How to Check Phone Coverage and Signal | What to Check Before Switching Carriers
Prices, point rates and sale details in this article were checked by the mottoku editorial team against each service's official site and API (as of the last update). Always check the official sites for current prices, stock and campaign terms.
Look at the “signal map” before the price table
Most articles about switching phone carriers start by comparing monthly fees and data allowances. Here we deliberately reverse the order. No matter how attractive a plan is, if the signal is unstable in the places where you spend most of your day, the savings remain just a number on paper. Videos that stall, no service once you go underground, only one bar in your own living room: these complaints are usually discovered only after you sign up, and a low price cannot make up for them.
How well a signal “gets in” comes down to which frequency bands are used, how many base stations transmit them, and in what kind of environment. This article does not recommend any particular carrier. Instead, it walks through the practical technical points you need to judge signal quality yourself before switching: what the platinum band means, the tricks behind the “coverage rate” on area maps, the physical reasons indoor and underground signals weaken, slowdowns during busy hours, and which bands your current device supports.
How this article is organized: frequency basics (why places differ) → how to read area maps correctly → indoor and underground fixes → lunchtime and evening congestion → device band support → on-site checks before signing. Low price comes last, as the factor that matters only at the end.
Platinum band versus higher frequency bands: what is the difference?
The single biggest factor in how well a signal gets in is the frequency (band). Roughly speaking, lower frequencies bend around obstacles and travel farther, while higher frequencies are faster but travel in straighter lines and are easily blocked. This is simply physics. Once you grasp it, area maps start to look different.
| Band name | Approximate frequency | Character |
|---|---|---|
| Platinum band (low band) | 700〜900MHz band (Band 8 / 18 / 19 / 28, etc.) | Reaches far and bends into buildings easily. The foundation of reliable connectivity in the suburbs and indoors |
| Main mid band | 1.5〜2.1GHz band (Band 1 / 3 / 21, etc.) | A balance of speed and reach. The workhorse that carries capacity in urban areas |
| 5G Sub6 | 3.5〜4.1GHz band | Fast, but travels in straight lines and weakens easily through walls and distance. Shines outdoors and in open spaces |
| 5G millimeter wave | 28GHz band | Extremely fast, but short-range and very vulnerable to obstructions. Limited to local spots such as stadiums and station concourses |
The key point here is that “5G-compatible” does not mean “fast everywhere.” If the 5G a carrier advertises is only in high bands such as Sub6 or millimeter wave, it may be fast outdoors in open spaces, but the moment you step indoors your phone can drop to 4G and the experience changes. Conversely, a carrier with plenty of low platinum bands may look unglamorous, yet it gives you the reassurance of “at least one bar even in the back room of your home.” When evaluating a carrier to switch to, look not at the top-speed figure but at which low bands it holds in your own area; that makes it much harder to misjudge real-world performance.
The pitfalls hidden in the “coverage rate” on area maps
Each carrier’s official area map is something you should always check as a starting point, but taking the colors and percentages at face value can trip you up. There are a few tips for reading them properly.
“Population coverage” and “area coverage” are different things
The “population coverage of XX%” often seen in advertising is a measure of how much of the inhabited area is covered, and it is frequently calculated in a way such as “if the signal reaches around the city hall, that municipality counts as covered.” In other words, even if population coverage is high, that does not mean your home address or the mountain road you often drive is actually included. “Area coverage,” on the other hand, is the share of the country’s land area, and that figure tends to come out lower. When looking at a map, rather than the percentage, the right approach is to zoom in on the exact addresses in your own daily life and check the color.
The map is only a guide, and it has update timing
Area maps often use different colors for planned areas and current areas, and mistaking the pale color of “planned expansion” for the present situation can cost you. The maps also do not reflect fine differences in signal strength from one building to the next. That is why, once you confirm “covered” on the map, you should not stop there but verify with the next steps.
Map-checking checklist: ① Instead of the percentage, zoom in to the maximum on the addresses of your home, workplace and commute route ② Do not confuse the colors for “planned area” and “current area” ③ Look at the same address with 4G and 5G switched separately (be careful if only 5G is colored and 4G is pale) ④ Maps and coverage status change, so check each carrier’s official information for the latest.
Overall aggregate figures and your own conditions are different things
The coverage rate in the previous section is misleading not because the figure is a lie, but because the unit of aggregation is “the whole,” while what you want to know is “your own address.” That is why the answer on how to read it took this form: not comparing percentages, but zooming the map to the maximum and looking at the color of your own daily area.
