What spectrum is

Every wireless device, from your phone to your car key fob, communicates by sending radio waves at particular frequencies. The full range of usable radio frequencies is called the spectrum.

That collision is called interference, and avoiding it is the whole point of managing spectrum: deciding who gets which lanes, where, and how loudly they can transmit.

Everyday examples: Wi-Fi and Bluetooth

Wi-Fi and Bluetooth use unlicensed bands, mainly 2.4 GHz, plus 5 GHz and 6 GHz for Wi-Fi. Nobody owns these lanes. Anyone can use them, as long as their equipment is certified and stays at low power. That's why your neighbor's router can slow down yours: you're all sharing the same lanes, and the low power limits keep the crowding local.

The basic trade-off: reach versus capacity

Frequency changes how a signal behaves:

• Lower frequencies (below 1 GHz) travel farther and pass through walls, trees and hills better. But they carry less data.
• Higher frequencies carry much more data. But they fade faster with distance and are blocked more easily.

How big is a band?

A band also has a width, the number of lanes it has. The wider the band, the more data it can carry at once. There's far more room for wide bands higher up the dial, which is the real reason higher frequencies carry more data. So when this post says a company holds "65 MHz", that's a width: how many lanes it owns.

Almost every decision in this post comes back to those two things: where a band sits, and how wide it is.

If spectrum is a shared highway, someone has to paint the lanes and hand out the keys.

Who decides who uses which frequencies

In the United States, two agencies divide the spectrum:

• The FCC (Federal Communications Commission) manages spectrum used by businesses, consumers, and state and local governments.
• The NTIA (part of the Commerce Department) manages spectrum used by the federal government, such as military systems, aviation radar and weather satellites.

When a band moves from government to commercial use, the two must coordinate. Internationally, a UN agency called the ITU sets broad rules so that neighboring countries don't interfere with each other.

Three ways spectrum is handed out

1. Exclusive licenses. These work like a private lane leased to one company. The FCC auctions the right to use a band in a geographic area, from a small region up to the whole country, for a term of roughly 10–15 years, usually with an expectation of renewal. The FCC's power to hold auctions comes from Congress; it lapsed in 2023 and was restored in 2025. Licenses can be resold, but every sale needs FCC approval, which is why the spectrum deals in this post go through the FCC.
2. Unlicensed bands. These are the public lanes: anyone can drive in them, within the speed limit, as Wi-Fi and Bluetooth do.
3. Shared bands. These work like a bus lane. In the CBRS band (3.55–3.7 GHz), Navy radar has first claim, paying license holders come next, and everyone else may use it when it's empty. A database decides, in real time, who may transmit where.

Strings attached

Licenses come with conditions:

• Power limits.
• Rules protecting the neighboring bands.
• Rules on whether the band can be used from the ground, from satellites, or both.
• Buildout obligations: deadlines to actually put the spectrum to use, typically covering a certain share of the population by a certain date. If a holder misses them, the FCC can shrink or take back the license. As you'll see in the spectrum race, that "use it or lose it" pressure is what pushed EchoStar to sell its spectrum to SpaceX.

Those rules decide who holds which bands. Here's what the biggest license holders, the mobile carriers, actually do with them.

How mobile carriers use spectrum

AT&T, Verizon and T-Mobile (often called MNOs, mobile network operators) buy exclusive licenses and organize them into three layers that work together:

Your phone switches between these layers constantly and often uses several at once.

Why every carrier wants low-band spectrum

• Physics. One low-band tower can cover many times the area of a mid-band tower. That's often the difference between rural coverage that pays for itself and coverage that doesn't. Low-band also helps your phone's weak transmitter reach the tower from the edge of a cell.
• History. Most low-band spectrum came out of TV broadcasting:
  • 850 MHz was the original 1980s cellular band.
  • 700 MHz was freed when TV went digital and auctioned in 2008.
  • 600 MHz was bought back from TV stations in a 2017 auction.
• Competition. A carrier without low-band can't match rivals on rural or indoor coverage, so the FCC watches closely when one company tries to gather too much of it.
• Scarcity. The whole 600–900 MHz range is only about 300 MHz wide, and it's shared with TV, public safety and others. A single mid-band band, C-band, is 280 MHz wide by itself. So carriers each hold many narrow slices of low-band, often just 10–20 MHz per band.

