The range of frequencies that make up the electromagnetic spectrum is extremely large, extending from direct current (0 Hz) through visible light (≈10⁶ GHz) and beyond. Because of this enormous span, it is convenient to divide the spectrum into bands that exhibit similar physical and propagation characteristics.

In communications engineering, we are mainly interested in those portions of the spectrum that are associated with the source or can provide carrier frequencies for transmitting information across real-world channels. The most useful regions for this purpose are the audio-frequency (AF) band (and the voiceband subset) and the radio-frequency (RF) band.

Radio Frequencies (RF) and Audio Frequencies (AF)

Within the AF and RF regions, the International Telecommunication Union (ITU) Radio Regulations (Vol 1: Articles) define standard frequency bands, summarized in Table 1 and described in the following paragraphs.

Extremely low frequency (ELF). The ELF band is characterized by its extremely narrow bandwidth and very long wavelengths, which require enormous antennas that are still electrically short and thus inefficient. For instance, a 650 kW transmitter might radiate only 150 W from a 25 km-long antenna—an efficiency of about 0.02 %. Despite this inefficiency, ELF signals experience exceptionally low attenuation—roughly 1,000 times less than that of higher RF signals—and can penetrate seawater and soil effectively. As a result, ELF is used almost exclusively for one-way submarine communications, where propagation occurs primarily by surface wave which exhibits minimal diurnal or seasonal variation and, importantly, good penetration though sea water.

Voice frequency (VF). In voice-communication systems, VF corresponds to the acoustic input (and therefore the output range of a VF communications system). Bandwidth remains limited, and efficient radiation at these frequencies would require impractically large antennas. VF therefore serves as a baseband source that must be modulated onto a higher-frequency carrier for transmission.

Very low frequency (VLF) and low frequency (LF). Both bands offer reliable long-distance propagation with low attenuation, though antennas are still physically large and bandwidths narrow. Like ELF, they are used for submarine communication, maritime radio navigation, and certain time-signal transmissions (e.g., LORAN, Omega). Propagation is primarily by surface wave, enabling beyond-line-of-sight coverage.

Medium frequency (MF). The MF band supports communication over moderate ranges. Antenna dimensions are more practical, though significant power is still required for dependable long-range service. The band is widely used for AM broadcasting, maritime and aeronautical navigation, fixed services, and amateur radio. Propagation occurs mainly by surface wave during the day and by sky wave at night when ionospheric reflection becomes effective.

High frequency (HF). HF provides long-range sky-wave propagation, allowing global communication with modest transmitter powers and antenna sizes. Channel bandwidths are typically limited to about 3 kHz, making HF suitable for voice, data, and telegraphy (but not useful for data rates above 2.4 kbps). Before the advent of satellites, HF provided the only means of reliable over-the-horizon communication. It remains in use for maritime, aeronautical, military, and amateur services.

Very high frequency (VHF) and ultra high frequency (UHF). The VHF and UHF bands are among the most heavily used for modern terrestrial communication systems. These frequencies support large bandwidths, and antennas are compact and easily directional, enabling efficient point-to-point and mobile applications. However, propagation is limited to line-of-sight and is subject to shadowing by terrain and structures. VHF and UHF are used for television broadcasting, FM radio, mobile and fixed services, ground-to-air communications, and public-safety and emergency networks.

Super high frequency (SHF) and extremely high frequency (EHF). These microwave and millimeter-wave bands provide very wide bandwidths and short wavelengths, allowing the use of small, high-gain antennas. Propagation remains line-of-sight and is subject to attenuation from rain, clouds, and atmospheric absorption. Nevertheless, through radio-relay and satellite links, these bands enable high-capacity data transmission, microwave television distribution, and satellite communication systems. SHF and EHF thus form the backbone of today’s global broadband and space-communications infrastructure.

Each region of the electromagnetic spectrum offers unique advantages and limitations in bandwidth, antenna size, and propagation behavior. As the frequency increases, available bandwidth expands and antennas become smaller, but propagation shifts from global (ELF–HF) to line-of-sight (VHF–EHF). Modern communication systems—from terrestrial broadcasting to deep-space telemetry—use specific portions of these bands to balance range, capacity, and reliability.

Table 1. The AF and RF portions of the electromagnetic spectrum.

Communications Frequencies other than RF and AF

While the RF portion of the electromagnetic spectrum contains the majority of frequencies used for traditional communications, modern systems increasingly employ optical and infrared frequencies for very-high-capacity data transmission.

