Study On Turbo Coded Ultra Wideband Communications Systems

In recent years, as a new spread spectrum system, Ultra Wideband (UWB) communications has attracted much attention and been considered as one of the key technologies in wireless communications. In this thesis, the design and the BER performance of Turbo coded UWB communications systems are analyzed on base of the UWB theory research. Based on all these efforts, some positive results are obtained and summarized as follow:1. The principle, features and received signal processing are systematically summarized in the UWB communications. The BER performance expressions are derived for a THMA-BPPM-UWB system.2. The characteristics of UWB indoor channel model are described, and the pulse impulse responses are simulated in four channel environments. The simulation parameters were proposed by the IEEE 802.15 task group. The analyses of the RMS delay spread and the path amplitudes fading distribution are represented respectively.3. The rake technology of UWB receiver is studied in the multipath environment. The impacts on received energy are analyzed in different multipath combine manners including ideal rake, selective rake and partial rake.4. The BER performance of the Turbo coded TH-UWB systems are investigated on AWGN channel and indoor multipath channel. By computer simulation, we show that the Turbo coded TH-UWB systems using low rate Turbo codes and small impulse repetition improves the BER when the bit rate is same.5. We propose a Turbo coded Ultra wideband (UWB) system with parallel modulation. The proposed system employs Turbo codes as forward error correcting codes, and a set of orthogonal Hermite pulses modulated parallel data respectively. Under required performance of system, the maximal data transmissions rate could be achieved by adjusting the parameters including the rate of Turbo codes, the number of path and the number of pulse repetitions. Our simulation results and analysis on an AWGN channel show that for the same data transmissions rate, we had better make the number of repetition pulses smaller and the rate of Turbo code lower to achieve the better BER performance.