Short range unlicensed remote controls, with typical range up to ~100 meters, are becoming increasingly popular, millions of these radios are used today in such applications as automotive keyless entry, tire pressure monitoring, gate openers, wireless security systems, data links, remote meter reading and many other applications to enumerate.
Nowadays, most short range remote control devices in market are using OOK modulation technique in transmitter and receiver, because OOK remote control transmitter and receiver’s working circuit is much more simpler than that of FSK, thus the overall cost is less when using OOK.
On the other hand, FSK has its own advantage, for example FSK can achieve a much higher data rate than OOK, because FSK doesn’t have to power off and on the whole transmitter circuit during every data bit transition, so FSK is used in computers WiFi link instead of OOK, but for most short range remote control devices such as garage door remote and other universal remote working at ~100m range, the data transmitted in pulse train contains only buttons, serial number and some encryption bits, in which case OOK can perfectly do the job.
We have found a interesting study online conducted by RFM Inc. that shows comprehensive comparision between OOK and FSK technology, the study paper came to following conclusion, especially for common short range devices applicaton.
- OOK transmitters are simpler than FSK
- OOK transmitter power consumption current is 50% lower than FSK
- SAW based OOK transmitters are more robust when exposed to extreme temperatures, vibration and shock
- FSK transmission requires 1.5 times the bandwidth compared to OOK
- OOK receivers are simpler than FSK
- OOK receiver sensitivity is equal to or better than FSK
- Properly implemented, OOK receiver performance in the presence of co-channel interference is generally better than FSK
- Properly implemented, OOK receiver performance with amplitude flutter is equal to or better than FSK
The paper also indicates that, in the past, although millions of OOK transmitter and receiver has been main drive for popularity of short range devices, OOK radio links have commonly been associated with the poor performance of superregenerative receivers and poorly implemented superheterodyne receivers.
It has been shown in this paper that properly implemented OOK links can outperform or equal FSK links in all areas of concern while maintaining simplicity, an example of the simplicity of a properly implemented OOK receiver is the RFM receiver whose performance was outlined in this paper, also in the paper includes a schematic diagram of the RFM receiver showing the external components necessary to achieve the performance illustrated in this paper.
The complete paper of this OOK vs FSK modulation technique for radio links study can be found here at our website, you can view it online or right click the link to download to your computer.