The development of optical fiber communication has extended practical use of the spectrum into the near-infrared and visible-light regions. In optical fibers, information is transmitted as modulated light waves rather than as radio waves. Carrier wavelengths typically range between 850 nm, 1,310 nm, and 1,550 nm, corresponding to frequencies of approximately 200–375 THz. At these frequencies, extremely high data rates (terabits per second) can be achieved with very low attenuation over long distances, making optical fiber the preferred medium for terrestrial and submarine trunk communications

Beyond guided transmission, free-space optical (FSO) and laser communication systems are increasingly used for short- and medium-range wireless links, as well as for satellite crosslinks and deep-space communication. These systems exploit narrow laser beams to achieve high directivity, large bandwidths, and strong resistance to electromagnetic interference, though they remain sensitive to atmospheric absorption, scattering, and turbulence.

At slightly lower frequencies, infrared (IR) radiation—lying between roughly 300 GHz and 430 THz—is widely used for wireless local area networks (WLANs), remote controls, and short-range point-to-point links. Infrared transmission provides immunity to radio interference and a degree of security due to its confined propagation, though it requires unobstructed line-of-sight paths.

At the upper end of the RF spectrum, terahertz frequencies (0.1–10 THz) are also emerging as candidates for ultra-high-capacity short-range communications. Research into THz technology aims to bridge the gap between millimeter-wave and optical systems, promising data rates exceeding 100 Gbps for indoor and inter-satellite links.

Collectively, these higher-frequency technologies expand the usable communications spectrum far beyond traditional RF and AF bands, enabling the next generation of broadband, optical, and space-based networks.

Satellite Communications Frequency Bands

Within the RF portion of the electromagnetic spectrum, there are well-defined frequency bands that have been allocated for satellite communications by the ITU. These bands are commonly referred to using legacy radar letter designations, as shown in in Table 2.

The letter designations have no obvious alphabetical or mnemonic structure, as they were originally assigned during the classified development of radar systems to obscure the actual operating frequencies. Although their security significance has long since disappeared, these designations remain widely used as convenient shorthand for both radar and satellite frequency bands.

In satellite communications practice, the distinction between K-band (18–27 GHz) and Ka-band (27–40 GHz) is often blurred, and both are commonly referred to collectively as Ka-band, particularly when discussing HTS systems. Strictly speaking, “K-band” refers to the range approximately 18–27 GHz, but because this region includes significant atmospheric absorption near 22 GHz, most operational systems avoid the center of the band and instead use the adjacent Ka allocation.

Table 2. Major frequency bands and principal usage for satellite communications.

The evolution of satellite communications has largely followed a progression toward higher frequencies, driven by the need for greater bandwidth and capacity. Most early commercial and military communication satellites operated in the UHF-band, C-band, or X-band, largely because they could adapt existing terrestrial microwave hardware with only modest modification. These bands, however, offer limited available bandwidth and data rates, and are now heavily congested due to widespread use by both terrestrial and space-based systems, restricting further capacity growth.

To achieve higher throughput, modern satellite systems increasingly operate in the higher Ku-band and Ka-band, which provide much wider bandwidths and enable more aggressive frequency reuse through multibeam architectures. These higher-frequency bands, however, introduce additional technical challenges, most notably increased susceptibility to atmospheric attenuation and more stringent requirements on antenna pointing and link margin.

The following sections describe the characteristics, advantages, and limitations of each frequency band used in satellite communications.

VHF and UHF (Including Military P-Band)

Since frequencies below approximately 30 MHz are trapped or refracted by the ionosphere, only frequencies above roughly 100 MHz are generally practical for satellite communications. The VHF and UHF bands are used mainly for MSS because the technology is mature, straightforward, and readily available. For example, receive antennas can be simple designs such as Yagi arrays or wire helices. At these lower frequencies, RF power is easier to generate on board the satellite, reducing hardware complexity and terminal cost. In addition, the longer wavelengths diffract more readily around obstacles and penetrate buildings better than higher-frequency signals, making them well suited for mobile and tactical use.

The main limitations are spectrum congestion—these bands are heavily occupied by terrestrial radio services—and very limited capacity. With only a few tens of channels available, data rates are typically limited to a few kilobits per second, compared with the many thousands of channels available in C-band and above. The use of simple, low-gain antennas also produces broad beams, which restrict frequency reuse and require larger spacing between satellites to prevent interference.

