Newtec MDM6000 - Roll off Factor and Occupied Bandwidth

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Feature Descriptions MDM6000 Satellite Modem
14.1.4 Roll Off Factor and Occupied Bandwidth
MDM6000 >> Modulator >> Roll-Off
Select the appropriate roll off factor.
The possibilities are:
• 35%;
• 25%;
• 20%;
• 15% (Clean Channel Technology™);
• 10% (Clean Channel Technology™);
• 5% (Clean Channel Technology™).
The following figure compares 20% roll-off with 5% roll-off.
By lowering the roll-off factor and accordingly increasing the symbol rate, the throughput can be
increased while maintaining the same occupied (leased) bandwidth.
Clean Channel Technology™
Clean Channel Technology™ is a combination of improved roll-off factors for DVB-S2 and advanced
filtering technologies to allow optimal carrier spacing. The combination can bring efficiency gains up
to 15%.
Clean channel technology consists out of the following three effects.
A first effect in the Clean Channel Technology™ is applying a smaller Roll-Off (RO) percentage than
currently used in the DVB-S2 standard. In the DVB-S2 standard the 20% and 25% Roll-Off factor
percentages are common. Basically this means that these percentages need to be added to the
desired bandwidth over satellite. Reducing these Roll-Off factors to 5%, 10% or 15% results in a
direct gain in bandwidth. This is reflected in the following formula:
Occupied bandwidth = Symbol Rate*(1+Roll-Off factor).