Secondary use of exclusively licensed but inefficiently used spectrum bands has been proposed as a solution to make more efficient use of spectrum resources. An important requirement for such secondary usage is to ensure that the primary services and systems performance are not degraded due to the presence of the secondary system. In this report three licensed primary systems are studied, namely digital video broadcasting, radar and aeronautical systems. In this initial report, the odelled tolerance limits for the primary users are investigated and verified by means of measurements for the case of DVB systems and literature review for the cases of Radar and Aeronautical systems. The impact of interference is evaluated as a functionof Desired to Undesired Power level (D/U) ratio for DVB systems, the pulse detection error for Aeronautical systems and the maximum interference-to-noise ratio (INR) for Radar systems. The main conclusions are that co-channel and adjacent channel interference need to be taken into account when assessing the tolerance limits for secondary systems in the TV bands. Also, non-continuous bursty-type users do not cause any higher interference compared to continuous data traffic users; thus, same tolerance limits can be used for both traffic behaviours.

For aeronautical systems, spatial separation and transmit power of the secondary system determine the feasibility of secondary usage of the L-band. For other radar systems e.g. in S band and C band, the INR value, the spatial separation, the transmit power of the secondary system and the IF separation effects determine the possibilities for secondary users. For DVB systems, multiple interferers cause accumulative interference effects on the co-channels and adjacent channels, and the total amount of interference caused by multiple interferers should be kept below the desired signal level.