Satellite Capacity Allocation types
There are following schemes by which resource pool is utilized by satellite users. These schemes are called access schemes. TDMA, FDMA and DAMA are three main types of satellite capacity allocations.
1. FDMA-Called as frequency division multiple access. In this scheme entire frequency band of satellite is divided into frequency bands with proper guard band in between to avoid interference. Here entire frequency band is used by allocated user on earth all the time. Hence earth user on earth is using dedicated frequencies all the time.
2. TDMA-Called as Time division multiple access. In this type, frequency spectrum is available to earth station user based on the time allocations. Hence frequency resources are not available all the time but are available at regular predetermined intervals.
There are two techniques used either the frequency/time resources are pre-assigned or they are available on demand based on request for it by earth station users to satellite.
Pre-assigned types of allocations is referred as PAMA i.e. Pre-assigned Multiple Access. Dynamic on demand type of allocation is referred as DAMA i.e. Demand Assigned Multiple Access.
In PAMA, assignment of resource is taken care at the start of the network deployment. In DAMA, assignment of resource is taken up at the time of initiation of the call. Now-a-days CDMA type is also explored in satellite network.