P-band is not an ITU frequency designation but is widely used in military satellite communications to denote UHF SATCOM in the 225–390 MHz range. This band is almost exclusively reserved for government and defense use, supporting narrowband voice and low-rate data services with high robustness and near-global coverage; the band is not used by commercial satellite operators. Representative systems include the US FLTSATCOM, LEASAT, UHF Follow-On (UFO), and MUOS constellations, as well as the UK’s Skynet, NATO IV, France’s Syracuse, Italy’s SICRAL, India’s GSAT-7/7A, and Brazil’s SGDC-1.

L-Band and S-Band

The L-band and S-band frequencies (1–4 GHz) are widely used in satellite communications because they combine relatively low propagation loss with line-of-sight transmission and modest atmospheric absorption. They support higher capacities than UHF systems, although still significantly less than C-band or Ku-band systems. While thermal noise levels are relatively low, operators must account for ionospheric effects such as scintillation and Faraday rotation. The use of axial-mode helical antennas and circular polarization is therefore common to mitigate polarization mismatch caused by Faraday rotation.

Like UHF systems, L-band and S-band satellite systems can employ relatively simple and inexpensive antennas, such as Yagi arrays or helices, which reduces terminal cost and complexity. However, these frequency bands are heavily shared with terrestrial services—including fixed and mobile radio systems—as well as with other space applications such as radio astronomy and deep-space research. As a result, spectrum congestion and coordination constraints are significant, particularly for geostationary-orbit operation, which limits the total capacity that can be deployed.

The first major use of L-band in satellite communications was the Marisat system, which provided ship-to-shore links and carried both UHF and L-band payloads for the US Navy. Today, L-band and S-band are allocated primarily for MSS and personal satellite communications. Examples of modern usage include:

Globalstar, which uses S-band (~2.5 GHz) for the satellite-to-mobile link and L-band (~1.6 GHz) for the mobile-to-satellite link.

Inmarsat, which operates at ~1.6 GHz uplink and ~1.5 GHz downlink for aeronautical, maritime, and land-mobile services.

Iridium, which uses ~1.6 GHz in both directions for global handheld communications.

Limited use of S-band broadcasting services in systems such as India’s INSAT, Arabsat, EchoStar Mobile, and earlier S-band MSS systems including ICO and TerreStar.

In addition, S-band is the standard choice for TT&C links across most satellite classes, including GEO platforms and LEO constellations, although some high-data-rate missions supplement TT&C with X-band. Modern LEO broadband constellations such as Starlink, OneWeb, and Amazon Leo do not use L-band or S-band for user traffic; instead, they rely on Ku-band and Ka-band to achieve the bandwidth, spectral efficiency, and antenna scalability required for high-throughput broadband services, with L-band and S-band retained only for navigation, TT&C, or legacy MSS applications..

C-Band

C-band was the first part of the spectrum to be widely applied to satellite communications because it leveraged components developed for terrestrial microwave, troposcatter, and radar systems, making equipment relatively inexpensive. It remains one of the most widely used satellite bands due to the low cost and wide availability of mature components. Importantly, C-band lies in the low-noise window of the microwave spectrum (approximately 1–10 GHz), where background sky noise is minimal, and its frequencies are low enough to avoid the severe rain attenuation that affects Ku- and Ka-band systems. Other propagation losses are also modest.

Typical C-band satellites carry multiple 36-MHz transponders, with 72-MHz units also available. Early platforms used 5–10 W TWTAs, while more recent designs may employ higher-power TWTAs or solid-state power amplifiers (SSPAs), typically in the 8–20 W class. Early C-band Earth stations required very large antennas (~30 m diameter), but with increased onboard transmit power, much smaller terminals (~1.8–3 m) are now common, particularly for VSAT and receive-only applications.

The main drawback of C-band is spectrum congestion: these frequencies are heavily used by terrestrial microwave radio relay systems, requiring careful frequency coordination and appropriate siting of Earth stations to minimize interference with terrestrial and other satellite systems operating in the same bands. In addition, portions of the C-band spectrum have been reallocated for terrestrial mobile services in some regions, further increasing coordination challenges.

Although most satellite TT&C functions use S-band, many spacecraft carry auxiliary or backup TT&C links in C-band. In addition, C-band continues to be used by some mobile-satellite service operators, such as Globalstar, for feeder and gateway links, and remains the preferred choice in tropical regions where its resistance to rain fading ensures high link availability.

