WiFi can be used to provide cost-effective last-mile IP connectivity to rural users. In initial rollout, hotspots or hotzones can be positioned at community centres such as schools, clinics, hospitals or call-centres. The research will investigate maximizing coverage using physical and higher layer techniques. The study will consider a typical South African rural region, with telecommunications services traffic estimates. The study will compare several IEEE 802.11 deployment options based on the requirements of the South African case in order to recommend options that improve performance. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

Exploiting the available diversity from various sources in wireless networks is an easy way to improve performance at the expense of additional hardware, space, complexity and/or bandwidth. Signal space diversity (SSD) and cooperative communication are two promising techniques that exploit the available signal space and space diversity respectively. This study first presents symbol error rate (SER) analysis of an SSD system containing a single transmit antenna and N receive antennas with maximal-ratio combining (MRC) reception; thereafter it presents a simplified maximum-likelihood (ML) detection scheme for SSD systems, and finally presents the incorporation of SSD into a distributed switch and stay combining with partial relay selection (DSSC-PRS) system. Performance analysis of an SSD system containing a single transmit antenna and multiple receive antennas with MRC reception has been presented previously in the literature using the nearest neighbour (NN) approximation to the union bound, however results were not presented in closed form. Hence, closed form expressions are presented in this work. A new lower bound for the SER of an SSD system is also presented which is simpler to evaluate than the union bound/NN approximation and also simpler to use with other systems. The new lower bound is based on the minimum Euclidean distance of a rotated constellation and is termed the minimum distance lower bound (MDLB); it is also presented here in closed form. The presented bounds have been validated with simulation and found to be tight under certain conditions. The SSD scheme offers error performance and diversity benefits with the only penalty being an increase in detector complexity. Detection is performed in the ML sense and conventionally, all points in an M-ary quadrature amplitude modulation (M-QAM) constellation are searched to find the transmitted symbol. Hence, a simplified detection scheme is proposed that only searches m symbols from M after performing initial signal conditioning. The simplified detection scheme is able to provide SER performance close to that of optimal ML detection in systems with multiple receive antennas. Cooperative communication systems can benefit from the error performance and diversity gains of the spectrally efficient SSD scheme since it requires no additional hardware, bandwidth or transmit power. Integrating SSD into a DSSC-PRS system has shown an improvement of approximately 5dB at an SER of 10-4 with a slight decrease in spectral efficiency at low SNR. Analysis has been performed using the newly derived MDLB and confirmed with simulation. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

Wireless Sensor Networks (WSNs) are infrastructureless wireless networks that combine sensing, embedded computing, and wireless networking technologies together. Despite the diversity of WSN applications, some functionalities are so fundamental that they are required by most WSN applications. We call them the fundamental services as we believe these services are most important and indispensable for a wide variety of WSNs applications. In this thesis work, we investigate solutions to three fundamental services, namely, localization service, joint scheduling service, and adaptive sampling service. Sim-ulation results and experimental results on real testbed demonstrate the effectiveness and efficiency of these solutions. Our solutions to these fundamental services can serve as the basic building blocks in most applications with WSNs.

This dissertation discusses some techniques to improve the medium access control in infrastructure multi channel wireless local area networks. Medium Access Control protocols (MAC) coordinate the stations and resolve the channel contentions so that scarce radio resources are shared fairly and efficiently amongst participating users. We propose different models to improve the medium access control performance. The models deal with improving the channel access and allocation. By proposing some backoff strategies for the collided users to retransmit, the performance is improved. A comparison amongst the proposed models is shown. We also investigate the quality of service provisioning in infrastructure-based wireless local area networks medium access control. We propose a multiple class traffic model to support quality of service. This model is a cross-layer model as we consider the error in the transmitted state. We also propose models for uplink channel utilizations for data channel transmissions that can be applied to different WLANs. Finally, we propose an integrated model that deals with error in both the request and data transmissions. That model applies in the single class and quality of service support models we develop. In this dissertation, we propose four techniques to improve the medium access control frame utilization by developing four backoff strategies to reduce the collision on the request channels. We propose a cross-layer model for the error control protocol. We propose another model for uplink channel utilization for data transmission in one class of traffic. We also propose a quality of service support model so high priority users get better performance compared to low priority class traffic. Furthermore, we propose cross-layer design for data transmission to guarantee safe data delivery to the receiver for the QoS model. Finally, we propose a model for uplink channel utilization in the QoS model. This model can be applied to different WLANs standards. This model also includes the channel error in both the request and data channels.

Conventional Wi-Fi location estimation techniques using radio fingerprinting typically require a lengthy initial site survey. It is suggested that the lengthy site survey is a barrier to adoption of the radio fingerprinting technique. This research investigated two methods for reducing or eliminating the site survey and instead build the radio map on-the-fly. The first approach utilized a deterministic algorithm to predict the user's location near each access point and subsequently construct a radio map of the entire area. This deterministic algorithm performed only fairly and only under limited conditions, rendering it unsuitable for most typical real-world deployments. Subsequently, a probabilistic algorithm was developed, derived from a robotic mapping technique called simultaneous localization and mapping. The standard robotic algorithm was augmented with a modified particle filter, modified motion and sensor models, and techniques for hardware-agnostic radio measurements (utilizing radio gradients and ranked radio maps). This algorithm performed favorably when compared to a standard implementation of the radio fingerprinting technique, but without needing an initial site survey. The algorithm was also reasonably robust even when the number of available access points were decreased.

Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (p. 67-68).

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 6 uppsatser.

Thesis (M.Eng.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 98-102.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 110-117) Also available in print.

Thesis (Ph.D.)--University of Melbourne, Dept. of Electrical and Electronic Engineering, 2008. / Typescript. Includes bibliographical references (leaves 149-158).