It makes sense that high power cell towers can reach cell phones. How do cell phones send signals back to towers?
In: Technology
Cell towers are much more sensitive to all the cell phone signals than your cell phone is, they also have much more processing of the signals to clean it up and fix bad packets,etc.
When you look at old cell phones from the really early generations, they were so big because their transmit power had to be so high since there were so many less cell towers around.
Like Zachs phone in saved by the bell.
If you have a flashlight, it will illuminate a few feet in front of you. Not very bright, definitely not as bright as a high-powered lamp. But, if you move quite far away from a person holding a flashlight, you can still see the flashlight, even if you can’t see anything it’s illuminating.
Same with cell phones. The signal may be weak, but it can still be “seen” by the tower from very far away.
Cell towers have to communicate with thousands of cell phones. Cell phones only have to communicate with one cell tower.
Cell towers have to be always on for you phones to find them while the phones can shut off to save power.
Get yourself on a noservice zone and enjoy your battery draining as if you were playing.
Think of it this way:
Cell towers are shouting really loud, so that your tiny cell phone can hear its message even when you’re far away.
Cell towers are also listening using extremely large ears (antennas) so that they can hear your tiny cell phone whispering from far away.
The important thing is the ratio between broadcast strength and receiver sensitivity. You phone and the cell tower should have the same ratio, but naturally the cell tower is going to have both better transmitters and better recievers.
1. one tower needs to serve many devices, your phone only needs to talk to the tower.
2. The tower has a bigger antenna, with a better ability to “focus” at a particular direction.
3. You typically upload much less than you download.
I’ll use the rock concert analogy.
Everyone can hear the music due to the huge speakers everywhere.
They can also hear the fans. When there are too many fans, it becomes hard for the band to make out what is being said (ever had “strong” signal but still can’t really do much?) by each individual fan. But one fan shouting back will not carry the same decibel level of noise as the numerous amount of speakers blasting out rock music.
First, These are NOT high power broadcast transmitters. Your average modern cell tower only radiates about 35 dbm (3 watts) . Standard 5g cell phones can transmit up to about 33 dbm (2 watts.)
Its all about the antennas. (we landed men on the moon with an 11watt radio…. and a very nice antenna…)…
The antennas focus the radio energy so the receiver can “see” the transmitter even though the power level is very low… A good receiver only needs to “see” about -90 dbm (0.000000000001 watts) to pickup the signal.
Cell towers receive, amplify and transmit. Cell towers have huge coverage radius, called a cell, and require a lot of power. Your cell phone only has to be powerful enough to communicate with the nearest cell tower. Tower coverage radiuses overlap for smooth signal handoff when traveling from one cell to another. Location, speed and directionality info are collected (among other things) constantly.
Cell towers tie into the main communications grid, and into the provider network, using fiber optic links. LOTS of them. The communications network itself is made up of server implementations called Master Switch Offices and Subordinate Switch Offices (I don’t think SSO is what they’re called but I can’t remember). The MSO is where the magic happens. Your call or text or whatever goes from phone to tower to MSO, and from there it gets routed either to another MSO or directly out to a tower to go back to another phone. The MSO is where the provider figures out where their phones are and how to most efficiently and economically communicate to/from those phones. As long as your phone is on, your provider knows exactly where you are at any given time (within n meters).
Cell tower service radius is based on terrain and how high the antennas are, in relation to the surrounding landscape.
Source: I worked as a Network Engineer for one of the biggest cell phone companies in the US.
Caveat: That was 20 years ago, so some of the concepts I touch on may be dated, but I believe this is all still applicable and current.
Low power transmitters sending signals back to huge antenna on towers.
If you can talk one way, you can talk the other.
In actual fact, I think you’ll find that mobile phones broadcast “stronger” for their signal than the relative portion of their signal coming from the tower. The tower is more powerful overall because it’s talking to hundreds of phones, but individually the phones are putting out more energy to talk to the tower than that tower did to talk to them.
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