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11. GNSS Scanning
11.1 GNSS Geolocation System Overview
LR1110 features a GNSS receiver allowing a fast and energy efficient outdoor geolocation. LR1110's GNSS Geolocation
System achieves low energy geolocation by offloading time- and compute-intensive operations to back-end system
components. In particular, the following three back-end system components are needed to operate LR1110's GNSS
Geolocation System:
•
GNSS Position Solving Component: LR1110 does not resolve the full position on-device. Instead, the measurements
from GNSS signals are combined into a binary message (the NAV message) and expected to be sent via any
communication channel to the GNSS Position Solver backend component for final position calculation. This
component is required in all operation modes.
•
GNSS Almanac Update Component (required in assisted mode): LR1110 is able to reduce the GNSS scanning time by
taking into account coarse orbital parameters for different GNSS constellations (the Almanac parameters). In
conjunction with a coarse time and position estimate, LR1110 uses this information to optimize the search an
acquisition of GNSS signals. Over time, the true satellite positions diverge from the fixed Almanac parameters, which
requires them to be updated. This can be achieved by a back-end component which estimates the quality of the
almanac image on device and issues updates when needed. This component is required if GNSS assisted mode is used.
•
GNSS Assistance Component (required in assisted mode): In order to operate GNSS Geolocation System in assisted
mode, coarse estimates of time and position must be provided to LR1110. This information can be obtained in a
variety of ways including application-level knowledge. In LoRaWAN® the Application Layer Clock Synchronization
protocol is suited to retrieve assistance time information. The assistance position information can generally be derived
from past position solutions.
LoRa Cloud™ offers these components in a single, easy to use, managed service as part of the Device and Application
Services (DAS). Visit www.loracloud.com for more information.
Figure 11-1: GNSS System Overview
mode, LR1110 searches for available GNSS signals and extracts the minimum set of satellite information needed for a
position calculation. The GNSS satellite signal data (also referred as NAV message) is then transmitted via the LPWAN
communication stack to a GNSS solver for the geolocation position calculation. If an update to the almanac parameters is
needed, the Almanac Update Component schedules appropriate downlink messages.
LR1110
User Manual
Rev.1.0
UM.LR1110.W.APP
March 2020
shows the system components for a LoRaWAN® -based integration. Once put in GNSS
www.semtech.com
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