Thesis (M.Sc.)--Memorial University of Newfoundland, 2000. / Bibliography: p. 44-46.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (Doctor of Philosophy in Electrical Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Clark Robertson. Includes bibliographical references (p. 85-87). Also available online.

Interference is fundamental to wireless networks. It is hard to achieve good performance when design routing metrics or algorithms without taking it into account. We study interference in wireless networks through empirical experiments and simulations. We find out that current routing protocols face difficulties in effectively managing it, which can lead to severe problems. For instance, a simple network of two links with one flow is vulnerable to severe performance degradation if interference is not properly accounted for. Motivated by these observations, we develop a simple and effective model to capture effects of interference in a wireless network. Different from the existing interference models, our model captures IEEE 802.11 DCF under both homogeneous and heterogeneous traffic and link characteristics, and is simple enough to be directly used as a basic building block for wireless performance optimization. Based on thismodel, we develop optimization algorithms for several objectives, such as network throughput and fairness. Given traffic demands as input, these algorithms compute rates at which individual flows must send to achieve these objectives. We implement these algorithms in Qualnet simulations and 19-node testbed. Our experiment and simulation results show that our methods can systematically account for and control interference to achieve good performance. More specifically, when optimizing fairness, our methods can achieve almost perfect fairness; when optimizing network throughput, they can lead to 100-200% improvement for UDP traffic and 10-50% for TCP traffic. / text

Heterogeneous cellular networks (HCNs) – comprising traditional macro base stations (BSs) and heterogeneous infrastructure such as microcells, picocells, femtocells and distributed antennas – are fast becoming a cost-effective and essential way of handling explosive wireless data traffic demands. Up until now, little basic research has been done on the fundamentals of managing so much infrastructure – much of it unplanned – together with the carefully planned macro-cellular network. This dissertation addresses the key technical challenges of inter-cell interference management in this new network paradigm. This dissertation first studies uplink femtocell access control in uncoordinated two-tier networks, i.e. where the femtocells cannot coordinate with macrocells. Closed access allows registered home users to monopolize their own femtocell and its backhaul connection, but also results in severe interference between femtocells and nearby unregistered macro users. Open access reduces such interference by handing over such users, at the expense of femtocell resource sharing. In the first analytical work on this topic, we studied the best femtocell access technique from the perspectives of both network operators and femtocell owners, and show that it is strongly contingent on parameters such as multiple access schemes (i.e. orthogonal vs. non- orthogonal) and cellular user density (in TDMA/OFDMA). To study coordinated algorithms whose success depends heavily on the rate and delay (vs. user mobility) of inter-cell overhead sharing, this dissertation develops various models of overhead signaling in general HCNs and derives the overhead quality contour – the achievable set of overhead packet rate and delay – under general assumptions on overhead arrivals and different overhead signaling methods (backhaul and/or wireless). The overhead quality contour is further simplified for two widely used models of overhead arrivals: Poisson and deterministic. Based on the overhead quality contour that is applicable to generic coordinated techniques, this dissertation develops a novel analytical framework to evaluate downlink coordinated multi-point (CoMP) schemes in HCNs. Combined with the signal-to-interference-plus-noise-ratio (SINR) characterization, this framework can be used for a class of CoMP schemes without user data sharing. As an example, we apply it to downlink CoMP inter-cell interference cancellation (ICIC), after deriving SINR results for it using the spatial Poisson Point Process (PPP) to capture the uncertainty in base station locations. / text

We demonstrate the existence of tunable bound-states in continuum (BIC) in a 1-dimensional quantum wire with two impurities by an intense monochromatic radiation field. We found that there is a new type of BIC due to the Fano interference between two optical transition channels, in addition to the ordinary BIC due to a geometrical interference between electron wave functions emitted by impurities. In both cases the BIC can be achieved by tuning the frequency of the radiation field. / text

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Not available / text

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