How to use GNSS modules to create location aware smart city solutions
percentage of the overall power budget.
Assisted GNSS
Power- save modes
Power consumption challenges While GNSS receiver power consumption has declined dramatically, the complexities of getting the optimal power/ performance solution have multiplied. Not every LAS design needs continuous GNSS position estimations or high levels of position accuracy. Designers have various tools to optimise GNSS performance and power consumption, including hardware optimisation and firmware-based approaches. The use of low-power components, especially low-noise RF amplifiers (LNAs), oscillators, and real-time clocks (RTCs), is the first step in developing energy-efficient GNSS solutions. The choice between active and passive antennas is a good example. Passive antennas are lower in cost and more efficient but don’t meet the needs of every application. An active antenna may be a good choice in urban canyons, inside buildings, or other locations with poor signal strength. The LNA in the active antenna significantly increases the ability to receive weak signals but also consumes significant amounts of power. When power consumption is critical, and antenna size is not as important, a larger passive antenna can often provide the same performance as
Update rate
Mulit- GNSS
Figure 2: In addition to using the most efficient hardware solution, designers have several firmware tools to optimise GNSS performance and energy consumption. Image source: u-blox
a smaller active antenna while still providing high position availability and accuracy levels. Most GNSS receivers can provide update rates of 10Hz or higher, but most LAS applications work well with much slower and less power-consuming update rates. Selecting the optimal update rate can have the largest impact on power consumption. In addition to the hardware-based considerations, designers have a range of firmware tools available when optimising power consumption, including update rates, the number of concurrently tracked GNSS constellations, assisted GNSS, and a variety of power-saving modes (Figure 2).
multiple GNSS constellations concurrently in challenging environments. While receiving signals using various bands can ensure a robust position determination, it also increases power consumption. It’s important to understand the specific operating environment, especially how open the sky view is, and use the minimum number of GNSS signals required to support the needs of the particular LAS application. Turning the GNSS function off saves the most energy but results in a cold start every time it’s turned on. The time to first fix (TTFF) for a cold start can be 30 seconds, or longer, depending on the availability and strength
It may be necessary to track
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