This thesis work consists of two different research projects. In the first project the optimization of the Frequency Shifted Reference-Ultrawideband (FSR-UWB) is discussed. After identifying the improvement areas in the FSR-UWB scheme, we performed analysis and proposed optimized values of the restricted integration and the front-end filter. It is observed that, by integrating the received signal over the entire symbol period, excess noise is allowed into the system and thus potentially degrades the performance. We showed that by restricting the integration period we get the expected gains in an Additive White Gaussian Noise (AWGN) channel but the gains are limited for a multipath fading channel. For these limited gains, the new integration block unnecessarily complicates the receiver structure. For front-end filter optimization the system performance is analyzed using a generic filter, h(t) and it is shown that a matched filter is the optimal filter for low values of Es/N0 whereas a unity gain band pass filter is optimal for high Es/N0 values, where Es is the symbol energy and N0/2 is the power spectral density of additive white Gaussian noise. In the second project we explored a general class of waveforms that can be used as separating waveforms to provide multiple-access for FSR-UWB systems. It is shown in this section that for single user scenario binary codes selected from {−1, 1} are optimal codes that can be used to separate data and the reference signals. For multiple-user access, a class of polynomials are discussed that can be used as separating waveform as they completely eliminate MAI. It is shown in the latter part that the optimal codes for multiple-user access are the binary codes selected from {−1, 1}. These codes are selected as the row vectors of the Hadamard Matrix. Simulation supported the application of this analysis to UWB systems, with either a small number of frames or operating over channels with small delay spread.