What are the two types of spread-spectrum transmission techniques?

Spread-spectrum transmission techniques are essential in telecommunications as they provide advantages such as resistance to interference and multipath fading. The two primary types of spread-spectrum techniques are frequency hopping and direct sequencing.

Frequency hopping works by rapidly switching the carrier frequency among many pre-determined frequencies during transmission, making it more difficult for unauthorized listeners to intercept the signal. It provides security and helps minimize interference from other signals.

Direct sequencing, on the other hand, spreads the signal over a wider bandwidth by modulating it with a pseudo-random noise code. This technique effectively increases the resilience of the transmission against interference and jamming while allowing multiple users to share the same frequency spectrum through code division.

In contrast, the other options listed do not represent the two established techniques for spread-spectrum transmission. Amplitude modulation and frequency modulation are conventional analog modulation techniques rather than spread-spectrum methods. Wavelength hopping and signal encoding refer to different aspects of communications and are not linked to the spread-spectrum designation. Direct modulation and frequency response describe signal modulation types and system characteristics, respectively, but do not specifically categorize spread-spectrum techniques.