What "managing" spectrum looks like on the ground

Three techniques do most of the work:

• Frequency reuse. A carrier might own only 20 MHz in a band, but must serve millions of people. So it divides the map into cells and reuses the same frequencies again and again, just never in neighboring cells, where they would interfere. Each cell gets the full 20 MHz, so more, smaller cells mean more total capacity. That's why cities have so many towers.
• Carrier aggregation. Your phone connects on several bands at the same time and combines them into one faster connection. Picture your data driving down three roads at once and meeting at the destination: speed roughly adds up across the bands. It also lets carriers mix strengths, for example sending uploads over low-band, which reaches the tower more reliably, while downloads arrive over wide mid-band channels. It only works when both the phone and the network support that particular combination of bands, and only where you're in range of all of them.
• Meeting buildout obligations. Carriers must actually deploy the spectrum on the FCC's timeline, or risk losing it.

Map: who uses which frequencies in the US

The map below shows the main bands used by each carrier, the two satellite players, and the unlicensed and shared bands. The bottom chart zooms into 1.5–2.25 GHz, where the satellite companies and the carriers sit side by side. Tap any block for details.

How a satellite talks to an ordinary phone

Until recently, satellite service meant a special phone or a dish. Direct-to-phone service (also called direct-to-device or direct-to-cell) connects a satellite straight to the phone already in your pocket.

Do you need a dish?

No. The satellite transmits on ordinary cellular frequencies your phone already supports, so to your phone it looks like a normal cell tower, just a very distant one. Dishes still exist, but only at a handful of ground stations the satellite operator runs, not with users.

Two links, two jobs

Every direct-to-phone satellite runs two separate radio links at once:

• The access link is the satellite talking to your phone on cellular frequencies. This is the "last hop" to you, and it's where the spectrum SpaceX and AST are buying gets used.
• The backhaul link is the satellite talking to the operator's ground station dishes (also called gateways), on high-frequency satellite bands that carry lots of data. On the ground, a cell tower connects back to the network through a fiber cable. A satellite can't, so the backhaul link replaces that cable with a radio beam.

So the switch between "phone frequencies" and "satellite frequencies" does happen, just in orbit: the satellite receives on one band and transmits on another.

Following a Claude prompt through space

To see both links at work, follow what happens when you ask Claude a question from a phone connected only to a satellite. Your prompt goes up the access link, down the backhaul link to a ground station, across the internet to Claude's servers, and the answer comes back the same way. Use the arrows to step through it.

A few things the animation simplifies:

• The space leg is fast. A low-orbit satellite is about 550 km up, so the radio trip adds only tens of milliseconds. Most of the wait is Claude writing its answer.
• The response streams. The answer comes back as many small chunks, which is why text appears word by word. Each chunk makes the same trip.
• Capacity matters more than distance. One satellite beam is shared by everyone in a large area. A text prompt is tiny, but uploading photos or files would feel the limit.

Satellite home internet (the familiar Starlink dish) is a different product. It uses satellite frequencies phones can't receive and delivers much higher speeds. Direct-to-phone trades speed for convenience: no extra hardware at all.

The animation makes it look easy. But a phone's signal only reaches a few miles on the ground, so how does it reach a satellite at all?

How a weak phone signal reaches space

Satellites orbit hundreds of miles up, yet cellular signals only reach a few miles on the ground. The answer is that on the ground, the limit usually isn't the frequency itself. It's everything in the way.

What limits range on the ground

• The horizon. A tower can only "see" so far before the Earth curves away.
• Obstacles. Ground signals travel sideways through buildings, trees and hills, losing strength at each one.
• Deliberate design. Carriers keep cells small on purpose so they can reuse frequencies (see frequency reuse).
• The phone's weak transmitter. Your phone sends a fraction of a watt, and that signal often decides how far the connection can stretch.

