Tag Archives: D2D

Have We Given Up on Expanding Rural Cell Coverage?

The number one concern I hear from most rural counties today is no longer broadband connectivity, but the availability of cellular connectivity. While there may be a few exceptions, I don’t know of any rural counties that have good cellular coverage. All that differs among counties is the degree to which they have poor coverage.

At one point, the FCC had a plan to subsidize more rural cell towers that it labeled as the 5G Fund for Rural America. In August 2024, the FCC adopted preliminary auction rules for distributing up to $9 billion to support new rural cell towers, while also issuing an NPRM that asked for industry feedback on several issues related to the new plan. This was going to be funded out of the Universal Service Fund, in what seems like a replacement use for the second round of RDOF that never happened.

Chairman Carr dissented from the 2024 FCC order, saying that he supported the idea of a reverse auction to build more rural cell towers, but he thought it was premature to announce the new plan until the FCC knew more about the disposition of the $42.5 billion in BEAD grants. He thought it was vital that any new rural towers have access to fiber.

Several big things have happened since August 2024. BEAD got delayed when the new administration completely changed the rules and made the states start over. The FCC has also decided to reexamine the Universal Service Fund from top to bottom, and if you read between the lines, the agency doesn’t seem to be a big fan of ongoing rural subsidies. Congress is also supposedly examining a major rework of the Universal Service Fund and said recently they should be able to propose specific legislation soon.

But the biggest change is that there is suddenly huge amounts of money being poured into creating a satellite-based cellular industry. The folks behind that effort are making claims that D2D (direct-to-device) technology will solve the rural cellular issue since everybody will have cell coverage. There are a lot of players suddenly in this space. Not surprisingly, SpaceX / Starlink already has hundreds of satellites in orbit and was recently approved to launch 15,000 satellites. AST SpaceMobile is partnering with AT&T and Verizon. Globalstar originally pioneered Apple’s SOS emergency test service and was recently acquired by Amazon, which recently applied for licenses for 5,105 satellites. Lynk Global has partnered with more than 45 cellular companies worldwide. EchoStar and Viasat have also announced plans to enter the market.

Today’s blog asks if the FCC is now assuming that the commercial sector will take care of the rural cellular issue so they can wash their hands of the issue. I find D2D to be intriguing, but there are still a lot of unanswered questions about D2D’s ability to substitute for local cellular service:

  • Are the D2D providers really aiming to compete where there is no coverage today? SpaceX just paid an astonishing $8 billion for 800 MHz spectrum from Grain Management that is intended for D2D service. But this spectrum is intended to be used at terrestrial towers to reach customers, with the backhaul for the service provided by satellite. This might create a new cellular competitor in urban and suburban markets (or this might be more intended to bring competition to parts of the world where cellular is the only broadband technology). But this application won’t reach any rural customer who is already within range of a cell tower.
  • Can’t Work Indoors. A cellphone transmits at under 0.5 watts of power – the maximum power level set by the FCC. Cell signals lose from 50% to 90% of the signal strength when passing through a wall. While that usually is enough power to reach a cell tower located within 2-3 miles of your house, it’s probably never going to be enough power to reach a satellite.
  • Receiver Limits. Starlink is now achieving data speeds up to 300 Mbps download for home broadband. However, speeds will be far less for an outdoor cellphone due to the tiny size of the antennas. Receivers for Starlink range from 11.75 X 15.7 inches for the Starlink Mini to 22.7 X 20.1 inches for the higher-performance receiver. The typical cellphone has a receiver of around 6.5 X 7 millimeters, meaning that even the Starlink Mini receiver has 2,600 times more surface area for receiving a signal from the satellite than a typical cellphone.

It’s already clear from early tests that this technology is wonderful for providing a connection to 911 for somebody who is outdoors. It seems to work for voice calls. But that’s a far cry from this being a technology that would make rural cell coverage equivalent to urban cell coverage. It’s hard to see this supporting websites and videos, and even so, only outdoors. I fear D2D will deliver ‘good-enough’ connections to allow regulators to decide they don’t need to deal with the issue of rural cellular coverage. But folks who live in rural areas will understand the differences and won’t have much better coverage than they have today.

Using Unlicensed Spectrum for D2D

The FCC recently adopted a Notice of Proposed Rulemaking that asks if it makes sense to give satellite providers access to unlicensed WiFi spectrum to support Direct-to-Device cellular service. The NPRM specifically looks at the use of 2.4 GHz and 5.8 GHz. The NPRM specifically rejected the idea of using 900 MHz for satellite service.

The FCC seems all-in on the idea of satellite cellular service and has taken a number of steps recently that favor this budding industry. However, Commissioner Anna Gomez, the only Democratic commissioner, voiced concern about how using this spectrum might affect the many devices that rely on WiFi spectrum today.

It seems like a valid concern. WiFi has turned out to be the most important and valuable spectrum we have. The whole broadband world seems to run off WiFi modems in homes and businesses. We have outdoor WiFi hotspots to provide outdoor broadband access. WISPs largely rely on WiFi spectrum to deliver fixed wireless broadband to rural homes.

