Comtech EF Data SNM-1002 - Manual (Page 97)

SNM-1002 LinkSync
 Modem
Revision 2
Theory of Operation MN/SNM1002.OM
4–3
4.1.2 Uplink Power Control
Uplink Power Control at the MIDAS Controller site compensates for outbound control
channel uplink degradation so that it always downlinks at a constant power at the
satellite.
A reference E
b
/N
o
is calculated for the received outbound control channel at the MIDAS
Controller site for clear sky conditions. The LinkSync™ Modem, at the MIDAS
Controller site, measures the received outbound control channel E
b
/N
o
on a continuous
basis.
• If the measured E
b
/N
o
differs from the calculated reference, the MIDAS
Controller calculates the offset to be applied to the transmit power level of the
outbound control channel to achieve the desired reference E
b
/N
o
.
• The transmit power is adjusted only when the difference exceeds a threshold,
which is configurable.
4.1.3 Circuit Power Management (Option)
Circuit power management is provided as an option. It includes:
• Circuits at setup.
• Site level call blocking based on available High power Amplifiers (HPA) power.
4.1.3.1 Site Level Call Blocking
The MIDAS Controller supports dynamic site level call blocking based on the available
HPA power. The MIDAS Controller keeps track of the HPA power for each site. A call
originating from a site is blocked if it would cause the total transmit power for that site to
exceed the recommended HPA power (less backoff). This leads to improved system
stability.
4.2 Monitor and Control (M&C)
The M&C monitors the modem and provides configuration updates to other modems
within the modem when necessary.
The modem configuration parameters are maintained in battery-backed RAM, which
provides total recovery after power-down situation. The M&C functions include
extensive fault and status reporting. All modem functions are accessible through a remote
communications interface. A block diagram of the M&C is shown in Figure 4-1.