Shopping plaza goes optical wireless

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Westfield UTC is a high-end outdoor shopping center in San Diego, CA, with a retail campus that is home to more than 180 shops, two dozen restaurants, and an ice-skating rink. Last year, Westfield UTC’s management company tapped independent engineering firm Wireless Facilities Inc. (WFI-www.wfinet.com) to design what was originally envisioned as a Wi-Fi network. But WFI had other plans.Th 227928

ClearMesh 300 (CM 300) nodes sit unobtrusively atop buildings in the Westfield UTC outdoor shopping center, enabling fiber-like networking without invasive underground or overhead fiber cables.

“When we designed the infrastructure, we did a long consulting and sales cycle with the customer,” recalls Desmond Wheatley, president of WFI’s Enterprise Services Division. “We said, ‘Look, there are two ways we can go about this. We can either deploy a hotspot, which will only ever be useful for people to connect their laptops to the Internet, or we can design a network that will support your future needs.’ Luckily, Westfield is a visionary company, and they said, ‘Go ahead and deploy something we can use later.’”

Thus, what began as a project to develop a Wi-Fi hotspot for customer use at the mall’s coffee shop morphed into a resilient optical mesh network that supports multiple applications, including voice over IP (VoIP), high-bandwidth streaming video from more than 70 surveillance cameras located around the mall, and mission-critical point-of-sale transaction traffic generated by the retail store owners.

The outdoor mall comprises 10 buildings, all of which were constructed individually over a span of several decades. On paper, WFI’s task seemed straightforward: Connect all the buildings to a single converged network with a common network operations center, data center, and security surveillance center in the main administrative office.

WFI first considered extending fiber laterally to each of the buildings in the retail campus, but this undertaking was deemed too expensive and invasive for the Westfield UTC application. “Trenching, in our experience, costs between $40 and $600 per linear foot,” reports Wheatley. “So while fiber itself is inexpensive and quite easy to deploy, what you need to do to the ground can sometimes be prohibitively expensive.” And invasive, he adds, noting that a key challenge in this particular deployment was one of aesthetics.Th 227929

Each node is rooftop mounted and connected to up to three other nodes, creating a resilient, highly available mesh network.

The Westfield UTC campus features tiled walkways, fountains, and meticulously landscaped grounds. “You can imagine when you have a premier Southern California shopping center, the last thing they want is for us to have to dig trenches between buildings where their customers walk,” Wheatley admits.

Wheatley himself is a proponent of fiber-where it makes sense. He says there are two primary reasons why WFI would implement a wireless infrastructure instead of a fiber-based infrastructure, and those reasons almost always are the same: cost and flexibility. “If there’s a free and easy conduit there or if there is existing fiber, then we would generally default to fiber,” he says. “But where that isn’t the case, we’re going to look at some kind of wireless solution to be a fiber replacement.”

Because aesthetics are so critical to its business model, Westfield UTC also vetoed the use of overhead cables. Fiber, both underground and aerial, was simply out of the question. For this reason, WFI opted to design a wireless network, but one that would provide fiber-like capacity. The bandwidth demands of the video surveillance application alone would tax the typical wireless network.

WFI tapped ClearMesh Networks (www.clearmesh.com) to provide its Ethernet-based optical wireless technology, which combines the flexibility and attractive price points of wireless networking with a bandwidth capacity similar to fiber.

ClearMesh Networks’ Metro Grid is a free-space optical (FSO) system, with a twist. Instead of lasers, it uses inexpensive 870-nm LEDs. Instead of point-to-point connectivity, it creates a wireless optical mesh that provides fiber-like resiliency, says ClearMesh chief executive officer Suresh Nihalani. “With our mesh concept, every building has more than one path coming to it. If one link goes down, the network node identifies an alternate route and keeps the service up and running. And it’s transparent to the end user that one link went down,” he adds.

The system is specifically designed for shorter link lengths of 250 m, far less than the 1- to 2-mile range of traditional FSO links. The shorter range improves the reliability of the system; its performance margin enables transmission even in quarter-mile visibility fog, a notorious FSO impairment. “To put it in perspective, most airports shut down in quarter-mile visibility fog,” says Nihalani.Th 0610lwcase

Each ClearMesh node features three individually activated LED-based transceivers, enabling the transport of multiple traffic types over the same mesh-based wireless optical network.

WFI liked the resiliency that the Metro Grid affords, as well as the bandwidth capacity: up to 300 Mbits/sec of wire-speed, full-duplex capacity at service injection nodes. Once Westfield UTC determined it would use the network to support multiple applications, the management company required more bandwidth than even it imagined.

According to Wheatley, this is a common problem. “What we are seeing in the market is that people are a) underestimating their current bandwidth needs, and b) underestimating their future bandwidth needs,” he says. In Westfield UTC’s case, the video surveillance application alone requires big bandwidth. Using the MPEG4 compression algorithm, the average video stream requires 3 to 4 Mbits/sec of capacity, multiplied by 70, for the number of surveillance cameras scattered throughout the mall.

The Westfield UTC network also supports mission-critical point-of-sale traffic that must be protected from the bursty Internet traffic. The ClearMesh Metro Grid features full, centralized management capability, allowing Westfield to manage competing priorities. Point-of-sale traffic, for example, can be given a higher priority and improved quality of service (QoS) versus basic Internet traffic.

WFI also cites the technology’s compatibility with Wi-Fi as another key advantage. The optical wireless network provides service aggregation for Wi-Fi hot spots located throughout the mall, a convenience that is helping Westfield UTC retain customers and attract new ones. Moreover, the Wi-Fi capability can be used to extend point-of-sale support to kiosks and temporary retail locations.

The optical wireless mesh network has been up and running at the Westfield UTC outdoor mall for about a year, and despite a few normal hiccups in the beginning of the deployment cycle, the network has operated with zero downtime, says Wheatley. In the fiber world, he says, people often talk about five-nines availability, and to date, the mall’s optical wireless mesh network has delivered just that.

Westfield UTC is now running VoIP; digital surveillance and closed-captioned TV (CCTV); security, including alarms at ingress and egress points; and building automation, including environmental and HVAC services-all from a network that was originally designed solely for laptop connectivity. “Have their bandwidth requirements gone up?” muses Wheatley. “You bet they have. Massively. To be able to add bandwidth and flexibility to the network inexpensively with fiber-like reliability, that’s been huge for us. Because bandwidth requirements never go down.”

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