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Frequency Division Multiple Access (FDMA)
Frequency Division Multiple Access (FDMA) is a channel access method where the available bandwidth is divided into multiple non-overlapping frequency bands and each user is assigned a specific frequency band. Each user can transmit or receive independently in its assigned frequency band without interference from other users. FDMA requires expensive bandpass filters for each frequency band and has strict linearity requirements for the transmission medium. The number of channels in an FDMA system is calculated by dividing the total available bandwidth minus the guard bands by the bandwidth of each individual channel.
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FDMA is a method for media access control where each user is assigned a unique frequency band. Users can transmit/receive on their channel without overlap.
The number of channels in FDMA is calculated using total bandwidth, guard band, and channel bandwidth. Example shows AMPS uses FDMA with 416 channels.
FDMA offers simplicity and fewer delay issues compared to TDMA but requires costly filters and strict linearity, impacting overall complexity.
Links to comprehensive resources on FDMA implementation and concepts are provided for additional information.
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Frequency Division Multiple Access (FDMA)
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- 2. Frequency Division MultipleAccess • implemented at the media access control (MAC) layer • the user is assigned a specific frequency band in the electromagnetic spectrum, and during a call that user is the only one who has the right to access the specific band
- 3. Frequency Division MultipleAccess • Total system bandwidth is divided into narrow frequency slots. Each user is allocated a unique frequency band or channel • A user is free to transmit or receive all the time on its allocated radio channel, but the cost of transceiver is high, as each has to be designed on a different band
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- 5. Numbers of Channelsin FDMA • Let Btotal be the total system bandwidth, Bguard be the guard band at edge, and Bch the single radio channel bandwidth. Then the number of channels in a FDMA system: N = Btotal − 2Bguard Bch
- 6. Numbers of Channelsin FDMA • Example: AMPS uses FDMA/FDD with Btotal = 12.5 MHz, Bguard = 10 kHz and Bch = 30 kHz N = 12.5 × 106 − 2(10 × 103) 30 × 103 N =416
- 7. FDMA vs TDMA •Frequency division is very simple: all transmitters sharing the medium have output power spectra in non- overlapping bands. – Many of the problems experienced in TDMA due to different propagation delays are eliminated in FDMA. • The major disadvantage of FDMA is the relatively expensive and complicated bandpass filters required. – TDMA is realized primarily with much cheaper logic functions. • Another disadvantage of FDMA is the rather strict linearity requirement of the medium.
- 8. Reference • http://lenst.det.unifi.it/~mucchi/DOCS/ING/3 bis.Multiplexing.pdf • http://www.thenetworkencyclopedia.com/ent ry/frequency-division-multiple-access-fdma/ •http://users.ecs.soton.ac.uk/sqc/EZ412- 612/RCL-19.pdf