PRELIMINARY
Radio Link Functions
3 Radio Link Functions
The packet radio operates within the 59–62 GHz frequency range, using 4, 16,
32, 64, 128, or 256 QAM, also supporting Adaptive Coding and Modulation
(ACM).
3.1
Adaptive Coding and Modulation
Adaptive Coding and Modulation (ACM) enables automatic hitless switching
between different ACM profiles, depending on radio channel conditions. Hitless
ACM makes it possible to increase the available capacity over the same
frequency channel during periods of normal propagation conditions.
Code rate and modulation (and thereby capacity) are high during normal radio
channel conditions and lower during less favorable channel conditions, for
example, when affected by rain or snow. ACM profile switches are hitless, that
is, error free. In situations where traffic interruption normally would occur, it is
possible to maintain parts of the traffic by switching to a lower ACM profile,
using hitless ACM.
Figure 3
shows how the capacity changes when the received input signal
crosses the receiver threshold for each ACM profile.
5
1/22102-HRA 901 17/9 Uen PU1 | 2016-07-04
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