Research On ToA Estimation Methods For UWB-DCSK-based System

With the explosive growth of Internet of Things(Io T)and 5G communication technologies,simply realizing communication or obtain positioning information is unable to meet the requirements.The joint communication and location technology is a major development trend in ranging field,since it can recover the symbol from the received signal and obtain the location information through relevant estimation simultaneously.Ultra Wideband wireless communication technology is one of the most popular wireless communication technologies due to its low power consumption,low cost and high bandwidth.In addition,UWB communication technology is a promising alternative in indoor ranging arena due to its inherent advantage of mitigating multipath interference.Therefore,UWB wireless communication technology can be an outstanding candidate for the applications of joint communication and location.The coherent receiver is usually adopted by the joint communication and location system.However,the coherent receiver needs complex channel impulse response estimation,which increases the system complexity and hardware cost.As an incoherent receiver,the differential chaos shift keying(DCSK)technology does not need the channel impulse response estimation,which effectively reduces the hardware cost.Therefore,DCSK technology is more suitable for joint communication and location system.A major challenge for conventional ToA estimation method is the ranging performance degradation due to the multipath fading.However,the chaotic signals adopted in DCSK technology have very desirable cross correlation property,which makes them capable of against the multipath fading.Hence,integrated the UWB techniques with DCSK technology,the TOA estimation methods is analyzed in multipath fading environment in this dissertation.To resolve the challenge for the multipath fading,two ToA estimation methods have been proposed in this thesis.The main contributions of this dissertation lie in:(1)In order to improve the positioning accuracy,we proposed a ToA estimation method based on variance detection for the UWB-DCSK system.Compared with the traditional energy-detection-based methods,the positioning performance is improved at medium and high signal-to-noise ratio.In this situation,we proposed a ToA estimation method based on variance detection with feedback,which called VDF.Before the signal is sent to the estimator,a preprocessing operation is performed on the signal.The ranging performance of VDF is significantly improved,compared with the conventional ToA estimation methods.(2)The theoretical limit of ToA estimation performance is derived for UWB-DCSK system.Two theoretical bounds,which called Cramer-Rao low bound(CRLB)and Ziv-Zakai low bound(ZZLB),are deduced based on relevant literature.CRLB can predict the theoretical limit under high signal-to-noise ratio,while ZZLB is more accurate than CRLB in low and medium signal-to-noise ratio.Both of them can be used as benchmarks to evaluate the performance of TOA estimation method.Based on the relevant literature and the correlation characteristics of chaotic signals,the theoretical limit of ToA estimation for UWB-DCSK system is obtained.On the other hand,an indoor ranging chip produced by Decawave Company is used to carry out the experiment in practical indoor environment.Conclusion has been made that the theoretical curves have a good match to the experiment curves,which proves the correctness of the theoretical derivation.