Scientists at the Fraunhofer Institute have developed a system that uses “artificial noise” to makes DSL systems more energy-efficient.

While the use of a low-power mode (L2 mode) in standard ADSL2/ADSL2+ systems could significantly reduce the amount of electricity consumed by the network, the L2 mode is not commonly used as it causes considerable interference to neighboring DSL systems.

When a modem connects to the internet while neighboring modems are in L2 mode, only a small degree of interference occurs and the data transmission remains high. However, if neighboring systems become active, the interference to the first system is so great that the connections crash and the modem needs to be restarted. What is more is that the restarted modem has a significantly low data speed transmission rate.

For this reason, many operators deactivate L2 more and do not include it in the standardization for future broadband connections.

The scientists at the Fraunhofer Institute for Communication Systems ESK have circumvented the problem by using artificial or virtual noise to stabilize DSL connections so that the L2 mode can be deployed.

The artificial noise simulates cable bundle interference to the broadband receivers. When a modem tries to connect to the internet, the system registers normal interference even if a nearby device is in L2 mode.

Though the connection does not get the highest-possible transmission rate, the noise allows the connection to stay stable even when a neighbor goes on line.

Using the noise, network operators could reduce their electricity consumption by several million kilowatt-hours per year.

The broadband DSL access network is said to consume about 20 billion kilowatt-hours of energy worldwide annually.


- Katrice R. Jalbuena

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Sources:

¹ http://www.fraunhofer.de/en/press/research-news/2009/06/ResearchNews062009Topic7.jsp
² http://www.fraunhofer.de/en/