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ROSS
6. The modem is now at home state waiting for TEK enable and hub grant to transmit
message.
7. Special power controls can be applied to assure connectivity to the hub station during the
burst entry cycle. See STDMA Power Hunt.
8. After TX enable and hub grant to transmit the modem sends a request for registration to
the managing VMS. It must receive acknowledgment before transitioning through IP
routing table changes and dynamic switching to dSCPC mode. During this process all
customer data traffic is blocked and only allowing management traffic to pass. This
prevents possible customer switching requests from being dropped during registration
processing.
Note during the modem query the ROSS server is also polling the ACU for location and
status. If the ACU has failed to respond during this initial sequence, ROSS will enter
Parked mode waiting for valid responses before changing states. Also during this process
the ACU maybe inhibiting transmit until signal lock is established.
3.3.3 Transmit Power Controls
STDMA Power Hunt
Summary
The STDMA default power value is a possible problem as remotes with incorrect or impaired
transmissions cannot close their return links during service area entry mode. By adding a power
hunt algorithm with limits will provide burst link closure reliability.
The STDMA Power Hunt (SPH) function has a maximum power limit of up to 9dB in 3dB
increments greater than initial default, base value. This modulator power value cycles during
burst transmission increasing or decreasing power until it receives a reply from its managing
STDMA controller. This is accomplished through burst map acquisition acknowledgement flag.
Throughout the process the remote will remain at base or modified set power value until
commanded otherwise or manual operator intervention. Once in SCPC mode and DPC enabled,
the value is over written by DPC and servos to targeted set Eb/No value. Any revert from SCPC
to STDMA will reuse last set DPC value as power delta offset over default set-point. Reboot or
forced revert will cause the unit to clear all temporary set power values.
Implementation
The hub and remote units both provide a role in SPH which allows the remote modulator to
increase its base configuration (Home State) power setting to a maximum of 9dB from initial set-
point if link reception is incorrect or impaired. The hub STDMA burst map contains a flag which
is used separately by each remote in the group. This flag indicates if either their burst ACK
message was missed or received at the hub. When the hub STDMA controller receives a valid
burst ACK from the remote it sets the flag for the corresponding remote in the next burst map
indicating completed transmission.
There are two counters initialized in the remote, one that reads missed ACK's and the other is
received ACK's.
Comtech EF Data, Vipersat Products
MN/13070
Page 25 of 87
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