L'équipe Texto SMS Gratuit
12 ottobre 2026 · 13 min di lettura
Introduction: the third option nobody talks about
Two conversations dominate the debate around fixed internet in France: fibre arriving everywhere, and copper shutting down. Between the two lies a grey area that gets little attention yet affects hundreds of thousands of households: addresses where fibre hasn't arrived yet, and where ADSL is about to be switched off.
The schedule for closing Orange's copper network, approved by Arcep, is advancing in batches: after the first pilot municipalities, technical shutdowns are rolling out in waves until the complete switch-off planned for around 2030. For an affected household, the question is no longer theoretical: the telephone wall socket stops working on a known date. And if an FttH connection isn't available at that address — an unconnected building, a hamlet outside the coverage zone, a house at the end of a private lane, a "complex" connection still pending — you need a fallback.
That fallback goes by several names depending on the operator: "4G box", "5G box", "internet over the mobile network", sometimes "THD radio". The principle is always the same: a unit that looks like a conventional router but picks up the mobile network instead of a fibre or telephone socket, then redistributes it over Wi-Fi inside the home.
Is it a real solution or a sticking plaster? The honest answer: it depends on a single number, and that number is not the headline speed on the brochure.
What it actually is
A fixed 4G/5G box is three things in one unit:
- a mobile modem equivalent to the one in a smartphone, with a SIM card (or eSIM) tied to a "fixed internet" subscription;
- internal antennas optimised for stationary use, therefore larger and better oriented than those in a phone;
- a Wi-Fi router with one or two Ethernet ports, so you can plug in a TV or computer over cable.
The difference compared with simply tethering from your phone is real: better antennas, permanent mains power, and above all a subscription designed for home use — whereas a standard mobile plan often prohibits using tethering as the household's main connection, or throttles it beyond a certain volume.
Technically, your traffic travels through the same mast as the mobile phones in the neighbourhood. That's the crux of the matter: you aren't renting a dedicated line, you're sharing a radio resource with your neighbours.
The only number that really matters: signal quality indoors
Forget the "up to 1 Gbps" claims on the sales pages for a moment. On a radio link, the speed you'll actually get depends on four factors, in this order:
- The band used by the cell that covers you. A low band (700 MHz) travels through walls and reaches far, but offers narrow channels: excellent coverage, modest speeds. A high band (2,100, 2,600, and above all 3.5 GHz in 5G) delivers far higher speeds but penetrates buildings poorly and doesn't reach as far.
- Distance and obstacles. A hill, a metal roof, a 60 cm stone wall or high-performance insulating glazing can knock tens of decibels off the signal.
- Cell load. At peak times (7 pm – 10 pm), the same mast serves dozens, sometimes hundreds of users. Your speed can be five times lower at 9 pm than at 3 pm without any fault having occurred.
- Your hardware and where you put it. A unit sitting in the basement behind a boiler will never match the same unit next to a window on the mast side.
Hence the rule to remember: test before you sign, and test at the exact spot where the box will live.
How to run that test in 20 minutes
- Identify the masts covering you via Cartoradio, the public site run by ANFR (France's national frequency agency): it lists every authorised radio site, the operator and the declared technologies. You'll know whether a 5G 3.5 GHz cell exists 800 m away, or whether the nearest site is 4 km off and 700 MHz only.
- Cross-check with "Mon réseau mobile", the Arcep tool that publishes coverage maps and quality-of-service indicators per operator down to address level.
- Then run the real test: with a handset on each operator if possible (a prepaid SIM or a trial eSIM is enough), record the download speed, upload speed and latency at several times of day, in the intended room. Also note the signal strength in dBm (under "network information" or "SIM status" in the phone's settings): beyond –100 dBm, a 4G/5G box will disappoint.
A small 4G/5G signal tester, or failing that your phone's dBm readout, is worth far more than the four bars of an icon, which have no standardised definition whatsoever.
