Integration interval and decision threshold issues were investigated for improved transmitted reference pulse cluster(iTRPC-)ultra-wideband(UWB)systems. Our analysis shows that the bit error rate(BER)performance of iTRPC-UWB systems can be significantly improved via integration interval determination(IID)and decision threshold optimization. For this purpose,two modifications can be made at the autocorrelation receiver as follows. Firstly,the IID processing is performed for autocorrelation operation to capture multi-path energy as much as possible. Secondly,adaptive decision threshold(ADT)instead of zero decision threshold(ZDT),is used as estimated optimal decision threshold for symbol detection. Performance of iTRPCUWB systems using IID and ADT was evaluated in realistic IEEE 802.15.4a UWB channel models and the simulation results demonstrated our theoretical analysis. Integration interval and decision threshold issues were investigated for improved transmitted reference pulse cluster (iTRPC-) ultra-wideband (UWB) systems. Our analysis shows that the bit error rate (BER) performance of iTRPC-UWB systems can be significantly improved via integration interval determination (IID) and decision threshold optimization. Two things can be made at the autocorrelation operation to capture multi-path energy as much as possible. (ADT) instead of zero decision threshold (ZDT), is used as an estimated optimal decision threshold for symbol detection. Performance of iTRPCUWB systems using IID and ADT was evaluated in realistic IEEE 802.15.4a UWB channel models and the analysis.