A satellite is straight overhead, with a clear line of sight through mostly empty space. At these frequencies, the air absorbs almost nothing. The signal simply spreads out and gets weaker with distance.

Your phone already does this

GPS satellites orbit about 20,000 km up and broadcast at around 1.5 GHz, close to cellular frequencies. Your phone receives them with a tiny built-in antenna. The signal is extremely faint, but it works because GPS sends very little data.

Paying the distance penalty

Signal strength drops with the square of distance. A satellite 550 km away versus a tower 5 km away is about 110 times farther, which means roughly 10,000 times weaker. Operators make up the gap in four ways:

• Huge antennas on the satellite. A large antenna focuses transmitted power into a tight beam and catches more of the phone's faint signal, like a bigger ear. This is why AST builds enormous antenna arrays.
• Narrow, steerable beams that aim energy at small patches of ground, each acting like a cell. Shaping these beams electronically is called beamforming.
• More transmit power on the satellite than any phone could manage.
• Slower, sturdier signals when needed. This is why early service was texting-only and why speeds per user are still modest.

The phone-to-satellite direction, the uplink, is the hardest, because you can't make the phone's antenna or battery bigger. Everything depends on the satellite's antenna.

Indoors is still hard

Walls weaken every signal, and the higher the frequency, the more they take: a concrete wall cuts an 800 MHz signal about sevenfold, but a 3.5 GHz signal about eightyfold. A tower can absorb that loss because it's close, which is how mid-band reaches you indoors. A satellite can't: the distance has already used up almost all of its spare signal. That's why today's satellite service works best outdoors with a clear view of the sky, and why SpaceX and AST want low-band (see the spectrum race). It improves the odds near windows, in cars and in lighter buildings, though no one has yet published proof that it works deep indoors from space.

Moving fast

Low-orbit satellites move at roughly 7.5 km per second. That motion shifts the signal's frequency slightly and adds small delays, and the network must keep handing your phone from one satellite to the next, a handover. The network corrects for these effects so the phone doesn't have to. Newer mobile standards (called "non-terrestrial networks") build that support directly into phones and networks.

Satellites never stand still: why laser links matter

Satellites in low Earth orbit, where Starlink and AST operate, circle the planet about every 95 minutes. Any one satellite is overhead for only a few minutes. That's why these networks need thousands of satellites, and why the handovers mentioned in Reaching space happen every few minutes.

The only satellites that stay fixed over one spot are geostationary satellites, about 36,000 km up. At that height they circle at the same speed the Earth turns. But they're roughly 65 times farther away than low-orbit satellites, which makes the signal far too weak for useful phone data.

The ground-station problem

A moving constellation creates a second problem: the satellite above you might not have a ground station in view. Mid-ocean, in polar regions or in remote areas, there may be none within reach. The fix is laser links between satellites, which let each satellite pass data to its neighbor until it reaches one that can see a ground station.

In the animation below, you are mid-ocean. The teal ring marks the satellite serving your phone; watch it jump as satellites drift past. The purple ring marks the satellite that can see the ground station. Turn the laser links off to see what happens without them.

Laser links matter for three reasons:

• Coverage where there are no ground stations, such as oceans, polar regions and remote areas.
• Fewer ground stations needed. Traffic can reach the internet through a handful of well-placed gateways.
• Speed over long distances. Light travels faster through vacuum than through fiber, so routing across satellites can sometimes beat undersea cables.

Starlink's newer satellites carry laser links, which is part of why it can serve ships and planes far from land. A bent-pipe system, one that relays each signal straight down to a nearby gateway, depends much more on having ground stations close to its users.

Laser links depend on what a satellite can do with a signal once it has it. That's where Starlink and AST diverge most.

