Since cognitive radio is a novel technology, the innovations beyond the current state of the art proposed and achieved by SCREEN can be roughly divided in two categories: those coming from the incorporation of cognitive radio technology in space applications and those brought by the project itself into the current research in the topic. The first is easy to understand, based on the considerations already presented in the previous sections. Cognitive radio revolutionises the way the communications spectrum is managed nowadays, going from static frequency allocations to adaptive and dynamic bandwidth usage, depending on the availability and performance requirements. Currently, there is no flexibility to adapt radio parameters in order to adapt them to the current needs. Frequencies are allocated beforehand and through a time consuming and complex process. Communications are then confined to that restricted part of the spectrum. The second category for innovation comes from evolving the maturity of the cognitive radio technology, when compared to on-going research in that area. These innovations are easier to identify, as they refer to practical achievements. At this level, SCREEN managed to raise the cognitive radio technology maturity levels from TRL3 to TRL4/5, which is a major breakthrough for a successful incorporation of the concept. SCREEN dealt essentially with implementation and representative testing of the CR algorithms and concept, unlike previous projects which focused on feasibility studies and algorithm simulation. SCREEN has faced the challenges of implementation and testing, such as real estate limitations, typical performance degradation or real-world constraints. This constitutes a major step towards concept validation and it also allowed defining a baseline transceiver architecture that is compatible with and optimised for cognitive radio algorithms.
The concept of cognitive radio was initially explored for terrestrial applications. The ability to decide at each moment and autonomously which part of the spectrum to use gives a level of flexibility, robustness and security in communications that is extremely attractive for defence applications. On the other hand, the ability to optimise the spectrum usage, which is a valuable resource in any application, is attractive by itself. Spinning the cognitive radio concept into space communications will lead not only to drastic improvements but also enable new approaches and a new generation of emerging missions based on multiple satellites. Particularly, it will enable major improvements in the two fields mentioned in the topic: technologies for flexible Satcom payloads and advanced ISL and downlink communications. For the Satcom market, the focus of SCREEN, cognitive radio can enable different approaches for managing the growing satellite communication demands and provide flexibility to explore new types of hybrid networks. An example is the hybrid networks studied in the project MONET, introducing Satcom capability in mobile wireless networks to provide remote connectivity. The biggest impact in the Satcom segment is however in performance. However, in terms of future space missions, the flexibility of cognitive radio, supported by the underlying SDR technology, holds promising advantages to a wide range of mission types, especially those involving multiple satellite platforms. Missions such as formation flying, on-orbit servicing or LEO communication networks have critical requirements in terms of communication, since the platforms need to interact permanently to coordinate actions. Having the capability of sensing the environment and detect which frequencies are available and more reliable to communicate would ensure robustness for critical operations. The fact that the process is entirely autonomous is also fully compatible with the nature of this new generation of missions.
