An Israeli company is proposing a more efficient successor to the DVB transmission system. Novelsat’s engineers have already tested their signals on Eutelsat’s W3A satellite as well as on AsiaSat 5, Amos-3 and an Intelsat craft. Novelsat say they gained an average improvement of 28 per cent over today’s DVB-S2 second-generation transmission standard.
The current consensus is that DVB-S2 transmission operates very close to the ‘Shannon Theorem’ which suggests there is a limit on the amount of transmitted data which can be handled within a certain bandwidth without being overwhelmed by noise.
The Israeli group say they looked again at the mathematical algorithms needed to compress digital TV signals and incorporate fresh algorithms into new modulators and modems. Company co-chairman David Furstenburg told Broadcast Engineering magazine that Novelsat’s solution improved the bit-rate carried by an average of 28 per cent.
However, Furstenburg admits that a portion of this gain results from reducing the ‘guard band’ at the end of each channel from 20 per cent of the channel’s spectral width to just 5 per cent. The first generation of DVB-2 transmissions had a guard band of 35 per cent of a channel’s width. “Novelsat says that by exploiting the greater processing power available now compared with the time over a decade ago when DVB-S2 was developed, it has been able to reduce the roll off band to just 5 per cent at each end of a channel. This accounts for much of the throughput improvement,” states Broadcast Engineering.