Microwave Radio Transmission Design Guide
A practical guide for engineers planning or building a microwave-based transmission system, with a special eye toward international standards.
TABLE OF CONTENTS Microwave Radio Transmission Design Guide
Chapter 8: Link Design
8.1 Introduction
In the previous chapters we studied the fading mechanisms due to propagation anomalies, interference effects, and equipment and antenna characteristics. In this chapter we will apply this knowledge to perform the design calculations for a radio link. The outages that are calculated need to be compared to the quality objectives that we studied earlier. In that chapter we learned that the availability requirements refer to events that occur for longer than 10 sec whereas the performance requirements refer to events that last less. Because ducting, diffraction fading, and rain fading are slow events (i.e., last longer than 10 sec usually some hours or more) they need to be considered from the availability point of view. Multipath fading, however, is a fast event and needs to be considered from the performance point of view. We start by analyzing multipath fading outages, which can be compared to performance standards such as G.821 or G.826.
8.2 Multipath Fading Mechanism
Multipath fading is a complex fading mechanism, especially on wideband systems. Since it is difficult to visualize the problem some mathematics will be used to illustrate the problem.
8.2.1 Multipath Channel Transfer Function
The first step in analyzing the problem is to derive the transfer function of the atmosphere under multipath conditions. The transfer function is amathematical concept used to analyze the effect of a signal through a network. It is represented by the output of the signal divided by the input.
In a multipath condition we input a microwave signal into the...
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