It’s easy to understand why the FCC would consider this. The agency is facing huge demand for spectrum from multiple industries. Cellular carriers want more spectrum to get ready for the upcoming introduction of 6G. Cellular carriers also need to feed the rapidly growing FWA home broadband industry. Satellite companies have an insatiable demand for spectrum since they envision eventually launching hundreds of thousands of broadband satellites. And now, the satellite cellular companies want to blanket the Earth with competing networks to deliver outdoor cellular service, and the Direct-to-Device (D2D) carriers have already requested approval to launch tens of thousands of satellites to provide outdoor cellular service. There are more requests for spectrum than what is available, so the FCC seems willing to raid the public WiFi bands to support a new industry.

This is not the first time that the FCC has allowed others to share WiFi spectrum. A number of years ago, the FCC allowed cellular carriers to use WiFi spectrum in busy markets. I recall a report from university students in Chicago who had documented that cellular usage of WiFi had killed outdoor WiFi on their campus. I don’t know if cellular companies are still dipping into WiFi now that they have been able to get more spectrum, but this was a failed effort that favored the carriers over the normal users of WiFi.

What seems to be different today is that the FCC is unabashedly pro-satellite. They seem to be giving satellite companies everything they ask for. It’s not unusual for regulators to make it easy for new technologies – the FCC took a hands-off approach to the creation of the Internet. But there seems to be a lot of risk in allowing satellite companies to broadcast WiFi from space. This idea is clearly favoring satellite carriers over WISPs.

I talked to several wireless engineers about the proposed use of WiFi spectrum, and they all voiced concerns. The satellites would blanket the countryside with new WiFi spectrum. The engineers told me that it is impossible for this to be completely neutral for a WISP. Every outdoor receiver will perceive the new use of the spectrum as interference. They said there was no way to tell how bad this might be without trying it, and that sounds like a scary experiment if it turns out that the impact is severe. It’s easy for the FCC to allow a new use of spectrum, but it’s unlikely that it would be undone quickly if there is a problem.

This is out of character for the historically slow and cautious approach that the FCC has always taken with spectrum ideas. And that’s even more the case when we’re talking about WiFi spectrum, which has proven its value many times over.

Is Satellite Cellular a Competitive Threat?

It seems that one of the hottest topics in the industry is Direct-to-Device (D2D) cellular service that can bypass terrestrial cell towers and connect cellphones directly to satellites. I’ve already seen claims being made that D2D technology will solve the rural cellular issue since everybody will have cell coverage. Today’s blog looks at some of the reality behind these claims.

There are a lot of players suddenly in this space. Not surprisingly, SpaceX / Starlink already has hundreds of satellites in orbit and plans for 15,000. AST SpaceMobile is partnering with AT&T and Verizon. Globalstar originally pioneered Apple’s SOS emergency test service and was recently acquired by Amazon, which recently applied for licenses for 5,105 satellites for D2D. Lynk Global has partnered with more than 45 cellular companies worldwide. EchoStar and Viasat have also announced plans to enter the market.

Basic Technology. The satellites will circle at heights between 200 and 550 miles above Earth and will be traveling at 17,000 miles per hour. At least for now, nobody has figured out how to hand off calls between a satellite and terrestrial cellular network. There are some limitations for D2D that are largely defined by physics.

  • Can’t Work Indoors. Your cellphone transmits at under 0.5 watts of power – the maximum power level set by the FCC. Cell signals lose from 50% to 90% of the signal strength when passing through a wall. While that usually is enough power to reach a cell tower located within 2-3 miles of your house, it’s not nearly enough power to reach a satellite.
  • Receiver Limits. Starlink has been achieving data speeds up to 300 Mbps download for home broadband. Expect speeds to be far less for a D2D due to the much smaller antenna surface area in a cellphone compared to a Starlink receiver dish. In general, the larger the size of the antenna, the more bits that can be gathered. Receivers for Starlink range from 11.75 X 15.7 inches for the Starlink Mini to 22.7 X 20.1 for the higher-performance receiver. The typical cellphone has a receiver of around 6.5 X 7 millimeters, meaning that even the Starlink Mini has 2,600 times more surface area for receiving a signal from the satellite than a typical cellphone.
  • Area Speed Coverage Limits. The planned coverage area for the next generation of D2D Starlink satellite is around 45 square miles. The newer satellites will be using massive adjustable antenna beams along with 40 to 65 MHz channels. This means that a single data stream from a satellite will have an overall data capacity between 40 and 150 Mbps download, depending on the spectrum being used. Starlink is planning on 16 simultaneous full-power beams from the next generation D2D satellites. The challenge is that this spectrum must be shared among all users inside a beam footprint. That means a maximum of 2.4 Gbps of bandwidth to share in a 45 square mile area – a minuscule amount of bandwidth compared to what can be delivered by cell towers serving the same area. This is compounded by a limitation on the simultaneous number of users that can be connected at the same time.

