Spanning A WAN's Last Mile With Optical Wireless

Futureway Communications (Richmond Hill, Ontario) is a facilities-based provider of voice, high-speed Internet, and digital television for business and residential customers. The company's communications technology infrastructure is based on broadband fibre optics. The company owns its entire carrier infrastructure (e.g. switches, routers) and touts itself as Canada's first multi-fibre, multiple service provider with 100% underground technology.

However, when a wide area network (WAN) needs to span several miles of metropolitan landscape, suddenly roads, rivers, and railroad tracks become obstacles. Furthermore, permit applications (and inevitable delays) further hamper these projects. It's because of problems like these that Futureway has begun employing a new type of "last-mile" technology for its Internet customers.

No Licensing Or Interference
The technology infrastructure that carries a signal from the broad telecommunication provider to the neighborhood level is known as last-mile technology. For example, ISDN (integrated services digital network), DSL (digital subscriber line), cable modem, and wireless are all last-mile technologies.

In December of 2000, Jay Gowans, VP of engineering at Futureway, was faced with determining a way to connect a customer in a single-story building in a strip mall with a Futureway POP (point-of-presence) in a two-story building 1 kilometer away. (A POP is an access point to the Internet with a unique IP [Internet protocol] address. Internet service providers [ISPs] often have multiple POPs located in rented space owned by the telecommunications carrier to which the ISP is connected.) "We had previously used microwave technology for connections requiring this type of distance," Gowans stated. "But, this method involved radio frequency licensing. Furthermore, it was often difficult to get a roof access agreement if other microwave carriers were already present."

Instead, Gowans chose an optical wireless (OW) solution from Plaintree Systems (Ottawa, ON). Optical wireless (also referred to as free space optics) systems provide network connections on a beam of infrared light. Using this LED (light-emitting diode) technology, OW requires no licensing and avoids the frequency interference problems associated with using the radio spectrum. However, this is a line of sight technology. Luckily, Gowans had that advantage with this project.

Up And Running In 4 Hours
The core components of this installation were two Plaintree WaveBridge WB511-H120 transceivers which transmit an eye safe (class 1) beam of light. To avoid perforations to the roofs, the Plaintree units were mounted on 4-foot by 4-foot waterproof pieces of plywood which were placed on each building's roof. Concrete blocks were put on top of the plywood to ensure the mounting was stable in windy conditions. The buildings' contractor installed an AC (alternating current) power outlet near the Plaintree units.

"We ran CAT5 Ethernet cable from the transceiver through an existing duct to the customer's interface in their equipment room. We did it this way to avoid perforating the roof membrane," explained Gowans. The other end was similarly installed at the Futureway POP, and CAT5 cable was run to the Ethernet port on the transport node.

After both units were installed, they were lined up by eye until the beam was close enough to use the units' built-in LEDs for fine-tuning. "The most difficult part of the project was lugging the concrete blocks up to the roof," Gowans quipped. He said the payback for the system was one year, and Futureway now has 10 installations of Plaintree OW equipment.