In theory the possibilities of IoT are endless, but in practice there are still limits to what is achievable with existing types of connectivity. Despite the telcos’ efforts to ensure seamless global communication – ensuring cellular connectivity everywhere and at all times – the investment needed to extend mobile technology to regions where it is commercially difficult to justify building terrestrial base stations is challenging.
Non-terrestrial networks (NTNs) are primed to address these challenges, but until now, have been technically constrained. That’s all about to change. With the evolution of 5G and 6G technologies, we’re entering an era where companies investing in satellite communications could soon make seamless cellular standard connectivity, even in the most remote areas, a reality.
Kevin Cobley and Richard Jacklin of Plextek explain how 5G and 6G integration with NTN has the potential to transform global connectivity with Direct-to-Device (D2D) communication.
From Backhaul to Direct-to-Device
While the intersection between cellular technologies and space and satellite communications has existed since the early days of 2G and GSM, when it comes to reaching remote and hard-to-reach areas, satellites have primarily been used for backhauling.
This process involves transporting traffic from the base stations to the mobile switching centre via satellite links, microwave radio links, or other methods of communication. However, current satellite coverage for mobile devices usually requires bulky antennas or offers very low data rates.
With 5G and 6G, satellites are now being considered for direct connectivity between base stations and user devices. This shift to D2D communication means devices – like smartphones or IoT sensors – can connect directly to a satellite without a ground-based intermediary. The benefits are enormous: global connectivity, no black spots in coverage, higher throughput, and access even in the most isolated areas. But it also means overcoming significant engineering challenges.
Overcoming Technical Hurdles
One of the main challenges in space and satellite communication is efficient frequency usage. High spectral efficiency is a hallmark of 5G, enabling more effective use of the frequency spectrum. However, achieving this in space-based systems and user devices is anything but straightforward. Large antennas are often impractical, making it essential to adopt lightweight, compact, and efficient solutions that maintain performance. Another critical factor is the integration of antennas and radios – particularly in massive MIMO (multiple-input, multiple-output) systems, which require numerous antenna elements. This has driven a shift toward fully integrated units, where the antenna becomes a core part of the electronics.
Another major hurdle is the power budget for handset-to-space communications, especially considering the constraints of both devices and orbiting base stations. The distance between a mobile device and a satellite is significantly greater than between a terrestrial base station and a mobile device (300 to 500 kilometres versus 15 kilometres). That alone creates a major power challenge. Satellites often spend extended periods in eclipse, during which they cannot generate power because they are on the dark side of the Earth. This limitation necessitates careful power management strategies.
And finally, higher latency as a result of distance between device and satellite compared to device and terrestrial network, will need to be mitigated so as not to impact the user experience. While it is not possible to eliminate latency, it is possible to minimise its impact. One way is to perform edge processing in space instead of relying on the bent pipe method that relays data back to and from Earth for processing. This approach provides the best user experience but is power-intensive.
To manage and balance these interlinking challenges, a system-level approach is essential – one that combines technical expertise, particularly in RF front-end design, low-loss and low-power solutions, with key design-for-excellence principles such as scalability, manufacturability, and testability.
Conclusion
The integration of 5G and 6G technologies with satellite networks has the potential to reshape global connectivity, but in practice the possibilities of IoT are still limited by current forms of connectivity. D2D communication could ensure reliable, low-power data transmission from remote sensors without requiring a local network. In defense, it could offer resilient and rapidly deployable networks. And for consumers, the dream of flawless mobile coverage – whether on land, at sea, or in the air – would finally become a reality. However, D2D is not without its challenges. Businesses need to invest in the specialist engineering expertise to navigate the harsh realities of space – such as radiation, extreme temperatures, and launch-related stresses – while designing products that are scalable and cost-effective.