Dramatic Powerline performance boost promised

Until now use of the electricity supply for distribution of video has not gathered steam as fast as expected because quality tends to suffer from interference when appliances are plugged into the same power supply. This has hampered efforts led by the HomePlug Powerline Alliance to promote use of the electricity supply, undermining its argument that this will provide more reliable transmission than wireless alternatives such as WiFi, while exploiting existing cabling.

But now leading System-on- Chip (SoC) vendor Sigma Designs, which specialises in home distribution, believes it has come up with the solution, which has been demonstrated at IBC. In fact Sigma has borrowed from the world of wireless by implementing a technique similar to MIMO (Multiple Input Multiple Output), according to Sigma’s VP of Corporate Marketing, Michael Weissman.

MIMO spreads the digitised video across multiple paths to provide greater resilience against interference affecting any single path. Sigma has applied the same principle to the signal frequencies used to transmit encoded digital bits over power cables, while also – unlike some rivals – making use of the earth wire which suffers less from interference anyway. This technique leads to a slight improvement in peak bandwidth attainable over the electricity cables in a home, but a much more dramatic increase in minimum performance when other appliances are plugged into the power supply nearby. “It’s all about improving the network’s worst performance,” said Weissman.

At IBC, Sigma demonstrated Powerline operating over alternative Powerline adapters, at around 80 Mbps during normal operation, coming down to 50 Mbps when an appliance was plugged in nearby. The Sigma adapters worked slightly faster at almost 90 Mbps normally, maintaining this level even when an appliance was plugged into the same supply.

This will transform the fortunes of Powerline, argued Weissman, especially in the US where many households have several TV sets and want to distribute HD to them over the home network. In practice if the physical bandwidth drops to 50 Mbps when appliances are plugged in, the actual usable bandwidth is half this at around 25 Mbps, which is not enough for several simultaneous HD channels plus broadband Internet. But the Sigma solution offers a usable 45 to 50 Mbps, sufficient for several HDs while leaving plenty to spare for other home network services.

Powerline devotees will have to wait a while to see if Sigma is right. “We expect to see deployments by late 2011 or more likely 2012,” said Weissman.

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