Invsat Solution Features DAMA
One of the most innovative maritime communications developments in recent years has been launched by telecom systems integrator, Invsat, with the introduction of a broadband data application communications solution configured to offer DAMA (Demand Assigned Multiple Access) protocol, which Invsat developed to operate initially on Loral Skynet’s Telstar 12 satellite.DAMA is typically a single-hop satellite transmission network that allows direct connection between any two nodes in the network among many users sharing a dedicated “pool” of satellite transponder space. With DAMA, customers sign up to a service level agreement (SLA) and can opt for a number of flexible usage bands, reflecting the size of their network. Subscribers also pay network maintenance.
In a DAMA control system, the network allocates channels on a demand-assigned basis, so when a caller at a remote terminal requests a service (lifting a receiver to make a phone call) the request is made to a Network Control System (NCS) over the shared DAMA common signaling channel.
The NCS – a virtual “switchboard in the sky” – determines if the call is valid before establishing the channel between the originating site and the called number. Circuits remain active only as long as needed, and are then broken to free bandwidth for other users.
When the call is completed, the remote terminals inform the NCS and the freed bandwidth is returned to the frequency pool. By using a DAMA system, a single transponder can support several thousand subscribers