Time division multiple access

Time division multiple access (TDMA) is used with digital transmission and shares the satellite transponder on a time basis. Individual time slots are assigned to the earth stations in sequence and each station has full and exclusive access to the whole of the transponder bandwidth during its assigned time slot. During its access period the earth station transmits a burst of digital information. All stations on the network need precise time synchronization. This is done using a synchronization burst at the start of each frame. A typical INTELSAT TDMA system has a frame period of 750 ^s.

The advantages of TDMA are that only one earth station is providing input to the satellite at any one instant so intermodulation does not occur, the system allows greater flexibility with the different user's EIRP and data rates, and is able to cope quickly with the dynamically changing traffic patterns. The disadvantages of TDMA are that very accurate timing is required for all stations on the network, there is some loss of throughput due to the frame overhead and large buffer storage is needed to cope with long frame lengths.

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