We’ve got a lot of products that talk about bands - we just released two products featuring Quectel's LG290P, the RTK Postcard and the Quadband Breakout Board. We also have products that boast triband reception, like the RTK Torch and the mosaic-X5. We talked about L-band a few months ago, the frequency at which GNSS communications are sent from satellites. But now that we know what bands are, why do we want more of them? Well, I’m glad you asked.
What are GNSS Bands?
GNSS signals are broadcast over multiple frequency ranges within the L-band, these ranges are referred to as “bands.” L1, L2, and L5 are common GPS bands that all transmit different types of data. As we talked about in our blog about l-band, we use this frequency band because these frequencies are low enough to penetrate atmospheric layers effectively, but high enough to provide reliable data transmission, even in challenging environments like forests or urban areas. The term “band” refers to a specific range of frequencies within the radio spectrum. This terminology originates from radio engineering, where the entire electromagnetic (EM) spectrum is divided into frequency “bands” (e.g., VHF, UHF, L-band) based on characteristics, regulatory allocations, and common uses..
Today, other GNSS constellations—such as Galileo (Europe), GLONASS (Russia), and BeiDou (China)—have their own allocated frequency bands within the L-band and other ranges, often close to the GPS frequencies. To prevent interference, international agreements and regulatory bodies , like the International Telecommunication Union (ITU), coordinate these frequency allocations. Through a system of shared standards and monitoring, GNSS constellations operate side-by-side with minimal interference, and “multi-constellation” GNSS receivers can pick up signals across multiple constellations to provide highly reliable, accurate positioning.
That’s a lot of bands! So if each one has a specific purpose and user group, why do we make products that tout multiband reception? The short answer is it gives you better accuracy. The long answer? Let’s get into it.
What’s so great about multiband?
The radio spectrum is broad, ranging from 3 Hz to 3000 GHz. This means radio waves can have a wavelength as small as 1mm all the way up to 100km. The frequencies used for satellite communications were chosen due to their ability to penetrate through objects and interference, but even within that small range, different frequencies have different characteristics that make them useful for different applications.
Lower frequencies penetrate through more material, but at the cost of having lower bandwidth (less data per second). Higher frequency signals with higher energy are absorbed/reflected more easily, but they can carry more data more quickly. Radio is perfect for satellite communications because of atmospheric windows.
Lower frequency radio waves penetrate the Earth's atmosphere more easily because of their longer wavelengths, which means they interact less with the molecules in the air, allowing them to pass through with minimal disruption, unlike higher frequency waves which are more readily absorbed or scattered by the atmosphere's components.
When a receiver can take in data from all these different bands, it raises the likelihood of that receiver getting a signal, which means a faster fix and a more accurate fix. More information paints a clearer picture of precision.
Dilution of Precision
Dilution of Precision is a dimensionless number that specifies the error in a GNSS positional fix. This number depends on a receiver's relative geometry to the satellites it's receiving signals from. The higher this number, the weaker the geometry and the lower the accuracy of the signals.
Complex geometry is used to calculate this number, but we've illustrated it for you in the figure set above. If you're relying on multiple satellites, their distribution in the sky is important - if they're too close to each other, your signal becomes less reliable because of the overlap between signals.
The more satellites and signals you get, the better your signal will be. This is why having access to multiple bands and multiple constellations is beneficial to your accuracy.
What kind of hardware is capable of multiband reception?
All receivers receive a base GNSS signal from at least one constellation; L1 (GPS), E1 (Galileo), B1 (Beidou), etc. Many receivers can acquire base signals from all constellations.
More advanced receivers can receive multiple bands from all constellations.
The most advanced receivers can receive across many bands (L1/L2/L5) and constellations.
The next time you're looking for hardware for your GNSS projects, think about what kind of accuracy you're looking for, as well as reliability in different environments. Multiband might be in your future!
Wow! Excellent post - thanks for distilling the important concepts into a digestible format!!