Wi-Fi Real-Time Location Services

RTLS systems based on Wi-Fi can track both people and equipment using 802.11-based clients equipped with location software and smart Wi-Fi asset tags.

September 8, 2006

9 Min Read
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Proprietary wireless real-time location services have been available to enterprises for years. Newer systems based on passive RFID technology also have garnered significant attention, especially for supply-chain applications where products are tracked. But some of the most interesting RTLS systems are being built on top of emerging Wi-Fi networks, with considerable success. Pending standards work on 802.11k and 802.11v will improve the interoperability of location services using conventional clients; such work--along with the increased use of Wi-Fi location tags, or "active RFID tags"--will help to drive adoption of RTLS systems from niche uses to a broader horizontal market.

Standards for location services are only beginning to gain attention, but the work under way in the IEEE 802.11k and 802.11v task groups will allow for more sophisticated Wi-Fi location capabilities. 802.11k will define and expose radio and network information to facilitate the management and maintenance of a wireless LAN. This will standardize some basic radio information required to support standards-based location tracking. 802.11v will provide extensions to the 802.11 PHY and MAC standards to improve management capabilities of WLAN clients.

Among vertical industries, Wi-Fi RTLS providers have focused in particular on the health-care market. Many hospitals are using inexpensive Wi-Fi location tags, attached to equipment, to track valued assets, including mobile diagnostic equipment that can be difficult to locate when needed.Although the value of Wi-Fi RTLS in hospital settings can be compelling, beyond asset tracking, the technology is making the transition from vertical to horizontal enterprise applications, including those for security, business-process improvement and network optimization. As enterprises install pervasive Wi-Fi networks to better meet data mobility needs, leveraging that infrastructure to support location services is a logical consideration. Accordingly, leading enterprise vendors are investing substantial resources to make Wi-Fi location services more accurate and easier to use.

Cisco, as expected, is a highly coveted partner for Wi-Fi providers and application developers. The company is both cooperating with others in the market and competing with them. It's obviously important for third-party Wi-Fi RTLS vendors to ensure that their products work with Cisco infrastructure. And since Cisco doesn't make Wi-Fi location tags, it must ensure that its location server is compatible with third-party tags. Cisco competes on the location server platform itself.

Location Technology

Rudimentary location services are available on every Wi-Fi network, at least at the granularity of a single access point's coverage area. If you know the coverage pattern of an AP and you know a Wi-Fi client is associated with that AP, you have a crude approximation of location, and one that's inadequate for asset-tracking.Another method for finding hardware is referred to as "closest AP." Its accuracy is directly related to the coverage footprint of your AP. A dense deployment of low-power APs will provide a more accurate view of location than a less-dense configuration of higher-power APs.

To get even higher accuracy, most vendors employ a system where location is tracked by multiple APs simultaneously. This technique is generically referred to as triangulation, in which the signal strength detected at three or more APs is used to predict the location of a device. More sophisticated techniques, such as RF fingerprinting, can be used to increase accuracy at the expense of somewhat higher installation and maintenance costs.

In some RTLS systems, 802.11 associations are used to identify device location, but the use of more efficient "blinking" protocols is becoming more popular. The location of standard Wi-Fi clients can be tracked, as can the location of expensive items that have miniature Wi-Fi location tags. When most people think of RFID tags, they think of passive, low-cost tags based on EPC standards. Active RFID tags are much more intelligent and can communicate across greater distances.

Offered by vendors such as AeroScout, Ekahau and PanGo Networks, active Wi-Fi location tags cost between $50 and $65 each and are designed to run up to two years or more without battery replacement. Battery power is conserved by using blinking rather than 802.11 association to transmit RF signals used to track location, though periodic association is usually required for system management maintenance. Some tags include motion sensors that turn off all transmission until the asset physically moves, while others include RS-232 connectors that allow telemetry data to be collected remotely.

Regardless of which technique is used on tags, a location server is required to keep track of the movement of people and assets. On a small network, a location service application can be installed on a WLAN controller.Location Applications

Today's bread-and-butter application for location services involves asset tracking. Hospital and manufacturing employees, for example, must know the physical location of mobile equipment. Wi-Fi RTLS systems can help to locate assets and avoid redundant equipment purchases.

After asset tracking, security is the next most prevalent application for Wi-Fi RTLS. When used in conjunction with a wireless intrusion detection/prevention system, such systems can detect the location of security threats, including rogue APs. RTLS systems also can be help optimize the performance of wireless networks. In addition, when used in conjunction with a wireless VoIP deployment, RTLS can be linked to enhanced 911 services.

