How does WiFi router/Cell towers receive signal from personal devices?

[crystal6tak]

This question popped in my mind a few hours ago. Cell towers/WiFi routers blasts out powerful signals for our laptops/phones/etc, I get that. But how does it work the other way around? How does data from my phone (like what website I want to browse) go to the WiFi router? 

 

Assuming my phone/laptop also blasts a signal to the router to pick up, does that mean my upload speed is limited by my personal devices? If so how does extremely powerful WiFi routers work? Am I to assume my phone is capable of blasting signals powerful enough to pass through multiple walls just as those powerful WiFi routers can?

 

How the heck does cellular data work then? My tiny ass phone can push out enough signal for a cell tower several miles away to pick up?!?!

[Rune]

In short, yes. That's why most standalone GPS devices are still so expensive for what they do as well. Devices like advanced routers often have beamforming or some similar technology to help pick up on weaker signals. I imagine cell phone towers have a larger equivalent.

[xentropa]

30 minutes ago, crystal6tak said:

This question popped in my mind a few hours ago. Cell towers/WiFi routers blasts out powerful signals for our laptops/phones/etc, I get that. But how does it work the other way around? How does data from my phone (like what website I want to browse) go to the WiFi router? 

 

Assuming my phone/laptop also blasts a signal to the router to pick up, does that mean my upload speed is limited by my personal devices? If so how does extremely powerful WiFi routers work? Am I to assume my phone is capable of blasting signals powerful enough to pass through multiple walls just as those powerful WiFi routers can?

 

How the heck does cellular data work then? My tiny ass phone can push out enough signal for a cell tower several miles away to pick up?!?!

Your laptop and cell phone does emit a signal which can be read by the router.  Signals emitted by your phone do not have to be very strong and there are noise filtering techniques possible with AC signals (in the microwave frequency range) which can pick up data even down to -60 dB relative to noise.

 

As far as how cellular data works...

 

Cell phones and their towers are all "locked" to a frequency.  Your cell phone has a built in signal filter to remove all signals except the frequency you want to use, and all towers do the same as well.  As far as how cell phone towers tell the difference between each individual phone, there are several methods, but I won't go into too much details.  Wiki up time division multiple access TDMA, and code division multiple access CDMA which are probably the most common schemes employed by cell phone communication.

[Mark77]

1 hour ago, crystal6tak said:

This question popped in my mind a few hours ago. Cell towers/WiFi routers blasts out powerful signals for our laptops/phones/etc, I get that. But how does it work the other way around? How does data from my phone (like what website I want to browse) go to the WiFi router? 

 

 

Assuming my phone/laptop also blasts a signal to the router to pick up, does that mean my upload speed is limited by my personal devices? If so how does extremely powerful WiFi routers work? Am I to assume my phone is capable of blasting signals powerful enough to pass through multiple walls just as those powerful WiFi routers can?

 

How the heck does cellular data work then? My tiny ass phone can push out enough signal for a cell tower several miles away to pick up?!?!

 

In the case of WiFi, basically the access point and the receiver points use identical (or nearly identical) hardware.  There is no collision control in Ethernet, so basically its a "free for all" on the airwaves.  Access points *may* be equipped with better quality antennas and sometimes can use antenna diversity in an attempt to receive a better quality signal, but WiFi (ie: 802.11) isn't really all that sophisticated.  Thus, it copes very poorly with malfunctioning hardware, weak signals, etc.  Ethernet with multiple stations (the classical example being coaxial Ethernet in 802.3, ie: 10base-2, but conceptually such extends to 802.11 as well) is notorious for suffering performance collapse very quickly due to collisions.  802.11 is dirt cheap, but its really not a viable technology for large numbers of users.

 

Cell networks, based on CDMA (and derivatives like WCDMA, which is the underlying technology used in 4G LTE) are set up for centralized control of the data transmission "problem".  In a nutshell, they can shut down errant/overly weak stations by minimizing their access to the system.  They also use antennas which are also, to some extent, 'steerable' (using techniques similar to that used for phased array radar), and they typically will use higher gain directional antennas as part of their overall schema to improve point-to-point RF performance.  If you look at a typical cell tower, for example, it probably will have a number of antennas facing different directions -- this directionality improves RF performance, at the cost of needing a lot more (very expensive/sophisticated) hardware. 

 

4G LTE tops out at around 2W for a typical client station in MIMO mode.  Non-highly-directional Wifi systems (ie: what people use on all but point-to-point links) are restricted to power levels far lower.  But there's some amazing things that can be done even with 802.11 Wifi when proper engineering is done.  For instance, there are people who use 802.11 with appropriate high-gain antennas and very little power to achieve links of 20-50km!  There are "Wireless ISPs" that do the same with directional antennas and tower-mounted systems in many rural communities around the world.  The City in which I live felt they were being ripped off on leased circuits from the telephone company, and hence, built its own network with 802.11 equipment for high bandwidth point to point links. 

 

 

[.spider.]

1 hour ago, Rune said:

 That's why most standalone GPS devices are still so expensive for what they do as well. 

It is not possible to compare GPS to 802.11, GSM, WCDMA...

GPS is not even a bidirectional communication!

[Rune]

27 minutes ago, .spider. said:

It is not possible to compare GPS to 802.11, GSM, WCDMA...

GPS is not even a bidirectional communication!

Yes, but I meant that comparison more in terms of signal strength and the cost of equipment used, not type.