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Location Based Services (LBS)
Background on beacon based positioning
Beacon based positioning uses radio beacons such as GSM/UMTS cell towers and 802.11 (WiFi) hot-spots to "anchor" the location of a mobile device. Basically, if the device is within radio range of a beacon, it is possible to declare the device as near the beacon. Furthermore, if the geo-location of the beacon is known then the mobile device must be located somewhere within the physical area covered by the beacon. Lower power beacons such as WiFi therefore have a finer grained positioning resolution.
Cellular Beacons
A cellular network consists of multiple Base Transceiver Stations more commonly referred to as Cell Towers. Each Cell Tower manages one or more cells, which in turn supports the management of a finite number of mobile phones. The coverage area of a single cell is dependent upon the power of the antenna. In order to provide capacity in densely populated metropolitan environments a large number of short range cells are used. In contrast, rural environments are configured with a lower number of cells providing coverage over a less densely populated geographic region.
Real-time access to the cells within range of a mobile handset has become increasingly available in mobile software APIs. This has enabled a new class of location service known as Cell ID positioning. Presently, mobile APIs provide access to the current serving Cell ID only. However, more information, such as all of the cells ‘visible’ from a handset as well the received radio signal strength, can improve the accuracy of a cell based location service. As device manufacturers experience an increased demand for this type of data, we envisage mobile APIs improving in the future.
WiFi Beacons
For devices with 802.11 wireless networking (WiFi), wireless access points can act as beacons within a beacon based location service. Compared to Cell ID beacons, WiFi has some advantages and disadvantages:
- WiFi beacons have a smaller radio coverage area so position accuracy is better than Cell ID (WiFi: tens of metres; Cell ID: 100m to 30km)
- Devices with WiFi report multiple access points which can be used to improve location accuracy (rather than just a single serving cell ID)
- WiFi beacons can be easily relocated meaning that it is more difficult to maintain a WiFi database than a Cell ID database
- Because of their smaller coverage areas, it is more difficult to discover WiFi beacons for inclusion in a database
- All mobile phones connect to cells while only a small percentage of phones have WiFi capability
In practice, it is best to use the two types of radio beacon positioning methods alongside one another. This improves the reliability of the location service and guards against situations where radio beacons are unknown in the database.
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