I'm a computer scientist, in college I had a (basic) telecommunications course. I've found it interesting, but had afterwards no opportunity to use apply it professionally, which is of course not surprising. However, once in the aftermath of a class, the professor posed a question to ponder:

"How do you think it is possible for a cell carrier to exactly deliver the signal to your phone, even when sitting in a bus with 50 other cell phones around and moving on the highway with high speed?"

Unfortunately, we never got around to obtaining the answer. I've often thought about it for the past few years, but came to no answer. Can someone help out?

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    \$\begingroup\$ It feels like the professor was laying the foundation for some more teaching. Unfortunately, the words "exactly deliver the signal to your phone" seem profoundly misleading. Maybe replace with "broadcast a signal so your phone can receive calls intended for it"? \$\endgroup\$ – gbulmer Sep 22 '14 at 15:19

What makes you think that the signal must be delivered 'exactly' to your cell phone? The transmitter just shouts loud enough that all phones in the cell receive its signal. It is up to each phone to sift through this signal and pick out the parts that are intended for it.

There is indeed an interesting problem for the towers and the phones when an active phone travels from the area of one tower to another one, this is called 'handover'. Basically the towers communicate and decide on the basis of signal strength when the next tower takes over the phone.

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  • \$\begingroup\$ Your handover comment is only really valid for 2G (and earlier) mobile telephony, e.g. GSM. WCDMA (3G) handover is far more graduated; a handset can be "connected" to some extent to multiple RN's. I've never read anything on the equivalent 4/5G processes but it seems likely that it's not going to be a step backwards from 3G. \$\endgroup\$ – markt Sep 23 '14 at 6:21

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