Effect of multiuser interference on subscriber location in CDMA networks

The last few years have witnessed an ever growing interest in the field of mobile location systems for cellular systems. The motivation is the series of regulations passed by Federal Communications Commission, requiring that wireless service providers support a mobile telephone callback feature and cell site location mechanism. A further application of the location technology is in the rapidly emerging field of intelligent transportation systems, which are intended to enhance highway safety, location based billing etc. Many of the existing location technologies use GPS and its derivatives which require a specialized subscriber equipment. This is not feasible for popular use, as the cost of such equipments is very high. Hence, for a CDMA network, various methods have been studied that use the cellular network as the sole means to locate the mobile station (MS), where the estimates are derived from the signal transmitted by the MS to a set of base station\u27s (BS) This approach has the advantage of requiring no modifications to the subscriber equipment. While subscriber location has been previously studied for CDMA networks, the effect of multiple access interference has been ignored. In this thesis we investigate the problem of subscriber location in the presence of multiple access interference. Using MATLAB as a simulation tool, we have developed an extensive simulation technique which measures the error in location estimation for different network and user configurations. In our studies we include the effects of log-normal shadow and Rayleigh fading. We present results that illustrate the effects of varying shadowing losses, number of BS\u27s involved in position location, early-late discriminator offset and cell sizes in conjunction with the varying number of users per cell on the accuracy of radiolocation estimation

Evaluating the Correlation Characteristics of Arbitrary AM and FM Radio Signals for the Purpose of Navigation

The Global Positioning System (GPS) provides position estimates on the Earth at anytime, anywhere and in any weather. However, to provide robust positioning, GPS requires an unobstructed path to satellite signals. As such, GPS performance generally degrades or becomes non-existent in environments such as large urban areas. This research investigates and analyzes the correlation characteristics of arbitrary AM and FM radio signals for the purpose of navigation. Simulations are conducted with different combinations of correlation methods (`fixed\u27 or `varying\u27), modulation types (AM or FM), and signal types (song or voice). Out of the eight different variations considered, only two provided promising results for the purpose of navigation. Both the FM voice and FM song signals exhibit distinct autocorrelation peaks (i.e., 5.0 dB peak-to-sidelobe ratios) using the `fixed\u27 reference correlation method. However, results for both FM signal types revealed limited potential for navigation when using the `varying\u27 reference correlation method. All the AM signals considered yielded relatively limited potential for navigation using either correlation method

System-level simulation of a third generation WCDMA wireless geolocation network

A wireless geolocation system for use in a WCDMA network was simulated in Matlab. In such a system, the multipath delays have a significant effect on the mobile location estimate.Ü si ul nk end-to-end model was created according to WCDMA system specifications, where the pilot signal was spread using 28400-chip complex Gold spreading and passed through a shaping filter. The effects of multipath fading and noise was added. The received signal was passed through a receive filter and correlated with the mobile station's locally generated Gold code to find the multipath delay. The mobile location was estimated using a hyperbolic time-difference-of-arrival approach. The estimation error was calculated for various environments and channel models and found to be less than 20m for the suburban ATDMA model and less than 110m for the rural CODIT model, which is acceptable considering that one chip time corresponds to 78 m. For comparison, the former WCDMA specification of 40960-chip spreading was evaluated and an error of less than 100m was obtained for the COST-231 suburban model using the CODIT Macro Channel where one chip time corresponds to 73m. This asynchronous system was found to be a satisfactory geolocation system for WCDMA under the given conditions

CSM-428: Techniques used for Location-based Services: A Survey

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Navigation Using Signals of Opportunity in the AM Transmission Band

Maintaining a precision navigation solution both in a GPS hostile jamming environment and also in a GPS non-compatible terrain area is of great importance. To that end, this thesis evaluates the ability to navigate using signals from the AM band of the electromagnetic spectrum (520 to 1710 kHz). Navigation position estimates are done using multi-lateration techniques similar to GPS. However, pseudoranges are created using Time Difference of Arrival (TDOA) distances between a reference receiver and a mobile receiver, allowing the mobile receiver to obtain absolute position estimates over time. Four methods were developed for estimating the cross-correlation peak within a specified (sampled) portion of the cross-correlation data for use in TDOA measurement generation. To evaluate the performance of each peak locating method, a simulation environment was created to attempt to model real-world Amplitude Modulation (AM) signal characteristics. The model simulates AM transmission sources, signal receivers, propagation effects, inter-receiver frequency errors, noise addition, and multipath. When attempting to develop a data collection system for real-world signals, it became clear that selecting a proper analog front-end prior to digitization is pivotal in the success of the navigation system. Overall, this research shows that the use of AM signals for navigation appears promising. However, the characteristics of AM signal propagation, including multipath, need to be studied in greater detail to ensure the accuracy of the simulation models

Super-Resolution TOA Estimation with Diversity Techniques for Indoor Geolocation Applications

Recently, there are great interests in the location-based applications and the location-awareness of mobile wireless systems in indoor areas, which require accurate location estimation in indoor environments. The traditional geolocation systems such as the GPS are not designed for indoor applications, and cannot provide accurate location estimation in indoor environments. Therefore, there is a need for new location finding techniques and systems for indoor geolocation applications. In this thesis, a wide variety of technical aspects and challenging issues involved in the design and performance evaluation of indoor geolocation systems are presented first. Then the TOA estimation techniques are studied in details for use in indoor multipath channels, including the maximum-likelihood technique, the MUSIC super-resolution technique, and diversity techniques as well as various issues involved in the practical implementation. It is shown that due to the complexity of indoor radio propagation channels, dramatically large estimation errors may occur with the traditional techniques, and the super-resolution techniques can significantly improve the performance of the TOA estimation in indoor environments. Also, diversity techniques, especially the frequency-diversity with the CMDCS, can further improve the performance of the super-resolution techniques

Average performance analysis of circular and hyperbolic geolocation

A comparative performance analysis of four geolocation methods in terms of their theoretical root mean square positioning errors is provided. Comparison is established in two different ways: strict and average. In the strict type, methods are examined for a particular geometric configuration of base stations(BSs) with respect to mobile position, which determines a given noise profile affecting the respective time-of-arrival (TOA) or timedifference- of-arrival (TDOA) estimates. In the average type, methods are evaluated in terms of the expected covariance matrix of the position error over an ensemble of random geometries, so that comparison is geometry independent. Exact semianalytical equations and associated lower bounds (depending solely on the noise profile) are obtained for the average covariance matrix of the position error in terms of the so-called information matrix specific to each geolocation method. Statistical channel models inferred from field trials are used to define realistic prior probabilities for the random geometries. A final evaluation provides extensive results relating the expected position error to channel model parameters and the number of base stations.Peer Reviewe