Ultra-wideband (UWB) communication system using short pulse modulation has been considered as a major candidate for low data rate (LDR) communication especially for wireless sensor network (WSN), whose main requirement is the low cost of the communication hardware in conjunction with a very low power consumption to permit a long life battery. From a practical point of view, recent research works on detection for UWB have focused on non-coherent detection schemes based on transmitted reference (TR), differential TR (DTR), or energy detector (ED) approaches. This is mainly because non-coherent receivers can avoid explicit channel estimation, reduce synchronization complexity, and are also robust to the possible channel distortion on pulse shape. Therefore, non-coherent receivers have been recognized as promising alternatives to coherent receivers in WSN. In this thesis we will focus on the study of TR receivers.
In a conventional TR system, a transmitter transmits pairs of identical pulses (called doublets) seperated by a time delay interval, which is known to its receiver. This delay time is realized by using a delay line (DL) at the receiver end. One main obstacle for TR systems is the implementation of the DL. In this thesis, aiming to solve the DL issues of practical TR receivers, design and evaluation of different performance improved TR receivers for impulse ratio (IR) UWB systems is addressed. The main contributions are as follows:
• Firstly, according to currently designed DLs, it is found that there is unavoidable phase distortion in practical DLs. This phase distortion generally leads to a group delay errors in signal bandwidth. Based on the quantized observations of the group delay errors in currently designed DLs, we propose a statistical group delay ripple (GDR) model to represent a practical UWB DL. The average bit error rate (BER) degradation caused by the GDR of practical DLs is thoroughly investigated in TR UWB communication systems. To mitigate the degradation in BER performance caused by the GDR, an improved auto-correlation receiver (AcR) is proposed.
• Secondly, considering the restraint of the delay time requirement for wideband DLs, based on a recently proposed TR pulse cluster (TRPC) structure, the thesis presents an improved TRPC (iTRPC) scheme. It is observed that by inserting a number of zeros at the end of each pulse cluster, not only inter-pulse interference (IPI) can be dramatically reduced, but also more multi-path delayed power can be captured for data detection. The performance of the proposed iTRPC scheme is analyzed and compared with that of traditional TR and the original TRPC (oTRPC) system. Our semi-analytical and simulation results verify that this iTRPC scheme, with quite low-complexity and not extra energy requirements, achieves more than 7dB Eb/N0 gain than the oTRPC scheme, provided that Pe = 10-3 or less.
• Thirdly, since the digital receiver design at the expense of high sampling rate of analog-to-digital convertor (ADC) can not only avoid the issues caused by using analog-autocorrelation but also provide flexibility in received signal processing, the digital architecture for the TRPC signaling scheme is considered and a digital reconfigurable TRPC receiver is proposed. The received signal-to-noise ratio (SNR) can be maximized by using the optimum number of DL branches. In addition, the complexity of the reconfigurable digital TRPC receiver is investigated from an implementation viewpoint and compared with that of the digital implementation of the oTRPC receiver.
• Finally, by using pulse-averaging approach, a new digital TRPC UWB receiver is further proposed in the thesis. The performance of the new digital TRPC receiver is analyzed and numerical and simulation results show that it can always achieve at least 3dB power gain over the oTRPC receiver.