| Wireless communication is one of the most popular and developed fields.Ultra-Wideband(UWB)communication systems have superior advantages over other wireless communication systems in terms of transmission rate,multiplexing with existing frequency bands,and resistance to multipath fading.Chaotic signals that inherent wide-spectrum characteristics can be easily generated,therefore,chaos-based UWB communication systems have unique advantages in low-cost,low-power short-range wireless communication applications.However,because UWB systems must share their bandwidth with coexisting narrowband systems and the number of Internet-of-Things device is increasing,the chaos-based UWB systems face some issues that need to be solved.Accordingly,in this dissertation,we focus on the anti-narrowband interference and the multiple access for the chaos-based UWB system,the main research contents will be briefly described as follows(1)In order to improve the Bit-Error-Rate(BER)performance of the chaos-based UWB system in the presence of narrow-band interference,the conventional Energy Detector(ED)in the chaos-based UWB is optimized by us to propose an enhanced energy detector(EED)for Multi-user(MU)Frequency modulation differential chaos shift keying(FM-DCSK)UWB system.The simulation results demonstrate that the EED-based FM-DCSK UWB system has better BER performance and anti-narrowband interference performance than the ED-based FM-DCSK UWB system.(2)In order to enhance energy efficiency in the transmission of the information from a base station to multiple user equipments in short-range wireless communication applications such as wireless personal area networks(WPANs)and wireless sensor networks(WSNs),a multiuser superposition coding pulse-position modulation(MU-SC-PPM)DCSK system is proposed in this dissertation.In the proposed system,the base station can simultaneously transmit information to multiple user equipments.According to the theoretical model of the proposed system,we perform a detailed theoretical analysis of the BER as well as the normalized throughput for the MU-SC-PPM-DCSK system.The simulation results demonstrate that the proposed MU-SC-PPM-DCSK system has advantages in BER performance and throughput compared with multi-resolution DCSK system and MU-PPM-DCSK system based on orthogonal multiple access.In addition,the MU-SC-PPM-DCSK system is extended into an MU-SC-PPM-DCSK UWB system,and the performance of the MU-SC-PPM-DCSK UWB system is analyzed by computer simulation,which demonstrates the superiority of the MU-SC-PPM-DCSK system and its feasibility in UWB communication.The chaos-based UWB system designed in this dissertation provides an important alternative technology for low-power and low-complexity short-range wireless communication applications. |
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