CDMA is an acronym of Code Division Multiple Access. It is a second generation mobile communication system; it is the combination of FDMA and TDMA, and in this system, a user has access to the entire bandwidth for the entire duration. Here different CDMA codes are used to distinguish different users i.e. each user is assigned a unique code which is called PN codes.
There are two types of technologies that are used for Code Division Multiple Access. They are
- Direct Sequence Spread Spectrum Modulation.
- Frequency Hopping Spread spectrum modulation.
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The first type of technology is used for mobile communication which works on Code Division Multiple Access. It allows up to 61 concurrent users in a 1.2288 MHz channel by processing each voice sample with two PN codes. Code Division Multiple Access uses different technologies, and they are
- IS-95 1 this is developed by QUALCOMM technologies and is considered as first generation mobile communication networks.
- CDMA 2000 it is Second Generation Wireless networks which support data up to 14.4 kbps.
- CDMA 1X EVDO It is 3rd generation wireless networks which support speed up to 3.1 Mbps.
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- Frequency diversity – frequency dependent transmission impairments have less effect.
- Privacy is available since it supports different codes for different users.
- Effect of noise will be less.
- Voice clarity is good, and same has been extended to the next generation data systems such as WCDMA, HSDPA, etc.
- The performance of the system degrades if the no. of users automatically increases.
- Signals from near receiver are less attenuated than the signals from the far receiver.
- Air interface is more complicated as compared to GSM.
- High power dissipation for Transmitter and receiver.
- Not Symmetrical.
CDMA service providers in India:
- Reliance Communications
- Tata Teleservices