This letter proposes the Pulse-position Multi-pulse Modulation (PMM) with multiple access DTR-UWB systems for the ECC's proposed radiation mask on September 2005 and Japan's radiation mask on March 2006. For the ECC's proposed radiation mask and Japan's radiation mask, the UWB system has to consider the effect from Remote Access Service (RAS) and Radar system between 4.8-5 GHz and 5-6 GHz, respectively. That will limit the bandwidth of the system to just 3.4-4.8 GHz. The simulation results show that the performance of the proposed system is superior to that of the conventional TR-UWB communication system. Moreover, compared to the FCC's system, the proposed PMM DTR-UWB and conventional system have better error performance and higher total throughput at low Eb/N0. So for power limiting system like UWB, ECC's and Japan's systems may become the strong candidates in the UWB communication system.

In this letter, the delay time error between transmitter and receiver that may be the main factor degrading TR-UWB system performance, is studied. Simulations show that although the MPM and PMM systems with using SCR have achieved high throughput performance, this advantage has been degraded by the delay time error effect. Therefore, in the real application, the delay time error effect is one of the main factors for selecting the suitable TR-UWB system.

In this paper, two new modulation schemes, Multi-Pulse Modulation (MPM) and Differential Multi-Pulse Modulation (DMPM) have been proposed in order to increase the total data rate and improve the error performance. By these schemes, the modulated pulse that had been used for transmitting only one data bit in each pulse-pair in conventional TR-UWB system, can be used for transmitting more than one bit data depending on the level of modulation. Moreover, the error performance has been improved by these new modulation schemes because for the same Eb/N0, the energy per pulse has increased. In addition, these new modulation schemes are applied to a multiple access system. The simulation results show that the total throughput performance of the proposed system has been improved, nearly 2-4 times when compared to the conventional TR-UWB communication system.