L-band Spectrum

[Latarsha Dorrance]

TheL band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz). This is at the top end of the ultra high frequency (UHF) band, at the lower end of the microwave range.

The Galileo Navigation System, the GLONASS System, and the BeiDou systems use the L band similar to GPS, although the frequency ranges are named differently. Modern receivers, such as those found in smartphones, are able to take advantage of multiple systems (usually only around the oldest L1 band) at the same time.[3]

About Ligado Networks

Building on 25 years of experience providing crucial satellite connectivity, our mission is to modernize American businesses by delivering secure and reliable 5G connectivity solutions needed to transform their operations and realize the efficiencies of a digital world. Our plans to deploy licensed mid-band spectrum in public and private 5G networks will help pave the way for future innovations and economic growth across America.

About Select Spectrum

Select Spectrum focuses solely on the market for FCC spectrum licenses in the U.S., providing marketing, brokerage and consulting services to a wide range of clients. The company actively represents clients holding licenses across 22 different FCC spectrum bands, including narrowband, broadband and millimeter wave frequencies, ranging from 150 MHz to 40 GHz. Select Spectrum is an industry leader, having facilitated over 300 FCC license transactions. Select Spectrum has also provided spectrum consulting services to major utilities, wireless operators and financial institutions that have invested hundreds of millions of dollars in spectrum-oriented ventures.

We've got a lot of exciting tech packed into our positioning products, and we wanted to give you a deeper dive into some of the concepts. We recently released a RTK mosaic-x5 that receives a few different L-band frequencies, and we offer some L-band specific products like the RTK Facet L-Band. So what does all this talk about bands actually mean? Let's get into it.

In simple terms, GPS frequency bands are like radio channels that GPS devices and satellites use to communicate. They operate at different frequencies, similar to tuning your radio to different stations. L-band refers to a segment of the electromagnetic spectrum with frequencies ranging between 1 and 2 gigahertz (GHz). This portion of the spectrum has proven to be crucial in enabling a ton of communication technologies.

The L-band itself is divided into parts as well, which you've probably seen in our product descriptions and mention on video. The L-band is split into four sub bands centered at 1060 MHz, 1170 MHz, 1280 MHz and 1390 MHz, each with a bandwidth of 120 MHz. These bands are called L1, L2, L3 and L5.

L1: The L1 frequency is perhaps the most familiar, serving as the backbone for the GPS system that most consumer devices use. Operating at 1575.42 MHz, L1 carries both the standard positioning service for civilian use and an encrypted service for military applications. Its widespread adoption in consumer technology makes it a cornerstone of global navigation satellite systems, facilitating everything from navigation in cars to tracking in smartphones.

L2:Then there's L2, humming along at 1227.60 MHz. Initially dedicated to military use, L2 has been increasingly incorporated into civilian GPS applications, primarily because accessing signals from multiple frequencies can significantly improve accuracy. By comparing the signals received at L1 and L2, receivers can correct for ionospheric delay, enhancing the precision of location data.

L3: Operating at 1381.05 MHz, L3 plays a critical role in national security and emergency services. This frequency is utilized for nuclear detonation detection and plays a part in the United States Nuclear Detonation Detection System (USNDDS), which monitors for nuclear explosions worldwide. Its usage is more specialized and less prevalent in consumer applications compared to L1 and L2.

L5: Lastly, L5, clocking in at 1176.45 MHz, is designed with advanced safety-of-life transportation and mobile applications in mind. The L5 signal provides higher power, greater bandwidth, and improved resistance to interference, making it ideal for critical applications such as aviation navigation, where safety and precision are paramount. It's set to enhance the capabilities of GPS receivers further by offering an additional signal for improved accuracy, integrity, and availability.

Multiband receivers, capable of tapping into these diverse frequencies, unlock the potential for more accurate, reliable, and versatile positioning and timing solutions. They can selectively or simultaneously use signals from L1, L2, L3, and L5, optimizing performance across different conditions and applications. This multiband capability is a leap toward enhancing the robustness and efficiency of satellite-based navigation and communication systems, underpinning the seamless operation of technologies that define our modern world.

