Frequency Division Multiple Access is defined as the division of the frequency band allocated for wireless cellular telephone communication of 30 channels, each of which can carry a voice messages with digital service,carry digital data. Frequency division multiple access is a basic technology in the analog AMPS(Advanced Mobile Phone Service) ,the most widely installed cellular phone system in America. With FDMA, each channel can be assigned to only one user at a time.Frequency division multiple access is also used in the Total Access Communication System (TACS).
Frequency Division Multiple Access is a channel access method used for multiple-access protocols as channelization protocol. Frequency Division Multiple Access gives users an individual allocation of one or several frequency bands, or channels. Frequency Division Multiple Access, like other Multiple Access systems, coordinates access between multiple users. The other alternatives include TDMA, CDMA, or SDMA. These protocols are utilized differently, at different levels of the theoretical OSI model.
Disadvantage: Cross talk may cause interference among frequencies and disrupt the transmission.
• in Frequency Division Multiple Access all users share the satellite transponder or frequency channel simultaneously,each user transmits at single frequency.
• Frequency Division Multiple Access can be used for both analog and digital signal.
• Frequency Division Multiple Access requires high performance filters in the radio hardware, in contrast with TDMA and CDMA.
• Frequency Division Multiple Access is not vulnerable to the timing problems that occurs in TDMA . Since a predetermined frequency band is available for the entire period of communication,a continuous flow of data that may not be packet can easily be used with Frequency Division Multiple Access.
• Due to the frequency filtering, Frequency Division Multiple Access is not sensitive to near-far problem which is pronounced for CDMA.
• Each user transmits and receives at different frequencies as each user gets a unique frequency slots.
Frequency Division Multiple Access is distinct from frequency division duplexing (FDD). While Frequency Division Multiple Access allows multiple users to simultaneous access to a transmission system, FDD refers how the radio channel is shared between the uplink and down link (for instance, the traffic going back and forth between a mobile-phone and a mobile phone base station). Frequency-division multiplexing is also distinct from Frequency Division Multiple Access. Frequency Division Multiplexing is a physical layer technique that combines and transmits low-bandwidth channels through a high-bandwidth channel. Frequency Division Multiple Access, on the other hand, is an access method in the data link layer.
Frequency Division Multiple Access also supports demand assignment in addition to fixed assignment.Demand assignment allows users apparently continuous access of the radio spectrum by assigning carrier frequencies on a temporary basis using a statistical assignment process. The first Frequency Division Multiple Access demand-assignment system for satellite was developed by COM SAT for use on the Intelsat series IV and V satellites.
There are two main techniques:
• Multi-channel per-carrier (MCPC)
• Single-channel per-carrier (SCPC)
For more details on the processing of FDMA and CDMA are as following:-
- Signal To Interference Ratio And Network Planning For CDMA System
- Digital Cellular System and Multiple Access Scheme
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