Mumbai University > EXTC > Sem 8 > Satellite Communication and Networks

Marks: 5M

Frame organisation

Figure (a) shows the organisation of a frame for a three-beam satellite. The frame contains a synchronising field and a traffic field. Bursts from traffic stations are routed to their destinations in the traffic field. The traffic field contains a succession of switch states. During a given switch state, the switching matrix retains the same connection state. The traffic field also contains a growthspace in case traffic demand is less than the capacity. The duration of a connection between an upbeam and a down beam is called a window. A window can extend over the duration of several switch states. Figure (b) shows the switch state sequence implemented by the switch matrix inorder to route traffic according to the frame organisation of Figure (a).

Three-beam SS-TDMA satellite: (a) frame organisation and (b) switch state sequence during theactive part of the traffic field.

Window organisation Figure below shows how bursts are positioned in a window time interval. The figure shows bursts that are transmitted by stations A, B and C in the window corresponding to a connection from beam 3 to beam 2. Each burst transmitted by a station during the window time considered consists of several sub-bursts which contain station-to-station information.