What is CDMA?

CDMA is used for mobile to mobile or cellular communication similar to GSM. CDMA is the short form of Code Division Multiple Access. It is more secured way of communication due to it spread spectrum property. In the spread spectrum modulation signal to be transmitted is modulated using spreading code or PN code, which will increase the bandwidth of the signal significantly. This makes signal power level below the noise power level, hence it makes impossible for intruders to intercept the signal and decode the signal. Only the receiver can decode the signal using correlation method provided the PN code is known at the receiver.

Various unique codes are used by mobile to differentiate them at Base station. These unique codes are called Walsh codes in CDMA. Base station to mobiles path is also differentiated by unique codes assigned. These codes are called PN codes.

Mobile to Base station is called reverse channel and Base station to mobile is called forward channel

QPSK modulation is used on forward channel and OQPSK modulation is used on reverse channel to modulate the information bits before RF frequency up conversion.

Useful Links

Refer our page on CDMA tutorial.
Refer our page on CDMA and GSM technology comparison.
Refer our page on Multicarrier CDMA.

This page explains what is a CDMA technology is all about and provides useful links as mentioned below.
TD-SCDMA Physical layer  CDMA versus GSM  Cell Re-Selection  what is CDMA  WCDMA compressed mode  CDMA tutorial  TD-SCDMA Tutorial   Multicarrier CDMA

What is?

what is RF?  what is wireless ?  what is zigbee?  what is Bluetooth?  what is lightwave RF?  what is z-wave?  what is microcontroller?  what is GSM?  what is GPRS?  what is infrared? 

RF and Wireless Terminologies