Basics of CDMA

In Code Division Multiple Access (CDMA) systems the narrowband message signals are multiplied by spreading signals. All users in CDMA uses same carrier frequency and can transmit simultaneously. The spreading signals are pseudo random code. The features of CDMA are as follows:

Basics of TDMA

Time Division Multiple Access (TDMA) systems divide the radio spectrum into time slots, and in each time slots only one user is allowed to either transmit or receive. Each user occupies a cyclically repeating time slot. Features of TDMA are as follows:

Basics of FDMA

Frequency Division Multiple Access (FDMA) assigns individual channels to individual users. The users is allocated a unique frequency band or channel. During the period of the call no other users can share the same channel. In Frequency Division Duplexing (FDD) systems the users are assigned a channel as a pair of frequencies; one frequency is used for forward channel, while other is used for reverse channel. The features of FDMA are as follows: