Interference between terrestrial, high-altitude platform and satellite systems at 28 GHz

Abstract

As a result of increasing demand of wireless communication services, the use of the same radio communication channel for different services is inevitable. Therefore, radio frequency interference is a major cause of telecommunication service interruption. Rain attenuation increases the interference by scattering signal or attenuating the carrier signals. The affirmative impact of rain attenuation is when the rain attenuation gives harmful interference and does the same negative impact, but over the interfering links. The aim of this thesis is to analyse the interference in a wireless network consists of terrestrial, receiving satellite ground station, and High Altitude Platform (HAP), under clear sky and rainy condition at 28 GHz. This study is divided into two sections: the first section is the analysis of three interference scenarios, based on the link budgets and data obtained from Maxis Communication Bhd, one of the mobile operators in Malaysia, in three scenarios. First and second scenarios, the interference from terrestrial and HAP to satellite ground station separately. The third scenario when the interference from both systems to satellite ground station. The contour maps of Carrier to Interference ratio (C/I) at satellite ground station are drawn. The results demonstrated that only the third interference has a severity and requires great separation distances. The second section is analysis of the impact of rain attenuation on the interference. The measurements of rain are used from several local measuring sources. Radar database is used to distribute the rain rate using the cell exponential profile, Excell model. The C/I contour maps when satellite ground station exposed interference from both terrestrial and HAP is used to identify the location of the three systems. The impact of the rain attenuation computed from excel model when it affects over the interfering path is analysed. It is showed that there was a significant improvement in the interference to noise ratio when rainfall on the interfering link. The improvement in interference to noise ratio reached 11.14 dB. Received Signal Level (RSL) is measured for one year over terrestrial sites operated by Maxis, provides 15-minute integration time attenuation statistics obtained from a digital microwave. ITU-R models are used to extract 1-minute rain rate and 1-minute rain attenuation from measured 15-minute rain attenuation. Furthermore, coefficients are proposed to convert rain attenuation from 15-minute to 1-minute integration time directly. The impact of the rain attenuation computed from Maxis database and ITU-R model when it affects over the interfering path was analysed. The results clarified that improvement in the interference to noise ratio was more than 15 dB. Moreover, results showed that the rainfall estimation from received signal level measurement over terrestrial links has a great potential. Next, the commercial microwave links’ network of an arbitrary geometry could be considered as a widely distributed source of rainfall observation network with high resolution and minimum supervision. Designers can benefit from the positive impact of the rain when designing wireless networks.