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:
The Features of TDMA and CDMA are discussed separately click on respective Links for CDMA and TDMA features.
- The FDMA channel carries only one phone circuit at a time.
- If an FDMA channel is not in use, then it sits idle and cannot be used by other users to increase or share capacity. It is essentially a wasted resource.
- The bandwidth of FDMA channels are very narrow (30 KHz in AMPS).
- FDMA is used in Narrow band only.
- The amount of intersymbol interference is low, thus no equalization is required for FDMA.
- The complexity of the FDMA systems is much lower than TDMA.
- FDMA systems have higher cell site system cost when compared to TDMA systems.
- FDMA uses duplexers because both transmitter and receiver acts simultaneously in FDMA.
- FDMA requires tight RF filtering to minimize adjacent channel interference.
- In FDMA fewer bits are used for overhead purposes.
The Features of TDMA and CDMA are discussed separately click on respective Links for CDMA and TDMA features.
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