X-Band

X-band serves government and military satellite communications in much the same way that C-band supports commercial systems. It offers a balance of moderate capacity, relatively low susceptibility to rain attenuation, and manageable antenna sizes, making it well suited to reliable, wide-area defense networks. Importantly, X-band is less congested than C-band because it is reserved primarily for military and governmental use, providing assured access to protected spectrum.

Major X-band operators include NATO, the UK’s Skynet system, and the US Wideband Global SATCOM (WGS) constellation, which also carries Ka-band payloads. Earlier US systems such as DSCS relied entirely on X-band transponders, while WGS introduced dual-band operation to expand capacity and flexibility.

Like C-band, X-band frequencies are coordinated with terrestrial services, particularly fixed links and radar systems, requiring careful spectrum management to avoid interference. Compared with C-band, X-band offers a smaller total bandwidth allocation but benefits from significantly lower rain attenuation than Ku-band or Ka-band, making it attractive for mission-critical military services. In modern defense architectures, X-band is often used for high-availability command-and-control links, complemented by Ka-band channels for higher-capacity data transfer.

Ku-Band

To relieve congestion in C-band, many satellites employ higher-frequency Ku-band transponders. Ku-band offers significantly greater capacity and, importantly, portions of the spectrum are not shared with terrestrial radio networks, reducing the need for frequency coordination. However, many modern FSS and DBS satellites carry a mix of C-band and Ku-band payloads, with the balance determined by service requirements, regional regulations, and the need to continue supporting legacy C-band customers.

The ITU Radio Regulations (Article 5) allocate Ku-band spectrum to the FSS and BSS through region-dependent frequency allocations and associated planning frameworks. In practice, three principal Ku-band usage regimes have emerged:

14/12 GHz FSS (Region 2). The 14.00–14.50 GHz uplink band paired with 11.70–12.20 GHz downlink is allocated primarily to the FSS in Region 2 (the Americas) and is not extensively shared with terrestrial fixed services, simplifying coordination.

14/11 GHz FSS (Regions 1 and 3). In Regions 1 and 3, the 14.00–14.50 GHz uplink is paired with the 10.70–11.70 GHz downlink band, which is shared with terrestrial fixed services. As a result, downlink coordination is generally required to control interference.

Ku-band BSS (global). BSS downlinks operate in the 11.7–12.7 GHz band, with feeder links in the 17.3–18.1 GHz band, under the planning frameworks of Appendices 30 and 30A of the ITU Radio Regulations [1]. Because these bands are pre-planned, BSS satellites can operate with higher transponder powers (typically 60–120 W compared with 20–40 W for traditional C-band FSS), enabling the use of smaller and lower-cost user antennas. BSS satellites are generally spaced 6–9° apart, whereas FSS satellites may be spaced as closely as 2°, subject to coordination constraints, particularly when small Earth-station antennas are employed.

The main drawback of Ku-band is its greater susceptibility to atmospheric attenuation, particularly rain fade. Link margins are often designed to be on the order of 6–10 dB, compared with approximately 2 dB for C-band, making Ku-band less suitable for tropical regions with frequent heavy rainfall. Nevertheless, higher satellite transmitter powers, adaptive coding and modulation, and reduced coordination requirements allow Ku-band systems to compensate for this disadvantage in many operating environments.

Compared with C-band, Ku-band provides substantially greater capacity and supports much smaller user terminals, but at the cost of increased vulnerability to rain attenuation, particularly in equatorial climates. Ku-band therefore occupies an intermediate position between the high availability of C-band and the high capacity of Ka-band.

Today, Ku-band supports both FSS trunking networks and DBS television services and remains the dominant band for mobility applications such as maritime broadband, aeronautical connectivity, and land-mobile VSATs. The availability of moderately sized antennas (typically 60–120 cm) and wide regional coverage has made Ku-band the workhorse for many commercial inflight connectivity and cruise-ship networks, although Ka-band is increasingly being adopted for these roles where higher throughput is required.

Ka-Band

As congestion in both C-band and Ku-band increased, significant interest developed in Ka-band (30/20 GHz) for commercial satellite applications. Early research dates back to the 1970s, with experimental satellites from Japan, the United States, Italy, and the European Space Agency (ESA), followed by NASA’s Advanced Communications Technology Satellite (ACTS) in 1993. Although only a small number of Ka-band satellites were in orbit by 2003, the subsequent two decades saw rapid growth, and Ka-band is now central to the delivery of interactive broadband and multimedia services.

