DSSS (Direct Sequence Spread Spectrum)
DSSS is the technique in which data bits are multiplied by a much faster spreading code and spread over a wide band. While the receiver applies the same code to compress the signal back, interference energy that does not know the code is spread out instead and weakened. The ratio between the two is called processing gain and adds directly to the noise margin.
The greater the ratio of the spreading code rate to the data rate, the higher the processing gain. The receiver correlates the signal with its own copy of the code; the correlated component is gathered into a narrow band, while uncorrelated interference is spread over a wide band and filtered out.
- Difference from FHSS: FHSS runs away from interference, DSSS suppresses it. FHSS works on the time axis, DSSS on the code axis.
- Bandwidth requirement: DSSS continuously occupies a wide band; it is difficult to apply in narrow SRD sub-bands.
- Receiver complexity: code synchronization and correlation hardware are required, and consumption increases.
For this reason narrowband FSK or frequency hopping solutions are more common in short range remote control applications; DSSS is met more often in wideband systems. Knowing the concept lets you read what a product bases its interference immunity on.
Context in which this term is used: Wireless remote control installation: pairing, relay, safety