Demand Assigned
Time-Division Multiplexing Access (DA-TDMA) is a
type of satellite access technology that is superior compared to Frequency
Division Multiple Access (FDMA) or Single Channel Per Carrier (SCPC) in terms
of efficiency in satellite bandwidth usage.
In DA-TDMA,
satellite bandwidth is shared among the users at different sites based on
allocation of time slots rather than frequency. Hence, all the earth stations of a DA-TDMA -based network will transmit at the same frequency, but not
at the same time. In a DA-TDMA -based network, each earth
station is usually allocated a fixed percentage of satellite bandwidth (time
slots). Besides, there is a certain percentage
of satellite bandwidth, which can be dynamically allocated to the earth
stations, basing on users¡¯ demands. As
a result, higher efficiency in the use of satellite bandwidth can be achieved. Due to their capability to dynamically
allocate satellite bandwidth based on demand, DA-TDMA -based satellite networks are more suitable to carry
¡°bursty¡± traffic than FDMA or SCPC-based satellite networks.
The efficiency of such satellite bandwidth
usage is achieved at the expense of timing delay. This is particularly so, as the traffic is using dynamically
assigned satellite bandwidth that imposes a certain amount of delay which is
proportional to the propagation delay of a typical satellite link. Hence, it is important to investigate the
effects of providing Quality of Service (QoS) over a DA-TDMA -based satellite network.