Subject : Satellite Communication and Networks

Topic : Space Segment Access and Utilization

With TDMA only one carrier uses the transponder at any one time and therefore the intermodulation products which results from nonlinear operation of amplifier working in multicarrier mode are absent.TDMA is suited for digital data transmission.

Digital data can be assembled in to bursts for transmission and reassembled from received bursts through use of digital buffer memories.Burst synchronization is required and only one station is assigned solely for purpose of transmission of its bursts to which other stations are synchronized.

The time interval from start of reference bursts to the next is termed as frame.Frame contains reference burst R and bursts from other earth stations.

Overall the transmission appears to be continuous because the input and output bit rates are continuous and equal.However within the transmission channel ,input bits are tempoily stored and transmitted in bursts.The buffer capacity

$M = R_b T f$

where $R_b$=bit rate and $T_f$=frame time interval

The transmission rate RTDMA=M/TB where TB=Bursts time

The basic units used in ground station of TDMA system consists of Multiplexer and demultiplexer units,preamble generator,phase modulator etc.

The reference bursts is required at the beginning of each frame to provide timing information for acquisition and synchronization of bursts.