Ka-band systems offer several important advantages. Most notably, they provide access to several gigahertz of contiguous spectrum—significantly more than is available in Ku- or C-band—and this spectrum is largely not shared with terrestrial services. The shorter wavelengths allow smaller and lighter components, more compact user terminals, and the formation of very narrow spot beams. This enables aggressive frequency reuse, dramatically increasing overall system capacity.

The primary challenge of Ka-band operation is propagation loss, particularly rain attenuation, which is severe at these frequencies. Typical systems are therefore designed with link margins on the order of 10–20 dB. These losses can be mitigated through a combination of techniques, including:

Higher satellite transmit power, with Ka-band payloads often operating at several decibels higher effective isotropic radiated power than equivalent C- or X-band systems.

Smaller, higher-gain antennas, as antenna gain increases with the square of frequency; however, Ka-band reflectors require much tighter surface-accuracy tolerances to avoid efficiency loss.

Adaptive techniques such as uplink power control, adaptive coding and modulation, and dynamic beam shaping.

Site diversity, in which multiple gateway stations are spaced more than approximately 10 km apart so that uncorrelated rain fades can be avoided by rerouting traffic. While effective, this approach is costly and typically reserved for large networks.

Ka-band component technology continues to improve rapidly. Low-noise amplifiers with noise figures of 3–4 dB are now common, and TWTAs routinely deliver output powers in the 45–90 W range. Although costs remain higher than for C-band or Ku-band hardware, they are steadily decreasing as Ka-band components are produced in larger volumes for HTS systems.

Ka-band is now central to many modern satellite architectures. It supports FSS, BSS, and especially HTS systems such as ViaSat (ViaSat-1/2/3), Hughes (Jupiter series), Eutelsat, O3b, Starlink, and Amazon Leo. It is also used by MSS operators, including Inmarsat, Iridium, and Thuraya, primarily for feeder and gateway links. Military systems also make extensive use of Ka-band: WGS satellites carry Ka-band payloads, while Milstar and AEHF employ Ka-band downlinks (around 20 GHz) in combination with V-band uplinks (around 44 GHz).

High-capacity mobile applications are a major driver of Ka-band adoption. The combination of wide bandwidth and high frequency reuse makes Ka-band well suited to in-flight connectivity, maritime broadband, and land-mobile services, where compact terminals can be deployed on aircraft, ships, and vehicles. These mobility services are now a core component of Ka-band satellite offerings, often integrated into global HTS networks to provide seamless connectivity for moving platforms.

In summary, Ka-band enables broadband-scale capacity and advanced mobility services, but at the cost of increased vulnerability to atmospheric attenuation and the need for sophisticated mitigation techniques and carefully engineered ground segments.

Q-Band

Sitting between Ka-band and V-band, Q-band (approximately 33–50 GHz) has emerged as an important candidate for next-generation satellite feeder links and high-capacity trunking. Interest in Q-band stems from growing congestion in Ka-band gateway allocations and the corresponding need for wider, less crowded spectrum to support high-throughput satellites and proliferated LEO constellations. Since the early 2000s, several demonstration missions in Europe, the US, and Japan have evaluated Q/V-band payloads, and satellite operators have increasingly included Q-band in regulatory filings for future gateway networks.

Q-band offers access to substantially wider contiguous spectrum than is typically available in Ka-band allocations, enabling multi-gigahertz feeder links capable of supporting terabit-class system architectures. As with Ka-band, the shorter wavelength permits compact, high-gain antennas and the formation of tightly focused spot beams, supporting aggressive frequency reuse. These characteristics make Q-band particularly attractive for gateway uplinks, where large, high-power Earth stations can exploit the available bandwidth while accommodating the more demanding propagation conditions.

Propagation effects remain the principal challenge. Rain attenuation, cloud and fog absorption, and gaseous losses increase significantly with frequency, although Q-band impairments are generally less severe than those encountered in V-band. Operational Q-band systems therefore require high link margins and rely on the same mitigation techniques used in Ka-band networks, including uplink power control, adaptive coding and modulation, beam shaping, and site diversity. In the latter case, geographically separated gateway stations ensure service continuity during heavy precipitation events. These techniques are well established from Ka-band deployments and scale effectively into the Q-band regime.

Hardware technology for Q-band continues to advance rapidly. Modern gallium nitride (GaN) and indium phosphide (InP) devices support low-noise amplifiers with competitive noise figures and high-power amplifiers suitable for feeder-link payloads. Antenna systems benefit from the small wavelength but must maintain tight surface tolerances to preserve efficiency, while thermal management becomes more demanding due to higher dissipative losses in active components.

