Research On Key Technology Of Joint Parameters For Mobile Terminal Location

There are numerous possible applications for location services in wireless network system ,such as communication,radar,sonar,earthquake reconnaissance and so on. Today position location has been widely applied in radar, TACAN, Loran C, VORTAC, JTIDS, GPS.In order to meet the need of market, high performance and low-cost position location is needed. In theoretically, no matter what systems are used, if a terminal can receive several signals from its position, then we can know where it is. Nowadays, we always use three methods called AOA, TOA and TDOA. Three BS are needed in TOA, two BS are needed in AOA and only one BS is needed in TDOA&AOA. Although TDOA&AOA is more complex, it's more accuracy and will lead the future.Several approaches for joint angle and delay estimation of each multipath for mobile terminal location are chiefly analyzed in this paper. First of all, the background of location techniques for wireless technologies, development, and the problems that are encountered when using networks for wireless location are introduced. And then several methods for estimating using high precision location parameter are analyzed. For example, nowadays, there are three methods for wireless location in mobile telecommunication networks. They are angle of arrival (AOA), time of arrival (TOA) and time-delay of arrival. Those three kinds of location approaches are compared with each other. At last, several methods which need only one BS for estimation of joint parameter for mobile terminal location in wireless system are presented in this paper. Two methods for estimation of joint parameter for mobile terminal location are chiefly presented in this paper.1. A method for jointly estimating the direction for arrival (DOA), time-delay and strength of same signal source in a TDMA system is presented in this paper. In multipath propagation model, arrival angle, delay and strength received by an antenna array for same signal source are estimated. Firstly the channel characteristic is estimated by the use ofthe training signal, then joint parameters of multipath signal is estimated based on the 2D-ESPRIT algorithm and matrix diagonalization method. The simulation illustrates that this estimation method is effective.2. A method for jointly estimating the direction for arrival (DOA) and time-delay of each multipath of the desired user in a CDMA system is presented in this paper. The respective spectra of the desired user and MAI components at the matched filter output are different. After pre-processing the spatial covariance matrixes at each frequency, we propose the 2D-unitary-ESPRIT algorithm as our estimator which provides closed-form as well as automatically paired DOA and time-delay estimates. The approach presented herein can give accurate estimates even under near-far conditions at low computation cost.After analyzing features and performance of multipath signal parameter estimation algorithms in wireless network environments, we find several shortcomings in the existing multipath signal parameter estimation algorithms, such as:1. The process of the existing algorithms is complex. MUSIC (multiple signal classification)-like algorithms require eigenvalue decomposition (EVD) and peak search. ESPRIT (estimation signal parameters via rotational invariance techniques)-like algorithms need twice EVDs.2. For joint DOA and delay estimation (JADE), because of vectorization (column stacking), Khatri-Rao product and Kronecker product, the dimension of the data matrix is increased, which influences real-time processing seriously.3. MUSIC-like algorithms only use the eigenvectors of data matrix to estimate signal parameters without making full use of the information of eigenvalues. On the other hand, ESPRIT-like algorithms only utilize the property of eigenvalues to estimate signal parameters.4. Most of the existing algorithms require extra processings to solve the pairing of the estimated DOAs and delays. Hence, we must develop some parameter estimation algorithms, which havelower computational complexity and high performance, to suit the complicated multipath propagation environments.In order to overcome the aforementioned disadvantages, two efective parameter estimation algorithms are proposed in this dissertation. For DOAs and delays estimation of multipath signals, we analyse two algorithms as follows.1. Space-time matrix method. A space-time matrix which includes the information of DOAs and delays of multipath signals is defined in this method. DOAs and delays are estimated by eigenvalues and eigenvectors of the space-time matrix, respectively. At the same time, the pairing of the estimated DOAs and delays is automatically determined by the relationship between eigenvalues and eigenvectors. It has a lower computational complexity, since Kronecker product and Khatr-Rao product etc are avoided.2. Modified space-time matrix method. It is a modified space-time matrix method. Compared with the space-time matrix method, it has better performance, such as it can resolve the incoming rays with very close DOAs or delays and it is more applicable to the complicated multipath propagation environments.Theoretical analysis and computer simulation verify that the stated above algorithms are practical, effective and easily achieved. The joint parameter estimation method is meaningful in mobile terminal location in future mobile communication networks.