1. Time Division Multiple Access (TDMA) :
TDMA is the channelization protocol in which bandwidth of channel is divided into various stations on a time basis. There is a time slot given to each station, the station can transmit data during that time slot only which is as follows:
Each station must aware of its beginning of time slot and the location of the time slot. TDMA requires synchronization between different stations. It is type of access method in the data link layer. At each station, data link layer tells the station to use the allocated time slot.
2. Code Division Multiple Access (CDMA) :
In CDMA, all the stations can transmit data simultaneously. It allows each station to transmit data over the 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 the code assigned with respective stations as c1, c2, c3 and c4.
Difference between TDMA and CDMA :
|1.||TDMA stands for Time Division Multiple Access.||CDMA stands for Code Division Multiple Access.|
|2.||In this, only the sharing of time of satellite transponder takes place.||In this, there is sharing of both i.e. bandwidth and time among different stations takes place.|
|3.||There is no need of any codeword.||There is no need of any codeword.|
|4.||In this, guard time of the adjacent slots are necessary.||In this, both guard bands and guard time are necessary.|
|5.||Synchronization is required.||No need of synchronization.|
|6.||There is average capacity of the system.||There is large capacity of the system.|
|7.||It is less flexible than CDMA.||Flexibility is high.|
|8.||In this, there is no Near-far problem.||There is existence of Near-far problem.|
|9.||Rate of data is average.||Rate of data is high.|
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