| Wireless position location has received considerable attention over the past few years due to the United States Federal Communications Commission's(FCC) 1996 report and order. The FCC mandate requires that all wireless service providers, including cellular, personal communications services(PCS), and some special mobile radio(SMR) licensees, provide location information for Enhanced-911(E-911) safety services. In addition to security service, the mobile station(MS)'s position can be also applied to network performance enhancement, system-design improvement, more effective resource management, location-sensitive billing, information services and cellular phone fraud detection. The process of calculating the location estimate can be views as consisting of two parts. The first part provides estimates of location parameters and the second part is the algorithm that uses the parameters to determine the MS's position. Due to multipath effect, multiple access interference(MAI), near-far effect, and mainly the non-line-of-sight (NLOS) propagation, the errors in the estimated location parameters and position location occur. Therefore, techniques must be developed to mitigate these impairments and improve the location accuracy. In this dissertation, the location estimation methods for mitigating the influence of the NLOS propagation and the location parameters estimation methods for DS-CDMA cellular radio systems are studied. Furthermore, the influence of the NLOS propagation on the performance of radiolocation systems is analyzed. Moreover, by using pilot sequences from the base station(BS) in wireless CDMA cellular networks, the techniques for detecting and locating and tracking for 3-D moving target are provided. The primary contributions included in this dissertation are summarized below:1. Based on the facts that time of arrival(TOA) of the first multipath signal is always most close to that of LOS propagation and angle of arrival(AOA) of the first multipath signal is not always most close to that of LOS propagation among all multipath signals in NLOS propagation environment, a location algorithm is proposed to mitigate the influence of NLOS propagation, which effectively reduces the feasible region of a MS in macrocells. First, the nonlinear LS problem without constraint is converted to that subjected to inequality constraints by putting constraints on the DO As of the received signals and TOAs of the first arrived signal with geometrically based single-bounce(GBSB) statistical channel model and COST-207 model. Then, a penalty function is used in the estimation of MS position. The proposed method is suited for diverse types of locating systems and utilizes all measured parameters. Moreover, it can achieve obvious performance improvement when the measured parameters are limited.2. A position estimate method is proposed, in which the LOS reconstruction and smoothing technique are combined to mitigate the influence due to NLOS propagation. At first, by using the feature that the excess delays of NLOS propagation follow the exponential distribution, the LOS propagation parameters are reconstructed and the TOA parameters measured from all BS are preprocessed. Then, the MS's position is estimated by the LOS locating algorithm with the preprocessed data. Finally, to mitigate the effect of the errors in reconstructed parameters, the estimated results are smoothed. The proposed method can provide unbiased estimate of the MS's position. It is characterized by high efficiency and small memory volume requirement. The robustness against the influence of NLOS propagation is shown in computer simulations. In conclusion, this method is simple yet practically feasible.3. The author analyzes the performance of location methods in the case of biased and unbiased measured parameters, and then a method is put forward to improve the location accuracy. First, the mean-squared-error(MSE) of the estimated position and the expectation of the error in estimated coordinate are calculated, based on which the performance of...
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