ANALIZA POUZDANOSTI LINKOVSKOG SISTEMA ZA ETERNET MREŽU NA FREKVENCIJSKOM OPSEGU 7 GHz i 18 GHz
LINK SYSTEM REALIBILITY ANALYSIS OF ETHERNET NETWORK AT FREQUENCY RANGE OF 7 GHz AND 18 GHz

Summary/Abstract: In this paper, an analysis of a microwave radio relay link for an Ethernet network is presented. The analysis is conducted from the perspective of the overall annual reliability of the radio relay link in the microwave frequency range. The radio relay link is divided into multiple paths. The reliability of the link depends on the conditions of electromagnetic wave propagation in free space and the condition of the equipment. The design process of a radio-link system consists of three parts. First, the relative position of the stations is calculated, including the calculation of the distance between stations, azimuth, and elevation for each antenna based on spherical geographical coordinates, the altitude of the station locations, and the height above the terrain. Second, it is verified whether the conditions along the path satisfy free-space propagation conditions, including the existence of optical visibility - Line of Sight (LOS) from transmitter to receiver and free first Fresnel zone. Third, it is necessary to calculate the attenuation on each path, as well as the total annual unavailability due to rain, annual link unavailability due to multiple reflections, considering both horizontal and vertical polarization of antennas, and various types of digital modulation. The aim of this work is to examine transmission parameters such as the annual link unavailability due to multiple ground reflections and unavailability due to rain. The reliability of the link is also considered in terms of channel bandwidth and type of digital modulation. Calculations are performed for the following types of digital modulations: QPSK, 8PSK, 16QAM, 32QAM, 64QAM, 128QAM, and 256QAM. The radio relay link is implemented using devices equipped with Adaptive Coding and Modulation (ACM), which means that the system can choose the type of digital modulation to automatically adapt to the current conditions of attenuation along the path to prevent fading in very poor weather conditions (heavy rain, storms, snowstorms, etc.). During extreme weather conditions that affect the quality of data and voice transmission over the wireless network, a radio system that supports ACM automatically changes the modulation, allowing real-time applications to continue without interruption. Changing the modulation type also changes the channel capacity, i.e., the data transmission rate per signal, thereby providing higher data throughput and better spectral efficiency. Annual unavailability due to rain and link unavailability due to multipath propagation are considered for four radio relay paths in the frequency range of 7 GHz and 18 GHz, for both horizontal and vertical polarization.

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