Dsss Vs Fhss

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Keywords: rf, rfic, dsss, fhss, direct sequency, frequency hopping, spread spectrum, wireless, jammer,
codesequence, rf ics, tutorial, rfics
TUTORIAL 1890

An Introduction to Spread-Spectrum
Communications
Feb 18, 2003
Abstract: This application note is a tutorial overview of spread-spectrumprinciples. The discussion
covers both direct-sequence and fast-hopping methods. Theoretical equations are given to allow
performance estimates. Relation to CDMA and TDMA is provided. A schematic of a codesequence
generator is shown. Spectral plots illustrate direct-sequence spread-spectrum (DSSS) and frequencyhopping spread-spectrum (FHSS) methods.

Introduction
As spread-spectrum techniques becomeincreasingly popular,
electrical engineers outside the field are eager for understandable
explanations of the technology. There are books and websites on
the subject, but many are hard tounderstand or describe some
aspects while ignoring others (e.g., the DSSS technique with
extensive focus on PRN-code generation).

Click here for an overview of the wireless
components used in a typicalradio
transceiver.

The following discussion covers the full spectrum (pun intended).

A Short History
Spread-spectrum communications technology was first described on paper by an actress and amusician!
In 1941 Hollywood actress Hedy Lamarr and pianist George Antheil described a secure radio link to
control torpedos. They received U.S. Patent #2.292.387. The technology was not takenseriously at that
time by the U.S. Army and was forgotten until the 1980s, when it became active. Since then the
technology has become increasingly popular for applications that involve radio links inhostile
environments.
Typical applications for the resulting short-range data transceivers include satellite-positioning systems
(GPS), 3G mobile telecommunications, W-LAN (IEEE® 802.11a, IEEE...