Why does a cell tower need to be massive to transmit data to a smartphone but the phone’s extremely small antenna can transmit data back over the same distance?
In: 52
The cell tower’s massive equipment can pick up even weak signal, while the phone’s small antenna needs to get a fairly strong signal to receive it reliably.
It is exactly because the phone has a small antenna and low powered. So if you think of a receiver and transmitter. The smaller the receiver ie the phone, the larger the signal it needs to “hear” things therefore the cell tower has to be large and powerful. And as the phone has a small transmitter, it emits a weak signal and the receiver (cell tower) needs to be large to “hear” it.
The cell tower’s massive equipment can pick up even weak signal, while the phone’s small antenna needs to get a fairly strong signal to receive it reliably.
It is exactly because the phone has a small antenna and low powered. So if you think of a receiver and transmitter. The smaller the receiver ie the phone, the larger the signal it needs to “hear” things therefore the cell tower has to be large and powerful. And as the phone has a small transmitter, it emits a weak signal and the receiver (cell tower) needs to be large to “hear” it.
Also your phone is only dealing with one communication – that between your phone and the transmitter.
The transmitter on the other hand is dealing hundreds or even thousands of transmissions to and from hundreds or thousands of devices simultaneously. It needs to be big and powerful to be able to do that.
Think of a cell tower as a big, loudspeaker that needs to talk to many people who are far away. It needs to be big and powerful to send its message far and wide to reach all the people it needs to talk to.
A smartphone, on the other hand, is like a small microphone that needs to talk back to the loudspeaker. It doesn’t need to be as big or as loud because it only needs to send its message back to the loudspeaker which is closer. It’s also really good at listening to quiet sounds, so even if the loudspeaker is far away, the smartphone can still hear it and talk back.
Think of a cell tower as a big, loudspeaker that needs to talk to many people who are far away. It needs to be big and powerful to send its message far and wide to reach all the people it needs to talk to.
A smartphone, on the other hand, is like a small microphone that needs to talk back to the loudspeaker. It doesn’t need to be as big or as loud because it only needs to send its message back to the loudspeaker which is closer. It’s also really good at listening to quiet sounds, so even if the loudspeaker is far away, the smartphone can still hear it and talk back.
Also your phone is only dealing with one communication – that between your phone and the transmitter.
The transmitter on the other hand is dealing hundreds or even thousands of transmissions to and from hundreds or thousands of devices simultaneously. It needs to be big and powerful to be able to do that.
Size of an antenna is correlated to how loudly it can transmit and how quiet of a signal it can receive.
Imagine a cellphone is your hearing-impaired grandma with laryngitis. If you want to have a conversation, with her, you have two options: get close enough for you two to hear each other, or get a loud enough voice and big enough ears to converse at your current distance.
A cell tower obviously can’t move and so has to just have a loud “mouth” and big “ears.”
To simplify it a bit, range is basically sqrt(Size1xSize2).
If you halve the size of one antenna the other needs to double to maintain the same signal between the two.
So since we can make the phone antenna/transmitter less powerful and sensitive in exchange for making the tower more powerful and sensitive we go with small phones and big towers. It keeps the big expensive parts on the tower, and phones small and with lots of battery life.
Note “Size” really doesn’t translate directly to physical size, it’s more about antenna directionality/gain + transmit power, and fancy hardware to do stuff like beamforming. But in general using large arrays of antennas, or stuff like a dish require more physical space so it’s close enough.
However if you look at a tower the physical antennas (on common cell phone towers the vertical rectangles up top attached to a triangle frame) , while much large than a phone, aren’t actually that big compared to the tower. The tower itself is used to get the antenna off the ground to keep line of sight between phones and the towers, since it’s really inconvenient to ask you to climb to the roof of the building to make a call 😀
Latest Answers