The same mismatch happens when you buy things. Average review scores and labels such as “best seller ranking” or “popular” are all the result of bundling many people into one, and do not include whether a product suits your way of using it. A high rating from someone whose use differs from yours is hard to rely on. Conversely, even a product with divided reviews becomes a strong candidate if people in conditions close to yours are satisfied.
What you do is the same as when checking signal: step down from the aggregate figure to something closer to you. For reviews, read the text instead of the score, and look for ones written for the same use and in the same environment as yours. With the small extra effort of not stopping at a row of stars, you can cut down a great deal of the mismatch after buying (→ A perspective for reading reviews).
Indoors, underground, upper floors: the physical reasons signals weaken, and what to do
A signal that showed four bars outdoors drops to two the moment you walk through the front door. This is not your imagination: radio waves weaken as they pass through building materials. Knowing the mechanism makes it easier to aim your countermeasures.
- Concrete, rebar and metal window frames block radio waves strongly: higher bands in particular (Sub6 and the 2GHz band) weaken more at walls, while the low platinum bands bend into rooms more easily. The metal-film Low-E glass in new, highly insulated homes also tends to block radio waves, often leaving the signal strong only by the window and weak further inside.
- Underground shopping streets and subway stations do not receive radio waves directly from base stations: many underground places are covered by indoor antenna systems that carriers install jointly, so coverage varies greatly from carrier to carrier. Whether the carrier you want has coverage in the underground mall you use often cannot be read from a ground-level map alone.
- Upper floors of high-rise apartments are surprisingly weak: base station antennas often tilt slightly downward toward users on the ground, so above about the 15th floor, signals from several base stations can mix and become unstable. This is why low and high floors feel different.
Realistic options when indoor signal is weak
Even if the signal in your daily area is not perfect, there is no need to give up on switching right away. Indoor connectivity can be supplemented.
- Home Wi-Fi and Wi-Fi calling (VoLTE/Wi-Fi Calling)With a compatible device and carrier, you can handle calls and data over your home Wi-Fi. Even if the indoor signal is thin, Wi-Fi supports everyday use.
- Measure strength by window and by roomEven within one home, rooms differ greatly. Measure where you spend time (bedroom, home-office desk) and use the place that needs signal most as your benchmark.
- Review your 5G settingIf it is unstable indoors, a device setting that does not cling to 5G (Sub6) and falls back to 4G more readily can sometimes be more stable.
- Check what indoor remedies are offeredDepending on the residence or office, a consultation desk for improving signal may be available. Check each carrier’s official information for availability and conditions.
“Speed” changes with the time of day: the gap between noon and night
You are in the coverage area, yet it is “slow only at lunchtime” or “heavy in front of the station in the evening.” This is a problem separate from signal strength: congestion from many people sharing the same base station. Even with four bars, speed drops if the line is crowded. If you can tell the two apart, you can greatly reduce the “this isn’t what I expected” feeling after signing up.
Own network (MNO) or rented network (MVNO)?
Major carriers that own their base stations (MNOs) and budget carriers that operate by renting part of those lines (MVNOs) differ structurally in how speed holds up when congested. Because an MVNO’s speed depends on the amount of bandwidth it rents, it tends to slow down at weekday lunchtime (around 11:30〜13:00) and during commuting hours. This is a trait shared by many rented networks, a feature of the mechanism rather than a matter of one carrier being better than another. Conversely, if you stay connected to home or office Wi-Fi and do not use heavy data outside, congestion will hardly be noticeable.
| Usage type | Impact of congestion | Suitable type of line |
|---|---|---|
| Heavy video or tethering outside | Large | Leaning toward own network (MNO), or a line with spare capacity |
| Mainly social media, maps and looking things up | Medium | Wide range of choices. Just check the lunchtime experience beforehand |
| Mostly Wi-Fi, minimal use outside | Small | The low price of a rented network (MVNO) is easier to take advantage of |
To gauge the effect of congestion, the most reliable way is to test speed at the time and place you actually want to use it. Accounts from people using the same carrier in the same area give you a vivid sense of weekday lunchtimes and evenings, and are more useful than the average figures in advertising.
Does your current device support all of that carrier’s bands?
