Frequency Division Multiple Access (FDMA)

1. Frequency Division Multiple Access (FDMA)

2. Frequency Division Multiple Access 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 Multiple Access 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

4. Frequency Division Multiple Access

5. Numbers of Channels in 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 :  

6. Numbers of Channels in FDMA Example: AMPS uses FDMA/FDD with Btotal = 12.5 MHz , Bguard = 10 kHz and Bch = 30 kHz  

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/3bis.Multiplexing.pdf http://www.thenetworkencyclopedia.com/entry/frequency-division-multiple-access-fdma / http:// users.ecs.soton.ac.uk/sqc/EZ412-612/RCL-19.pdf