4 ms·

They use a custom low power basestation. Cf : "The prototype basestation uses an unlicensed frequency, limited to low-power transmissions. ... Real cell towers

They use a custom low power basestation. Cf : "The prototype basestation uses an unlicensed frequency, limited to low-power transmissions. ... Real cell towers have a hundred times as much power, and would increase the range to perhaps a kilometer,"

mostlyskeptical 9y ago
Real cell towers may use more power than unlicensed is allowed to in some cases, but not significantly much and definitely not hundreds of times. I worked at Clearwire (Clear wimax) and even on the spectrum we owned we generally used less than 1W of power per sector. Very small ones would only use a couple of hundred mW and our longest range sites in rural Texas were either 2W or 5W (memory is fuzzy). To be fair, we used more sites closer together instead of a few larger ones, but the point stands. Cell sites biggest advantage is elevation and line of site, not massive transmit power.
- flashdance 9y ago
  I work at Ericsson (one of the largest radio companies in the world) and we have towers that crank out 80w for 4g/5g. Mind you, I'm a software guy, not a hardware guy. Elevation and line of sight are important but power is too! Ctrl-f "watts" on this page to see what I'm talking about: https://www.ericsson.com/en/networks/offerings/connecting-the-unconnected https://www.ericsson.com/en/networks/offerings/connecting-th...
  - Johnythree 9y ago
    You are confusing peak power with average power. The law of reciprocity says that nothing is to be gained if the base transmitter is more powerful than the mobile TX. However because the base has multiple (hundreds) of low-power transmitters, it must cater for a very large instantaneous peak power when they momentarily add up. And more importantly, excess Transmit power reduces the re-use ability of that frequency in nearby cells.
    - deleted 9y ago
      [deleted]
    - Dylan16807 9y ago
      > The law of reciprocity The what? The only thing I can find about reciprocity is that antennas have the same characteristics in either direction. That doesn't mean your noise levels are the same, and you very often have different bandwidth requirements in each direction.
    - flashdance 9y ago
      > The law of reciprocity says that nothing is to be gained if the base transmitter is more powerful than the mobile TX. Late response, but that assumes that the mobile RX is as good as the tower's RX, and I can assure you that's not the case. The gear up on a tower has a way better low noise amplifier than a mobile phone, so it's able to "hear" the phone at a greater distance than you'd expect. That's why it's a-okay to have a base transmitter with a quite a bit more power than a mobile TX.
contravariant 9y ago
Unless I'm mistaken about how these things work, 100 times as much power would only increase the range 10 fold to about 150 meters.
- BenjiWiebe 9y ago
  That would be with an isotropic radiator, right? I'd assume a cell tower antenna would send very little energy straight up or down, which would mean it was somewhat focused.
  - contravariant 9y ago
    It assumes the cell tower is just a scaled up version of the small antenna. If a cell tower has better technology that allows it to focus its signal better then obviously it is going to perform better.
    - Johnythree 9y ago
      No, it allows the focused Transmitter to use less power. Any excess power prevents re-use of the frequency in adjacent cells.
  - Johnythree 9y ago
    Directivity (eg gain) makes no difference. An increase of X, is still an increase of X.
    - BenjiWiebe 9y ago
      My point was, the inverse square law is for an isotropic radiator.

mostlyskeptical 9y ago

Real cell towers may use more power than unlicensed is allowed to in some cases, but not significantly much and definitely not hundreds of times. I worked at Clearwire (Clear wimax) and even on the spectrum we owned we generally used less than 1W of power per sector. Very small ones would only use a couple of hundred mW and our longest range sites in rural Texas were either 2W or 5W (memory is fuzzy). To be fair, we used more sites closer together instead of a few larger ones, but the point stands. Cell sites biggest advantage is elevation and line of site, not massive transmit power.

flashdance 9y ago
I work at Ericsson (one of the largest radio companies in the world) and we have towers that crank out 80w for 4g/5g. Mind you, I'm a software guy, not a hardware guy. Elevation and line of sight are important but power is too! Ctrl-f "watts" on this page to see what I'm talking about: https://www.ericsson.com/en/networks/offerings/connecting-the-unconnected https://www.ericsson.com/en/networks/offerings/connecting-th...
- Johnythree 9y ago
  You are confusing peak power with average power. The law of reciprocity says that nothing is to be gained if the base transmitter is more powerful than the mobile TX. However because the base has multiple (hundreds) of low-power transmitters, it must cater for a very large instantaneous peak power when they momentarily add up. And more importantly, excess Transmit power reduces the re-use ability of that frequency in nearby cells.
  - deleted 9y ago
    [deleted]
  - Dylan16807 9y ago
    > The law of reciprocity The what? The only thing I can find about reciprocity is that antennas have the same characteristics in either direction. That doesn't mean your noise levels are the same, and you very often have different bandwidth requirements in each direction.
  - flashdance 9y ago
    > The law of reciprocity says that nothing is to be gained if the base transmitter is more powerful than the mobile TX. Late response, but that assumes that the mobile RX is as good as the tower's RX, and I can assure you that's not the case. The gear up on a tower has a way better low noise amplifier than a mobile phone, so it's able to "hear" the phone at a greater distance than you'd expect. That's why it's a-okay to have a base transmitter with a quite a bit more power than a mobile TX.

contravariant 9y ago

Unless I'm mistaken about how these things work, 100 times as much power would only increase the range 10 fold to about 150 meters.

BenjiWiebe 9y ago
That would be with an isotropic radiator, right? I'd assume a cell tower antenna would send very little energy straight up or down, which would mean it was somewhat focused.
- contravariant 9y ago
  It assumes the cell tower is just a scaled up version of the small antenna. If a cell tower has better technology that allows it to focus its signal better then obviously it is going to perform better.
  - Johnythree 9y ago
    No, it allows the focused Transmitter to use less power. Any excess power prevents re-use of the frequency in adjacent cells.
- Johnythree 9y ago
  Directivity (eg gain) makes no difference. An increase of X, is still an increase of X.
  - BenjiWiebe 9y ago
    My point was, the inverse square law is for an isotropic radiator.