Publication
In this thesis we study Impulse-Radio Ultra-Wide Band (IR-UWB), a physical layer radio technology offering many features that make it a promising choice for future short-range wireless networks. The challenges in such networks are many, ranging from the cost-complexity constraints of devices, through the presence of interference created by other users, up to stringent security requirements imposed by sensitive applications. Our main goal is to understand and show how a low-complexity IR-UWB receiver can be designed such that it is able to cope with the difficult environment that it will face in such networks. Although IR-UWB systems promise to provide a solution for some of the above-mentioned challenges, IR-UWB is not a panacea: More often than not, it will be able to live up to its promises only if the entire system is carefully designed. One example is robustness to interference from concurrent users, which is the topic of the first part of this thesis. Short-range wireless networks are expected to be self-organized and uncoordinated rather than centrally organized. This in turn leads to uncontrolled interference due to concurrent transmissions from uncoordinated devices. Thanks to its large bandwidth, combined with low duty-cycle transmissions, IR-UWB should in theory be able to accommodate a large number of concurrent users while keeping multi-user interference (MUI) levels low. We show that, if not properly addressed, MUI can severely affect the performance of an IR-UWB receiver, making this benefit of IR-UWB void. This is especially true if low complexity architectures, such as the popular non-coherent energy-detection receiver, are used. Further, we show that MUI affects all aspects of physical layer packet reception and appropriate algorithms to deal with it are thus required at every level. The first crucial step to receive an IR-UWB data packet is signal acquisition. We present a robust and low-complexity algorithm that allows for reliable signal acquisition with an IR-UWB energy-detection receiver in the presence of MUI, even in near-far scenarios. After signal acquisition, the receiver performs a phase of channel estimation. Channel estimation is of particular importance for interference mitigation: it allows the receiver to distinguish the signal of the user of interest from MUI. In the case of energy-detection receivers that are compliant with the IR-UWB standard IEEE 802.15.4a, channel estimation is especially challenging because with this standard the signalling structure changes within a data packet. We introduce a novel receiver structure that takes this peculiarity into account and allows for the design of robust low-complexity receivers for IEEE 802.15.4a networks. The final step in receiving a data packet is demodulation and decoding of the payload. We show that an adaptive thresholding scheme that uses the channel state information, obtained during channel estimation, can yield very good robustness against MUI. We also intr