It is often overlooked, but even if you choose a carrier with good signal, it is meaningless if your device does not support its frequency bands. Be especially careful if you plan to keep using your current device and just swap the SIM. Here are common pitfalls.
- The platinum band support problem: Overseas versions and some SIM-free devices may not support the low bands (e.g. Band 18/19/28) of a given Japanese carrier. The result is a hard-to-diagnose fault: everything works normally in cities, but signal is extremely weak only in the suburbs or indoors.
- Only partial 5G band support: A device may support all 4G bands but not the carrier’s 5G (such as n79), so “5G does not appear.” It cannot deliver its full speed.
- Whether the Giteki mark is present: To use a device legally in Japan, it needs the technical standards conformity (Giteki) mark. Avoid devices of unknown origin, and check both supported bands and the Giteki mark.
The way to check is simple: compare your model name with the carrier’s bands on the device maker’s spec page or on each carrier’s “verified devices” list. If you are also buying a new device, choosing one that supports all bands for the Japanese market from the start removes the worry altogether. If you want “one device that works on any carrier,” the breadth of supported bands matters more than price as a selection criterion.
Before you swap just the SIM and switch, check these two things together: “model name + supported bands” and “the destination carrier’s verified devices list.” Skipping this leads to the most frustrating outcome: the area is fine, but only your own device will not connect.
What to prepare along with your contract, and what can wait
Signal issues do not end when you sign the contract. In practice, people insert the SIM, hit “huh, it won’t connect” or “I’m in range but it’s slow,” and rush to buy something extra. Here, from the standpoint of signal and coverage, we separate what is reassuring to have ready first from what is often recommended but can wait.
Things that prevent you from getting stuck if prepared first
- Completing the SIM unlock: It is not a physical item, but it is the biggest gate. If you are reusing your current device, check before switching whether it is already unlocked. If it is not, the device cannot pick up the new carrier’s signal at all.
- A SIM ejector pin, or a thin piece of metal that opens the SIM tray: Needed when swapping a physical SIM. It is often in the device’s box, but if you have thrown the box away it is surprisingly hard to find. Not needed if you sign up with an eSIM.
- A Wi-Fi environment: Issuing an eSIM profile, entering APN settings, and updates after activation are sometimes done without a mobile connection. If you switch with no Wi-Fi at home, the activation work itself stalls.
- A backup while your old line still works: For services set to send verification codes by SMS, even if your number stays the same there can be a window around the switchover when you cannot receive them. Before switching, check your login details on paper or in a password manager to be safe.
Things often said to be “nice to have” but not a high priority
- Stickers and antenna gadgets that claim to boost signal: A phone’s reception depends on the antenna inside the body and the bands it picks up. There is no explanation for how a goods item stuck on the outside could change reception. Rather than spending money on this, considering a device with more supported bands is more reliable.
- A mobile router bought right away: Before adding a router on another line because your home signal is weak, the better order is to find out which carrier gets a signal at that spot. Adding another line of the same kind in the same weak spot changes nothing.
- A high-end latest device: Features available only on top models, such as 5G millimeter-wave support, are attractive, but if that signal does not reach your daily area, you cannot receive it. Deciding the device grade after checking the area is the more natural order.
Things that work under certain conditions
When indoor signal is weak, carriers sometimes offer small base stations they lend out (femtocells) or systems that carry calls and data over your home broadband line. These are not things you “buy” but things provided to subscribers, so consulting the carrier’s service desk first is the way to go. Also, if only call quality is the problem, checking whether you can use VoLTE over Wi-Fi (Wi-Fi calling), which makes calls over Wi-Fi, may let you avoid the weak indoor signal.
If you have a dual-SIM device, keeping your old line for a while right after switching lets you judge whether the new line really works in your daily area by comparing the two. Check beforehand whether your model supports a physical SIM + eSIM combination.
“Band 1 / n78 / downlink up to XX Mbps”: decoding the symbols in a spec sheet
Device spec sheets and carrier guide pages are full of unfamiliar symbols and numbers. Once you can read them, you can judge “whether it suits me,” which the colors on an area map alone cannot tell you.
The difference between Band and n
What is written in a spec sheet as Band 1 / 3 / 8 / 18 / 19 / 28 are the numbers of the bands used for 4G (LTE). On the other hand, those with an “n” in front, such as n77 / n78 / n79 / n257, are 5G (NR) numbers. The same number means something different with or without the n, so even if it says 5G-compatible, you cannot know the reality without checking which n bands are supported.
