Difference between FDMA and CDMA

1. Frequency Division Multiple Access (FDMA) :
FDMA is channelization protocol in which bandwidth is divided into various frequency bands. Each station is allocated with band to send data and that band is reserved for particular station for all time which is as follows:

The frequency bands of different stations are separated by small band of unused frequency and that unused frequency bands are called as guard bands that prevents interference of stations. It is like access method in data link layer in which data link layer at each station tells its physical layer to make a band pass signal from data passed to it. The signal is created in allocated band and there is no physical multiplexer at physical layer.

2. Code Division Multiple Access (CDMA) :
In CDMA, all the stations can transmit data simultaneously. It allows each station to transmit data over entire frequency all the time. Multiple simultaneous transmissions are separated by unique code sequence. Each user is assigned with a unique code sequence.



In the above figure, there are 4 stations marked as 1, 2, 3 and 4. Data assigned with respective stations as d1, d2, d3 and d4 and code assigned with respective stations as c1, c2, c3 and c4.



Difference between FDMA abd CDMA :

Sr. No. FDMA CDMA
1. FDMA stands for Frequency Division Multiple Access. CDMA stands for Code Division Multiple Access.
2. Sharing of bandwidth among different stations takes place. There is sharing of both i.e. bandwidth and time among different stations takes place.
3. There is no need of any codeword. Codeword is necessary.
4. There is only need of guard bands between adjacent channels are necessary. In this, both guard bands and guard time are necessary.
5. Variable transmission rate is difficult. Variable transmission rate is easy..
6. There is no Near-far problem. There is existence of Near-far problem.
7. In this, power efficiency can be reduced. In this, full power efficiency is required.
8. Capacity of system is low. Capacity of system is large.
9. It is costly. In this, only installation is costly and operating cost is low.
10. It is less flexible. It is more flexible.

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