Adaptive Coding and Modulation (ACM)

Optimizing the outbound per remote

Use of ACM on the outbound channel allows Hughes to vary the “mod/code” (modulation and coding) combination of the outbound channel per remote.

Typical satellite “footprints” have a varied “contour” where the downlink power (measured as EIRP) varies geographically.

Sample satellite footprint with downlink EIRP values. (Click to enlarge)

With ACM Hughes can configure exactly the right carrier “mod/code” combination per remote or per contour.

ACM – Optimizing The Link Per Satellite Contour

(Click to enlarge)

In this example ACM brings a 38% increase in satellite throughput over CCM (Constant Coding and Modulation). Without ACM – or in Constant Coding and Modulation – the designer must size the network for the worst case contour.

ACM – Common Antenna Size

An additional benefit and option of DVB-S2 with ACM is the ability to configure all of the remote antennas to be the same size. In this mode the designer can simply take advantage of varying “mod/codes” to deliver the same Es/No to remotes using identical antenna sizes in different contours. Thus an entire network could be deployed using the same small antenna regardless of location. This lowers the cost installation and simplifies inventory.

ACM – Dynamic Rain Fade Mitigation

When a remote experiences local rain fade it can request that its outbound channel frames (addressed to that remote) are modulation and coded to suit the local conditions.

8PSK Rate 9/10 Remotes >>
Most efficient coding and modulation combination for clear sky conditions.

QPSK Rate 1/2 Remotes >>
Most robust coding and modulation combination for rainy conditions.

Closed Loop Link Control Provides High Availability With Efficiency.