Can Wi-Fi Scale?

Vendors Tackle Large Deployments from All Angles

In a campus environment, BelAir 200 installs on an existing light pole to provide Wi-Fi coverage.

As Wi-Fi is expanding beyond SOHO and rogue enterprise deployments to serve increasingly larger properties and even campuses, the access point (AP) architecture is undergoing a transformation to meet the challenges of scale.

“With small deployments you only need a few access points, but with large ones it becomes too complicated,” explains Bernard Herscovich, president and CEO of BelAir Networks, during an interview at the CTIA Wireless IT and Entertainment Expo in Las Vegas in October, where the company debuted its wireless LAN architecture. The company claims its solution delivers 10 times more capacity and five times more coverage than conventional approaches.

The traditional way of doing things is deploying intelligent APs, a market dominated by Cisco Systems Inc., but also including heavyweights such as 3Com Inc. and Avaya Inc., as well as newcomers like Proxim Corp. Vendors of standalone APs have adapted them for larger deployments with the addition of stronger and “smarter” antennas. Still, multiple APs are required to cover large buildings. But managing, upgrading and scaling these distributed devices that reside in the ceiling has proven to be complex, time-consuming and costly.

Experts say WLANs based on traditional APs are complex because they rely on adding new APs to broaden coverage. Each AP must be individually configured for security policies, and APs whose coverage areas overlap can’t operate on the same channel. As a result, coverage patterns must be determined via site surveys to minimize channel interference. Usually, this results in coverage gaps. In addition, mobile users must reassociate and reauthenticate with the network as they move out of one AP’s coverage area and into the next, and their bandwidth drops as they near the boundary between coverage areas.

In order to simplify management, standalone AP vendors have introduced centralized controllers wherein security and mobility components are overlaid on the existing intelligent WLAN infrastructure. Cisco, for example, offers a Wireless LAN Solution Engine (WLSE) for management and control of a large deployment of its APs.

Enter the WLAN switch. “The vision for WLAN switching is that it moves normal AP processing functions above the physical layer into a centralized switch,” explains In-Stat/MDR analyst Gemma Paulo. “How much of this processing, and specifically what features are moved to the WLAN switch, depends on the specific vendor.”

Paulo says some vendors design the network so that APs — now access ports on a central switch under this model — are dumb, meaning all security, management and mobility processing are done at the central switch. Others choose to have more integrated APs where some of the processing is done at the access port layer.

As an example, she cites APs from Aruba Wireless Networks, which are simplified and perform only transceiver and air monitoring functions with authentication and encryption performed at the switch level. In contrast, she says, Symbol Technologies’ Wireless Switch System includes access ports containing the WLAN radio and antenna that function as pure media access control (MAC) bridges, passing packets to the wireless switch. Startup Trapeze Networks Inc. offers a more integrated architecture in which APs it calls “mobility points” include enough processing power to encrypt messages and collect statistics. Basically, Paulo says, these mobility points can carry out tasks performed near users, off-loading some processing from the central AP/switch.

In another variation on the theme, upstart AirFlow Networks introduced in September its packet antenna architecture, which uses a single AP with multiple antennas throughout the building to support hundreds of simultaneous users with just one AP. Brian Jenkins, vice president of marketing for AirFlow, says it boils down to a lower total cost of ownership. “If you have only one device to configure and manage, it makes administrations and deployment easier,” he says, adding that AirFlow’s architecture has made WLANs as easy to install and administer as wired LANs by also eliminating the need for RF site surveys. Filling coverage holes or scaling the WLAN is done by plugging in an additional AirHub antenna. In the case of installation, labor and equipment for a 100-user WLAN site, for example, AirFlow says its AirSwitch system is about one-fourth the cost of a typical intelligent AP deployment.

Jenkins adds that one of the benefits of AirFlow’s approach — which eliminates RF channel management, interference and coverage gaps — is that its AirSwitch and AirHubs can be used to overlay channels for different uses — one for data, one for video and one for voice, for example (see diagram, below).

AirFlow’s AirSwitch/AirHub combination eliminates AP interference and allows different channels to be used for data, voice and video.

Vivato also had an eye out for lowering total cost of ownership when it launched its “switch” in June for both large building and indoor/outdoor campuses, by consolidating the number of components needed. Unlike the controller-based architectures described earlier, a Vivato Wi-Fi switch is packaged as a single integrated unit, including the planar phasedarray antenna and electronics needed to run the switch. Indoor switches are designed to be installed in the corner of a building and provide coverage for an entire floor. This approach enables a new type of Wi-Fi deployment with one manageable Wi-Fi switch per floor rather than many conventional APs/antennas. Vivato’s outdoor switches can be used to deliver Wi-Fi to an entire building, campus or much larger areas up to 4 kilometers away. Because of its range, the Vivato switch also can be used to aggregate backhaul, eliminating costly wireline services at each AP.

And, instead of multiple antennas, the Vivato switch is integrated with a high-gain, electronically steered transmitting antenna. It directs and delivers packets to the clients, rather than to floor space used by the traditional microcellular, pointto- multipoint architecture. The smart antenna design enables the panel to simultaneously receive on one channel while transmitting on another, giving the switch more functionality.

Newcomer BelAir Networks is taking yet another approach to large Wi-Fi deployments, but like Vivato, it has cut down on the number of manageable components. “A typical hotel is covered with 35 APs; we cover it with four,” says Herscovich. “We are trying to optimize the cost of the network, not the cost of the unit,” he adds, claiming that cost can be reduced by two-thirds.

Vivato Wi-Fi switches are packaged as a single integrated unit, including the planar phased-array antenna and all electronics needed to run the switch.

BelAir Networks solutions are built on a patented, multiple point-to-point mesh architecture that integrates wireless access and backhaul. Multiple backhaul radios in each platform are configured point-to-point with directional antennas. Each platform can connect to multiple others and the combined connections form a cellular LAN.

There are no extra switches, routers or cables required to connect multiple platforms.

The company’s platforms can be deployed within line of sight or near line of sight to a building, at which point the radio waves penetrate the building windows or walls to illuminate the entire interior. In this way, a single BelAir Networks platform can cover multiple floors at once. With a BelAir Networks solution, a typical 10-floor midsized building can easily be covered with two to four BelAir200s located outside the building 50 to 100 feet away. Providing the same coverage with an indoor solution would require a minimum of 20 indoor APs (i.e. a minimum of two per floor), with thousands of feet of associated wiring.

BelAir Networks cellular LAN platforms can be deployed on existing infrastructure such as light poles and adjacent buildings. The same BelAir Networks platforms also can cover very large, near-lineof- sight areas as well, at distances of three-quarters of a mile or more.

“In today’s environment, enterprises considering WLAN technologies are looking for solutions that are cost-effective from both a capital and operational standpoint,” says Aaron Vance, industry analyst with Synergy Research Group. “BelAir’s unique wireless solution eliminates cabling and backhaul costs, [and] obviates the need for additional hardware, both wired and wireless, while increasing wireless network coverage and capacity.”

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