Multi-carrier ultra wideband communication systems

This thesis deals with the multi-carrier ultra wideband (UWB) communication systems. Specifically, we study the effects of duty cycle and band hopping speed on the performance and complexity of the multi-band UWB systems, propose new ranging techniques and discuss analog-to-digital and digital-to-analog conversion issues.; Two new multi-band multi-carrier UWB systems are proposed and their performance and complexity are evaluated and compared with other emerging systems under consideration by the IEEE 802.15.3a standard. The multi-band pulsed-OFDM system is a slow hopping scheme that utilizes low duty cycle pulses in orthogonal frequency division multiplexing (OFDM) signals. The low duty cycle produces a diversity gain and leads to very low complexity and power consumption implementations with superior or comparable performance to similar systems. The UWB-OFDM system is a fast hopping scheme that provides maximal diversity in a given channel and can be used to design a very high bit rate high performance system. Different transmitter and receiver structures are proposed for these two systems and their performances in multipath fading channels are evaluated. The effects of different system parameters on the performance and complexity of the system are studied. Algorithms are provided to select the parameters to reach desired goals.; Range and time delay estimation resolution in multi-band systems is also studied and new schemes are proposed to enhance this resolution. In particular, a new scheme based on a digital Fourier transform is proposed and its superior resolution is established. Then, we generalize this scheme and propose a coherent combining scheme using full-tree perfect reconstruction wavelet filter banks. The new schemes achieve much higher accuracy than traditional schemes using the same probing time and energy.; Finally, a new sigma-delta structure, named N-tone sigma-delta, is proposed and used to design high speed digital-to-analog and analog-to-digital converters for OFDM UWB systems. We use these converters to design all-digital transceiver implementations for the UWB-OFDM system.