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Comment by __s | Hacker News Reader

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__s·

> 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

For hexagons you can get by with 3, https://en.wikipedia.org/wiki/Hexagonal_tiling#Uniform_color...

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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.

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

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.

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..

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)

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