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This design of the HyperPulse network leverages the existing network attachment of an uplink to deliver downlinks, a strategy specifically chosen to minimize the energy overhead.

Message scheduling

Downlink messages (messages to the UE/device), also called Control Messages can be scheduled from Device Manager (or from an external service through the API):

Key limits:

• Maximum message size: 250 bytes
• Maximum number of downlink messages per day: 10

Message scheduling timeline

When the UE/device is reset and does not have an existing NTN connection/session, receiving a downlink requires two subsequent uplink messages:

• First Uplink: Initiates the connection and establishes a valid session.
• Second Uplink: Triggers the transfer of the scheduled downlink message.

Subsequent Downlinks (After a Valid Connection): Once the device has successfully connected (i.e., after the first uplink and connection transfer), downlinks can be scheduled. Only one subsequent uplink is then necessary to trigger the transfer of the downlink message.

Future Library Improvement: In a future version of the library we will eliminate the need for the second uplink; downlinks will be received asynchronously.

Here is a timeline comparing a successfully downlink scheduling/reception and one that is lost:

Lost Message (DL#1): The Control Message DL#1 is lost because it was scheduled before the device successfully sent the first uplink and established a valid session. A subsequent connection attempt resets the session. The Control Message can only be scheduled from Device Manager after the device has successfully scheduled and sent an uplink, thus establishing a valid session.

Successful Message (DL#2): DL#2 is received by the device because it was scheduled while the device had a valid, active session (it had previously connected and had not reset before sending the next uplink).