Subelement M: M – Communications Technology— Topic 82: Types of Transmissions
Question 3-82M3
Element 3 (GROL)What is the term used to describe a spread spectrum communications system where the center frequency of a conventional carrier is altered many times per second in accordance with a pseudo-random list of channels?
Explanation
Frequency hopping spread spectrum (FHSS) systems achieve spectrum spreading by rapidly changing the carrier frequency of a signal over a wide range of frequencies. The sequence of these frequency changes, or "hops," is determined by a pseudo-random code known to both the transmitting and receiving stations. This rapid, pseudo-random alteration of the center frequency across a list of available channels is the defining characteristic of FHSS.
Direct sequence spread spectrum (DSSS) is a different technique where the data stream is multiplied by a high-speed pseudo-noise code, spreading the signal across a wide bandwidth *without* changing the carrier frequency. "Time-domain frequency modulation" and "frequency compandored spread spectrum" are not recognized terms for this method of spread spectrum communication.
Related Questions
3-82M1 What term describes a wide-bandwidth communications system in which the RF carrier frequency varies according to some predetermined sequence?3-82M2 Name two types of spread spectrum systems used in most RF communications applications?3-82M4 A TDMA radio uses what to carry the multiple conversations sequentially?3-82M5 Which of the following statements about SSB voice transmissions is correct?3-82M6 What are the two most-used PCS (Personal Communications Systems) coding techniques used to separate different calls?