Edit: More about how two towers figure out which cellphones need to be connected to each other
In: Technology
pretty similar to how your computer can access website information stored on a server across the globe.
records of which devices (phone numbers) are connected to which towers; then a shared record of all that information so your phone can find a tower, that tower can relay through other towers (or underwater cables or satellites) to connect to the destination phone
The antenna in your phone is not directional, radio waves go in every direction away from you.
So the phone does not need to know where this tower is, it can just send radoawaves and knows some tower will pick it up(reality is a a bit more complex and there is a back and fort).
The tower acts a bit like an internet router then, they are in a network for a provider and country and have routing tables that tell what number can be found in what network and this signal is send over traditional ground wires like normal phine calls too then.
Your phone is constantly listening to different towers, keeping a list of the ones it can hear best. Each tower broadcasts its own identity code (each panel, in fact, has its own code). When you make a call, your phone reaches out to the the tower it hears the best and works its way down the list until one of them accepts the call (all depends who has room, towers *can* be “full” if a lot of people are on their phone at the same time).
Now for the other end. The network doesn’t know exactly *where* you are, but it has a general idea because the network is divided into Local Areas, and each area has its own Local Area Code (LAC). You phone knows what local area it is in; it’s part of the tower’s identity code. When it all of a sudden hears towers with one LAC better than towers with the LAC it had been hearing, it knows (even without GPS) that it has crossed into a new Local Area, so your phone reaches out to the network and sends a Local Area Update message. The network files that information away.
Back to your call. You dial your friend’s number, your phone reaches out to the towers it hears the best, and establishes a connection with the network. It then sends the number you’re trying to call. The network looks up which Local Area your friend’s phone last said it was in, and the entire Local Area, every single tower and panel, sends out a page over a separate channel that all phones are monitoring. The whole Local Area essentially yells, *”Marco!”* Your friend’s phone, which is always listening, reaches out to the tower it can hear the best and says, “*Polo!*” Your friend’s phone establishes a connection with the network through that tower, and now your call is routed to them through the network.
It’s a good deal more complicated than that (and some of my information may be out of date, I haven’t studied this in about 10 years), but that’s the ELI5 version.
The towers broadcast a “can you hear me?” signal and all the phones reply “yes!”
The towers are all talking to each other through the internet, and so it doesn’t matter if 3 different towers can hear u/Hasanatir. They figure out which tower can hear you loudest, and that tower takes responsibility for talking to you.
And they repeat this calculation all the time, so when you’re on the highway, the towers pass responsibility as you drive.
There are many directories in the phone network, both local to your nearest tower, right up to every SIM card the network manages across the world. Your phone places a call, asking the tower to find your friends phone, then it simply starts querying directories starting with its own local cell, and moves up to larger cells/providers until it finds a match.
All phones are constantly checking in, updating the network about which tower they are closest to (even when roaming) so when a call is placed, the network knows how to route it to you.
By each hop in the process only worrying about where to send the call next.
Your phone doesn’t work out how to get the call all the way across the world. It just shouts at the local cell towers saying it wants to make a call.
The cell towers and your phone agree between them which tower your phone should send the call via.
The cell tower also doesn’t work out how to get the call to its destination. It just shouts at a computer that it is connected to somewhere in the cell company and tells it that it has a call to handle.
The computer at the cell company looks at the number and uses it to work out whether it is the number of one of their customers, a number for someone else in your country or a number for someone else in another country.
If it is for someone else in another country it will look the number up in a big table to work out which country and which phone company is going to take the call. It then shouts at a computer in that phone company and says it has a call for it.
The same process happens in reverse at the other end. The cell company keeps track of which cell tower everyone is connected to, by the cell towers telling the cell companies computers about it when they see a new phone shout at the tower.
At least that is roughly how it will work…
The Internet works *roughly* the same way.
I like to imagine my phone like the sun in one of the episodes of Rick and Morty. It’s just constantly screaming to anyone that is around to listen.
Your phone doesn’t care which tower, because *they’ll all work*. That’s the point of cell towers – they’re interchangeable, it doesn’t really matter that much if you’re connected to one in particular.
Every tower will ultimately connect to one or more phone exchanges. An exchange receives a call, and gives it to someone else. It just passes it through. For local calls, it receives a nearby call and gives it to a nearby phone. For longer distance, however, it gives the call to another exchange – which might give it to another exchange, then another, and so on across the world.
When a cellphone needs to reach another cellphone halfway across the world, it first connects to nearby cell towers. These towers are identified by unique codes. The cellphone then registers with its home carrier’s network. When a call or message is sent, it travels through the home network to reach the destination. If the destination is on a different network or in another country, the request is routed through international connections until it reaches the right network and cellphone. This process uses global standards and agreements between carriers to ensure connections are made accurately and efficiently.
They don’t, they’re only aware of devices in the immediate vicinity.
They consult **routers**, which can find a path to most other devices on the Internet or mobile networks.
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