Research On The Key Technologies Of Non-cooperative Location For CDMA2000 Mobile Station

CDMA cellular mobile communication system is widely applied because of its low power consumption and high degree of safety. In a CDMA system mechanism, the position coordinates of users can be provided through interaction between the mobile station and base station, which is known as the cooperative location. Beyond the system mechanism, the technology that uses equipments provided by the third party to determine mobile station position is called non-cooperative location. As the CDMA system has high security, its level of difficulty in techniques is higher through using the wireless signal to monitor the call of users, or proceeding non-cooperative location. In the national prevention and fighting crime action, it puts forward a technical difficult problem for the security department. As the foundation of developing CDMA non-cooperative location equipments, the study of its theoretical basis and technical methods becomes a necessary approach. Thus it forms research topic of this paper.CDMA non-cooperative location equipment is of the special instruments field and its critical technical issues are of the ranging problem. Ignoring the undulated height of the earth's surface, the location of position coordinates can be assimilated to the determination of coordinates on the plane. Take this location equipment as detection station, receive radio signals between base station and mobile station from the air, calculate the distance difference between each detection station and mobile station, and then determine the position coordinates of mobile station according to the geometrical relationship. Thus the key technical problems in this paper are as follows:1,Hearable area search problem: As the detection station can only receive the transmit signal of mobile station within a specific distance and the coordinates of mobile station are unknown, it becomes a key problem of CDMA non-cooperative location that how to effectively and quickly determine the plane area where the mobile station is.2,Reverse pilot channel tracking problem: To determine the validity of the received signal and calculate the relative time difference, it needs to quote accurately the reference time in CDMA signals and the long code sequence fragments in the system. CDMA signal system takes the long code of 42 rank as the foundation of division access and synchronization, the uplink pilot signal of mobile station is inserted into irregular power control bit sequence and the transmit signal is shut off aperiodically, therefore time difference measurement between mobile station and detection station faces bottleneck restriction problem.3,Detection station optimal layout approximation problem: To determine mobile station position, the layout position of detection station must be at a stated geometry. In the unknown mobile coordinates premise, exploring the optimal layout of detection station becomes the key technical problem of non-cooperative location.4,Location equations calculating problem: The position coordinates of mobile station come down to the solution of location observation equations. However, the delay difference and the position parameters of detection station exist inevitably errors, which cause the ill-posed problem to the solution of general nonlinear equations. In order to look for the more robust and optimal solution method, it needs to combine the characteristics of non-cooperative location.5,Location performance bound problem: Solution of non-cooperative location problem must be divers, but the few existing research results, lack of integrity, are hard to be judged for good and bad. In accordance with the basic rules of the study measurement issues, it need determine the quantitative measurement errors and derive the theoretical upper limit of location errors.To solve the key technical problems, through the theory abstract in this paper, the complex CDMA system and actual location scene are converted into relatively simple signal and system model and ranging and location model(equation). According to the principle and analysis method of unified space and time, the solutions to solve the front four problems are given and the CRLB of non-cooperative location error is presented as the answer for the fifth problem.From the theory back to practice, this paper introduces the test prototype system of CDMA non-cooperative location which is designed by oneself. In the indoor hypothetical conditions, the test verified the feasibility of the solution afore mentioned. Through actually using in Changsha, Chengdu, and Chongqing, the practicability of the system and solution project gets the certification. The actual system and its theory research production has passed science and technology achievements appraisal and gets the full affirmation.