Designing reliable microwave networks requires more than establishing line of sight and calculating link budgets. Atmospheric conditions, particularly rain and snow, can significantly affect link performance at higher frequencies. HTZ incorporates advanced propagation modelling into the planning process, enabling engineers to assess these effects and predict link availability before deployment.
From Rainfall to Link Availability
HTZ supports ITU-R P.530-19 for microwave link reliability calculations and ITU-R P.837-8 for rainfall data. Using location-specific climate data, HTZ extracts the 0.01% annual rain rate (R0.01) from P.837 digital maps, alongside geoclimatic parameters such as dN75 and LogK from P.530 digital products. These inputs calculate rain attenuation and clear-air multipath fading, which we compare with the available fade margin to predict link availability and annual outage time. This provides engineers with a realistic assessment of link reliability under varying atmospheric conditions.
Understanding the Impact of Rain
Rain attenuation becomes increasingly significant at higher microwave frequencies. HTZ calculations demonstrate rain fade at 0.01% ranging from 4.4 dB at 7 GHz to 31.8 dB at 80 GHz. In the 80 GHz example, rain was the limiting factor, with a predicted annual outage of 154 minutes. This highlights the importance of accounting for atmospheric effects when designing high-availability microwave networks.
Modelling Rain, Snow and Atmospheric Conditions
HTZ provides several options for evaluating precipitation and atmospheric effects. In addition to ITU-based rain attenuation calculations, the software supports the Crane model for rain and snow, including parameters such as the 0°C isotherm height.
The software assesses clear-air multipath fading using ITU-R P.530 methodologies and relevant geoclimatic data, helping engineers identify environmental factors that could compromise link reliability.
Integrated Microwave Network Planning
Atmospheric modelling forms part of HTZ's comprehensive microwave planning capabilities. Engineers can analyse terrain profiles and Fresnel clearance, optimise antenna heights, calculate link budgets and availability, and evaluate adaptive modulation, XPIC, space diversity and frequency diversity.
Batch calculations across multiple bidirectional links further streamline network planning, with results available for reporting and analysis. By combining terrain, equipment characteristics, and atmospheric propagation modelling in a single environment, HTZ enables engineers to identify potential vulnerabilities early, optimise network performance, and design more resilient microwave networks.
