WHAT IS GNSS?
GNSS (Global Navigation Satellite System) does not specifically refer to any single satellite system, but a combination of several of the aforementioned systems and their enhancements.
When it comes to satellite positioning, the first thing we think of is #GPS, The American GPS (Global Positioning System). Now there are others with global coverage, including China's #Beidou, Russia's #GLONASS and Europe's #Galileo. In addition, and there are also some regional satellite navigation systems, such as Japan's #QZSS and India's #IRNSS.
A GNSS module can capture signals from different satellite systems, which vastly improves the accuracy and stability of positioning. A GNSS module is usually getting three signals from multiple systems to achieve better measurements than from a single system. As radio signals enter earth’s atmosphere the signals run into ionosphere which has a timing effect on the signals. Using triple-best-frequency it can eliminate a lot of the errors by improving accuracy.
#IoT applications such as autonomous driving, smart drones and robots, increasingly demand positioning solutions with improved precision, so how do you choose a suitable poistioning module for your product? If you understand the following 5 basics about satellite positioning modules, it will be much easier to choose the right one for you.
GPS OR GNSS?
For maximum stability and greater accuracy. it is far better to use a GNSS module which can capture satellite signals from several different satellite systems, which greatly improves the accuracy and stability of positioning. Using GPS alone would limit your system to the US GPS system which would automatically reduce the accuracy that can be achieved. AIoT applications such as autonomous driving, smart drones and robots, clearly demand positioning solutions with improved precision - you can't navigate a vehicle if your data is only accurate to the nearest 10m. SIMCom GNSS module can provide the accuracy within a few meters required by by these navigation-based applications.
Take SIM68D series as an example, it is a high performance and reliable GNSS module with simultaneous GPS, GLONASS, BeiDou, Galileo and QZSS open service capabilities. Utilizing multiple systems ensures the accessibility of signals when interference and obstructions appear, providing increased security and future-proofing features to your products. Combining with advanced AGPS (Assisted GPS) system, SIM68D achieves the highest performance to meet all relevant industrial standards.
SINGLE BAND OR DUAL BAND?
Multiple satellite systems increase the sources of signals, therefore improving positioning accuracy. Another viable option to improve positioning accuracy is to increase frequency diversity. Compared with the single-band positioning modules, dual-band positioning modules can receive satellite signals at two different frequencies. Dual-band technology can substantially decrease errors generated by the atmosphere and improve positioning accuracy.
The SIM68D series supports reception of signals of bands L1 and L5. Band L1 is supported by GPS, GLONASS, BeiDou , Galileo and QZSS.Band L5 is supported by GPS, BeiDou , Galileo and QZSS. As a result, the positioning accuracy is further enhanced due to multiplied signal accesses and multiple frequencies.
Receiver sensitivity refers to the minimum input signal intensity (power) required for normal operation, which is generally measured in dBm, the smaller the more sensitive. Receiver sensitivity is a core index for the overall performance of a positioning module. The receiver sensitivity of a positioning module is equivalent to the CPU in a mobile phone. The sensitivity of the SIM68D series is generally measured with three sensitivity metrics : tracking (-166dBm), reacquisition ( -160dBm) and initial acquisition or cold starts ( -148dBm), which meets or exceeds the latest industry standards.
TIME TO FIRST FIX
At least 3 satellites are needed to position an object. To search for the satellite signals and acquire a position takes a certain period of time, which is known as the TTFF (Time to First Fix). It is measured by three different conditions. Cold starts are to search for signals without historical data. Warm starts are when the device has been off for several hours (more than 2 hours) while the data is not outdated. Hot starts mean the data is still valid (normally the device has been off within 2 hours). Usually for a GPS module, Cold starts take more than 40 seconds and around 30 seconds for warm starts. The SIM68D series has decreased the acquisition time to 27s for cold starts and 25s for warm starts.
The ultimate mission of positioning modules is to acquire an object’s position as accurately as possible. Positioning accuracy is the average deviation value from the actual position and is measured in meters. The SIM68D series can achieve an accuracy of 1.5 meters, making it suitable for many applications such as smart wearable devices, fleet management, vehicle navigation, drones, scooters etc.
Besides these specific features of positioning module, you should also consider the usual factors of any component design when selecting your wireless modules such as chipset, size, form factor and power consumption. Ineltek can help you through the process and provide the other components necessary to get your design up and running. We have fast track access to SIMCom engineers that can assist us in the development process. Get in touch now to discuss your project.