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I'm newbie in wireless communication and have many questions with spread spectrum. I've learned that spread spectrum method for transmission RF signal is less susceptible to intentional jamming or unintentional interference from outside sources and multipath interference problem. Because it uses range of frequencies that it has.

I don't understand this point. How does spread spectrum technologies that use spread spectrum method send its data by using range of frequencies?

Given that, There is one Wi-Fi device that uses dsss technology to transmit its data with channel 1 that has 22 MHz wide from 2.401 GHz to 2.422 GHz. How does this device transmit its data that consist of 1.000 bits by using this 22 MHz wide?

Does this device transmit its data as a beginning 2.401 GHz at a given time, and after some time 2.402 GHz and after some time 2.403 until 2.422 GHz? Does it use range of frequencies like that?

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Please see below:

"The original 802.11 standard used an 11 chip Barker code modulation. For each data symbol, an 11 chip sequence is transmitted. The symbol rate is 1 Ms/sec, so the chip rate is 11 Million chips per second. This yields the resulting spectrum (i.e. null to null) is +/- 11 MHz around the center frequency. The exact shape of the spectrum is determined by the filtering of the modulated chips.

IEEE 802.11b introduced a new modulation format called Complementary Code Keying, but it employs the same 11 Million chips per second as the original 802.11. So the output spectrum has the same nulls at +/- 11 MHz relative to the center carrier."

source: link

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  • Thanks for reply. But This answer explain why? But i want to know how? How 22 mhz wide is used to spread data. Like fhss, does Dsss use hopping technique within its channel? – Pioneerhfy Oct 9 '17 at 14:07
  • 22Mhz spectrum don't spread data accross frquencies and don't "jump" channels. It does shorten pulse duration and than increase bandwitch which could be transmitted. – Datagram.Network Oct 10 '17 at 10:00
  • Thanks for reply. I understood your first explonation about jumping. But i didn't understand "It does shorten pulse duration and than increase bandwitch which could be transmitted." this section. Could you explain more clearly? What is pulse duration? – Pioneerhfy Oct 10 '17 at 10:33

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