In summary, Q-band occupies a transitional position between Ka-band and the higher-frequency V- and E-bands. It offers wide bandwidth and substantial growth capacity with more manageable propagation penalties than V-band. For the foreseeable future, Q-band is expected to play a central role in satellite gateway and feeder links, while user-terminal applications may follow as component technology matures, regulatory frameworks stabilize, and propagation mitigation techniques continue to evolve.

Emerging Bands (V-band and E-band)

In recent years, satellite operators have begun exploring frequency bands above Q-band to support next-generation high-throughput applications. Operators such as Amazon Leo and Starlink have filed for the use of V-band (approximately 37–52 GHz) and E-band (71–86 GHz), particularly for gateway and feeder links, where large, high-power Earth stations can mitigate the increased propagation losses.

Military satellite systems have also pioneered operation at these higher frequencies. The US Milstar and AEHF satellites employ V-band uplinks around 44 GHz, exploiting the additional bandwidth and reduced congestion relative to traditional military satellite bands.

Although V-band and E-band offer substantial bandwidth for future expansion, their propagation characteristics present significant challenges. Rain attenuation, gaseous absorption, and atmospheric losses are more severe than at Ka-band, necessitating advanced countermeasures such as site diversity, adaptive coding and modulation, uplink power control, and high-power payloads. As a result, near-term applications are largely confined to gateway and feeder links, with direct user links expected only once technology maturity, regulatory frameworks, and economics permit.

Looking to the future, the vast bandwidths available at V-band and E-band are widely regarded as key enablers for terabit-per-second class satellite constellations. If propagation challenges can be effectively managed and supporting technologies continue to mature, these bands may eventually extend beyond gateways to support ultra-high-capacity broadband services for end users in the longer term.

Summary of Frequency Use in Satellite Communications

FSS systems primarily operate in the C-band, X-band, Ku-band, and Ka-band, reflecting their need for large contiguous bandwidths to support trunking, data, and broadband services. Much of the C-band, X-band, and portions of the Ku-band spectrum are shared with terrestrial fixed services, leading to congestion and greater reliance on Ka-band, which offers wider bandwidths and frequency reuse despite higher propagation challenges. Recent filings also explore V-band feeder links to support future high-capacity networks. This progression toward higher frequencies reflects not only engineering capability but congestion economics: as lower bands become saturated and orbital slots densify, operators migrate upward in frequency to access wider contiguous spectrum and to sustain capacity growth.

BSS allocations are designed to support both individual reception (small, low-cost user terminals such as TV receive-only dishes) and community reception (larger head-end or community antennas). BSS is characterized by high satellite transmit power, enabling reception with inexpensive home antennas. Downlink allocations exist in the S-, Ku-, and Ka-bands, while feeder uplinks typically share FSS allocations. Examples include Ku-band DBS systems such as DirecTV, Dish Network, and Sky, as well as Ka-band BSS/DBS satellites such as KA-SAT (Eutelsat) and Viasat. S-band has been used experimentally (by GSAT in India, for example) but remains limited in scope.

MSS frequency choice reflects a trade-off between terminal size, antenna performance, and propagation reliability. Frequencies must be high enough to avoid excessive man-made noise, but not so high that free-space loss and rain attenuation overwhelm low-gain mobile antennas. As a result, L-band (around 1.5–1.6 GHz in ITU MSS allocations) remains the dominant MSS allocation for civilian services, supporting networks such as Inmarsat, Iridium, Thuraya, and Globalstar. These satellites transmit at relatively high power to compensate for small, low-cost mobile terminals. S-band has also been used in some regions for mobile multimedia services, while modern constellations such as Amazon Leo and Starlink are extending MSS into the Ku- and Ka-bands for broadband mobility markets (maritime, aviation, and land transport).

[1] ITU, Radio Regulations, Article 5, Table of Frequency Allocations, Geneva, Switzerland: ITU, 2024.
ITU, Radio Regulations, Appendix 30 — Plan for the Broadcasting-Satellite Service in the 11.7–12.7 GHz Band, Geneva, Switzerland: ITU, 2024.
ITU, Radio Regulations, Appendix 30A — Feeder Links for the Broadcasting-Satellite Service in the 17.3–18.1 GHz Band, Geneva, Switzerland: ITU, 2024.

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