One of the key factors that significantly affects the performance of an asset tracker is energy efficiency. The more energy efficient a tracker is, the longer its battery will last. This is not only good for the environment, but also saves the customer from having to regularly recharge or replace batteries reducing the associated costs and downtime.Efficient tracking with Assisted-GPS
Sebastian Boll – Product Manager IoT
One of the key factors that significantly affects the performance of an asset tracker is energy efficiency. The more energy efficient a tracker is, the longer its battery will last. This is not only good for the environment, but also saves the customer from having to regularly recharge or replace batteries reducing the associated costs and downtime.Energy efficiency also plays an important role in our product Asset Solar, which can charge its battery independently thanks to a built-in solar panel. Therefore, the focus in the development of hardware and software was on the consistent reduction of energy consumption right from the start. This enabled us to choose a smaller solar panel and also to dimension the built-in battery smaller. Overall, we were able to make the Asset Solar much more compact compared to other solar trackers and further reduce manufacturing costs.
One of the biggest leverages to reduce the power consumption of an asset tracker is to shorten the so-called “cycle time”, i.e. the time the device needs to perform an entire tracking cycle and has to be switched on at the same time. In analyzing this cycle time, we discovered that the time it takes to search for satellites and determine the GPS position takes an average of 36 seconds. This accounts for more than 50% of the total cycle time. So we had to try to reduce this GPS search time further. This is where the implementation of Assisted-GPS helped us.
What is Assisted-GPS?
Assisted GPS, or A-GPS for short, represents a further development of the well-known Global Positioning System (GPS). The device sends information of the connected mobile cell to an A-GPS server. This information can be used to make a rough determination of the tracker’s position and , to use it to provide necessary orbital and correction data for precise location determination from a database. This auxiliary data is then sent back to the device via the cellular connection. In other words, A-GPS “assists” the GPS receiver, enabling faster and more accurate location determination. This approach not only shortens the time required for position determination, but also helps reduce power consumption.
An important prerequisite for the use of A-GPS is the connection to a mobile network. Other GPS devices (smartwatches, bike computers, mobile navigation devices, etc.) usually do not have a connection to a mobile network and therefore have to search longer for the GPS position. Our trackers are all equipped with an integrated SIM chip and use the IoT services of Vodafone, one of the global market leaders in IoT.
Savings
For the implementation of the A-GPS service, we chose our technology partner Nordic Semiconductor, whose location service of nrf Cloud allows a smooth integration into our system. With the Nordic A-GPS service, we were able to drastically reduce GPS satellite search times. For our device, this means that we have been able to reduce the average GPS search time from 36 seconds to less than 10 seconds. Over the entire tracking cycle, that’s a reduction of over 35%. In conclusion, A-GPS technology has helped us drastically reduce energy consumption. Together with other measures, this has enabled us to offer one of the most energy efficient trackers on the market.