Speeds, latency, data caps: what to honestly expect
Here's what is observed in practice in France in 2026, depending on signal quality. These ballpark figures don't replace your own test, but they set expectations.
| Radio situation | Typical download speed | Latency | Comfortable uses |
|---|---|---|---|
| 5G 3.5 GHz, strong signal | 150 to 500 Mbps | 15–30 ms | Everything, including video-call remote work and 4K |
| Multi-band 4G, good signal | 30 to 100 Mbps | 25–45 ms | HD streaming, video calls, cloud |
| 4G 700/800 MHz, average signal | 8 to 30 Mbps | 40–80 ms | Browsing, SD/HD, two-person video calls |
| Weak signal (< –105 dBm) | 1 to 8 Mbps, highly variable | > 80 ms, unstable | Email, messaging, little video |
Three points the brochures mention in the small print:
Upload speed is the real weak spot. On 4G it often tops out between 5 and 20 Mbps, sometimes less. That's enough for a video conference, not enough to back up 200 GB of photos to the cloud or for intensive remote work that sends large files.
Latency is fine, jitter less so. For competitive online gaming, variability hurts more than average latency. A game that runs smoothly at 3 pm can become unplayable at 9 pm.
Data caps exist, even on so-called "unlimited" plans. 4G/5G box offers have historically been sold with data allowances (100, 200 or 500 GB per month, for example) or, for plans with no stated cap, with a traffic management clause: beyond a certain threshold, the operator may deprioritise your traffic relative to other customers on the cell. That clause sits in the terms and conditions, not on the poster. Read it: it's the only place that tells you what happens at the 300th gigabyte.
For reference, a household that watches television via streaming routinely uses 150 to 400 GB per month. A 100 GB plan isn't a "home broadband" plan, it's a stopgap.
Improving the signal: what works, what's illegal
If your test shows an average signal, all is not lost — but mind the legal framework.
What's allowed and effective:
- Moving the unit. The biggest gain for zero euros. Near a window, up high, on the side facing the mast you identified on Cartoradio. One floor gained can be worth 10 dB.
- A directional outdoor antenna connected to the unit's antenna ports, where it has them (SMA or TS9 connectors depending on the model). A properly aimed outdoor MIMO 4G/5G antenna mounted on a gable wall or on the roof often adds 5 to 15 dB, which can triple your speed. You'll need a short low-loss coaxial cable and weatherproof connectors: the loss in 15 m of mediocre cable wipes out the antenna's entire gain.
- A Wi-Fi repeater or a mesh kit indoors, to spread the connection to distant rooms. This doesn't improve the radio link to the mast, only the internal distribution.
- A UPS for the box, if you suffer frequent brief power cuts: the radio link stays available as long as the mast has power.
What is illegal: mobile signal repeaters bought freely online and installed yourself. In France, installing a mobile signal amplifier is reserved for operators or must be done under their responsibility; non-approved equipment disrupts the cell and jams your neighbours. ANFR regularly runs operations to seize this kind of hardware, and the penalties are real. If your problem is indoor coverage, the right door to knock on is your operator's — they may offer a properly supervised solution — not an online shop's.
Four operators, four philosophies
Without getting into prices that shift every quarter, the commercial logic differs markedly.
- Orange positions its radio offers as a continuity solution in areas where copper is being switched off, dovetailing with the support arrangements set out in the Arcep timetable. Eligibility is tested address by address, and the offer isn't always proposed where fibre is announced in the short term.
- SFR and Bouygues Telecom sell consumer 4G/5G boxes, often with a contract term and a defined data allowance, sometimes with a TV option. The selling point is speed of installation: the box is delivered, plugged in, and works the same day, with no technician visit.
- Free has long played the card of a supplementary 4G/5G unit tied to a mobile subscription, on a "speed not guaranteed, lower priority than mobile handsets" basis.
- Among the virtual operators and specialist providers, you'll find 4G-network offers with dedicated data SIMs, attractive for seasonal or secondary use.
