Why does a phone get poor reception in certain buildings?

You are right in the city centre, your operator advertises excellent network coverage… and yet, as soon as you step inside a building, the signal disappears or calls become difficult.

Rest assured, this is not necessarily a problem with your operator. In most cases, it is simply the way radio waves travel.

---

Walls block radio waves

The mobile network works thanks to radio waves emitted by mobile phone antennas.

As they pass through a building, these waves are partly absorbed or reflected by the construction materials.

The thicker or denser the walls, the weaker the signal becomes before it reaches your phone.

---

Some materials are particularly problematic

Not all buildings are equal.

The following materials can significantly weaken the signal:

• reinforced concrete;
• metal structures;
• modern glazing with thermal or metallic coating;
• façades insulated with certain specific materials.

This is why a recent, very well insulated building can sometimes offer poorer reception than an older house.

---

Basements are often the most difficult

Underground car parks, cellars, technical rooms and lifts are surrounded by concrete and sometimes located several metres below ground.

Radio waves then have far more difficulty reaching your phone, which explains the frequent loss of network in these places.

---

Distance to the antenna also plays a role

The further you are from a mobile antenna, the weaker the signal you receive.

Inside a building, this loss adds to the one caused by the walls and windows.

The result can be reception that is insufficient to make a call or to use the internet comfortably.

---

Not all frequencies behave in the same way

Operators use several frequency bands.

Lower frequencies generally penetrate better inside buildings, while higher frequencies offer more bandwidth but pass through obstacles less easily.

This is why your phone can sometimes show excellent reception outdoors and much poorer reception once inside.

---

The phone itself also matters

Not all smartphones have the same radio performance.

Two devices placed side by side, with the same operator, may display a different reception level depending on the quality of their antennas and components.

Software updates can also improve how the network is handled.

---

How can reception be improved?

A few simple measures can sometimes make the difference:

• move closer to a window;
• avoid basements whenever possible;
• enable Wi-Fi Calling if your phone and your operator support it;
• keep your smartphone up to date.

For businesses or large buildings, professional solutions are also available to improve mobile coverage inside the premises.

---

In summary

Poor reception inside a building does not necessarily mean a poor mobile network.

The thickness of the walls, the construction materials, the distance to the antenna, the frequency bands used and even your phone model all influence signal quality.

So before concluding that an operator covers your region badly, it is important to take into account the environment you are in.