Code division multiple access (CDMA) is a channel access method used by various radio communication technologies.

CDMA is an example of multiple access, where several nodes transmits the data simultaneously. This allows several users to share the frequencies. To permit this without undue interference between the users, CDMA employs spread spectrum technology and a special coding scheme.

Multiple data signals can be transmitted over a single frequency by using Code Division Multiplexing. FDM divides the frequency in smaller channels but CDM allows its users to full bandwidth and transmit signals all the time using a unique code. CDM uses orthogonal codes to spread signals.

Each station is assigned with a unique code, called chip. Signals travel with these codes independently, inside the whole bandwidth.The receiver knows in advance the chip code signal it has to receive.