Where the "tower brains" live: Starlink vs AST

Every cell tower has a base station: the electronics that turn raw radio waves into data and decide which phone gets to talk when. The two leading satellite companies put that base station in different places:

• Starlink puts the base station on the satellite. SpaceX describes its satellites as cell towers in space.
• AST SpaceMobile keeps the satellite mostly as a giant relay and beam-shaper. Much of the base-station work happens on the ground, where it plugs into partner carriers' networks. This is the bent-pipe approach from the previous section.

Can a satellite and a tower share a band?

Satellites that talk to phones often use the same frequencies carriers already use on the ground, and that creates a problem towers never had. A tower's signal covers a few miles. One satellite beam covers an area that would hold dozens of towers. If the beam transmits on a frequency a carrier is using anywhere underneath it, it can drown out every one of those towers.

The FCC's answer, adopted in March 2024, rests on three rules:

• The carriers must agree. A satellite company can use a carrier's band only by renting it from whoever holds it across an entire region, such as the whole continental US. A beam can't stop at a license border, so a patchwork won't do.
• The ground comes first. If the satellite interferes with the towers, the satellite has to give way.
• No spilling over. Satellites may leak only a tiny amount of signal into the neighboring bands.

That's why "nationwide" matters so much for satellites, and why every deal below comes with FCC conditions. Owning a band outright removes the need to rent one, which is a big part of why SpaceX started buying.

Renting a carrier's airwaves comes with strings attached. Owning them doesn't, so the satellite companies have started buying.

The spectrum race: SpaceX and AST

To serve phones from space, a satellite company needs the right to transmit on frequencies phones understand. There are two ways to get that right:

1. Borrow a carrier's spectrum. Until recently, Starlink's direct-to-cell service ran on T-Mobile's PCS spectrum, and AST beams AT&T's and Verizon's low-band frequencies, such as 850 MHz.
2. Own spectrum outright, either bands reserved for satellites (called MSS, mobile satellite service) or flexible bands that allow both ground and satellite use.

The deals at a glance

Four deals since 2025 have reshaped who holds what:

AST SpaceMobile: partner first, plus its own L-band

AST's own spectrum comes out of Ligado Networks' bankruptcy: long-term rights, for 80+ years, to L-band satellite spectrum in the US and Canada. AST says the extra spectrum, combined with its partners' cellular bands, could support speeds up to 120 Mbps to unmodified phones. Analysts noted this was a change for AST, which had previously argued that low frequencies were better because they get into buildings.

SpaceX: becoming a carrier

EchoStar. The FCC had questioned whether EchoStar was meeting its buildout obligations, with SpaceX among those arguing EchoStar wasn't using its spectrum. EchoStar responded by selling: its 3.45 GHz and 600 MHz bands to AT&T, and three mid-band bands (AWS-4, H-block and AWS-3) to SpaceX. In approving the SpaceX transfer, the FCC let SpaceX use the spectrum on the ground, from space, or both. Instead of the usual tower-building requirements, SpaceX must meet performance targets for signal quality and efficiency.

Grain Management. The 800 MHz licenses belonged to T-Mobile until Grain bought them in August 2026. They add the low-band coverage layer SpaceX was missing: 800 MHz penetrates walls far better than 2 GHz, and most phones already support it. SpaceX is targeting 2027 for its next-generation direct-to-cell satellites, and says the combination makes it the first operator to deploy both satellite and ground-based spectrum.

Put together, once the 800 MHz deal clears the FCC, SpaceX will hold the same kind of low-band plus mid-band mix that AT&T, Verizon and T-Mobile hold, delivered from satellites and potentially from ground equipment too. That's why it's increasingly discussed as a potential fourth national carrier, while AST positions itself as a partner to the existing three.

Do these bands overlap with the carriers' bands?

No. AST's new band sits in a range set aside for satellites, apart from the carriers' bands; you can see the gap in the zoomed map in Figure 1. SpaceX's bands don't overlap the carriers' either, but they sit right up against them with no gap. Signals leak slightly past their edges, which is exactly what the FCC's "no spilling over" rule (see sharing a band) is there to police.

Most of this points to the next few years. Here's what actually works as of October 2026.

