The Receiver Optimization Research And Performance Analysis For Transmit-Reference UWB System

Ultra-Wideband (UWB) impulse radio has attracted growing interest since it is capable of offering very high data rates by the transmission of ultrashort pulses. UWB has many advantages, such as low cost, low-power consumption, low-complexity implementation, and immune to multi-paths. Especially, UWB systems can coexist with the existing wireless communication systems at the same frequency band. Consequently, Ultra-wideband technology has been becoming a hotspot in wireless communication research and development, and is regarded as one of the key technologies in next generation wireless communication. It will become the best choice for short-range high rate wireless communication in the foreseeable future.Due to the rich scattering indoor environment, UWB channel generally contains hundreds of multipaths. Conventional UWB systems employ RAKE receivers to collect the available multipath diversity. However, estimation of all the tap gains and delays which are needed for RAKE operation is a formidable task. Even if these estimates were available, the resulting RAKE receiver would be very complex due to the large number of fingers required. Alternatively, the transmit-reference UWB (TR-UWB) systems have attracted substantial interests because it avoids explicit channel estimation, reduces synchronization requirements and also is robust to possible channel distortion on pulse shape.In this dissertation, the fundamental knowledge of Ultra-wideband technology is introduced first, and then several key technologies of the UWB systems. After that, we focus on the analysis and summing-up of the detection schemes designed for TR-UWB system. Through the research and analysis on the existing detection algorithms, it's found that the main challenge for TR-UWB system is to design a transceiver structure with minimized complexity but optimized performance, especially taking the data rate and inter-pulse-interference (IPI) into account. To address the task, a novel m-sequence coded transmit-reference signaling and detection scheme is proposed in this paper, where by invoking m-sequence codes the reference and data pulses are transmitted side by side to increase the data rate. This structure enables demodulation with a conventional correlation receiver despite existing server IPI. Relying on the Cycle-and-Add property (CAP) of m-sequence, the resultant IPI is skillfully reduced by the conventional receiver which only employs one short delay line and one correlator. Especially, the short delay line requirement overcomes a major hurdle (long delay lines) of practical implementation of the TR system. We then analyze the detection performance and give a close-form expression of bit error probability (BRP) for our binary system. Simulation results show that the proposed TR system achieves significant improvement by comparing with other designs in terms of detection performance related to the data rate and power efficiency.An improved detection scheme is then presented to achieve better BEP performance, inheriting all the benefits of the first algorithm. Taking full advantage of the newly designed frame structure and nearly orthogonal m-sequence codes, we can construct clear demodulation templates. The construction process is not only an IPI reduction operation but also an averaging operation which reduces the noise level in demodulation templates. It is expected to significantly improve the BEP performance in contrast with the previous scheme while adding little complexity. Both analysis and simulations are performed to demonstrate the promising performance of the proposed scheme.