ach receive the use of the entire bandwidth for a small period of time. This turns out to be a suitably flexible setup for packet traffic. TDMA unfortunately requires a large antenna size and since the time slot synchronization adds complexity to the system, the earth-bound hardware cost is increased.A slight variation of the TDMA access method is the Code-Division Multiple Access (CDMA) technique, also known as spread-spectrum systems. In this scheme, transmissions from the earth stations are spread over the time slots using a unique code identifier. This helps to combat signal jamming. For this reason, this scheme is used frequently by the military.Another variation of the TDMA access method that is projected to be used in most future satellite systems is the Multifrequency Time Division Multiple Access (MF-TDMA). This method extends the single frequency scheme used by conventional TDMA into the use of multiple frequencies that can be shared by all earth stations. MF-TDMA therefore increases bandwidth and reduces antenna size. The third existing satellite link access method is Demand-Assignment Multiple Access (DAMA). This technology allows dynamic allocation of bandwidth based on the needs of the network user. DAMA is suitable for use when communication between satellites is not required to be continuous. This permits the alternation of channels by which the ATM cells are transmitted as opposed to establishing a single channel and maintaining this connection continuously.DAMA can be combined with other access methods such as MF-TDMA or SCPC. Using these separate technologies together will allow the system to take advantage of the benefits of both. For example, as mentioned above, DAMA is suited for non-continuous transmissions. Coupling this with SCPC which is suited for continuous connections can help to achieve greater efficiency in the ATM over satellite network configuration. Error ControlA well-known problem facing...