Smaller numbers tend to mean lower frequencies, and around Band 8, 18, 19 and 28 are the so-called low bands (bands that reach far and bend around obstacles). Bands 1 and 3 are the urban workhorses: they earn capacity but do not reach far. 5G in the 200s, such as n257, uses very high frequencies (millimeter wave), and the supported area is limited.
How to read “downlink up to XX Mbps”
The “maximum downlink” in guides is a theoretical value for ideal signal and no congestion. You will almost never actually see that number, so it is weak as a basis for comparing carriers. What you should look at instead is how the speed after throttling is described. If notations such as “XX Mbps when throttled” or “up to XX kbps when throttled” differ by an order of magnitude, usability changes completely. This figure tells you whether the speed can handle maps and messaging or whether you will be left waiting for pages to load.
The legend of an area map
The color coding on a map usually includes distinctions like the following.
| 4G / LTE | The basic coverage. Where this is blank, practical use is difficult even if 5G is colored in |
| 5G (sub6) | The 5G rolled out relatively widely. n77, n78 and n79 fall under this |
| 5G (millimeter wave) | Often colored only in dots. Such as stadiums and inside major stations |
| Repurposed 5G / 5G (partial) | A method of using 4G bands as 5G. It displays as 5G, but speeds may not differ much from 4G |
| Planned area | Radio waves are not yet being transmitted. Do not use it as a basis for current decisions |
The fine print “uses the XX network”
MVNO pages carry notes such as “docomo network / au network / SoftBank network.” You can basically assume the coverage area is the same as that major carrier, but you need to understand separately that the usable bands are not necessarily the same and that speed during congestion is a different matter. The area map can be consulted directly for the network being rented, but lunchtime speed will not be the same.
When looking for supported bands in a device’s spec sheet, look for items named “supported frequency bands” or “supported networks.” Overseas models and parallel imports may have bands removed even when the model number looks the same as the Japanese version, so confirm that the model number matches all the way to the end.
What you notice only after switching: real signal-related stumbles
Here we list trouble that actually tends to occur because of signal and coverage, not because of fees or device choice. All of them can be avoided with a little effort beforehand.
Signal is fine at home, but the bedroom and bathroom have none
Area maps are based on outdoors, so they do not show differences from place to place inside a home. Bathrooms that do not face an outer wall, spots surrounded by metal doors and pipes, and north-side rooms in reinforced concrete buildings in particular can have different reception even at the same address. If you want to check before switching, walking around inside the house and watching how the signal bars change is the quickest way. If possible, borrow the device of a family member or friend who uses that carrier and ask them to show you the display in the bedroom, bathroom and entrance.
“It’s a 5G device but never gets 5G”
Either the supported bands do not match, or 5G simply has not reached that spot. Pay particular attention to support for n79. This band is used as a main band by some carriers, so a device that does not support n79 cannot receive part of that carrier’s 5G. This tends to happen with used devices or models sold by other companies that you bring over.
Calls work but data does not, or the reverse
If the APN is not set correctly, the bars show but only data communication fails. Conversely, if the VoLTE setting is not enabled, data may work while calls do not connect, or are extremely unstable only during calls. When you switch with your own device, checking data and calls separately lets you find the cause faster.
The signal drops cleanly on the same stretch of your commute every day
Even if the whole route is colored on the map, spots that are locally weak remain, such as inside tunnels, underground sections and on elevated bridges over rivers. On subways in particular, station platforms may be well covered while coverage inside the tunnels between stations can differ by carrier. If you have a habit of watching video or listening to the radio while traveling, checking on site during commuting hours is effective.
At the time of an MNP switch, there is a period when you can’t connect that day
Line switching procedures often have set acceptance hours, and applying late at night is treated as the next day. On a day when you are waiting for a work call, or if you try to switch while out, there will be a period of waiting for activation when you cannot use the signal. It is safest to switch somewhere with Wi-Fi, on a day when you have time to spare.
Signing up without checking your new address
If you plan to move soon, check coverage not at your current address but at the one you are moving to. Even within the same city, hilly areas, developed land and new housing developments can get base stations later.
Do not underestimate the signal at your parents’ home or travel destinations. Even a place you visit only a few times a year can leave the impression that “this carrier is unusable” if you have no signal there for several days in a row. If your hometown is in the mountains or by the sea, be sure to check the area map at its maximum zoom.
