Ultra-wideband Systems, Channel Estimation Methods

In UWB communication systems, to guarantee the reliability and efficiency of the communication, the propagation characteristic of the UWB channel should be known clearly. Therefore, channel estimation is a significant issue in UWB communication systems. In chapter 1 , the principles of the UWB communication systems are introduced, and the UWB communication systems are classified into two types: Single band UWB system (based on the narrow pulse) and multiple band UWB system (based on the OFDM technology). In chapter 2, characteristics of the wireless and mobile channels are introduced as a basis. And then, the propagation characteristics of the UWB channel are introduced. Finally, the classic standard UWB channel model is given and the main parameters of this model are described in detail. In single band UWB communication systems, data symbols are conveyed with UWB pulses and Rake receivers are employed to boost system performance. Therefore, the accuracy channel estimation is of significant importance. In chapter 3, two channel estimation methods are proposed for use in DS-UWB systems: DA (Data Aided) channel estimation and NDA (Non Data Aided) channel estimation. These two channel estimation methods are based on the maximum-likelihood criterion. In DA channel estimation, we propose two estimation methods: KD (Known Delay) method and UKD (Unknown Delay) method. In KD method, only path attenuation factors at predetermined probable path delays should be estimated. But in UKD method, both the path attenuation factors and the path delays must be estimated. The simulation results show that: the KD method outperforms the UKD method. The performance loss of the UKD is mainly due to the illusive paths induced by autocorrelation and cross-correlation of user signature waveforms. In NDA channel estimation, the orthogonal modulation is introduced to realize blind estimation so as to improve the system...