Intersystem interference analysis between Have Quick II, Saturn, Marlin and DAB, DVB-T2

Within the FMV (FMV: Swedish Materiel Administration) funded project Gransknings- och expertstöd telekonfliktfrågor, an analysis has been performed regarding coexistence between military and civil systems in the lower part of the harmonized military band 225-400 MHz. The issue is important and has been actualized when the government has allocated frequency spectrum for digital radio in the 174-240 MHz band. In addition, there is a need to move parts of the television services from the 700 MHz band to the lower part of the military band in favor for mobile services. This means that the transmissions of digital radio (T-DAB), and TV broadcasts (DVB-T2) will increase in use in the lower part of military band. In the meantime, to meet the future needs for tactical communications for land, sea and air forces, the Swedish Armed Forces foresee a greater utilization of the entire frequency band 225-400 MHz. Therefore, an analysis is performed if the military systems Have Quick II (HQII), Saturn and Marlin can coexist with DAB and DVB-T2 without degradation of the civilian systems. In the analysis, two important scenarios are identified, the air and land scenario, where military systems may interfere with the civilian systems. The influence is quantified in terms of the necessary distance, which is a safety distance between the civil system and the military system, where the civil system is on the level to exactly fulfill a given well-defined service requirement. Several parameters have been shown to have a major impact on the safety distance. In particular, the wave-propagation model selected for the interference signal as well as the system parameters antenna gain and transmit power are of great importance. Another important parameter is the out-of-band characteristics of the transmitter. Furthermore, the adopted service requirement for DAB has a major impact on the calculated safety distances. In this work, we use the service requirement defined by ETSI. It can be stated that the safety distance becomes very long in the air scenarios. In some cases, the safety distance exceeds the so-called line-of-sight (LOS) distance of about 400 km, which is the maximum possible distance for the interfering signal. Hence in those cases, the safety distance is limited to the LOS distance. The large size of the buffer zone (a zone with a radius of 400 km) makes it reasonable to assume that neighboring nations' military networks might affect DAB and DVB-T2 systems in Sweden. For the land scenario, the interference signal is stronger attenuated, why the safety distances becomes much shorter than in air scenario. Generally, interference from airplanes is difficult to predict. For fixed installations on the contrary, as for examples ground stations, safe zones can be defined and as a recommendation we propose a safe distance around HQII and Saturn transmitters of 10 km for the DAB system and 17 km for DVB-T2. For Marlin transmitters with a bandwidth of 25 and 500 kHz a safety distance of 22 and 35 km, respectively, is recommended for the DAB system and 20 km for the DVB-T2 system (valid for both 25 and 500 kHz option).