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Frequency Division Multiple Access Used for AMPS and TACS, the two key analog systems and their variants, this system gives each conversation its own unique radio channel. Division of a radio frequency into several channels by splitting the frequency band into distinct segments, which are assigned to various callers. This allows a single base station to serve many callers. For example, a typical AMPS network will have 832 channels spaced approximately 30 kilohertz apart. - Frequency Division Multiple Access, digital transmission technology that combines elements of TDMA and spread spectrum.

Frequency Division Multiple Access. A method allowing multiple carriers to share a single satellite transponder or range of frequencies. The transponder bandwidth is divided into sub-channels, each of which is allocated to a particular earth station (carrier). The earth stations transmit continuously and the transponder conveys several carriers simultaneously at different frequencies.

A method employed to permit several users to transmit simultaneously on one satellite transponder by assigning a specific frequency within the channel to each user. Frequency Division Multiple Access. FDMA systems transmit one voice circuit per channel. Each conversation gets its own, unique, radio channel. The channels are relatively narrow, usually 30 KHz or less and are defined as either transmit or receive channels. A full duplex conversation requires a transmit & receive channel pair. For example, if a FDMA system had 200 channels, the system could handle 100 simultaneously full duplex conversations. (100 channels for transmitting and 100 channels for receiving) Example: FDMA channel

With FDMA users share the transponder by prior allocation of individual channels. Single Channel Per Carrier (SCPC) is an FDMA scheme in which the input data stream is used to modulate an RF (radio frequency) carrier and assign dedicated carrier frequency to each client.
Frequency Division Multiple Access system for cellular radio.

Frequency Division Multiple Access The analog communications technique that uses a common channel for communication among multiple users allocating unique time slots to different users.
The process of dividing bandwidth into multiple frequencies which can be shared out among base transceiver stations (BTS)within the network.

Frequency division multiple access or FDMA is a channel access method used in multiple access protocols as a channelization protocol. FDMA gives users an individual assignment of one or more frequency bands, or channels. It is particularly common in satellite communication. FDMA, like other multiple access systems, coordinates access between multiple users. Alternatives include TDMA, CDMA or SDMA. These protocols are used differently at different levels of the theoretical OSI model.

Disadvantages:

Crosstalk can cause interference between frequencies and interrupt transmission.
• In FDMA, all users simultaneously share the satellite transponder or the frequency channel, but each user transmits to a single frequency.
• FDMA can be used with both analog and digital signals.
• FDMA requires high performance filters on radio hardware, in contrast to TDMA and CDMA.
• FDMA is not vulnerable to TDMA timing problems. Since a predetermined frequency band is available throughout the period of communication, flow data (a continuous stream of data that can not be packaged) can be easily used with FDMA.
• Due to frequency filtering, FDMA is not sensitive to the problem near the end that is pronounced for CDMA.
• Each user transmits and receives at different frequencies as each user receives a unique frequency.

FDMA is different from frequency division duplexing (FDD). While FDMA allows multiple users simultaneous access to a transmission system, FDD refers to how the radio channel is shared between the uplink and the downlink (eg, traffic coming and going between a mobile phone and a station base of mobile telephony). Frequency division multiplexing (FDM) is also different from FDMA. FDM is a physical layer technique that combines and transmits low-bandwidth channels through a high-bandwidth channel. FDMA, on the other hand, is an access method in the data link layer.

FDMA also supports demand allocation in addition to the fixed allocation. Demand allocation allows all users apparently continuous access to the radio spectrum by allocating carrier frequencies on a temporary basis using a statistical allocation process. The first FDMA demand allocation system for satellite was developed by COMSAT for use in the Intelsat series IVA and V series satellites.
There are two main techniques:
• Multi-channel per carrier (MCPC)
• One channel per channel (SCPC)

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