Smart Environment Technologies

From MobiComp

1 Technologies

Technologies

In this section we describe a range of sensor, communication and information delivery technologies currently used with the MobiComp infrastructure. In each case we outline the characteristics of the technology.

Wireless Systems

[edit]

Infrared Beacons

Infrared beacons are the oldest and simplest location technology for mobile guides used with MobiComp. A static PC placed at or near the point of interest is fitted with a simple 'dongle', usually connected to a USB port. The dongle is placed where it can be seen easily, usually directly in front of the visitor and at an approprate height when they are looking at the point of interest. When the visitor points the mobile device at the dongle, the mobile device and static PC exchange some information using a temporary infrared link. The information passed between the static and mobile devices may be used in several different ways:

The mobile device receives a identifier from the static PC which it uses to find and display appropriate information about the point of interest. This information may have been pre-loaded on the mobile or may be fetched using a wireless network connection.
Either, or both, the static and mobile devices may report the presence of the visitor to the MobiComp service to provide visitor tracking data.
If the static device offers some form of kiosk display, the mobile device may be used to control the display, either directly, or by providing information about the visitor's interests and what they have previously seen at the site or museum.

Infrared dongles are inexpensive, typcally costing about €20. They project a narrow beam of harmless invisible light with an effective range of less than one metre. Most current PDAs and Tablet PCs, and a decreasing number of mobile phones, are equipped with an infrared sensor, although the choice of device is effectively limited because only a few have them mounted in a convenient location for handheld use. The main drawback of this approach is that it requires a PC to drive the dongle. Costs might be reduced by driving several dongles from a single PC, or by using purpose-built embedded processors with infrared output. However, this approach is best suited to situations where a PC is already in use, for example, as part of a kiosk display.

[edit]

Radio Frequency IDentification (RFID) Tags

RFIDs provide a fine-granularity location method. The tags are small (2-5cm) plastic objects which are typically stuck to a surface close to the point of interest. For example, they may form part of a display label. A mobile guide equipped with an RFID reader is used by the visitor. When the reader is placed within about 5cm of the tag, the visitor presses a button on the mobile device to capture the unique identifier carried by the tag. This identifier is then used to fetch and display appropriate information, either pre-loaded on the mobile device or fetched using a wireless network connection.

RFIDs may also be included in a Smart Ticket or card. Here, their purpose is usually to identify the visitor to a display device, such as a kiosk. The kiosk may then obtain visitor profile information from the MobiComp service so that it can personalise the display content to match the visitor's interests.

A further use for RFIDs is in controlling the issue and return of mobile guides at the museum desk. A tag is attached to each guide and the device is passed over a static reader when it is issued and returned. In a smart ticketing scenario where each user carries a distinct ticket, this mechanism can also be used to associate the individual visitor with a specific guide device. Such associations can be used to provide Web-based Pre and Post-Visit Support for visitors.

Similarly, RFIDs may also be used in inventory control. By attaching tags to objects or storage locations, a museum can provide a reliable mechanism by which staff equipped with a mobile device can identify objects and locations and fetch or update information held in an inventory database.

RFID tags are inexpensive, typically costing €1 or less. Readers cost between €30 for simple USB devices to €600 for desk mounted systems. Readers suitable for mobile devices (PDAs, TabletPCs, etc.) can be obtained for about €300.

[edit]

Bluetooth

Bluetooth is a short range radio communication technology that has largely replaced infrared as a way of linking mobile devices and desktop computers. It is also used extensively for communication between small devices such as GPS receivers or wireless headsets and mobile phones, PDAs and laptops. Depending on the specification of the wireless chipset, the maximum range can be either around 10m or up to 30m. Such figures are normally only achieved in large open spaces without intermediate obstructions. In typical indoor environments the range is highly unpredictable due to the effects of reflections from surfaces and absorbtion by obstructions.

There have been several experimental attempts to measure precise location of a receiver by measuring the signal strengths of multiple Bluetooth transmitters placed around a space. In general, the results have been poor, particularly in spaces where variable numbers of people are moving around. As a location technology, therefore, the best that can be expected from Bluetooth in the short term is a coarse, room-level location granularity.

Apart from general communication use between sensors and computing devices, one of the more promising uses of Bluetooth in a smart environment lies in 'pushing' applications to mobile phones and other mobile devices. Today, many visitors will be carrying a modern 'smart phone', that is, one that is capable of downloading and running programs. On arrival at a museum or site, such a visitor can be offered the opportunity to download and install a phone-based version of a visitor guide, perhaps one that uses the phone's built-in camera to capture and decode Optical Tags and so retrieve location-specific information at various points of interest.

[edit]