What is Adaptive Coding Modulation (ACM)?
Adaptive Coding and Modulation (ACM) is a technology which automatically changes the Forward Error Correction (FEC) and modulation utilized on a satellite link to compensate for changes in link conditions, so that it is operating at the most efficient coding and modulation scheme available.
Why use ACM?
Commonly the changes in link performance are due to atmospheric conditions like rain (rain fade), changes in the RF levels, solar events, noise or interference. Previously these conditions could result in the link dropping out of network and making the users angry. ACM prevents these outages and will provide an uninterrupted service and the link will only drop out under extreme conditions.
- More robust link
- Maximises link availability
- Required to meet SLA (Service Level Agreements)
- More spectrally efficient for the outbound carrier and remote sites – more data per Hz
- MODCOD automatically altered per remote link
- Happy Satellite VSAT users 😊
How does ACM Work?
ACM evaluates current link conditions and throughput requirements through a return channel to determine the ideal modulation and FEC used (MODCOD). This optimizes the bandwidth efficiency for maximum throughput on a remote-by-remote basis in real time without any intervention from the Network Operations Centre (NOC). The ACM can be limited at a set MODCOD (e.g 16APSK) to stop any CRC errors if the remote is uncapable of receiving these higher level MODCODs in clear sky conditions.