Acm - Summary Of Specifications - Comtech EF Data CDM-750 Installation And Operation Manual

CDM-750 Advanced High-Speed Trunking Modem
Adaptive Coding and Modulation (ACM) Option
•
Es/No is the preferred metric for driving the adaptation – this is the value displayed on the
monitor screens. If the user wants to convert this to Eb/No then remember that the relationship
is simply Eb/No = Es/No – 10log(Spectral Efficiency).
•
To achieve minimum latency, set the WAN buffer to the smallest practical value. The default
setting is 20ms, and Comtech EF Data recommends keeping it at this level.
•
ACM is 100% compatible with DoubleTalk Carrier-in-Carrier (CnC).
•
ACM maximizes throughput not only when Es/No varies due to atmospheric conditions, but it
also mitigates the effects of other impairments such as antenna pointing error, excessive phase
noise, and certain types of interference. However, rapidly fluctuating impairments, such as
scintillation at low antenna look-angles at C-band, will generally not be improved by ACM or
will require abnormally large Target Es/No Margin.
•
ACM modes are not compatible with CCM modes, due to differences in frame preambles.
7.9 ACM – Summary of Specifications
For the complete table of specifications, refer to Sect. 1.4.7 Adaptive Coding and Modulation
(ACM) in Chapter 1. INTRODUCTION.
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