With the advances in wireless communications and low-power electronics, accurate position location may now be accomplished by a number of techniques which involve commercial wireless services. Emerging position location systems, when used in conjunction with mobile communications services, will lead to enhanced public safety and revolutionary products and services. The fundamental technical challenges and business motivations behind wireless position location systems are described, and promising techniques for solving the practical position location problem are treated.

Position location using wireless communications on highways of the future

In an overlay Wireless Location System, an Abis interface is monitored to obtain information used to locate GSM phones (S116). Signaling links of the Abis interface are passively monitored to obtain certain information, such as control and traffic channel assignment, called number, and mobile identification, which is not available from the GSM air interface of the reverse channel (S110-S116). This approach also applies to IDEN and can be broadened to include CDMA systems where the GSM architecture has been used and the system includes a separated BTS to BSC interface.

Monitoring of call information in a wireless location system

A multiple pass location processing method, for use in a wireless location system (WLS), comprises identifying a received transmission as requiring multiple pass location processing whereby the WLS produces a first, lower quality location estimate and then subsequently produces a second, higher quality location estimate. The WLS then produces the first location estimate and provides it to a first location application, and then produces the second location estimate. The second location estimate may be a more accurate estimate than the first location estimate and/or of a higher confidence than the first location estimate. This method is suitable, but not limited, for use in connection with locating a wireless transmitter involved in an emergency services call and routing the call to a call center.

Multiple pass location processor

Method and systems are employed by a wireless location system (WLS) for locating a wireless device operating in a geographic area served by a wireless communications system. An exemplary method includes monitoring a set of signaling links of the wireless communications system, and detecting at least one predefined signaling transaction occurring on at least one of the predefined signaling links. Then, in response to the detection of the at least one predefined network transaction, at least one predefined location service is triggered.

Advanced triggers for location-based service applications in a wireless location system

A method, used in locating a mobile transmitter, includes providing a set of cross-correlation values, wherein each cross-correlation value is associated with a corresponding TDOA and/or FDOA estimate and is produced by cross-correlating a reference signal with a cooperating signal. The reference signal comprises a copy of a signal transmitted by the mobile transmitter as received at a first antenna and the cooperating signal comprises a copy of the same signal as received at a second antenna. The method further includes determining a most likely range of TDOA and/or FDOA estimates, and then identifying an optimal cross-correlation value within a subset of cross-correlation values corresponding to the most likely range of TDOA and/or FDOA estimates. The TDOA and/or FDOA value corresponding to the optimal cross-correlation value is then employed in calculating the location of the mobile transmitter.

Method for estimating TDOA and FDOA in a wireless location system

We compare the performance of conventional subspace-based direction-of-arrival (DOA) estimation techniques such as ESPRIT and MUSIC with the integrated approaches that combine the constant modulus algorithm with subspace-based techniques. Simulated and measured results are presented for a variety of signal conditions. The integrated approach was found to perform significantly better than the conventional ESPRIT approach. Also, multipath present in the channel significantly degrades the performance of the DOA estimation algorithms, and this has been confirmed by measurement and ray tracing simulation. This work has application to smart antennas and position location.

http://faculty.poly.edu/~tsr/wp-content/uploads/CV/ICP/1996-10-Performance%20Comparison%20of%20Subspace-Based%20Algorithms%20and%20the%20Integrated%20Property-Restoral%20with%20Subspace-Based%20Algorithms%20for%20DOA%20Estimation.pdf

R. Muhamed

Papers

Comparison of conventional subspace based DOA estimation algorithms with those employing property-restoral techniques: simulation and measurements