3 ms·

> Here you have 7 different frequencies used in different groups of cells. You should only need 4 different frequencies: https://en.wikipedia.org/wiki/Four_col

by __s 5y ago

> Here you have 7 different frequencies used in different groups of cells. You should only need 4 different frequencies: https://en.wikipedia.org/wiki/Four_color_theorem https://en.wikipedia.org/wiki/Four_color_theorem For hexagons you can get by with 3, https://en.wikipedia.org/wiki/Hexagonal_tiling#Uniform_colorings https://en.wikipedia.org/wiki/Hexagonal_tiling#Uniform_color...

PaulHoule 5y ago
You'd think so but practically the signal bleeds across to second-adjacent cells and a real channel plan needs more than that. Look at how the 3 WiFi channels in 2.4GHz land is nowhere near sufficient for good spatial diversity and it is even a struggle with the 5GHz channels that aren't gated to avoid interference with radar.
- __s 5y ago
  Indeed. In fact, the link I responded to shows a pattern matching the 7 color 3-uniform distribution I linked to
p_l 5y ago
That only works if you have exact edges and that each BTW uses only one base channel (iirc, they mix and match as much as possible)
zw123456 5y ago
Yes, each cell interferes with the next, that is call co-channel interference. That is a major factor that limits the capacity of a cellular network. There are a number of approaches used to manage that, carriers spend a lot of money and employ many engineers designing around that. SON (Self Optimizing Network) is the latest tech that is being deployed on 4G and 5G to help combat that. BTW, this is one of the reasons you can get much higher tputs with mm-wave because the beams do not propagate very far which makes keeping co-chan down, that's the good news, the bad news is it doesn't propagate well, which means you need way more nodes.
kabouseng 5y ago
It's not a hard stop between cells. You don't have radio signals and then suddenly nothing because of reflections, absorbtions and the very nature of log scale of signal distance drop off..

by __s 5y ago

PaulHoule 5y ago

You'd think so but practically the signal bleeds across to second-adjacent cells and a real channel plan needs more than that. Look at how the 3 WiFi channels in 2.4GHz land is nowhere near sufficient for good spatial diversity and it is even a struggle with the 5GHz channels that aren't gated to avoid interference with radar.

__s 5y ago
Indeed. In fact, the link I responded to shows a pattern matching the 7 color 3-uniform distribution I linked to

p_l 5y ago

That only works if you have exact edges and that each BTW uses only one base channel (iirc, they mix and match as much as possible)

zw123456 5y ago

Yes, each cell interferes with the next, that is call co-channel interference. That is a major factor that limits the capacity of a cellular network. There are a number of approaches used to manage that, carriers spend a lot of money and employ many engineers designing around that. SON (Self Optimizing Network) is the latest tech that is being deployed on 4G and 5G to help combat that. BTW, this is one of the reasons you can get much higher tputs with mm-wave because the beams do not propagate very far which makes keeping co-chan down, that's the good news, the bad news is it doesn't propagate well, which means you need way more nodes.

kabouseng 5y ago

It's not a hard stop between cells. You don't have radio signals and then suddenly nothing because of reflections, absorbtions and the very nature of log scale of signal distance drop off..