Selecting an appropriate modulation scheme is a critical design decision in UWB communications systems. Data modulation can directly affect the performance of UWB receivers in the presence of various channel conditions, such as multipath, multiple access, and various forms of interference. The proper modulation technique can also prevent a UWB device from causing harmful interference to existing radio services. This is done by reducing the number of discrete spectral lines on the UWB pulse's PSD, also called spectral smoothing. The data rate can also be affected by the modulation method used to transmit and receive data. Therefore, depending on the specific application, each of these design considerations should be taken into account prior to selecting a modulation scheme for transfer of information.
In this chapter, we introduced various modulation techniques used for UWB single-user channels, such as OOK, PAM, PPM, biphase modulation, and TR modulation. We explained the detection method for each modulation option and pointed out the advantages and challenges of each modulation scheme.
Furthermore, we explained multiple access in UWB communications and reviewed the modified PAM, PPM, biphase, and TR modulation methods for multiple-access channels. In addition, we briefly discussed time-hopping and delay-hopping techniques, which prevent data collision in UWB multiple-access channels. For further information on any of the modulation schemes presented here, consult the cites in the references and bibliography that follow.