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
Section 7.7: Frequency Re-Use
7.7 Frequency Re-Use
Frequency re-use refers to a situation where the same frequency pair is re-used in a route. In the interests of good spectrum management, when doing frequency planning one should start from the assumption that the frequency can beused.
7.7.1 Two-Frequency (One-Pair) Plan
The most efficient re-use plan is one in which a single pair of frequencies is used throughout a route. One needs to consider the interference from two perspectives: the interference at the repeater (nodal) site and the problem at sites further down the route (overshoot).
7.7.1.1 Nodal Sites
Consider a case where at site A two links on the same frequency are transmitting in two opposite directions. Let the left-hand link be called Link x and the right hand link be called Link y. The situation is as shown in Figure 7.11.
Figure 7.11: Nodal interference.
Site A is transmitting frequency f 1 in both directions. Site X is therefore rransmitnng on frequency f? 1. At sire A, the antenna (X) panned for Link x will receive the signal on frequency f? 1. The antenna (Y) panned for Link y will also receive this signal from x, but attenuated by the F/B ratio of the Y antenna. To re-use the same frequency f 1 on Link y, the minimum carrier (signal f? 1 from Link y) to interference (signal f? 1 from Link x attenuated by F/B ratio of Y) ratio must be maintained into...
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