Satcom Frequency Bands and How They Affect Maritime Users

Last Revised: August 2022

Opening an email, connecting to the shore-side office network, delivering engine and route data for efficiency gains, providing wi-fi and voice calling for passengers and crew. Regardless of the application, satellite services are a core enabler of voice and data communications at sea. And although the end-user should not be concerned with how their message reaches its destination, it’s important to understand that different vessel types, locations and communication needs drive the approach of a hybrid network based on multi-band services over all frequencies.

Satellite Communication (satcom) is based on a specific range of frequencies. The useable radio spectrum ranges from 1Ghz to 300Ghz, where its use for communications ends as the signal becomes infrared, X-Ray and visible light. For maritime satcom, we use the frequencies from 1Ghz up to approx. 30Ghz.

The frequency utilisation, wavelength used and antenna size depicts a satellite signal’s properties, i.e. is it prone to disruption during precipitation or can it penetrate the atmosphere at certain elevations? The size of range per frequency is also important – how much bandwidth does it provide? This is important as it affects coverage availability, or the suitability of certain services for specific circumstances.

Maritime Satcom Bands

A basic understanding of the available frequencies to maritime users will also help to understand why different frequencies provide different qualities which again can affect the service quality.

L-Band (1-2GHz): Mobile Satellite Services (MSS). Based on a wide beam, so less pointing accuracy is needed to receive a strong signal. This means on board equipment can be smaller and lower cost. However the scarcity of available bandwidth means lower throughput and services are of the managed variety – Inmarsat, Iridium and Thuraya. L-Band services are global and are resilient to rain fade, so offer reliable, but low bandwidth communication.

C-Band (4-8GHz): Very Small Aperture Terminal (VSAT). Requires more power so larger (2.4m+), more expensive antennas are needed but bandwidth is relatively cost-effective. Frequencies in the C-band perform well under adverse weather conditions (rain fade) making it a very reliable solution. It’s ideal for passenger vessels and business critical usage on offshore vessels that have the real estate available for the large antenna in addition to multi-user, high bandwidth requirements on board. C-band can cause microwave interference meaning that it cannot be used too close to shore in certain areas whilst the antenna size means that it cannot be installed on smaller vessels.

X-Band (9-12GHz): Very Small Aperture Terminal (VSAT). Reserved for government and naval use only, X-band offers similar throughput potential as C- and Ku-band, and good resistance to rain fade.

Ku-Band (12-18GHz): Very Small Aperture Terminal (VSAT). The most common maritime VSAT band in use, Ku-band satellite coverage has grown along the commercial trading routes making it a global VSAT alternative to C-band for merchant vessels. With significant bandwidth available, Ku-band services are less costly, but are more susceptible to rain fade. However, less power is required for a stable connection, so smaller (generally 60cm – 1.5m) and less expensive antennas can provide a reliable, high throughput service relevant for a wide range of vessels.

Ka-band (26.5-40GHz): Very Small Aperture Terminal (VSAT). A very large frequency range so there is more available spectrum, making it the least costly of all four bands in terms of satellite ‘airtime’. However, because it is a very high frequency it requires high pointing accuracy and though the antennas are basically the same as Ku-band, Ka-band requires a different feed. So in areas with high precipitation or low satellite elevation, it’s important to ensure a back-up service (L- or Ku-band) is available.

Global Multi-band

When discussing VSAT frequencies, it’s important to note that the speed of your connection is not depicted by the band your service uses. None of the VSAT bands are necessarily ‘faster’ than the others. Capability, coverage, reliability and power (antenna size) are the key factors. In terms of capabilities and suitability for specific vessels, satcoms is not black and white. When looking to install or upgrade your satcoms, choosing a provider that offers global multi-band service – so they have access to all bands – will help to ensure that specific needs and circumstances are catered for.

It’s the service providers job to ensure that services on the most suitable networks are specified for vessels and fleets, depending on a huge range of factors.

Where does the vessel operate? Knowing a vessel’s route and operating area is one of the key factors in choosing the type of communications and network services. Most satcoms networks offer regional coverage at sea so what frequency you communicate over, is often depicted by your location. Precipitation is also an important factor. One of the key factors that differentiates satcom bands is their resilience to rain fade, which is where the size of the wavelength matches that of the moisture, meaning the signal cannot get through or must be modified to work properly.

What communication needs does your vessel have? If you have a crew of fifteen, and a job to sail from port to port to deliver cargo, then your vessel will most likely not be a heavy bandwidth consumer. However, you might have a seismic survey vessel, needing the ability to transfer large amounts of data over the Internet to shore. That makes your vessel and applications bandwidth hungry so availability and cost is a key factor.

What type of vessel is it? Do you have the real-estate on board for a large antenna, or even two antennas? Does your route involve lots of course changes, that might put your antenna into a blocking zone, so the satellite can’t link with the antenna at times? These physical attributes of the vessel and operation will have an effect on the network and frequency used.

For vessels to receive the best quality, most reliable voice and connectivity services, a huge number of factors must be considered. Only when the above questions have been answered is it possible to decide what is right for any specific vessel. But once the most appropriate solution has been decided on, can the provider deliver it? Do they have access to all the frequencies available for maritime communications, ensuring that the right solution can be developed for your specific circumstances?

It even offers the flexibility to change bands, for instance, allowing simple migration to HTS services or continuity of service should a vessel’s operational location change to a new area.
It’s important that the end-user of maritime satcoms is only be concerned that they have a connection that works and offers, sufficient, reliable access to voice and data connectivity. To achieve this, ship-owners looking to install or upgrade satcoms should choose a service provider that can offer all options, on all bands, and that has the knowledge and experience to identify the best solution for any vessel, regardless of where it operates.

For vessels to receive the best quality, most reliable voice and connectivity services, a huge number of factors must be considered. Only when the above questions have been answered is it possible to decide what is right for any specific vessel. But once the perfect solution has been decided on, can the provider deliver it? Do they have access to all the bands available for maritime communications, ensuring that the right solution can be developed for your specific circumstances?

It’s important that the end customer can fully rely on a stable, efficient and also protected connection to access data and voice. To achieve this, ship-owners looking to install or upgrade satcoms should choose a hybrid network from a service provider that can offer all options, over all frequencies, beams and orbits for the best solution for any vessel, regardless of where it operates.

Click here to find out more about Marlink’s Smart Network Solutions, which include the management of hybrid networks.