Design And Implementation Of Wireless Positioning System Based On Chirp Signal

Chirp is the signal whose frequency changes linearly with time. CSS is short for Chirp Spread Spectrum which worked on2.45GHz of License-free called ISM was one of standards at physical layer of the IEEE802.15.4a proposed in October2006as a supplement to the UWB impulse radio technology. CSS has considerable application in the field of wireless positioning as its advantages of low power spectral density, resistance to multipath effects, far transmission distance and good ranging ability.The thesis studied the design and implementation of wireless positioning system based on chirp signal and analyzed the advantages of using Chirp Spread Spectrum in the field of wireless locating. Besides, the view that advantages and disadvantages of the common approach of locating were involved as well. For the characteristics of engineering applications considered, the thesis had chosen LLOP as positioning algorithm and SDS-TWR as ranging algorithm. The thesis had shown the whole design of wireless positioning system based on Chirp signal and low-power tag, which made the system more economical at the expense of the software complexity. The results of the system test had shown the system a high positioning accuracy. The thesis analyzed positioning accuracy of the system and found a common phenomenon when tackling ranging experimental data. The thesis found the source of ranging deviation by analyzing the model of deviation which concluded from the combination of the principle of SDS-TWR ranging algorithm, factors of practical and the ranging experimental data into consideration. Estimation of real distance ultimately convert to a math model by further analysis and simplification of deviation model result from the property of experimental data and source of deviation. Maximum likelihood estimation of real distance in the positioning system was solved by mathematical methods. Combined with tracking performance of the positioning system, reasonable analysis for number of sampling data was discussed. The test results from the improved positioning system had shown that effect of positioning is significantly improved by using the method above.