Seattle ferries offer Wi-Fi to passengers with WiMax over water

Tides and signal reflections made deployment a challenge

The Washington State Ferry system is now using wireless WiMax to connect 15 boats near Seattle with on-shore antennas to bring Wi-Fi to ferry passengers.

The system, which has been up and running for several months, was a challenge to deploy mainly because the ferries travel on the waters of Puget Sound, and water can act like a mirror and bounce wireless signals in different directions, said Milt Gregory, the CEO of Cupertino, Calif.-based Sunrise Wireless, the project's integrator. The ferry boats vary in size, as do the local tides, which means that wireless pathways are constantly fluctuating.

"We had problems at first getting performance up to where we wanted it, and it took some time getting the frequency over water," Gregory said in an interview. Another problem was that boats coming to downtown Seattle passed by Wi-Fi radios on cranes used in the Port of Seattle. "That Wi-Fi radiates everywhere, which caused interference."

Ultimately, Sunrise kept installing onshore radios to communicate with the boats more reliably. The project started in late 2006, but it took until late 2008 to complete. It uses 60 different radios in all, including the 15 aboard the boats. Sunrise used WiMax gear that relies on the outdoor routing protocol, which helps eliminate hidden radio nodes, Gregory said. The protocol involves a polling procedure conducted by each transmitting radio to find the nearest receiving radio.

Gregory chose Tsunami base stations from Proxim Wireless Corp. to provide the WiMax network after trying three others that wouldn't work. Today, the network offers well over the 12Mbit/sec. of throughput Sunrise was required to provide, Gregory added. The system also allows a person to keep an Internet session intact while walking from a car parked on a ferry to a passenger seating area.

The WiMax feed connects to Wi-Fi networks that largely rely on radios from Cisco Systems Inc. The Wi-Fi network was originally built and operated by Parson Corp. of Irvine Calif., which sold the operation to last year.

The ferries carry about 25,000 passengers a day.

Copyright © 2009 IDG Communications, Inc.

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