CDMA (Code division multiple access) Interview Question:

Please differentiate between CDMA and FDMA?

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CDMA

Same frequency is used by every user and simultaneous transmission occurs
Every narrowband signal is multiplied by wideband spreading signal, usually known as codeword
Every user has a separate pseudo-codeword, i.e., orthogonal to others
Only the desired codeword is detected by the receivers and others appear as noise
It is mandatory for the receivers to know about the transmitter's codeword

FDMA

When the channel is not in use, it sits simply idle
Bandwidth of Channel is relatively narrow (30 KHz), known as narrowband system
Little or no equalization is needed for spreading symbol time
Analog links are suitable for FDMA
Framing or synchronization bits are not needed for continuous transmission
Tight filtering is needed to minimize interference
Combined with FDD for duplexing
Submitted by: Administrator