CDMA is a multiple access technique that utilizes neither frequency channels or time slots. Here, the narrow band message is multiplied by a large bandwidth signal that is a Pseudo random Noise code( PN code ).All users in a CDMA system use the same frequency band and transmit simultaneously. The transmitted signal is recovered by correlating the received signal with the PN code used by the transmitter. An important advantage of CDMA over both FDMA & TDMA is that it can provide for secure communications. The figure below shows the general use of the spectrum using CDMA.
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Division Multiple Access
