Research On Ultra-wideband Chaotic Communication Technology

Ultra-wideband (UWB) technology is considered as one of the most promising candidates for short-range wireless communications. IEEE 802.15.4a study group is chartered to investigate solutions for low-rate WPAN (LR-WPAN). The device of LR-WPAN possesses some characteristics such as low data rate, low cost, weak power consumption and low complexity. Chaotic signals are wideband, deterministic, non-periodic and random-like signals, which offer a number of attractive features for IEEE 802.15.4a applications. The use of chaos for the UWB is put in this thesis under survey with a more particular interest to meet the requirements of the IEEE 802.15.4a standard.First, this thesis presents an overview of the UWB technology, including the definition, history, main characteristics and domestic and foreign research present situation of UWB. A brief overview of the chaotic communication is also introduced later. Second, the basic principle of MB-OFDM-UWB system and DS-UWB system is introduced. The simulation model of system is built, and both of systems are simulated and analyzed. Third, the thesis introduces the definition, basic concepts and characteristics of chaos system. It also concretely analyzes some familiar chaotic maps. Then three chaotic digital communication methods are addressed. At last, this thesis studies the ultra-wideband chaotic communication technology. Chaotic on-off keying (COOK) and differential chaos-shift keying (DCSK) are two simple modulation schemes. A typical COOK system has a drawback: it requires optimal threshold estimation which depends on signal to noise ratio. However,the optimal threshold is hard to obtain in practice. A balanced orthogonal code is adopted to improve the typical COOK UWB and avoid optimal threshold estimation. The simulation results show that the BER performance of the improved system is better than that of the typical COOK UWB system. After that, the ultra-wideband channel model is expressed in detail. The channel model based on IEEE 802.15.4a standard is studied and realized by simulation.