capable of connecting to 5G networks, so the older 4G networks will be around for quite a while. The higher capacity promised by 5G requires new radio frequency allocations – and those new radio frequencies take time to allocate. Thus, the transition to 5G takes a while since you need all three things: new frequencies, new network equipment, and new devices.


How will 5G affect the speeds of cell phone service? How will it affect everyday life?

So far, 5G is mostly offering a somewhat faster download experience than 4G. For example, this may improve the video quality while watching movies on a cell phone. Also, longer-term, delays may decrease, making playing interactive games on mobile devices more enjoyable. Interestingly, carriers are also starting to use their 5G networks for home internet access, called fixed wireless access, thus providing competition to the cable companies and sometimes the local telephone company. (Obviously, two of the three wireless carriers are also local phone and internet companies.) Thus, the impact on most consumers has been fairly modest so far.


Why is it important to have 5G service?

As more consumers switch to phones capable of 5G service and use more data for applications, networks need to be upgraded to provide this capacity. 5G is the only realistic option to add more capacity to wireless networks.


How can 5G affect airplane frequencies? Why is the Federal Aviation Administration (FAA) concerned about it?

This is a classical collision of an old, but important, technology with a new one. The Federal Communications Commission (FCC) is looking to provide new radio bands, a range of radio frequencies, that 5G systems can use, so they auctioned a part of the spectrum that was only lightly used for some older satellite technology. All the major cellular providers have bought this spectrum at auction in early 2021, for more than 80 billion dollars, and are hoping to use it to increase their network capacity. The frequency band, called the C-band, happens to be ideal for 5G service – it offers high capacity, but still can cover a reasonably large geographic area from one cell tower.

But this band is adjacent to the frequency band used by altimeters, navigation instruments using radar carried by commercial aircraft. These altimeters provide very precise altitude information, telling the pilot how many feet above ground they are flying. They are primarily used for landing, particularly when visibility is poor. Clearly, a bad height-above-ground reading could be quite dangerous during approach. Unfortunately, the altimeters were designed when the frequencies below the radar frequency they use were pretty quiet. The 5G cell towers use much higher power, so the altimeters already installed may not be able to filter out these frequencies and thus get confused. Nobody seems to know exactly whether this affects all altimeters most of the time or is limited to a small number of altimeter models, and maybe even only under unusual circumstances. The FAA is concerned that these new cell towers will lead to misleading altitude readings and thus affect aviation safety. 

Currently, as a temporary fix, the carriers have agreed to turn off the C-band cell towers within about two miles of major airports.


You have been following this issue, what do you think should be done by the FCC and the FAA?

This dispute between federal agencies, the FCC and FAA, is unfortunate. We have very little trustworthy, neutral data on whether these cell sites would affect altimeter readings, even though these frequency auctions were well known to everyone since at least 2018. In general, the problem of devices being disturbed by radio signals outside their operating frequency range is not new. It occurs whenever one system relies on very faint signals, and a new “noisy” neighbor arrives – similar to having a subway, airport, or music club built next to a music recording studio. As in these acoustic cases, the noise-sensitive party may need to install additional sound insulation. More than a decade ago, a very similar issue arose for bands next to the GPS frequencies – and the problem still hasn’t been resolved completely.

Traditionally, the FCC has only regulated that radio transmitters stay within their assigned frequencies so that one radio station does not interfere with a station next to it on the radio dial. But then manufacturers build devices that rely on a quiet radio neighborhood, making it difficult to put these bands to better use, e.g., for cellular service. Thus, the FCC should get the authority to require devices to be sufficiently robust against neighboring noise with defined “loudness”, so that manufacturers cannot come back later and complain that new radio neighbors can’t move into the desirable neighborhood.

The FAA should have evaluated actual aircraft systems early on, as the proposal for the C-band auction was being discussed, rather than more or less waiting to raise safety objections when the new cell sites were about to be turned on. The FCC lacks the research capacity to do these experiments, while the FAA lacks the radio interference experience. 

As the radio spectrum gets more crowded, “not in my neighborhood” (NIMBY) will not work. We need to make radio “zoning” work – and make the zoning process sufficiently predictable so that this doesn’t devolve into arguments between federal agencies relying on paid consultants, with the confused public left to figure out whether it is safe to fly and carriers wondering whether they wasted their auction bids.

Bringing High-speed Internet to More Americans

Columbia Engineering professor Henning Schulzrinne unpacks President Biden’s $1 trillion infrastructure bill and its promise to expand broadband access for people in rural and low-income areas.

How Will the Infrastructure Bill Improve Internet Access for Americans?

Professor Henning Schulzrinne unpacks the infrastructure bill and how it will expand broadband access for Americans.

The $1 trillion dollar Bipartisan Infrastructure Deal will deliver $65 billion dollars to improve internet access. Currently, 30 million Americans live in areas where broadband internet is not available like in rural areas and lower-income urban areas. The plan is to build broadband networks, improve internet infrastructure, and help lower internet service cost. We asked Henning Schulzrinne, the Julian Clarence Levi Professor of computer science and an internet networks expert, how the bill will impact internet access.

Q: What is the current state of internet access in the US? Why is it important that the bill allots $65 billion to improve access for rural areas, low-income families, and tribal communities?

