How do cell phones work?

We use our mobile phones, also known as cell phones, every day and see lots of other people doing exactly the same. But do you sometimes wonder how our mobile phones actually work? If you have ever used Walkie Talkies or baby monitors, then you may know that those devices connect directly to each other on certain frequency channels.

Cell phones, however, work differently and connect to a cellular network which then allows them to communicate with other phones and devices through the network. Mobile cellular networks use advanced technologies to establish a connection between the cell phone and the strongest available base station used by the mobile service provider.

Mobile service providers can either be mobile network operators who own the network or they can be MVNOs (Mobile Virtual Network Operators) who use someone else’s mobile network to offer their services. More on the difference between mobile operators and MVNOs in this post.

What are cells in cell phones?

Let’s have a look at the diagram below to understand the concept in a simplified way. The base stations are part of the mobile radio access network that is responsible for the wireless connectivity for mobile phones. These base stations have something called transceivers (transmitter + receiver) that can receive signals from the cell phone and transmit signals from the network back to the phone for enabling two-way communication. The emission of radio waves from the base stations creates network coverage which cell phones use to connect to the mobile network. The network coverage area created by the radiations through a particular radio unit within a base station is called a cell.

how cell phones work
Conceptual diagram of how a cell phone connects to a mobile network

The hexagonal shape is just for the conceptual view and in real-life cells do overlap also so that a handover can take place when someone is moving from one cell into the other. The range of a regular cell, also known as a macrocell is in tens of kilometres. There are different kinds of cells including microcells and other small cells which you can read more about in this post.

The radio network that the base stations belong to is only one part of the overall mobile network. Mobile radio network connects to the mobile core network which then connects to external networks like PSTN and the Internet. That way a mobile service provider is able to connect you to anyone no matter which mobile or fixed network they are on.

Let’s now talk a little bit about the advanced technologies that we referred to earlier. Mobile networks use technologies like GSM, UMTS, LTE and NR to enable 2G, 3G, 4G and 5G services for us. In some countries especially on the US side, 2G and 3G services were also enabled by IS-95 and CDMA2000 respectively. Depending on the technology, the network architecture looks different however in all cases there is a cell phone and there is a base station that creates cellular coverage.

What happens when we move from one cell to the other?

Our mobile phones are always communicating with the mobile network even in the idle mode when no one is using the phone. The mobile phone keeps the network updated about its location and presence. In cases when we are moving e.g. driving from home to work, we may come out of the range of one cell and move into the range of another cell. When that happens during any active session e.g. during a voice call, our session (or call) gets ‘handed over’ from one cell to another. This way, throughout a journey, our call or data session keep hopping from cell to cell to make sure we stay connected without dropping the call or interrupting the data session.

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