MPM-1000A Operator Manual
1000-7075 Rev E
8-5
Figure 8-2 shows how an NC will provide Orderwires and DCOM bursts to a NM. In the
figure, time is shown along the bottom of the diagram, 0.40 seconds representing one
frame, while assigned frequencies, called carriers (or channels), are shown in the depth
(z-axis) of the diagram.
The time, assigned frequency and number of Orderwire and DCOM bursts vary with
each frame based on the requests for network resources found in the AROW s
transmitted by the NMs to the NC. In addition, varying link conditions such as signal
strength could also influence how these Orderwire and DCOM bursts are assigned by
the NC.
8.3 Network Initiation
Any Terminal designated to be NCC within the NCW network may operate as the NC.
The first Terminal (thus enabled) to begin operation under the Satellite initiates the
network and becomes the NC. Subsequent Terminals joining the network assume the
role of a NM.
In order to initiate a network and assume operation as the NC, the Terminal must have
a stored Message Seed Key (MSK) and a valid Pass Phrase. MSKs have an effective
period identified along with the seed key data. This effective period is set at the MSK
generating station and is logically bound to the MSK seed key data.
The effective period of an MSK is specified by an Effective Date value, which identifies
the beginning of a six-month period in which the MSK may be used for network
initiation. Terminals will not initiate a network if the current UTC date falls outside the
effective period identified within the MSK. MSK Effective Dates are calculated at
12:00:00 AM Greenwich Mean Time (GMT) on the first Monday of the month in January
or July in any given year.
Note
It is important to observe that the MSK effective date governs only
the use of the MSK for network initiation. It is possible, and
permissible, for operational TRANSEC keys derived from an MSK to
be used outside the effective date period of the MSK. This will occur
during the six-
week “grace” period that follows the nominal six-
month effective period of the MSK. If the network is restarted after
the nominal six-month period, however, it must be restarted using
the new MSK.
8.4 Network Operation
NMs report Terminal transceiver information at the time of network login and via
configuration updates during operation to the NC. NMs request resources each frame in
their AROW assignment. The NC produces the MF-TDMA network slot plan (burst
schedule) for each frame based on resource requests and current link-quality
conditions. The NC maximizes network data throughput by maintaining a tight power-
control loop and minimizing link budget margins and spectral usage. The NC maximizes
