It is difficult to coexist with radio access networks and military radio radars, even though they are two distinct radio services. The frequency allocation for military radars is relatively limited, while radio access networks need a large amount of spectrum. Both systems need to work together to avoid interference. However, there are many uncertainties about the potential for coexistence between them. Documentary research was done to determine if coexistence solutions were possible.
The research method involved three main parts. The researchers first examined the current situation in military radars, radio access networks and other related technologies. Second, they interviewed experts in order to determine the feasibility of coexistence. Third, they examined possible technologies to allow coexistence between military radars or radio access network.
Because they are not transparent in their operation, coexistence can be a problem for military radars. They use frequency hopping to avoid interference and detection. They may also need to leverage state-of-the-art filtering techniques. Additionally, equipment may have to only be sent when needed. A shared database may require them to supply the data they need.
Experts however stressed the importance for cross-industry coordination as well the need for greater economic and policy involvement. The experts also suggested the implementation of agreements that involve the use of shared data bases and the use of radar imaging results to improve the accuracy of individual radar imaging. Experts mentioned the US's CBRS in the 3 - 3.7GHz band as an example for coexistence of radio access networks and radars.
On a scale of 0-10, the experts ranked the most viable coexistence options. The highest rankings were given to the resource allocation coexistence, the location-based coexistence, and the cognitive radio coexistence methods. The researchers found that different information exchanged between the systems could lead to the classification of the methods into coordinated and uncoordinated.
Researchers also examined the conditions for frequency coexistence of military radars with radio access networks. They found that the primary precondition for frequency coexistence between military radars and radio access network is secondary users being able to detect and avoid the primary users. If they spot radar activity, the secondary WAS and RLAN users need to switch channels within ten secs. Users must also perform regular channel availability checks.
These studies have shown that radio access and military radars could coexist. This technology is still very early in development. The methods currently being studied may not be sufficient to prevent interference between the systems. It is therefore necessary to continue research in order to find efficient methods of spectrum sharing.
Researchers found that the most viable coexistence options between military radars, radioaccess networks, and radioaccess systems are resource allocation coexistence. They also recommend location-based techniques, cognitive radio coexistence, and location-based method. However, there were also some safety concerns.