Wireless Location Determination for Mobile Objects Based on GSM in Intelligent Transportation Systems

The mobile object (MO) location determination technologies which can be used in intelligent transportation system (ITS) are studied in this paper. The principles and characteristics of wireless location determination technologies are introduced and the characteristics of GSM useful for location determination are also summarized. An experimental positioning system based on GSM is proposed, and the architecture is described. TOA method based on GSM signals and TDOA method are used in the experimental system. Moreover, the methods are simulated. The performance of the positioning methods is assessed in the simulation environment, and the accuracy for 67% mobile stations (MS) is 70m in urban areas.

Robust location algorithm for NLOS environments

One of the main problems facing accurate location in wireless communication systems is non-line-of- sight （NLOS） propagation. Traditional location algorithms are based on classical techniques under minimizing a least-squares objective function and it loses optimality when the NLOS error distribution deviates from Gaussian distribution. An effective location algorithm based on a robust objective function is proposed to mitigate NLOS errors. The proposed method does not require the prior knowledge of the NLOS error distribution and can give a closed-form solution. A comparison is performed in different NLOS environments between the proposed algorithm and two additional ones （LS method and Chan＇s method with an NLOS correction）. The proposed algorithm clearly outperforms the other two.

TOAesti mation algorithm based on multi-search

A new time of arrival （TOA） estimation algorithm is proposed. The algorithm computes the optimal sub-eorrelation length based on the SNR theory. So the robust of TOA acquirement is guaranteed very well. Then, aceording to the actual transmission environment and network system, the multi-search method is given. From the simulation result, the algorithm shows a very high application value in the realization of wireless location system （WLS）.

A Novel Routing Strategy to Provide Source Location Privacy in Wireless Sensor Networks

In order to secure the source location privacy when information is sent back to the base station in wireless sensor network, we propose a novel routing strategy which routes the packets to the base station through three stages： directional random routing, h-hop routing in the annular region and the shortest path routing. These stages provide two fold protections to prevent the source location from being tracked down by the adversary. The analysis and simulation results show that proposed scheme, besides providing longer safety period, can significantly reduce energy consumption compared with two baseline schemes.

A Novel Adaptive Cooperative Location Algorithm for Wireless Sensor Networks

To overcome the disadvantages of the location algorithm based on received signal strength indication(RSSI) in the existing wireless sensor networks(WSNs),a novel adaptive cooperative location algorithm is proposed.To tolerate some minor errors in the information of node position,a reference anchor node is employed.On the other hand,Dixon method is used to remove the outliers of RSSI,the standard deviation threshold of RSSI and the learning model are put forward to reduce the ranging error of RSSI and improve the positioning precision effectively.Simulations are run to evaluate the performance of the algorithm.The results show that the proposed algorithm offers more precise location and better stability and robustness.

CRLB analysis of wireless cognitive location with different short-range measurements

Because of the wide application and great market potential of location-aware services, the research of wireless location techniques for the fourth generation （4G） mobile communications is being paid more attention. Wireless cognitive location （WCL） techniques for next generation wireless networks have been proposed in recent years. This article investigates the changes of the positioning accuracy of WCL algorithm when different methods are adopted to measure the short-range （SR） information. By fJrst completing Cramer-Rao lower bound （CRLB） analysis of the WCL algorithm with SR measurements based on time of arrival （TOA） and received signal strength （RSS）, it is discovered that TOA-based or time difference of arrival （TDOA） -based SR measurement can make WCL algorithms achieve higher accuracy than RSS mode, which is also verified by numerical simulation in the article. The conclusions can instruct the design of novel WCL-based location algorithms.

UWB positioning enhancement using Markov chain in indoor NLOS environment

The accuracy of the positioning system in indoor environment is often affected by none-line-of-sight(NLOS) propagation. In order to improve the positioning accuracy in indoor NLOS environment, a method used ultra-wide-band(UWB) technology, which based on time of arrival(TOA) principle, combining Markov chain and fingerprint matching was proposed. First, the TOA algorithm is used to locate the target tag. Then the Markov chain is used to identify if blocking happened and revise the position result. And the fingerprint matching is used to further improve the position accuracy. Finally, an experiment system was built to test the accuracy of the proposed method and the traditional Kalman filter method. The experimental results show that, compared with the traditional Kalman filter method, the proposed method can improve the positioning accuracy in indoor NLOS environment.