Abstract
The 21.4-22 GHz frequency band has been internationally allocated for fixed, mobile and broadcasting satellite for countries in Regions 1 and 3 including Saudi Arabia. This frequency spectrum allocation makes the downlink Direct Broadcasting Satellite (DBS) system undergoes rain attenuation due to using the high frequency band, and experiences external interference caused by the wireless Fixed Service (FS). Such critical situation can degrade the DBS signal quality and performance. This paper presents an interference scenario to investigate the effect of the terrestrial FS signal on downlink DBS link in the presence of different measured precipitation rates throughout Saudi Arabia state in the 21.4-22 GHz frequency band. The system performance is studied in two propagation mechanisms: clear-sky and rainy conditions, and within two environments: urban and suburban areas. The results have shown that DBS receiver under the effect of both precipitation and FS interference in Saudi Arabia has three cases: (i) areas with high rain rate, such as Albaha, Abha and Makkah, do not support DBS receiver to operate with FS unless strict distance restrictions are taken, (ii) areas with moderate rain rates, such as Riyadh, can make DBS and FS work under some possible and moderate physical separation constraints, and (iii) areas with low rainfall rates, such as Tabuk district, support concurrent DBS and FS operation at very short physical separation.