We’re currently working with the Quectel BG770A-SN module to explore NTN (Non-Terrestrial Network) communication over Monogoto’s satellite IoT service. The setup includes configuring NB-IoT-only mode, enabling NTN bands (255/256), and setting up the APN data.mono as per Monogoto’s documentation. GNSS is also activated using AT+QCFG="ntn/pos","ignss",1 to support NTN positioning requirements.
One question we’re investigating: is GNSS strictly required for establishing an NTN connection with the BG770A-SN, or is it possible to register and operate without a GNSS fix?
We’d appreciate any insights or experiences on this—especially for scenarios where GNSS reception might not be feasible.
Additionally, would it be possible to provide GNSS information to the module from an external GNSS modem in order to connect to NTN? If so, how would that integration typically work? Would the BG770 be able to accept positioning data via AT commands or some other interface?
I don’t have the BG770 AT command set to hand but it is certainly possible with he CC600 and other non-Quectel NB-IoT NTN SoCs. Ostensibly you register for an GNSS-request event, wait on that event and then write the position via the relevant AT command when the event is received.
The (GNSS) position is required in order for the module to calculate and report the TA (timing advance) to account for the uplink delay between itself (UE) and the base station (eNodeB) via the spacecraft in orbit.
The module knows the spacecraft position (ephemeris) via the SIB31 information block that is broadcast by the eNodeB via the spacecraft…and you (or the internal GNSS) provide the module GNSS position hence the module can now calculate the time-of-flight delay and hence timing advance in order for the eNodeB to avoid uplink and downlink scheduling misalignment and hence synchonization in the message exchange