No snowboarding today, but a high-tech adventure
In March 2013, I made a short trip to Austria; not for an adventurous holiday of snowboarding, but for a high-tech adventure. However, if I would have brought my snowboard I could have put it on :-)
Telesat and Newtec performed a joint test campaign in Aflenz, Austria. The purpose of these tests was to demonstrate the performance of the Newtec modems, loaded with features to improve bandwidth efficiency, on a Telesat satellite; Telstar 12.
The two main technologies which were tested were:
- Clean Channel Technology; or the use of low roll-off factors (5% RO)
- Bandwidth Cancellation; loading the transponder with two carriers in the same allocated bandwidth
Why are these technologies important?
Renting satellite bandwidth weighs a lot on the operational expenses of any service provider. Every Hertz or bit which can be saved or gained means a reduction of costs or an increase of profit.
Let's be honest: who doesn't want to achieve this?
Telesat, as a satellite provider, is interested in deploying this technology on its satellites for any potential future customers. Before being able to do this, they want to know how the technology performs, and what to use in which scenario.
Clean Channel Technology (CCT), or the application of low roll-off factors to a modulated carrier is a technology which can be used in every possible link: IP trunking, Telco, DTH, etc.
Going for "extreme" roll-off factors
During the test campaign, the most "extreme" option of CCT was demonstrated; a roll-off factor of 5%.
For the less technical people among us: this means that the carrier will occupy space segment equal to the baudrate of the carrier multiplied by 1.05. Typical SCPC carriers for example use roll-off factors of 20% and more, which means that using 5% RO can give you 15% or more gain in occupied bandwidth.
The other technology which was used is Bandwidth Cancellation, as mentioned earlier. Bandwidth Cancellation is a technology that allows to use, typically two, carriers in the same allocated bandwidth. The main application where this technology is useful, is in point-to-point links; for example in IP trunking or telco links.
Two symmetrical 45Mbaud carriers
For this test, two symmetrical 45Mbaud carriers were loaded in the transponder. After optimizing the transponder settings, the total throughput achieved in this transponder could be measured.
The result was that two 45Mbaud carriers were operating error free, using DVB-S2 16APSK-5/6 coding. In terms of throughput, this meant 285Mbps being transmitted in this transponder; or 5.278bits/Hz (the same efficiency as a high FEC 64APSK modulated carrier).
To know why someone would implement bandwidth cancellation over a standard dual carrier (side by side) setup, the throughput in this scenario has to be known as well.
This was done by loading two identical carriers of 25.7Mbaud with a roll-off factor of 5%. The highest possible DVB-S2 coding was achieved, being 32APSK-9/10. This resulted in a total throughput of 210Mbps.
The conclusion of using these technologies is, that in this case, the efficiency gained is 35.7%. A very practical approach to this is that 35% more bits can be transmitted over the same bandwidth, or 35% more bits can be sold.
If you want to know more about the products in this test case, check out these pages:
- Newtec EL478 High Speed IP Satellite Modem
- Newtec BWC0900 Bandwidth Canceller
- Newtec AZ730 Up and Down Converter