Who hasn’t been without coverage on their mobile phone? Everyone has had this experience when moving away from urban areas, for example, when we are in the middle of the mountains. This happens because our mobile phone cannot find a base station nearby to connect to by radio, so it loses coverage. The deployment of a cellular network involves placing these base stations on the ground. In some areas that are difficult to access this is not possible, e.g. in mountainous or maritime areas. It is also very common to see this scenario in emergency or natural disaster situations where the terrestrial network has been down and it is not possible to deploy a new one quickly. The new sixth generation mobile communications standard, 6G, seeks to provide a solution to these situations. To do so, it makes use of what are known as non-terrestrial networks (NTN) and the concept of Edge-Cloud Continuum. In this article we will explain what these systems consist of and what they will contribute to the new 6G standard.

Satellites to enable global coverage

NTNs are based on the idea of extending terrestrial network coverage via a non-terrestrial platform, most commonly a satellite. This would allow the user the possibility of having global coverage on their device, without the need for a nearby base station on the ground. However, one of the main drawbacks of this type of network is the delay caused by the distance between the satellite and the Earth. A high orbit satellite (called GEO or geostationary) offers a wider coverage because of its height, the area of the earth it can cover is larger. However, the signal will take longer to travel the distance between the communication point on the ground and the satellite, which will penalise the response time.

At the other extreme, low earth orbit satellites (known as LEO satellites), being closer to the earth’s surface, have less coverage but also shorter response times.

In the middle ground, medium orbit satellites (known as MEO satellites) offer a compromise between delay and coverage. This is why in NTN networks it is important to identify the communication needs of applications and, if available, to use the NTN infrastructure that best fits.

Roaming, the management of device movement between one network and the other

The integration of the satellite network into today’s network architecture is a key area of research. One of the main areas of interest is the management of device movement between one network and another. This process is known as roaming and is what allows our device’s connection to be maintained when we switch between base stations as we move. This procedure is not trivial in NTN networks and is one of the most interesting areas of research at the moment. The ultimate goal is for a user to be able to transit between terrestrial and satellite networks in a completely seamless way.

Edge-Cloud Continuum

In parallel to non-terrestrial networks, at 6GDIFERENTE we also work with the novel concept of Edge-Cloud Continuum. It could be said that Cloud Computing (or Edge Computing) are paradigms that are already integrated in our day-to-day life, but what is sought with continuity is to aggregate the different elements of each layer to form a single distributed architecture. That is, the Edge-Cloud Continuum is a novel concept that describes a connected infrastructure from the edge to the cloud, integrating computing devices so that the deployment of applications and services is done by leveraging the capabilities of the entire continuum. Thus, the different loads can be orchestrated across the network gaining flexibility, efficiency and speed compared to a deployment in each layer in isolation.

Connecting autonomous vehicles

In this regard, the continuity of resources between the Edge and the Cloud plays a key role in NTN networks. By integrating satellite base stations with the resources available in the Edge-Cloud Continuum, the user can access applications or process information ubiquitously and transparently. Furthermore, it does not suffer any kind of penalty: neither in connectivity nor in the execution of tasks.

For example, imagine an autonomous vehicle driving on a road connected to a 6G network and communicating with the nearest Edge to perform traffic-critical data processing. In the continuum, this processing will migrate between the different edge centres to ensure that the vehicle does not pose a risk to the traffic… But what if we enter an area without terrestrial coverage and the vehicle connectivity is replaced by a satellite network? Thanks to the Edge-Cloud Continuum, we could migrate the loads to the infrastructure environment closest to the satellite base station, while maintaining the vehicle’s needs depending on the satellite-to-base station latency.

In short, the marriage of NTNs with the novel concept of the Edge-Cloud Continuum provides an intelligent, adaptive and connected environment in which to manage resources transparently. In doing so, it makes the vision of universal coverage feasible under a network of networks being researched under the umbrella of 6G networks.

In the 6GDIFERENTE project we work on the implications and challenges of combining both technologies. In this statewide initiative, we support the research of each line by implementing a mobility use case in which the user experiences these shifts between terrestrial and non-terrestrial networks.