1. Frequency Division Multiple Access (FDMA) :
FDMA is the 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 the 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 prevent 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 bandpass signal from data passed to it. The signal is created in allocated band and there is no physical multiplexer at physical layer.
2. Time Division Multiple Access (TDMA) :
TDMA is channelization protocol in which bandwidth of channel is divided into various stations on time basis. There is time slot given to each station, station can transmit data during that time slot only which is as follows:
Each station must aware of its beginning of time slot and location of the time slot. TDMA requires synchronization between different stations. It is type of access method in data link layer. At each station data link layer tells station to use allocated time slot.
Difference between FDMA and TDMA :
|1.||FDMA stands for Frequency Division Multiple Access.||TDMA stands for Time Division Multiple Access.|
|2.||Overall bandwidth is shared among number of stations.||Time sharing of satellite transponder takes place.|
|3.||Guard bands between adjacent channels is necessary.||Guard time between adjacent slots is necessary.|
|4.||Synchronization is not required.||Synchronization is necessary.|
|5.||Power efficiency is less.||Power efficiency is high.|
|6.||It requires stability of high carrier efficiency.||It does not require stability of high carrier efficiency.|
|7.||It is basically used in GSM and PDC.||It is basically used in advanced mobile phone systems.|
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