What does this all mean from a practical perspective? The D2D satellites will be able to connect to a large number of people who are outdoors, within the overall limitation of the number of simultaneous people that can be connected at one time. We won’t know until somebody shows us what this will mean for connecting a lot of people in a small area, like at a rural rock concert.

Early trials have shown that D2D has some capacity for making a connection to a moving vehicle. This is never going to be as guaranteed as when standing outdoors, and it will likely depend on the type of vehicle and the speed being driven.

D2D is not going to work directly indoors. It’s possible that somebody will develop an outdoor receiver that can bounce a signal to go in through a window. It would make sense to do this in conjunction with something like a Starlink receiver.

It’s hard to envision D2D as a standalone cellular service other than possibly for the rare person who spends most of their time outdoors.

To be fair to the industry, at least for now, the big D2D providers aren’t touting it as a standalone cellular service. They are talking about this being an add-on to normal cellular plans. This doesn’t make much sense in urban areas where normal cell coverage is already ubiquitous and strong. But this could be an interesting additive to a cell plan for folks who either live or travel a lot in rural areas. It’s a cool technology, but a lot of the excitement could be empty hype, which seems to be the norm for most new technology products.

There is only one statistic that is really going to matter for D2D, which is the number of people willing to pony up a monthly fee to use it. The one thing going for the new technology is that there is a lot more serious demand for any kind of cellular coverage in the third world than there is in the rural U.S. Maybe that’s the real market they are shooting for.

The Evolution of 5G

Technology always evolves and I’ve been reading about where scientists envision the evolution of 5G. The first generation of 5G, which will be rolled out over the next 3-5 years, is mostly aimed at increasing the throughput of cellular networks. According to Cisco, North American cellular data volumes are growing at a torrid 36% per year, and even faster than that in some urban markets where the volumes of data are doubling every two years. The main goal of first-generation 5G is to increase network capacity to handle that growth.

However, if 5G is deployed only for that purpose we won’t see the giant increases in speed that the public thinks is coming with 5G. Cisco is predicting that the average North American cellular speed in 2026 will be around 70 Mbps – a far cry from the gigabit speed predictions you can find splattered all over the press.

There is already academic and lab work looking into what is being labeled as 6G. That will use terabit spectrum and promises to potentially be able to deliver wireless speeds up to as much as 1 terabit per second. I’ve already seen a few articles touting this as a giant breakthrough, but the articles didn’t mention that the effective distance for this spectrum can be measured in a few feet – this will be an indoor technology and will not be the next cellular replacement for 5G.

This means that to some degree, 5G is the end of the line in terms of cellular delivery. This is likely why the cellular carriers are gobbling up as much spectrum as they can. That spectrum isn’t all needed today but will be needed by the end of the decade. The cellular carriers will use every spectrum block now to preserve the licenses, but the heavy lifting for most of the spectrum being purchased today will come into play a decade or more from now – the carriers are playing the long game so that they aren’t irrelevant in the not-too-distant future

This doesn’t mean that 5G is a dead-end, and the technology will continue to evolve. Here are a few of the ideas being explored in labs today that will enhance 5G performance a decade from now:

  • Large Massive Network MIMO. This means expanding the density and capacity of cellular antennas to simultaneously be able to handle multiple spectrum bands. We need much better antennas if we are to get vastly greater data volumes into and out of cellular devices. For now, data speeds on cellphones are being limited by the capacity of the antennas.
  • Ultra Dense Networks (UDN). This envisions the end of cell sites in the way we think about them today. This would come first in urban networks where there will be a hyper-dense deployment of small cell devices that would likely also incorporate small cells, WiFi routers, femtocells, and M2M gateways. In such an environment, cellphones can interact with the cloud rather than with a traditional cell site. This eliminates the traditional cellular standard of one cell site controlling a transaction. In a UDN network, a cellular device could connect anywhere.
  • Device-to-Device (D2D) Connectivity. The smart 5G network in the future will let nearby devices communicate with each other without having to pass traffic back and forth to a data hub. This would move some cellular transactions to the edge, and would significantly reduce logjams at data centers and on middle-mile fiber routes.
  • A Machine-to-Machine (M2M) Layer. A huge portion of future web traffic will be communications between devices and the cloud. This research envisions a separate cellular network for such traffic that maximizes M2M communications separately from traffic used by people.
  • Use of AI. Smart networks will be able to shift and react to changing demands and will be able to shuffle and share network resources as needed. For example, if there is a street fair in a neighborhood that is usually vehicle traffic, the network would smartly reconfigure to recognize the changing demand for connectivity.
  • Better Batteries. None of the improvements come along until there are better ‘lifetime’ batteries that can allow devices to use more antennas and process more data.

Wireless marketing folks will be challenged to find ways to describe these future improvements in the 5G network. If the term 6G becomes associated with terabit spectrum, marketers are going to find something other than a ‘G’ term to over-hype the new technologies.