Why does 5G need small cells, and what is the surprising capacity benefit of having more, smaller cells?
mmWave's short range forces a dense network of small cells (with femtocells for indoor coverage). Beyond just compensating for range, more cells means more capacity: each device in a cell talks on a dedicated channel, and channels are limited — so more cells means more total available channels and more devices served.
Why small cells are needed:
- To compensate for mmWave's limited range, 5G needs small cells
- "Small" is relative to traditional large cell masts
- Because they have correspondingly shorter range, the idea is a dense network of them, with femtocells ensuring indoor coverage (home / small office)
The non-obvious capacity argument:
- It seems cost- and labour-intensive — and there are downsides — but more cells brings a real advantage
- Each device in a cell communicates with the antenna on a dedicated channel
- The number of available channels is limited
- So using smaller cells with shorter range pays off in more available channels — smaller cells can collectively accommodate more devices
Why this works (spatial reuse): because a small cell's signal doesn't travel far, the same channel can be reused in another small cell nearby without interference. Shrinking cells multiplies how many times each scarce channel can be reused across an area — turning "limited channels" into "limited channels × many cells."
Tip: Small cells solve two problems at once: they reach mmWave's short range AND multiply capacity through spatial frequency reuse. This is the cellular concept (frequency reuse) pushed to its extreme.
Go deeper:
Cellular network — frequency reuse (Wikipedia) — the foundational idea this card extends: the same channels reused in non-adjacent cells, which is exactly why shrinking cells multiplies capacity.