Major carriers, sub-brands, MVNOs and home lines: sorting them by signal
If you put “signal and speed stability” rather than “low price” at the center, the order of the options changes. Here we organize the types people often compare by what kind of person each suits.
| Type | Coverage | Speed when congested | Suitable conditions |
| The major carrier itself | Can use its own network in full | High priority, hard to drop | You sometimes go to mountains or remote islands, or your work suffers if indoor calls drop |
| The same carrier’s sub-brand | Nearly the same as the main brand | Stability close to the main brand | You don’t want to compromise on coverage but want to keep fees down |
| MVNO (renting a network) | Nearly the same as the network it rents | Tends to drop at noon and in the evening | A Wi-Fi-centered life without heavy data use while on the move |
| Own network + partner network combination | Partner networks fill in where its own is thin | Partner-network sections may be restricted | Mostly in cities, with few trips to rural areas |
When you can’t decide between the major carrier itself and its sub-brand
The coverage colors are nearly the same, but there can be differences in how congestion is handled. The deciding factor is what you do on your phone at weekday lunchtime. If you watch video during your lunch break or work outside while checking maps, lean toward the main brand. If you are on Wi-Fi at noon almost all the time, there are few situations where a sub-brand causes problems. Also, during large events or disaster-related congestion, the design may give main-brand contracts priority.
What to check if you choose an MVNO
With an MVNO there is less worry about coverage, but speed during busy hours varies greatly between providers. The basis for judgment is two-tiered: which carrier it rents from (that is, whether the signal reaches your daily area) and how much bandwidth the provider secures. The latter is often not published as a figure, so looking for the real-world experience of people using it in the same area and time of day gets you closer to reality.
Add a line, or change your home setup?
Before considering adding another line just because the signal at home is weak, there is another option: shifting indoor calls and data over to Wi-Fi. If you have a fixed line and Wi-Fi, choosing a device and plan that support Wi-Fi calling can greatly reduce the effect of weak indoor signal. Conversely, if you plan to live without a fixed line and rely only on smartphone tethering, you should reconsider that plan itself once indoor signal is weak.
If you want to try before deciding
Some providers offer services usable for just a few days to a few weeks, or short-term data-only eSIMs. The advantage is that before moving your number, you can check on a real device how that carrier’s signal reaches your home and workplace. This order involves far less rework than moving your number and then realizing “it still doesn’t get a signal.”
If you go through your comparison priorities as ① whether the signal reaches your home, workplace and commute route → ② whether calls hold indoors → ③ whether you get the speed you need at noon → ④ fees, you are less likely to get lost. A line that fails at ① does not remain an option, however good the conditions below it.
On-site checks before signing: don’t stop at the map
Here we turn the knowledge so far into concrete actions to take before you press the contract button. Simply following them in order wipes out a good share of signal failures.
- Write out your daily area on a mapList your home, workplace, school, parents’ home, and the underground malls and stations you use often. If the family will use it, do this for everyone.
- Check the official map address by addressNot the percentage: check each listed point at maximum zoom. Switch between 4G/5G and current/planned.
- Be aware of whether it has a low band (platinum band)If you are worried about the suburbs or indoors, whether the carrier has a low band matters. Weigh it more for the points you are most worried about.
- Verify with accounts from the same areaFor the feel of weekday noon and evening congestion and the differences underground and indoors, voices from users in the same area are the most real.
- Measure with a trial or short-term useIf possible, actually try it where and when you spend time. Use the room and time that need signal most as the benchmark.
- Check your device’s supported bandsEssential if you are swapping the SIM. Compare the verified devices list against your model’s specs.
- If doubts remain, don’t force a switchDeciding not to jump in just because “it’s cheap” is also a sound choice. Also consider the room to supplement indoor signal with Wi-Fi.
Safety note: suspicious emails, SMS messages and fake websites (phishing scams) that pose as mobile carriers and talk of “generous cashback,” “billing notices” or “unpaid fees” are increasing. Always go through each carrier’s official website, authorized app or store for contracts and switching procedures. The more extremely good a pitch sounds, the more calmly you should look at the conditions. Do not carelessly enter ID documents or login details, and if anything seems even slightly suspicious, check with the official service desk. Fees, rewards and campaign conditions change, so please check each official source for the latest.
Frequently asked questions
If a carrier is “5G-compatible,” is it fast everywhere and safe to choose?