One detail that can cost you dearly: some offers are not transferable to another home. If you move, eligibility is reassessed — and the contract may not follow.
The satellite alternative, and where it starts to make sense
For addresses where even the mobile network is weak, low-earth-orbit satellite access has become a credible option. Advertised speeds often exceed those of a 4G box on an average signal, with latency now acceptable for video conferencing. The entry cost (hardware + monthly subscription) remains higher, and installation requires a clear view of the sky.
Public schemes supporting high-speed internet equipment for homes that cannot be connected have existed and evolved; ask your town hall and your département, which often run complementary subsidies through public initiative networks (RIP). Before you buy any kit, also check the fibre rollout schedule for your address on "Ma connexion internet", Arcep's mapping tool: if connection is planned within twelve months, a 24-month commitment on a radio box is a bad bet.
The five contract traps
- A 12- or 24-month commitment on a non-guaranteed link. Insist on a trial period or check the withdrawal terms. For a contract concluded remotely, the 14-day right of withdrawal applies (French Consumer Code): use those 14 days to test seriously, including on a Sunday evening.
- The "up to" on speeds. No operator guarantees a speed on a radio link. Ask in writing for the speed estimate at your address: European open internet rules require the provider to state the estimated speeds in the contract, along with the remedies available in the event of a significant and lasting discrepancy.
- TV use. The television stream over a radio box is often degraded or absent. For television, DTT or an app-based solution is often more stable, and a well-placed indoor DTT antenna costs less than a monthly surcharge.
- Hardware billed if not returned. As with a fibre router, the unit remains the operator's property: keep the box and the return slip.
- Landline telephony. The landline number supplied by a radio box runs over VoIP: it depends on mains power and the radio link. For emergency calls, a charged mobile remains the reference fallback.
How to decide: six steps
- Check fibre eligibility at the exact address ("Ma connexion internet", Arcep) and the provisional connection date.
- Check the copper switch-off schedule for your municipality: if your batch has already been announced, you have a firm deadline.
- Map the masts with Cartoradio (ANFR) and note which operator is best placed, band by band.
- Test on site, at the intended location, morning and evening: download speed, upload speed, latency, strength in dBm.
- Choose the operator that won the test, not the one with the best promotion.
- Use the 14-day withdrawal period as a genuine validation phase: work video calls, streaming at 9 pm, a large download, Wi-Fi calling.
FAQ
Can a 4G/5G box replace fibre? For everyday use (browsing, HD streaming, video calls, office-style remote work) with a good signal: yes, it's perfectly liveable. For a household needing heavy upload, several simultaneous remote workers or competitive gaming: no, it's a stopgap.
Can I use my unlimited mobile plan instead? Mobile plans' terms and conditions restrict tethering and generally prohibit using it as the household's main fixed access. Beyond a certain volume, speeds are throttled. Technically possible, contractually risky.
Does Wi-Fi calling work behind a 4G box? Yes, but the voice traffic then goes back out over the mobile network via the box: there's little point if your phone already has signal. On the other hand, in a home where only the box's location gets decent reception, it can make calls possible throughout the house.
What if the promised speed doesn't materialise? Document it: timestamped readings, screenshots of speed tests, at different times of day. Written complaint to customer service, then refer the matter to the médiateur des communications électroniques after two months without a satisfactory response. Arcep also provides a reporting platform, "J'alerte l'Arcep", which feeds into its market monitoring.
Key takeaways
Fixed internet over the mobile network is neither a scam nor a miracle: it's a shared link whose quality depends entirely on your address. The 20-minute test before signing is worth more than any comparison chart, and the 14-day withdrawal window is your best negotiating tool.
To go further on related topics, see our guide to working out which operator really gets signal at your place and our practical answers in the FAQ on networks and mobile plans. And if your problem is indoor coverage rather than the absence of fibre, the legal solutions for better reception at home tackle the issue from the radio angle.
