Study On Key Technologies Of Noncoherent UWB Communication Systems

Noncoherent(NC) ultra-wideband(UWB) communication systems have received considerable attention due to their low-complexity and low-power consumption without the need for channel estimation and accurate synchronization. Recently, the popularity detection technologies used in NC UWB communication systems include energy detector(ED) and autocorrelation receiver(AcR). EDs always connect with pulse position modulation(PPM) and become a kind of classical and practical NC UWB receivers. Transmitted reference(TR) signaling in conjunction with AcRs has become the NC implement scheme of IEEE 802.15.4a alternative physical layer. However, the long delay line between reference pulse and data pulse is a major challenge for the implementation of TR-UWB systems. Transmitted reference pulse cluster(TRPC) was proposed as an improvement of time domain for TR signaling to avoid the long delay line. In order to further improve the performance of NC UWB systems, this thesis focuses on the channel coding and receiver optimization. The main contributions of this thesis are summarized as follows.Low-density parity-check(LDPC) codes are used in NC UWB systems to improve the bit error rate(BER). When implementing belief propagation(BP) decoding algorithm, the variance of channel noise is necessary for prior probability. Based on the feature of NC system, training sequence is used to obtain variance. According to the relative error of different training sequence, the appropriate length of sequence can be chosen. Compared with the codes specified in IEEE 802.15.4a and proposed in other articles, LDPC coded systems can provide better performance. Simulations are implemented in NC-PPM, TR and TRPC systems respectively, and TRPC is researched as the main target.Improved transmitted reference pulse cluster(iTRPC) was proposed as an improved proposal for TRPC in an article. Based on iTRPC, two modifications are investigated in this dissertation. Firstly, considering the dispersive energy distribution of multi-path components, the integration interval is determined at the autocorrelation receiver. Moreover, since iTRPC cannot completely remove the IPI, zero decision threshold(ZDT) is not the optimal decision threshold and hence the decision threshold is optimized by employing adaptive decision threshold(ADT). Due to the similar structure to TRPC, NC-PPM can be modified as iNCPPM. The integration interval is determined at the energy receiver to improve the energy capture efficiency. According to the simulation results and analysis, the modified system can provide significant and reliable improvement.