Direct-sequence spread spectrum: Difference between revisions

Revision as of 07:55, 15 November 2018

Revision as of 23:10, 9 March 2019

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{{Use American English|date = March 2019}}

{{Short description|Modulation technique to reduce signal interference}}

{{Use mdy dates|date = March 2019}}

{{Modulation techniques}}

{{Multiplex_techniques}}

In [[telecommunication]]s, '''direct-sequence spread spectrum''' ('''DSSS''') is a [[spread spectrum]] [[modulation]] technique used to reduce overall signal [[Interference (communication)|interference]]. The spreading of this signal makes the resulting [[wideband]] channel more [[White noise|noisy]], allowing for greater resistance to unintentional and intentional interference.<ref name="Haykin4E">{{cite book|last1=Haykin|first1=Simon|title=Communication systems|date=2008|publisher=John Wiley & Sons|pages=488–99|edition=4|url=https://archive.org/details/CommunicationSystems4thEditionSimonHaykinsolutionsManual|accessdate=11 April 2015}}</ref>

A method of achieving the spreading of a given signal is provided by the modulation scheme. With DSSS, the message signal is used to modulate a bit sequence known as a [[Pseudorandom noise#PN code|Pseudo Noise (PN)]] code; this PN code consists of a radio pulse that is much shorter in duration (larger bandwidth) than the original message signal. This modulation of the message signal scrambles and spreads the pieces of data, and thereby resulting in a bandwidth size nearly identical to that of the PN sequence.<ref name=Haykin4E/> In this context, the duration of the radio pulse for the PN code is referred to as the [[Chip (CDMA)|chip]] duration. The smaller this duration, the larger the bandwidth of the resulting DSSS signal; more bandwidth multiplexed to the message signal results in better resistance against interference.<ref name=Haykin4E/><ref>{{Cite web|url=http://www.telecomabc.com/d/dsss.html|title=DSSS - Direct Sequence Spread Spectrum - Telecom ABC|website=www.telecomabc.com|access-date=2016-11-11}}</ref>