Even though radio access and military radars are two separate radio services, coexistence has been difficult. While military radars can use a small amount of spectrum, radio access networks require large amounts. Both systems need to work together to avoid interference. But there are still many unknowns about their potential coexistence. To determine whether coexistence solutions can be found, documentary research was carried out.
Three main components were required for the research process. First, the researchers studied the current situation of military radars and radio access networks. Second, the researchers interviewed experts to evaluate the feasibility of possible coexistence. Third, they looked at the technologies that could allow for coexistence of radio access networks and military radars.
Due to their limited transparency of operation, military radars make coexistence difficult. Furthermore, they use frequency hopping as a means of avoiding detection and interference. They may also need to leverage state-of-the-art filtering techniques. Their equipment may also need to be sent only when it is needed. Furthermore, they may be required to provide the required data to a common database.
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. As an example of possible coexistence between radio access networks (radars and radio), the experts mentioned the US CBRS operating in the 3.55 to 3.7 GHz band.
The experts ranked the most feasible coexistence methods on a scale from 0 to 10. On a scale of 0-10, experts ranked the most feasible coexistence methods. The cognitive radio coexistence method, location-based coexistence and resource allocation coexistence received the highest ranking. The researchers found that the methods could be divided into uncoordinated or coordinated depending on how the information was exchanged among them.
Researchers also investigated the preconditions of frequency coexistence among military radars and 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. Secondary WAS, including RLAN users, must change to another channel within ten seconds of radar activity detection. A channel availability check must be performed on a regular basis.
These studies have shown that radio access and military radars could coexist. It is still in its early stages and may not be able to prevent interference or mutual harmful interference. Therefore, more research is needed to find effective methods for spectrum sharing.
The researchers found that the most feasible methods for coexistence between military radars and radioaccess networks are the resource allocation coexistence, the location-based methods, and the cognitive radio coexistence methods. However, there were also some safety concerns.