WLAN Location Services

The term location-based services (LBS) is sometimes used interchangeably with WLAN location services, but LBS more correctly denote services that provide the user with information about the physical location of the client device. Conversely, WLAN location services provide telemetry information on WLAN devices. This information is used by many applications to provide visibility of mobile devices, asset location and tracking information, inventory and supply chain management support, presence data, Emergency 911 (E911) event triggers, and many others.

Note

The term LBS is also used in cellular telephone networks to denote services offered to subscribers. For example, cellular phone users might receive a Simple Message Service (SMS) message notifying them of sales or special offers in retail stores nearby. However, in the context of this chapter, this discussion focuses on LBS and WLAN location services as they relate to 802.11-based wireless networks only.

With a robust LBS solution, an organization can easily answer questions such as the following:

• What do I have?

• How much of it do I have?

• Where is it?

• What is its status?

The following sections demonstrate why the capability to answer the aforementioned questions is valuable for various industries and provide an overview of technical considerations that need to be made when deploying LBS capabilities.

Business Rationale for WLAN Location Services

WLAN location services incorporate location information with pertinent content to provide incremental value to a user. In essence timely and accurate information on the whereabouts and status of an entity is used to provide a more relevant service. These services are typically classified into three families, as follows:

• Tracking services These services provide the location and utilization information to optimize processes in workforce, and asset and logistics management. For example, tracking services can reduce duplication and accelerate logistics in inventory management.

• Information services These services use location data to identify which information is most relevant for a specific position. For example, different maps might be presented to you depending on your whereabouts. LBS can be integrated into mobile resource management solutions (MRM) that target mobile workforce productivity.

• Safety and security services These services rely on location information to provide safety and security enhancements. For example, the whereabouts of children in theme parks can be tracked by providing them with active wristbands.

The location information can be of significant benefit in multiple industries by enabling otherwise difficult-to-realize efficiencies. The following sections take a closer look at how various industries are using these location services.

Healthcare

Hospitals spend millions of dollars on the latest technology to provide the best level of care to their patients. This often results in the use of very expensive, but mobile, assets, such as electronic and automated IV pumps, vital signs monitors, and even gurneys. Not only can the loss or misplacement of these devices create a financial burden for the hospital, but the lack of the device can also prohibit timely patient care. The ability to track, locate, and recover these mobile assets is, therefore, absolutely critical for the hospital or health center.

Some hospitals combine WLAN voice with location services. This allows hospital staff to carry WLAN-based VoIP handsets that include a "panic button" or key-code that, when pressed, will page all appropriate staff that are located nearby.

In some instances, patients themselves have been provided with location tags. The WLAN can then be used to locate the patient, and even provide an automatic link to the patient information system. The synergy of an existing WLAN infrastructure, location services, WLAN voice, and back-end hospital systems thus enables a faster response time and improved patient care.

Manufacturing

Location services can offer improved business knowledge by automating and simplifying supply chain management. The ability to identify exactly how many items are in production, where they are located in the assembly line, and the current rate of manufacture is critical for operations managers who rely on timely and accurate information to finely tune the production process. Intimate knowledge of the goods and their whereabouts is, therefore, essential.

Location services can also be used by robotic delivery mechanisms and warehousing vehicles to automatically store and retrieve equipment, and monitor stock levels in real time. The use of a WLAN-based solution avoids the enterprise from having to deploy a proprietary, nonstandard RFID solution instead.

Entertainment and Leisure

Personal security for customers is very important in the entertainment and leisure industries. In Europe, some theme parks have used WLAN location services to provide an online, active, and real-time positioning solution for visitors to track the location of children. Children are provided with active location tags embedded in wristbands or name badges. This provides additional safeguards for security staff and park management, and peace of mind for parents.

Logistics

The most common logistics operation performed with handheld wireless devices is inventory taking. Almost every large retail chain and distribution center use some type of wireless network to assist with the mundane, but necessary, task of counting things.

WLAN location services can provide incremental value in these environments by providing online, active, and real-time information on asset location. In the car rental business, identifying whether vehicles have been returned and whether they are in the garage, workshop, or cleaning bay improves the response time and productivity of the business. The business can improve its operating margins by ensuring quick turnaround of its vehicles.

Transport and Shipping

Transport and shipping companies are in the business of timely delivery of packages on time. This is only possible by ensuring that distribution and dispatch centers operate smoothly, accurately, and expeditiously. Location services assist in this by making sure that pallets and crates can be tracked and identified accurately. By attaching asset tags to the pallets and crates, the transport and shipping business can guarantee that the data provided to its back-office system is accurate.

Components of WLAN Location Services

WLAN location services are usually provided by leveraging the existing infrastructure to provide information on the location of 802.11 client devices. These devices not only include standard wireless network client devices (laptops, PDAs, WLAN phones, and so on), but also asset or location tags.

Note

WLAN asset or location tags are small devices about the size of a box of matches. They contain a battery and an 802.11 transmitter that regularly transmits beacons. The beacons are received by the access points and interpreted by location service applications.

There are three ways location can be calculated, each with increasing accuracy. The options are identifying the closest access point, using RF triangulation to determine an approximate position, or making use of RF fingerprinting to pinpoint the exact location. Use the method that gives you the desired degree accuracy:

• Closest AP This method is the simplest way to identify location, but it is also the least accurate. The WLAN location service queries the access points to determine where a particular client is associated or which AP reports the strongest signal. While this gives general location information, the accuracy is limited to the size of the radio cell.

• RF triangulation This method is considerably more accurate than the closest AP method. In this scheme, signal strength readings are reported from the access points that detect the location tag or client device. This allows the WLAN location service to calculate the general area using triangulation algorithms. RF triangulation does not take into account environmental factors, such as interference, multipath, and signal attenuation. As such, RF triangulation results can be rendered inaccurate due to these adverse environmental effects.

• RF fingerprinting This method uses a record of the radio signature of the entire area that is monitored. Effectively, the "fingerprint" of each location (usually on a grid basis) is compared to real-world data transmitted by the tag. By comparing both, the WLAN location system can quite accurately determine the tag or client's location. For example, RF fingerprinting can incorporate a building map that includes the known propagation effects of the building topography such as attenuation from walls or furniture. Knowing these propagation effects, the WLAN location system can more accurately determine the tag or client's location.

Location services are computationally intensive, especially when real-time information is required. As more devices are tracked, the more difficult it becomes without dedicated resources. Although many WLAN vendors offer location services, the more robust and scalable enterprise solutions rely on dedicated servers or appliances to offload the CPU-intensive activity from the access points or WLAN controllers.

WLAN Location Services Implementation Considerations

In addition to the type of location service you want to provide and how you want to support and integrate it, you need to carefully consider privacy matters, tag battery life, and tag security when implementing WLAN location services in your organization.

Privacy is a concern when tracking the location and historical movement of users. Inform the user when utilizing WLAN location services in the enterprise to track wireless client devices such as laptops, user ID tags, or WLAN phones.

Tag battery life for WLAN-based asset or location tags range from three to five years. Although this might sound like a sufficient amount of time for most business applications, some thought should be put into scalability and longevity of the system. The more accurate the real-time information you need, the more often the tag must transmit its location. (This is a configurable option on most tags.) The more often a tag transmits its location, the quicker it exhausts its battery. A careful compromise is thus required. Ensure that you fine-tune the system to collect location information on a sufficiently regular basis, without expending more battery life than necessary.

Tag security should be considered. When tags are used to track the location of valuable assets, it is important that they are securely fixed and, if possible, hidden from view. Also make sure that the tag can be removed when required.