What PHY, Modulation, and Coding Actually Solve
Wireless rates change. A device may use a high rate near the AP and fall back near the coverage edge. BLE can choose between 1M PHY, 2M PHY, and LE Coded PHY. NB-IoT accepts low speed to improve coverage and power behavior.
The underlying issue is not simply “strong signal is fast, weak signal is slow.” PHY, modulation, and coding make the same trade-off: how much useful information can be carried with the current channel condition, and how much failure risk is acceptable.
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