And RTLS systems can be used to provide location-relevant content to mobile devices. Newbury Networks and PanGo, for example, developed applications that allow museums to provide guests with a PDA that interfaces with a Wi-Fi RTLS system. The applications present location-relevant information about museum exhibits depending on the location of a guest within the facility.

While the location services market is clearly drawing interest, it is best thought of as a value-added application for Wi-Fi networks. To achieve granularity, you need a dense deployment of APs. And adding a location server, installing and maintaining Wi-Fi tags and implementing applications that leverage this infrastructure can be an expensive and complex undertaking. In the future, it is likely that costs will decrease and functional location services will become a standard component of enterprise WLAN infrastructure.Dave Molta is a Network Computing senior technology editor. He is also assistant dean for technology at the School of Information Studies and director of the Center for Emerging Network Technologies at Syracuse University. Write to him at [email protected].

Location Services Product Landscape


AeroScout's (formerly Bluesoft) "enterprise visibility" systems, as the company calls them, are based on Wi-Fi and other wireless networking standards. The company introduced the industry's first Wi-Fi-based active RFID tag, the AeroScout T2 Tag. In addition, the AeroScout Visibility System uses standard Wi-Fi networks to locate and track assets, and it supports both signal strength (RSSI) and time difference of arrival location algorithms. Aeroscout's MobileView provides basic visualization, asset tracking, alerting and reporting as well as interfaces to provide location services to third-party applications. Target markets include general enterprise, health care, manufacturing, logistics, automotive, retail and government. www.aeroscout.com

Aruba NetworksAs a major provider of enterprise Wi-Fi infrastructure products, Aruba includes location services within its platform. The company is also a leading advocate of dense AP deployment, an architecture the company says can provide granular location tracking without the need to implement and maintain a system based on RF fingerprinting and related systems that require "walkabouts" for calibration. Aruba formed partnerships with Newbury for some of its server technology, as well as with Ekahau and PanGo, both providers of Wi-Fi location tags. www.arubanetworks.com


Cisco, with well more than a 50 percent share of the market in enterprise WLAN infrastructure, has been a strong proponent of Wi-Fi location services. It bills its 2710 Wireless Location Appliance as the industry's first location solution that simultaneously tracks thousands of devices from within the WLAN infrastructure. Cisco's business value proposition for location services focuses on asset tracking, wireless network management and location-based security. Cisco's location system relies on WLAN controllers and Cisco lightweight access points and is not supported on the older Aironet smart-AP wireless architecture. Using RF fingerprinting, the system tracks the physical location of wireless devices to within a few meters. Not surprisingly, Cisco is a highly coveted partner for Wi-Fi tag manufacturers and application developers. www.cisco.com/en/US/products/ps6386/index.html


Ekahau offers the Ekahau Real Time Location System, which includes the Ekahau Positioning Engine, a software-based real-time location system, as well as Wi-Fi tags and PC client software that allows people and assets to be tracked using any 802.11b/g network infrastructure. Ekahau says it provides floor-, room- and door-level accuracy using signal-strength calibration algorithms. Its primary target markets are health care, manufacturing, supply-chain and heavy industry. www.ekahau.comNewbury Networks

Newbury Networks products are designed to let enterprises locate, manage and secure applications running over WLANs using its location-based technology. Products include Active Asset, a real-time asset tag tracking system; Digital Docent, a location-based content provisioning application that delivers on-demand and dynamic content relevant to users based on their location; Wi-Fi Watchdog, a location-enabled security solution; Wi-Fi Workplace, which uses location attributes to enhance the efficiency, coverage and capacity of a WLAN; and the Newbury Presence Platform, which allows third-party application developers to leverage Newbury's location services. www.newburynetworks.com

PanGo Networks

PanGo's product line includes the PanOS Location Management Platform; the PanGo Locator asset tracking application; and the PanGo Active RFID Tag, a Wi-Fi asset tracking tag. PanOS is built with a service-oriented architecture and serves as a platform supporting the development, integration and deployment of location-aware applications. PanGo Locator works in conjunction with PanGo Active RFID Tags to allow enterprises to track assets and equipment. The company is focused on selling to the health care, supply chain, retail, government, visitor attractions and enterprise IT markets. www.pangonetworks.com

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