Abstract:

The NIST Location System is designed to report the position of a mobile node indoors, where GPS is unavailable.  Rather than reference satellites, we employ reference access points stationed at fixed locations, each equipped with IEEE 802.11b WLAN cards.  The system operates under the physical principle of measuring the received signal strength (RSS) from available access points to a mobile node (also equipped with such a card).  The system estimates the position of the mobile with accuracy between one and three meters.  While the current implementation accepts a two-dimensional map to report the position of the node, it can be readily extended to 3D through the use of multiple 2D maps, each representing for example different floors of a building.

Simple triangulation reports the position of the mobile node by estimating its distance from three access points, transforming each RSS into a range through some attenuation model in function of distance.  Due to severe multipath fading and shadowing present in the indoor environment, this model does not hold.  Rather, we train the system a priori by recording the RSS at a number of anchor positions throughout the deployment area, or mapping the RSS to an anchor position.  To estimate the position of a mobile node, we perform the inverse-mapping, hence the mobile collects readings from the available access points at a query location, and compares them to those recorded at the anchor positions.  The estimate is reported as the anchor position whose RSS are closest to the those recorded.  In addition, the memory system takes into account the positions of the mobile in the past and uses this information to preclude physically impossible anchors positions of the current estimation in a Markov-state framework.  Details of the algorithm are provided in (ICC04 paper).

Download:

NIST Localization System (2MB)
Entire Paper (Robust Location using System Dynamics and Motion Constraints)

System Requirements:

· A IEEE 802.11b WLAN device running Windows XP (WRAPI claims hardware-independence)

· Java™ 1.4 (lower versions should work too, but have not been tested)

· At least one access point in the vicinity of the mobile node.

Installation:

1. Download the NIST Localization System and extract its content in any directory.

2. If you don’t have Java™ then download the latest version from here.

3. Install the RAWPacket NDIS Protocol Driver (included in archive):
> Click on Control Panel -> Network Connections.
> Select a connection (any) and right-click on Properties.
> Click on Install.
> Select protocol and press add.
> Select Have Disk and browse for “ndisprot.inf” located in the binary distribution.
> Press OK and ignore all warning.

4. Disable the Wireless Zero Configuration Service in Windows XP. This step has to be repeated after every system start:
> Click on Control Panel -> Administrative Tools -> Services, or
> Type “net stop wzcsvc” from a command prompt.

5. Run the program by either:
> double-clicking the location.jar archive, or
> typing “java –jar location.jar” in a command prompt.

Screenshot:

Contact: Dominik Kaspar

since 12-MAR-04