Code Division Multiple Access technology overview

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

  1. Direct Sequence Spread Spectrum Modulation.
  2. Frequency Hopping Spread spectrum modulation.

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

  1. IS-95 1 this is developed by QUALCOMM technologies and is considered as first generation mobile communication networks.
  2. CDMA 2000 it is Second Generation Wireless networks which support data up to 14.4 kbps.
  3. CDMA 1X EVDO It is 3rd generation wireless networks which support speed up to 3.1 Mbps.

CDMA Advantages

  • 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.

CDMA Disadvantages

  • 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:

  1. Reliance Communications
  2. Tata Teleservices
  3. BSNL


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