Explain spread spectrum techniques and their benefits.

Spread spectrum techniques spread the signal over a bandwidth much wider than necessary for the data rate. FHSS (Frequency Hopping Spread Spectrum): Signal hops between frequencies in a pseudo-random sequence; used in Bluetooth. Processing gain = number of hopping frequencies. DSSS (Direct Sequence Spread Spectrum): Data is multiplied by a high-rate spreading code (chips); used in GPS, CDMA. Processing gain = chip rate/data rate. Benefits include: resistance to narrowband interference, low probability of interception, resistance to jamming, multiple users can share same spectrum (CDMA), and reduced multipath effects. Trade-off is increased bandwidth requirement.