Future SATCOM networks will span multiple orbits, like geostationary equatorial orbit (GEO), medium Earth orbit (MEO), and low Earth orbit (LEO), among others. In addition, they will also cover multiple frequency bands, satellite operators and network designs. These multi-layered, hybrid networks allow for enhanced communications and protect against potential disruptions or attacks. This research studies the future implementation and use cases of such networks. It will focus on examining current technology trends and assessing probable markets that could utilize multi-layered SATCOM applications. The aim is to achieve a system design that is able to support both current and future satellite service types, interoperability, and increased spectral efficiency.
Finding a solution that serves remote and hard to reach places, rather than providing more satcom services to already data rich areas. A multi layered solution exploiting existing constellations needs to interoperate with different latency and form factor standards. There is no one terminal that will meet all the requirements of an MLS solution and the cost of developing a new terminal are economically prohibitive. Compromise and collaboration with existing technologies and vendors is the only way.
The MLS system provides an economic and sustainable solution for currently underserved market segments and regions. The system has been carefully conceptualised to be affordable, available, capable, and easy to use for the customer, whilst minimising environmental impact and maximising sustainability. By combining the best of LEO and GEO systems, the MLS system simultaneously addresses capacity, latency and SWAP-C needs, whilst reducing capital expenditure requirements compared with either LEO or GEO single orbit systems. MLS combines a LEO-lite constellation, carefully designed to complement the counterpart GEO capability and avoids the need for a mega constellation of high mass satellites and the associated environmental impact.
Many regions of the world remain underserved, notably Barents Sea/Arctic Ocean (Northern Norway and Canada), Northwest passage, Latin and South America, Africa and parts of Eastern Europe. MLS enables economic service provision to these regions and helps bridge of the digital divide in under-developed areas. Whilst modern HTS services bridge some of these gaps, MLS adds coverage and resilience against weather and network impacts (outages, congestion) for a more reliable service.
MLS provides an economic and sustainable path to providing cost effective service. Key features include:
- Low SWAP-C user terminals
- A range of user terminals depending on application, including high performance and small form-factor
- Use of mmWaves (E band) offering more available, uncontested bandwidth and minimisation of user terminal form factor
- Combining (rapid switching) of signals from LEO and GEO systems to optimise performance and reduce capital expenditure requirements whilst maintaining coverage and service performance. Rapid switching is implemented at network level via a smart router.
- Inter-satellite links, deployed judiciously to simultaneously optimise performance, cost and sustainability
- Capacity steering satellite capability
- Sophisticated waveforms, possibly including MF-TDMA, offering improved power efficiency and enabling reduced terminal size and cost
- Minimised LEO constellation size and LEO satellite mass to minimise environmental impact and maximise sustainability
- Economically and environmentally sustainable
- Optimal delivery according to service type - low latency when needed, high capacity when needed.
- Designed for flexibility, providing insulation from market upheavals
This MLS system consists of a concurrent GEO + LEO network for high speed, low latency, affordable internet access. Smart routing exploits the latency, data rate, capacity economics, and geographic coverage of the constituent networks and can provide path resilience by using one, or both, of the constituent networks based on user experience or requirements, weather, jamming, cyber-attack, etc and leverages the individual benefits of GEO and LEO to deliver cost effective bandwidth with the perception of LEO-like latency.
The GEO segment will be procured as a commodity from existing capability. The baseline delivery will consist of 3 GEO satellites providing Ka-band capacity with near-global. As markets fluctuate and more GEO capacity is made available through new on-orbit capability.
The LEO segment will consist of a constellation of ~1,000 satellites of 24kg mass, operating in 4 shells of varying inclination at altitudes around 1000km, providing global coverage at LEO with the majority of capacity covering the majority of the global population. The LEO satellites will operate in E-band with RF V-band ISL capability on ~25% of the fleet to minimise gateway demands and extend coverage to those gateways.
The project comprised 6 tasks, each deriving technical notes that provide the data.
Task 1: Market and Technology Assessment
Task 2: Scenario Development, Trade Off, and Selection
Task 3: System Requirements and Trade Off Analysis
Task 4: System Definition, Modelling, and Simulation
Task 5: Economic and Regulatory Analysis
Task 6: Gap Analysis and Roadmap
All task notes submitted and reviewed with ESA feedback issues resolved. Viasat has designed a conceptual 1000 satellite LEO constellation that utilises GEO as a commodity service to provide a concurrent LEO/GEO MLS system.