COBHAM Sailor 250 FleetBroadband, Руководство по обучению, Страница: 22 / 270

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Chapter 1
Inmarsat Network
1.6 Distribution architecture
BGAN radio resource is managed by a group of distributed entities
which control satellite the capacity collectively.
Figure 1-23: Radio Recourse Management
RNC (Radio Network Controller) at the SAS manages the radio
resource for individual FleetBroadband Terminals. The LRM (Local
Resource Manager) is an entity within the RNC. It continuously
measures the demand in each spot beam and decides if the
number of satellite channels serving each regional or narrow
beam is adequate to meet demand. If there is unmet demand in a
beam the LRM will ask the GRM (Global Resource Manager) for
more channels. If the LRM has unused channels it will return them
to the GRM.
The GRM manages the radio resource for the entire satellite. Its
role is to arbitrate between the competing demands of the various
services on the satellite. The GRM provides fi xed capacity (used
by FleetBroadband in the global beam and regional beams). It also
maintains a pool of dynamic satellite channels which it supplies
to LRMs when they make requests (such as the FleetBroadband
traffi c bearers in the narrow beams which are deployed on
demand). If an LRM makes a request for capacity in a beam where
the GRM has no capacity, the GRM will ask the PCS (Payload
Control System) to switch a satellite channel into the beam. Such
reconfi gurations take no more than a couple of seconds. It is
not possible to anticipate precisely how many channels an LRM
needs because instantaneous demand for channels is inherently
unpredictable. However approximate estimates are useful for
planning purposes. The GRM gathers utilisation statistics from the
LRMs. These statistics are used for capacity planning by the FPS
(Frequency Planning System).