You'll see some of these multiband capabilities in our products, like our products that include the Septentrio mosaic-x5, which receives L1, L2 and L5 signals. You can also check out the Facet L-band and the GNSS Correction Data Receiver, which receives L-band corrections.

The L-band as defined by IEEE is a frequency range from 1 to 2 GHz. IEEE uses letters to signify a range of frequencies from 1 to 170 GHz. This band is used for a wide range of applications including radars, mobile & satellite communication, satellite navigation (like GPS, GLONASS etc.) and satellite broadcasting (DAB) applications.

- The International Telecommunication Union has allowed the 1240 to 1300 MHz band to be used for amateur radio operations. In addition to this the 1260 MHz to 12 70 MHz band are used for amateur satellite up-links.

- The FCC has also allocated the 28 MHz of spectrum (14 MHz for Earth-to-space transmissions and 14 MHz for space-to-Earth transmissions) internationally coordinated in the L-band for only the U.S. mobile-satellite service ("MSS") system authorized to operate in the upper L-band.

NATO had a separate frequency band notation system which is now obsolete. They also had a frequency band represented by the letter L. This band had a frequency range from 40 to 60 GHz and a wavelength from 5 to 7.5 mm.

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Mid-Band spectrum (1-6 GHz) is critical to 5G as it comes with both favorable propagation characteristics and relatively wide channel bandwidth. Within the mid-band spectrum, there is higher mid-band (2-6 GHz) with larger blocks of spectrum that facilitates faster data speeds, but fares relatively poorly in in-building penetration and wider propagation. On the other hand, lower mid-band (1-2 GHz) has superior propagation, in-building penetration, and deployment flexibility to provide economical deployment of 5G.

Ligado networks claims that their lower mid-band spectrum in the 1.5-1.6 GHz range is a perfect complement to higher mid-band spectrum to broaden network coverage. Working together, the two spectrum categories can enable a cost-efficient, broad-based, and capacity-rich solution that supports the full suite of 5G services. They also stress that their greenfield spectrum creates an opportunity for both commercial and technical innovations while avoiding the delay and complexity associated with use of existing spectrum already deployed in 4G networks.

Ligado (and any future purchaser of this spectrum), also will need to reach a financial settlement with Inmarsat, the satcoms operator that contributes some of the channels needed for the Ligado band plan.

Wall street firm New Street Research first noted that Ligado had asked FCC to allow it to operate a terrestrial network (instead of a satellite network) in up to 40MHz of its lower mid-band spectrum. While this spectrum can potentially be used as standalone, its proximity to CBRS 3.5GHz and C-Band, also raises the possibility for it to be paired with those higher mid-band spectra. Thus, we can think of two potential use cases -

The radio spectrum is the part of the electromagnetic spectrum with frequencies from 30 Hz to 300 GHz. Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication.

A radio band is a small contiguous section of the radio spectrum frequencies, in which channels are usually used or set aside for the same purpose. To prevent interference and allow for efficient use of the radio spectrum, similar services are allocated in bands. For example, broadcasting, mobile radio, or navigation devices, will be allocated in non-overlapping ranges of frequencies.

While most scientists using remote sensing are familiar with passive, optical images from the U.S. Geological Survey's Landsat, NASA's Moderate Resolution Imaging Spectroradiometer (MODIS), and the European Space Agency's Sentinel-2, another type of remote sensing data is making waves: Synthetic Aperture Radar, or SAR. SAR is a type of active data collection where a sensor produces its own energy and then records the amount of that energy reflected back after interacting with the Earth. While optical imagery is similar to interpreting a photograph, SAR data require a different way of thinking in that the signal is instead responsive to surface characteristics like structure and moisture.

Optical sensors such as Landsat's Operational Land Imager (OLI) and Sentinel-2's Multispectral Instrument (MSI) collect data in the visible, near-infrared, and short-wave infrared portions of the electromagnetic spectrum. Radar sensors utilize longer wavelengths at the centimeter to meter scale, which gives it special properties, such as the ability to see through clouds (view electromagnetic spectrum to the right). The different wavelengths of SAR are often referred to as bands, with letter designations such as X, C, L, and P. The table below notes the band with associated frequency, wavelength, and the application typical for that band.

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