Lu Xiaochun

Research on UWB indoor positioning based on TDOA technique

Ultra wideband (UWB) wireless communication technology has been regarded as a very important way of indoor short distance, high speed transition at present. In this paper the system structures and working principles of indoor positioning using UWB are introduced. The basic location principles and realization ways based on TDOA (Time-Difference-Of Arrival) are discussed and a new method to estimate the value of TDOA is proposed. In the indoor positioning system, the content being transmitted are simple, the system complexity is low, and it is prone to link with other outdoor positioning system such as GPS to realize accurate positioning.

Implementation of MB-OFDM Transmitter Baseband Based on FPGA

Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) is a suitable solution to implementation of high speed data transmission in ultra wideband spectrum by dividing the spectrum available into multiple bands. The baseband of transmitter is one of the most important parts in MB-OFDM system. The structure of MB-OFDM system transmitter is introduced in this paper and the design of transmitter baseband based on FPGA is described in detail. The design has been validated with Xilinx Virtex II FPGA. The results show that all modules designed has achieved the expected purpose both in precision and resource, with simplicity and high efficiency, and can meet the demand of MB-OFDM systems.

Design and Implementation of Channel Estimation and Equalization of Indoor Positioning System Based on UWB

Precise indoor positioning is becoming increasingly important in commercial, military and public service applications for tracking people and asset. Ultra Wide Band (UWB) can provide high accuracy position with strong anti-jamming and low power consumption. It is very suitable for indoor positioning application. This paper will put emphasis on indoor positioning system based on UWB.Analysis and implementation of indoor positioning systems based on UWB require an accurate channel model to determine that can be achieved, to design efficient modulation and coding schemes, and to develop associated signal-processing algorithms and effective method of hardware implementation. The structure of indoor positioning system based on UWB is introduced and some system parameters and modulation are determined in this paper. After description the structure of receiver and transmitter of system, a detailed analysis of UWB indoor channel characteristics is given and some algorithms of channel estimation and equalization are discussed in this paper. Some channel estimation techniques based on preamble training sequences and pilot sub-carriers are researched in depth. Further more, the linear estimations of least square (LS) and minimum mean square error (MMSE) are analyzed and compared under different UWB channel conditions and then suitable algorithm for this system is selected. Based on this selection, a scheme for FPGA implementation is proposed, and then some most significant modules for channel estimation and equalization has validated with Xilinx Virtex IV FPGA. It has been shown by some modelsim simulations that this channel estimation and equalization approach has some merits, such as simple implementation and less consumption of resource. It can meet the requirement of system design and some good performances can be achieved.

Design and Simulation of Indoor Positioning System Based on UWB

In this paper, Ultra wideband technology and the main features of indoor positioning technology is introduced, focusing on the design and establishment of a UWB-based indoor positioning system model, the transceiver structure of the system is determined, and then location algorithm, the receiver synchronization and channel estimation and other key technologies conducted in-depth study. On this basis, the detailed simulation of the entire system using Matlab/Simulink software platform is carried out. It has been proved by simulation results s that UWB indoor positioning system provides good positioning accuracy and better performance.

Application of data fusion in multi-sensor integrated navigation system

Integrated navigation system can help to solve the performance and application problems and limitations of the navigation equipment. Data fusion technology is one of the kernel parts in integrated navigation systems. In this paper, the current advances of this technology are introduced, with the architecture of a multi-sensor navigation system given and its principles and structure presented in detail. The emphasis is laid on the discussion of the algorithms of state estimation, track association and track fusion, on the basis of which the simulation results are given. The simulation results show that targets can be tracked well and the efficiency and accuracy of the information can be enhanced by using multi-sensor data fusion technology.

Anchor stations for inter-satellite link and design for its time synchronization

Inter-satellite link technology is one of hot issues in current satellite navigation field and construction of inter-satellite link system cannot be completed without the cooperation and supports of ground anchor stations. In this paper, with respect to time synchronization issue which is of great importance in the construction of anchor stations for inter-satellite link, key technological issues such as time system design for anchor station, method of synchronization with standard time, clock error of anchor station and the determination of its precision have been deeply discussed and studied. On the base of relevant studies, a complete design method and solution of time synchronization system for anchor station has been proposed herein, thereby offering solution ideas and technological supports for resolving key problems encountered during the construction of anchor stations for inter-satellite link in China. The anchor station time system proposed in this paper can better ensure the time difference between ground station and BDT is less than 1us and the time synchronization precision of anchor station is less than 5ns, thereby guaranteeing the reliability of anchor station acting as Pseudolite being connected to inter-satellite link while offering further reference for subsequent testings and development of inter-satellite link.

The optimum selection method and performance analysis for Weil code of satellite navigation system

With the development of GNSS, the design and optimum selection of the ranging code is of significant importance for navigation system design. This paper describes the generation of the Weil code based on the design of ranging code. And then in order to select ranging codes of better performance, the paper describes a new optimum selection method in detail. This method is a combination of code selection method which is based on MFL and performance analysis method which is based on the peaks of correlation. And the performance of the selected Weil codes is analyzed by the methods based on peaks of correlation and Welch bound. The results demonstrate that the optimum selection method is of good rationality and of great importance for the design of navigation signals.

Multipath performance analysis of GNSS navigation signals

Nowadays, multipath remains as an unsolved key problem for high precision applications, such as satellite navigation and position. Because GNSS broadcasted signals are subject to reflection and diffraction, just like any other type of electromagnetic waves, multipath is caused by the reception of direct signal together with the reflected or/and diffracted signals at the same time. Multipath will result in errors in pseudorange measurement and carrier phase measurement, and thus affect the positioning accuracy. To verify the effects of multipath propagation on positioning performance, the principle of multipath is introduced in the beginning of this paper. Then based on a simulation platform and mathematical verifying model, the multipath performance and its impact on positioning performance of received GNSS signal is comprehensively demonstrated from different aspects, such as pseudorange multipath error, waveform shape, modulation error, and correlation characteristics and so on. Results indicate the degradation of positioning performance when multipath signals were present, causing position error with several meters to tens of meters. Those results and data we have obtained from this paper could be used as a valuable reference for BDS future signal design and system constructions.

Analysis Methodologies of GNSS Inter-system Interference

Since the research on compatibility is becoming a worldwide “hot spot”, decision has been made to improve the anti-jamming performance between satellite systems. Nowadays, primarily been driven, amongst other motivations, by the desire to ameliorate the compatibility performance of GNSS, speculation has continued on the possibility of further optimization. Of special interests is the inter-system interference that one satellite navigation system will suffer due to another satellite navigation system. This paper reports our recent studies in seeking methods for analyzing the inter-system interference.

Study on the Communication Performance of GNSS Baseband Signals and Its Software Development

In this paper, a control method for making automated distributed management decisions is studied. And the consequences of externalized management on services and the system architecture is studied also. A simulation is performed to evaluate the suggested control method. The simulation results show that the automated manager needs 1) a system view classifying the current system state based on local knowledge, 2) a learner providing an optimal decision policy, and 3) an adaptive service architecture with abilities to compensate disturbance.