Explain Concepts of Spread Spectrum.
Mobile phone technology had a reincarnation from first generation analogue (using FDMA) to second generation digital (using TDMA).
The next incarnation is from second generation digital TDMA to third generation packet (using CDMA).
CDMA is a specific modulation technique of Spread-Spectrum technology.
Third generation or 3G is more of a generic term to mean mobile networks with high bandwidth.
In a conventional transmission system, the information is modulated with a carrier signal and then transmitted through a medium.
When that transmitted, all the power of the signal is transmitted centered around a particular frequency. This frequency represents a specific channel and generally has a very narrow band.
In spread-spectrum we spread the transmission power over the complete band as shown in figure.
Fig. Spread Spectrum Technology
In spread-spectrum the transmission signal bandwidth is much higher than the information bandwidth.
There are numerous ways to cause a carrier to spread; however, all spread-spectrum systems can be viewed as two steps modulation processes.
First, the data to be transmitted is modulated.
Second, the carrier is modulated by the spreading code, causing it to spread out over a large bandwidth.
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