Scenario - LoRa Basics™ Almanac Update¶

Introduction¶

The LR1110 chip is able to reduce GNSS scanning time by taking into account coarse orbital parameters for different GNSS constellations (the almanac). In conjunction with a coarse time and position estimate, the LR1110 chip uses this information to optimize the search for, and acquisition of, GNSS signals. Over time, the true satellite positions diverge from those stored in the almanac, as a result the almanac has to be updated regularly.

The LoRa Cloud™ Modem & Geolocation Services Almanac Update Over-the-Air (AUOTA) feature allows a device built on the LR1110 chip with LoRa Basics™ Modem-E firmware to automatically perform efficient partial almanac updates over a LoRaWAN® network. The almanac is stored entirely in flash memory; therefore it is kept after power-off and after sleep mode without retention.

Once enabled, AUOTA is carried out by the LoRa Basics™ Modem-E without any action on the host MCU side.

Compatibility¶

Prerequisites¶

Common:

• The end device must have joined the network.

• The application server forwards uplinks on a configured modem management FPort (199 by default) to the LoRa Cloud™ Modem & Geolocation Services.

• The application server forwards LoRa Cloud™ Modem & Geolocation Services downlinks to the end device.

Step-by-Step Procedure¶

To use the LoRa Cloud™ Modem & Geolocation Services Almanac Update Over-the-Air feature, the LoRa Basics™ Modem-E must include the almanac status in the modem management uplinks.

To enable this function, add the field DM_INFO_TYPE_GNSS_ALMANAC_STATUS to the modem management frame, using the set_dm_info_field() command. The almanac will then be kept up-to-date by the Modem & Geolocation Services, without further action from the device application.

Sample Code¶

Use the following sample code to activate automatic almanac updates on the device:

#include "lr1110_modem_lorawan.h"
lr1110_modem_dm_info_fields_t dm_info_fields;
lr1110_modem_response_code_t set_dm_info_field_response_code;

/* Set modem management info field */
dm_info_fields.dm_info_field[0] = LR1110_MODEM_DM_INFO_TYPE_GNSS_ALMANAC_STATUS;
/*
 * This command erases the previous fields activated in the
 * modem, and adds all the fields required by the application.
 */
dm_info_fields.dm_info_field[1] = LR1110_MODEM_DM_INFO_TYPE_CHARGE;
dm_info_fields.dm_info_field[2] = LR1110_MODEM_DM_INFO_TYPE_TEMPERATURE;
dm_info_fields.dm_info_field[3] = LR1110_MODEM_DM_INFO_TYPE_VOLTAGE;
dm_info_fields.dm_info_length   = 4;

set_dm_info_field_response_code = lr1110_modem_set_dm_info_field(
  &context,
  &dm_info_fields
);

Adjust the modem management frame interval to trigger almanac updates:

#include "lr1110_modem_lorawan.h"
lr1110_modem_response_code_t set_dm_info_field_response_code;

/*
 * Set modem management interval to 1 hour
 * Units can be:
 * - LR1110_MODEM_REPORTING_INTERVAL_IN_SECOND
 * - LR1110_MODEM_REPORTING_INTERVAL_IN_DAY
 * - LR1110_MODEM_REPORTING_INTERVAL_IN_HOUR
 * - LR1110_MODEM_REPORTING_INTERVAL_IN_MINUTE
 */
set_dm_info_field_response_code = lr1110_modem_set_dm_info_interval(
  &context,
  LR1110_MODEM_REPORTING_INTERVAL_IN_HOUR,
  1
);

In-Depth Behavior¶

A value representing the almanac state is embedded in the modem management frame every time it is sent by the modem. The Modem & Geolocation Services can then determine whether the device’s almanac needs to be updated. If it does, the Modem & Geolocation Services creates a downlink with updated almanac data to be sent to the modem.

Used By¶

GNSS

Troubleshooting¶

References¶

1. LoRa Basics™ Modem-E API Reference Manual

2. LoRa Cloud™ Modem & Geolocation Services Documentation