Digi M10 Manuel d'utilisateur télécharger pdf (Page 14)

Digi m10 Technical Overview

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inaccessible by the satellite constellation. The stored messages are transmitted when an

ORBCOMM Gateway comes into satellite-transmission range. This concept applies to both

sending (SC-Originated) and receiving (SC-Terminated) from a satellite modem point of view.

More documentation can be found on the kit installation CD. To learn more, navigate to

C:\Program Files\Digi\Digi m10 JumpStart Kit\documents please refer to either ORBCOMM Serial

Interface Specification > Figure 4.5 SC-Originated Globalgram & Figure 4.6 SC-Terminated

Globalgram or ORBCOMM Serial Interface Specification > SC-ORIGINATED GLOBALGRAM &

SC-TERMINATED GLOBAL.

3.7 Message Blocking

Message Blocking is an optional feature that allows customers to restrict the addresses to which

their satellite modems can send messages, and those addresses that are allowed to send to a

satellite modem. The Speed Dial addresses are used as permitted addresses.

3.8 Message Priority

Message priority is a feature that allows messages to be processed in order of importance. The

higher the priority, the faster the message moves through the network. However, the ORBCOMM

message switch (OMS) does not terminate message sessions in progress; a new urgent

message will remain queued until any active lower-priority message is completed.

ORBCOMM will only implement priority restrictions during periods of very heavy usage. If the

system is lightly loaded and no queues, or only very short queues, are formed, there is little user

benefit gained from the priority feature.

Functionally, within the ORBCOMM gateway congestion control mechanisms use priority to stop

satellite modems from sending messages not meeting a customer-designated priority threshold.

The satellite broadcasts the identification number of connected gateways and their minimum

message priority thresholds in the downlink control information. All listening satellite modems that

have messages queued for a listed gateway must refrain from sending messages below the

specified priority threshold. Only queued messages with a priority at or above the minimum

priority threshold are sent. Messages below the minimum priority remain in the queue until

channel utilization falls below the threshold.

The available priority levels are:

0. Non-urgent

1. Normal

2. Urgent

3. Special Delivery

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Digi M10 Manuel d'utilisateur Page 14