Can your phone do this today?

• T-Mobile and Starlink. T-Satellite launched in July 2025. It handles texting, plus data for a short list of apps built to work on a weak connection, such as WhatsApp, Google Maps, AccuWeather and AllTrails. Ordinary phone calls aren't supported yet. It's included in some T-Mobile plans and costs $10 a month otherwise, including for AT&T and Verizon customers. T-Mobile keeps a list of phones that work. Faster data and calls depend on SpaceX's next-generation satellites, planned for 2027, and those will need newer phones to use SpaceX's new airwaves from space.
• AT&T, Verizon and AST. Not available yet. After rocket setbacks, AST moved its full launch to early 2027. A limited test service, with gaps in coverage, is planned with AT&T and Verizon first.
• What your phone may already have. iPhones since the iPhone 14 can send emergency and regular texts by satellite through a company called Globalstar, which uses its own satellite airwaves rather than a carrier's. That's why the phone asks you to point it at the sky. Recent Pixel phones, and the Galaxy S25 on Verizon, offer satellite texting through a company called Skylo, at least for emergencies. These are slow, text-only services, separate from the Starlink and AST networks this post describes.

Here's everything above, in six lines.

Key takeaways

• Spectrum is a limited, shared resource. Governments decide who may use which frequencies so signals don't collide.
• Lower frequencies reach farther and get indoors. Higher frequencies carry more data. Carriers combine low-band for coverage with mid-band for capacity.
• Direct-to-phone satellites act like very tall cell towers. They talk to your phone on cellular frequencies (the access link) and to ground stations on satellite frequencies (the backhaul link). No dish is needed on your end.
• Low-orbit satellites are always moving. Constant handovers and laser links between satellites keep the connection alive, even mid-ocean.
• Starlink puts the base station in orbit; AST keeps it on the ground. Each choice has trade-offs in cost, flexibility and coverage.
• SpaceX has moved from borrowing T-Mobile's spectrum to owning mid-band spectrum outright, with a low-band deal awaiting FCC approval, making it a potential new national carrier. AST is betting on partnering with existing carriers plus its own L-band.

Glossary

Access link

The radio link between a satellite (or tower) and your phone.

Backhaul link

The connection from a tower or satellite back to the core network: fiber for towers, a radio beam to a ground station for satellites.

Band

A defined range of frequencies, such as "AWS" or "Band 70."

Base station

The electronics that turn radio signals into data and manage which phones can transmit, and when.

Beamforming

Steering a radio signal into a narrow beam by coordinating many small antennas, rather than moving a dish.

Bent pipe

A satellite that relays signals without decoding them, like a mirror in the sky.

Buildout obligation

A license condition requiring the holder to actually deploy the spectrum by a deadline.

Carrier aggregation

Combining several frequency bands into one faster connection.

Downlink / uplink

Network-to-phone and phone-to-network directions.

Frequency reuse

Using the same frequencies in non-neighboring cells to multiply capacity.

Geostationary orbit

An orbit about 36,000 km up, where a satellite stays fixed over one spot.

Ground station / gateway

A site with large dishes that connects satellites to the internet.

Handover

Passing a phone's connection from one cell or satellite to the next.

Ka / Ku band

High-frequency satellite bands (roughly 12–40 GHz) used for backhaul and satellite home internet.

Laser link

A direct optical connection between two satellites.

LEO (low Earth orbit)

Orbits a few hundred to about 2,000 km up, where Starlink and AST operate.

MNO

Mobile network operator, such as AT&T, Verizon or T-Mobile.

MSS

Mobile satellite service, spectrum reserved for satellite-to-device use.

NTN (non-terrestrial networks)

The part of the mobile standards that lets phones and networks work with satellites as well as towers.

Paired / unpaired spectrum

A pair is two blocks, one for each direction; an unpaired block is a single chunk used one way, or both ways by taking turns.

Unlicensed spectrum

Bands anyone may use under shared rules, such as Wi-Fi and Bluetooth.