What is the difference between ASK/OOK and FSK/GFSK modulation?
OOK/ASK carries information in the amplitude of the carrier; it is simple and low-consumption but directly exposed to amplitude noise such as inverters and welding arcs. FSK/GFSK carries the information in frequency, is largely independent of amplitude noise and gives a clear sensitivity advantage at the same data rate. Typical maximum sensitivity in FSK receivers is reported in the range of -125 to -130 dBm.
OOK (on-off keying) is the simplest form of ASK: the carrier is either there or not. The circuit is simple, consumption is low and cost is small. The price is that the receiver's decision threshold has to stay above the noise floor. On an industrial site, when the noise floor rises, OOK performance collapses suddenly rather than gradually.
In FSK the bit information is carried by two different frequencies. The receiver looks at the frequency difference, not amplitude; amplitude noise does not directly corrupt the decisions. GFSK smooths the transitions with a Gaussian filter and suppresses sideband spreading, so both spectral efficiency and adjacent channel behaviour improve.
Comparison summary:
- Cost and consumption: OOK is favourable.
- Noise robustness and sensitivity: FSK/GFSK clearly superior.
- Spectral cleanliness and certification compliance: GFSK is favourable.
A 6 dB improvement in sensitivity doubles the theoretical range, all else being equal. That is why, at the same output power, an FSK system works both further away and in a noisier environment than an OOK system. For remote controls working in electrically harsh environments, the choice of modulation is a more effective improvement than raising output power.
Full article: Wireless remote control installation: pairing, relay, safety