Q&A on SDR for Small Satellites: Preconfigured vs. Customised ...

More and more missions require a Software Defined Radio (SDR) solution. Is your company working on putting a CubeSat (or a constellation) into orbit in order to capture, process and send data? If the answer is yes, your project could benefit from the functionalities offered by a SDR for small satellites.

With competitive price and timely delivery, Highmesh sincerely hope to be your supplier and partner.

The possibility of having a reconfigurable SDR in orbit is a perfect fit for missions that require flexible communications systems and have specific needs in terms of frequency bands, protocol, modulation, and data rate.

Before choosing the SDR and the different subsystems your small satellite will carry, you should be clear about what kind of configuration you want for your software and the differences between preconfigured vs. customised solutions.

If you choose custom software, you will need an SDR that allows you one of two options:

• Develop your own solution in-house.
• Rely on your provider's capabilities to tailor the software to your requirements.

In either case, the aim is to be able to adapt to the protocol and modulation needs of the mission, customise the implementation of the flowgraphs) and access the computing power of the Zynq processor and the Field Programmable Gate Array (FPGA).

On the other hand, there are preconfigured SDRs that already incorporate applications that are 100% ready to provide a given service from space. These options are already developed, successfully tested in orbit and ready to be integrated in record time in any mission, saving time in terms of development, integration and testing.

This short explanation is just a preview of the differences you can find between the different SDR options for small satellites. Throughout this post, we will answer some frequently asked questions, explain which solution is the most suitable at any given time and what factors influence that choice.

What kind of CubeSat missions depend on software configuration?

There are infinite possibilities for the development of missions in space, with different objectives and requirements. As no mission is exactly the same as any other, it is difficult to categorise them in order to know what kind of needs fit best with the development of customised SDR for small satellites. There are a number of aspects that could influence this decision.

Even so, we are going to group the missions into two main areas: those that require a high degree of customisation due to their characteristics and those that use common standards that allow the use of preconfigured applications.

• Missions that require custom developments tend to have a high level of specialisation. Within this same group are:
  • Missions requiring new software developments.
  • Missions that seek to update or create new applications not previously seen on the market.

• Missions with preconfigured applications often rely on standards that do not require customisation or custom configuration, such as: 
  • Missions for high data rate communications, such as DVB-S2 (Digital Video Broadcasting by Satellite), which allow the transmission of large files or high-speed downloading of data.
  • Information gathering missions in sectors such as aviation or maritime, with applications for AIS, ADS-B, etc.
  • IoT communications missions.
  • Missions with simple spectrum monitoring applications (SIGINT).

Preconfigured vs. customised SDR: which option is more affordable?

A fundamental aspect in deciding to undertake a space mission is its economic viability. Many factors come into play here, but it is possible to establish some parameters for choosing between one option or the other.

As a quick answer, the fastest and most affordable way to move forward with your project, without a doubt, is to have a quality supplier provide you with a preconfigured application in line with your mission objective.

In situations where it is more important to gain development experience (e.g. in educational projects) or to look for solutions that are currently not available on the market, the idea of a customised solution that allows you to take full advantage of all these possibilities is probably attractive.

What are the main technical features for a SDR configuration?

We could argue for hours about the technical aspects associated with SDR configuration for small satellites, but what is clear is that depending on the choice between a preconfigured or customised payload, the integration and implementation will differ.

On the one hand, a customised solution will use a software development kit (SDK) or Linux embedded systems with open source applications that allow the software to be adapted to the specific needs of each mission.

Preconfigured payloads, on the other hand, come with applications that are already integrated and ready to fly. They are well-defined, clearly focused solutions for different services and needs, which offer after-sales support and do not require special configurations.

Photo: Study and analysis of a SDR - Alén Space

How long does it take you set up your own SDR application?

As mentioned above, if you need an SDR for small satellites and are looking for immediacy, preconfigured software solutions will allow you to move more quickly through phases for which you would otherwise have to allocate time and resources.

In the case that your technical team or your provider has to deal with a customised solution, there are some factors that will directly influence the development time of the SDR, such as the following:

• The experience of the development team.
• The level of complexity of the application, which could even involve the creation of new protocols.
• Integration and testing prior to the satellite launch.
• The need to test the application in space and to dedicate more time to ensure that everything works properly during the LEOP (Launch and Early Orbit Phase).

How easy is SDR integration with small satellite platforms?

One important aspect is the integration of the SDR with your CubeSats platform. In cases where the technical team is going to develop a customised application of their own, it will always be necessary to dedicate more effort to testing to ensure that the payload works correctly with other subsystems.

In preconfigured platforms, there is already a guarantee that all of the subsystems are compatible and communicate correctly with each other. This is why we refer to it as a plug-and-play solution, as integration is almost instantaneous.

Why can our TREVO and TOTEM SDR be a solution?

Having seen how the choice between a custom or preconfigured software defined radio, as well as its integration with other subsystems, it is time to better understand what factors to consider when choosing SDR for small satellites.

Any SDR is expected to be able to provide different applications at different frequencies and bandwidths. For example, Alén Space's SDR solutions, under the trade names TREVO and TOTEM, allow the development of applications in a frequency range of 70 MHz to 6 GHz, a bandwidth of up to 56 MHz and the ability to integrate interfaces for different frequency bands: UHF, VHF, S-band and L-band.

This includes the ability to remotely perform in-flight reconfigurations, a comprehensive flight heritage with a 100% success rate, an SDK tool including training and support, and the ability to implement algorithms directly on the FPGA or integrate GNU Radio files.

These characteristics make Alén Space a company already established in the communications market, with years of experience with payloads for communications and information gathering.