Not necessarily. 5G also has bands that differ in how far they reach, and if the carrier’s headline high-speed 5G is mainly Sub6 or 28GHz millimeter wave, it may be fast outdoors in open spaces, but once you go indoors it can switch to 4G and the experience changes. Everyday usability depends less on top speed than on whether the carrier holds plenty of low platinum bands (the 700〜900MHz band) in your own area. Check maps with 4G and 5G switched separately.
If it says “99% population coverage,” is my home included?
Not necessarily. Population coverage is a measure of how much of the inhabited area is covered, and depending on the calculation, reaching the center of a municipality can count as covered. There is no guarantee that your address or the mountain road you take is included. Rather than the percentage, it is more reliable to zoom to the maximum on your home and workplace addresses on the official map and check the color directly (current area or planned area).
What is so good about the platinum band, anyway?
It refers to the low frequencies around the 700〜900MHz band, whose advantage is that radio waves travel far and bend into buildings easily. It is the foundation that supports whether you get bars in the suburbs and indoors. Higher bands (such as 5G Sub6) are fast but weaken easily through walls and distance. The more you live in the suburbs or use your phone indoors, the more it matters whether the carrier has this low band.
Why do I get four bars outdoors but weak signal only inside my home?
Because radio waves weaken as they pass through building materials. Concrete, rebar, metal window frames and insulating metal-film Low-E glass block radio waves strongly. Higher bands in particular weaken more indoors. Countermeasures include using home Wi-Fi and Wi-Fi calling, measuring in the rooms where you spend time, and settings that do not cling to 5G. Some residences provide a consultation desk for improving signal, so check each carrier’s official information for availability.
Is it slow only at noon and in the evening because the signal is weak?
It is a problem separate from signal strength; the cause is “congestion” from many people sharing the same base station. In particular, budget carriers (MVNOs) that operate by renting part of a major carrier’s network get speed in proportion to the bandwidth they rent, so they tend to slow down at weekday noon (around 11:30〜13:00) and during commuting hours. This is a characteristic of the mechanism, and using home or workplace Wi-Fi and avoiding heavy data use at busy times helps maintain the experience.
If I switch while keeping my current device, will the signal be okay?
You must check whether your device supports that carrier’s frequency bands. Overseas versions and some SIM-free devices may not support the low bands (such as Band 18/19/28) of a given Japanese carrier, producing a hard-to-diagnose fault where it works in cities but is extremely weak only in the suburbs or indoors. Compare the device’s spec page with the destination’s “verified devices” list. Also check whether the Giteki mark is present.
Is it okay for the whole family to use the same carrier?
Even within the same home, each person’s workplace, school and commute route differ, so check the signal in each family member’s own daily area. It is not unusual for things to be fine inside the home but weak only at someone’s workplace or school. Check everyone’s main places with maps and user accounts, and if someone is worried, choose a carrier with extra weight on that spot to have fewer regrets.
The map says “covered,” so why can’t I connect in the underground mall?
Because underground, radio waves from base stations do not reach directly and the area is often covered by indoor antenna systems that carriers install jointly. Which carriers take part in that system and how far they build it makes a big difference. An above-ground area map cannot show the differences underground, so it is most reliable to confirm, through accounts from the same area or a trial on site, that the carrier works well in the underground malls and stations you use often.
Why is it slow even though I have three bars?
The number of bars shows the strength of the signal being received, not how crowded the line is. If many people are connected to a base station, speed drops even when the signal is strong. You can tell them apart: if it slows during lunch breaks or commuting hours, congestion is the cause; if it is slow regardless of the time of day, you are probably latched onto a weak signal.
Why does toggling airplane mode sometimes bring the signal back?
A device tries to stay connected to the base station it has latched onto, so even if you move and a better base station is nearby, it may stay on a weak signal. Toggling airplane mode resets the connection and searches again for the best base station at that spot. This is why it works right after leaving an elevator or the underground.
The area map shows my home as covered, but in reality there is no signal. Is there a way to spot this before applying?
The map is an estimate based on outdoor reception, so it does not reflect attenuation caused by a building’s structure. The surest way is to ask a family member or friend who uses that carrier to show you the display at your home. If that is difficult, you can confirm on a real device with a short-term data-only eSIM or similar before moving your number.
* This article is for reference only. Sale dates, point rates and campaign terms can change, so check each store's official page for the latest details.