CDMA

 CDMA:

CDMA is a purely digital techniques. It is also known as spread spectrum because it is a digitized version of the analog signal and is distributed over a wider bandwidth on a lower power level. This method is called Direct Sequence Spread Spectrum (DSSS) and (fig. 4). The digitized and compressed voice signals in serial data form distributed after processing in an XOR circuit chip comprises a ping signal having a higher frequency. In CDMA IS-95 standard , a 1.2288 – Mbit / s signal Chipping circulation of the digitized compressed voice at 13 kbit / s.

cdma4

Spread spectrum techniques of CDMA. The compressed and digitized speech signal is processed in an XOR logic circuit is provided with coded chipping of a high-frequency signal. The result is that digital voice is divided can be shared over a larger bandwidth with other users with different codes.

The shard is derived from a pseudo-random code generator that assigns a unique code to each channel. This code spreads the speech signal over a bandwidth of 1.25 MHz. The resulting signal on a low power, and appear more like noise. Many such signals may occupy the same channel simultaneously. For example, using 64 unique code chipping up to 64 users on the same 1.25 MHz channels can occupy at the same time. In the receiver, find a correlating circuit and displays a specific calling code and restores.

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The third generation (3G) mobile phone technology referred to as wideband CDMA (WCDMA) using a similar method to compressed speech and 3.84 Mbit / s chipping code with a 5-MHz channel, multiple users can share the same band.

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Posted by on Jul 23 2016. Filed under Latest Updates, Mobile Communication, CDMA, TECHNOLOGY. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

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