Optimizing the coexistence between HAPS platform and terrestrial system in 5.8GHz band

The 5850–7075MHz band is profoundly utilized for the fixed service such as Terrestrial Systems (TS) and microwave access (WiMAX) in various parts of the world. Nowadays, the High Altitude Platform System (HAPS) became a recognized system in this band. Therefore, terrestrial links are one of the most considerable interference with the HAPS gateway (HAPSGS) links. Hence, the legitimated interference level between HAPS and TS must be investigated to prevent performance degradation to both systems. This paper investigates the compatibility between HAPS and TS for microwave access (WiMAX) when both systems operate in co channel sharing scenario. This is done by evaluating the downlink (DL) and uplink (UL) performance of both systems. The compatibility results are based on the theoretical derivation of spectrum sharing scenario between HAPS and Terrestrial WiMAX user (TS) located in the coverage area of HAPS in high rain attenuation areas by using the deterministic methodology. This assessment has been executed in the urban area elevation angle. The performance of the system is evaluated in terms of interference to noise ratio (INR) of TS receiver inside the urban area coverage (UAC) of HAPS. Based on the study results, the minimum separation distance should be between 15 to 18 kilometers away from the reference point (i.e. Nadir Point (NP)). The isolation technique is applied in the distances less than 15 km and above 18 km in order to mitigate the interference. Consequently, the maximum isolation values should be 30.92 dB and 13.4 dB inserted between the FS and HAPS Gate Station (HAPSGS) and HAPS airship (HAPSAS) respectively to prevent the co-channel interference.