Data transferred 382km over WLAN

Modified WLAN antenna

Venezuelan scientists recently sent and received data over a distance close to 400 km through WLAN. The distance probably qualifies as a world record for wireless (WLAN) data networks, beating the record previously held by some Swedish scientists who managed to transfer data 310km between a balloon and a ground station.

Wireless networks based on the 802.11x-standards, often called WLAN or Wi-Fi, are normally designed for distances up to a 100 meter radius. However, by targeting the signal to a single point one can increase this distance significantly. Further enhancements can be obtained through larger antennas and adjustments to the equipments MAC-layer (Media Access Control) corresponding to the increase in distance.

In May, Ermanno Pietrosemoli president at Fundación Escuela Latinoamerica de Redes in Venezuela, and his colleagues (scientists) tested how far they were able to communicate through modified WLAN equipment.

Due to the earth’s rounded shape the antennas needed to be installed fairly high. Two mountain tops were selected.

Sketch of the transfer

In their first attempt the scientists managed to set up a 3 Mbit/s in each direction over a distance of 279 kilometer. As mentioned above the swedes had previously made it over a longer distance . Therefore the Venezuelans made a second attempt between the mountains Aguila and Platillon Mountain.

Approximately 382 kilometres separates these two ground points, and from a total of 58 packages 57 were received successfully.

The purpose of the experiment was to see how relatively ordinary WLAN equipment could be used for long distance point-to-point connections, and thus replace the need for more expensive cables and equipments.

There’s however several challenges linked with this method:

  • First, aiming the transmitter and receiver precisely towards each other over long distances is extremely difficult.
  • Second, earth movements/disturbances will break/slow the connection or result in severe data loss.

While long distance WLAN is a less expensive solution it is (unfortunately) for the time being to unstable compared to e.g. WiMax. That said, the scientists seemed fairly optimistic in their conclusion. It could perhaps be used as an inexpensive backup solution in case of cable failure and/or similar…

Continue reading the “Long Distance WiFi Trial” report.

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