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Statistical analysis of multiuser and narrowband interference and superior system designs for impulse radio ultra-wide bandwidth wireless
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- Author / Creator
- Shao, Hua
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Ultra-wide bandwidth (UWB) wireless is a fast emerging technology which exploits major advances and offers unprecedented opportunity to impact wireless communications. In UWB systems, several users should coexist viably in the same coverage area. The multiuser interference (MUI) caused by asynchronous transmissions in UWB systems is difficult to eliminate, and becomes a limit to the system performance. It has been shown that the MUI in impulse radio (IR) UWB systems is impulse-like, and poorly approximated by a Gaussian distribution. Therefore, the performance of the conventional matched filter (CMF), which is the optimal receiver structure for signals embedded in additive white Gaussian noise (AWGN), degrades severely when the interference is significant, and alternative models for the MUI are thus motivated. Novel models which can provide more accurate descriptions of the UWB MUI than the Gaussian model are proposed, and new receiver structures are designed based on these novel models. It is shown that these new receiver designs can outperform the CMF receiver which is used extensively in UWB systems, and the performance gain is significant in interference-limited scenarios. Channel coding is an effective method to overcome the effects of noise and interference encountered in the transmission of signals through channels, where some redundancy is introduced in a controlled manner in the information sequence. Early studies of IR UWB systems used the repetition code for signaling and considered the Gaussian distribution for modeling the total disturbance in the channel. However, the repetition code is a trivial channel coding scheme and not all the potentials are explored by this channel code. On the other hand, the Gaussian distribution is not necessarily valid for modeling the disturbance in UWB wireless with the presence of the MUI. A framework for evaluating the coding performance of IR UWB systems is constructed where a more accurate model for the disturbance is adopted. This framework represents valuable tools for evaluating the coding performance of IR UWB wireless, especially when long codes are adopted or low data levels are of interest, cases where system performance evaluation based on simulation is time-consuming or impossible. More generally, these tools can also be applied to other communication systems where the ambient noise shares similar characteristics with the disturbance in IR UWB systems. The huge bandwidth brings unique advantages to UWB, but it also brings challenges to UWB system deployment. The UWB band overlaps with several frequency bands already allocated to established narrowband (NB) services. Successful deployment of UWB systems requires that UWB devices contend and coexist with services operating within the dedicated bands. Therefore, the coexistence problem between UWB and narrowband systems and the effects of their mutual interference are topics that warrant investigation. Two effective UWB sequence designs are proposed to suppress the mutual interference between NB and UWB systems, which clears a crucial hurdle for UWB device deployment. These designs can adapt to the spectral occupancy state of current channels; this information can be provided by cognitive radio (CR) or by a priori knowledge of the spectrum usage in the network.
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- Graduation date
- Fall 2011
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.