Internet access has two facets: availability and adoption. Currently, there is no precise data of how many homes have access to basic fixed internet service, defined as a speed of 25 megabits download. (That is much slower than most current cable or fiber offerings.) A recent effort using a variety of data sources estimates that about 93%of households could subscribe to basic broadband or faster, leaving about 14.3 million households without access except via expensive and unreliable satellite service or very slow DSL. But only about 77% of adults use the internet at home (“adoption”). Affordability is an important reason for the discrepancy between availability and adoption.

The bill is the first large-scale effort to address both availability and adoption; earlier efforts largely provided money to rural areas to build out broadband internet, about $5B a year, but did not address affordability except for the emergency broadband benefit program started in May 2021.

Q: How far behind is the US when it comes to broadband compared to the rest of the world?

Almost all large countries struggle with making high-speed broadband available to rural areas. But many other countries have lower prices and more competition for broadband service, maybe explaining why the United States ranks 16th out of 38 OECD countries. The United States ranks 13th worldwide on average broadband speed, but such comparisons can be difficult and the differences are not that large among the top 20 countries.


Q: Why is broadband not available in most rural areas?

Most rural areas have some broadband, typically using older technology based on phone lines (DSL = digital subscriber line). However, it can be quite slow and connections are often overloaded and unreliable. Only about 67% of rural households have access to higher speeds of 100 Mb/s that are typical in urban areas. The reasons are complex: cable companies provide most high-speed broadband in the United States, but have largely chosen not to build out in rural areas. Telephone companies have relied on their old phone lines to provide broadband service, with limited investment in modern fiber technology. Since houses are further apart and since disposable incomes are often lower, private investment in rural broadband has not been considered sufficiently profitable; thus, much of the rural broadband deployment has been subsidized by various federal programs. Many of these programs have been supporting broadband that is now considered obsolete.


Q: It also contains $1 billion for enabling the build-out of “middle mile” broadband infrastructure, what is this and how can it help?

The internet infrastructure can be roughly divided into the backbone network connecting major cities, middle mile networks going from those cities to smaller population centers such as county seats, and access or “last-mile” networks that connect homes to the internet. Many smaller communities do not have good fiber connections, or have only one expensive provider. Adding more regional middle mile networks allow smaller network operators to build out access networks, as such small operators cannot afford to build their own fiber network to the next large city.


Q: The bill offers an additional $2.75 billion for digital equity and inclusion efforts, which could end digital redlining. What is redlining? Do you think the bill can help with the issue?

Providers in urban areas have been accused of failing to upgrade slower broadband networks in lower-income urban areas. Competitors such as fiber providers often don’t build out new networks in such areas, either. The lower speeds and higher prices for such neighborhoods are referred to as digital redlining. It is not quite clear yet what kind of projects will be funded. There are promising ideas of providing free Wi-Fi in lower-income apartment buildings, for example.


Q: It seems that the pandemic has been helpful in revealing how inadequate broadband service is in the US. Can you talk about the key findings of your NSF Broadband Research 2020 Report and if the infrastructure bill will actually help achieve those goals?

The NSF Broadband Research Report emphasizes the need to consider measuring and addressing both availability and adoption, including providing training and devices, so the infrastructure bill offers many of the tools envisioned in the report. However, the report is largely about research questions and recommendations for facilitating such research, not policy mechanisms. Even with new, substantial funding, we have to make sure that the programs are effective and reach the right people. For example, the report recommends that all broadband agencies gather and release data as these programs are initiated so that we can learn from successes.


Q: How happy are you with the infrastructure bill? Do you think that it will help fast track the broadband situation in the US? Prior to its passing, how long do you think it would have taken the US to catch up?

The bill is really the first large-scale, all-in, and comprehensive attempt to finally address broadband availability and affordability. It is both a visionary and necessary step towards digital inclusion. My main concern is implementation and coordination. For example, the bill relies on private entities, from for-profit companies to electric cooperatives, to deploy broadband, but cannot force companies to build out everywhere or use the best long-term technology. Grants are made to states who may not have the institutional capacity to ensure that the most efficient organizations build out networks that will still be sufficient to meet local broadband needs 20 years from now. We want to avoid having to spend another few ten billion dollars of taxpayer money ten years from now, after all.

Since the effort is very state-centric, making it possible for researchers and public interest organizations to monitor and evaluate the build-out and digital inclusion efforts will be challenging. (My research group is currently attempting to analyze the existing, much smaller, subsidy efforts, run by two federal agencies, and finding it quite challenging to get a good picture of the impact.)


Q: What are the positive effects that you see will come out of this effort? 

Broadband has become a must-have infrastructure for any community, just like clean water or reliable electricity. For education, universal broadband will make it much easier to provide the same learning experience to everyone. Right now, teachers often cannot assign projects or homework that relies on internet resources since not all students have easy access. Continuing education and training will become a bit easier for adults looking to gain new skills. Rural areas lack access to specialists and mental health resources; telemedicine can bridge at least some of these gaps. Some rural areas located within maybe a hundred miles of major cities may be able to attract younger residents who can now work from home and only drive to their office occasionally. Many small businesses need reliable, high-speed internet to offer their goods and services.

That said, I would not expect to fix all societal challenges – broadband access is necessary and even helpful for education, health care and public services, but it is not a replacement for providing high-quality education, health care, and public services more generally.