In this paper, we introduce a clean-slate architecture for improving the delivery of data packets in IEEE 802.11 wireless mesh networks. Opposed to the rigid TCP/IP layer architecture which exhibits serious deficiencies in such networks, we propose a unitary layer approach that combines both routing and transport functionalities in a single layer. The new Mesh Transmission Layer (MTL) incorporates cross-interacting routing and transport modules for a reliable data delivery based on the loss probabilities of wireless links. Due to the significant drawbacks of standard TCP over IEEE 802.11, we particularly focus on the transport module, proposing a pure rate-based approach for transmitting data packets according to the current contention in the network. By considering the IEEE 802.11 spatial reuse constraint and employing a novel acknowledgment scheme, the new transport module improves both goodput and fairness in wireless mesh networks. In a comparative performance study, we show that MTL achieves up to 48% more goodput and up to 100% less packet drops than TCP/IP, while maintaining excellent fairness results.

There are several applications that use sensor motes and researchers continue to explore additional applications. For this particular application of detecting the movement of humans through the sensor field, a set of Berkley mica2 motes on TinyOS operating system is used. Different sensors such as pressure, light, and so on can be used to identify the presence of an intruder in the field. In our case, the light sensor is chosen for the detection. When an intruder crosses the monitored environment, the system detects the changes of the light values, and any significant change meaning that a change greater than a pre-defined threshold. This indicates the presence of an intruder. An integrated web cam is used to take snapshot of the intruder and transmit the picture through the network to a remote station. The basic motivation of this thesis is that a sensor web system can be used to monitor and detect any intruder in a specific area from a remote location.

No / Initial ranging is the primary and important process in wireless networks for the customer premise equipments (CPEs) to access the network and establish their connections with the base station. Contention may occur during the initial ranging process. To avoid contention, the mandatory solution defined in the standards is based on a truncated binary exponential random backoff (TBERB) algorithm with a fixed initial contention window size. However, the TBERB algorithm does not take into account the possibility that the number of contended CPEs may change dynamically over time, leading to a dynamically changing collision probability. To the best of our knowledge, this is the first attempt to address this issue. There are three major contributions presented in this paper. First, a comprehensive analysis of initial ranging mechanisms in wireless networks is provided and initial ranging request success probability is derived based on number of contending CPEs and the initial contention window size. Second, the average ranging success delay is derived for the maximum backoff stages. It is found that the collision probability is highly dependent on the size of the initial contention window and the number of contending CPEs. To achieve the higher success probability or to reduce the collision probability among CPEs, the BS needs to adjust the initial contention window size. To keep the collision probability at a specific value for the particular number of contending CPEs, it is necessary for the BS to schedule the required size of the initial contention window to facilitate the maximum number of CPEs to establish their connections with reasonable delay. In our third contribution, the initial window size is optimized to provide the least upper bound that meets the collision probability constraint for a particular number of contending CPEs. The numerical results validate our analysis.

No description available.

As a license-exempt technology, Ultra Wideband (UWB) can be used for numerous commercial and military applications, including ranging, sensing, low-range networking and multimedia consumer products. In the networking and consumer fields, the technology is envisioned to reach the mass market, with a very high density of UWB devices per home and office. The technology is based on the concept of transmitting a signal with very low power spectral density (PSD), while occupying a very wide bandwidth. In principle, the low emissions mask protects incumbent systems operating in the same spectrum from being interfered with, while the wide bandwidth offers the possibility of high data rates, in excess of 250 Mbps. UWB has been regulated to operate in the 3.1 to 10.6 GHz portion of the spectrum, with an emissions mask for the lower and upper bands outside this range. The commercial wireless mobile services based on third generation (3G) networks occupy a portion of the spectrum in the 2 GHz band, falling under the UWB emissions mask. UWB and UMTS (Universal Mobile Telephone Systems) devices will coexist, sharing the same spectrum. In this research, we investigate the UWB-3G coexistence problem, analyzing the impact of UWB on UMTS networks. Firstly, we review the mathematical model of the UWB signal, its temporal and spectral properties. We then analyze and model the effects of the UWB signal on a narrowband receiver. Next, we characterize the response of the UMTS receiver to UWB interference, determining its statistical behavior, and establishing a model to replicate it. We continue by proposing a link level model that offers a first order quantitative estimate of the impact of a UWB interferer on a UMTS victim receiver, demonstrating the potentially harmful effect of UWB on the UMTS link. We elaborate on that initial evidence by proposing and implementing a practical systemlevel algorithm to realistically simulate the behavior of the UMTS network in the presence of multiple sources of UWB interference. We complete the research by performing UMTS system level simulations under various conditions of UWB interference, with the purpose of assessing its impact upon a typical UMTS network. We analyze the sensitivity of the main UWB parameters affecting UMTS performance, investigating the coverage and capacity performance aspects of the network. The proposed analysis methodology creates a framework to characterize the impact that mass-deployed UWB can have on the performance of a 3G system. The literature on UWB-3G coexistence is inconclusive, and even contradictory, as to the impact UWB can have on the performance of third-generation wireless networks. While some studies show that UWB can be highly detrimental to 3G networks, others have concluded that both systems can gracefully coexist. Through this study, we found that at the current emissions limits regulated for UWB, a mass uptake of this technology can negatively affect the performance of third-generation (3G) wireless networks. The quality of service experienced by a 3G user in close proximity to an active UWB device can be noticeably degraded, in the form of reduced coverage range, poor voice quality (for a voice call), lower data rates (for a data session) or, in a extreme situation, complete service blockage. As the ratio of UWB devices surrounding a 3G user grows, the degradation becomes increasingly more evident. We determined that in order for UWB tocoexist with 3G networks without causing any performance degradation, a minimum power backoff of 20 dB should be applied to the current emission limits. / Ph. D.

Over the last two decades, wireless technology has become ubiquitous in the United States and other developed countries. Consumer devices such as AM/FM radios, cordless and cellular telephones, pagers, satellite televisions, garage door openers, and television channel changers are just some of the applications of wireless technology. More recently, wireless computer networking has seen increasing employment. A few reasons for this move toward wireless networking are improved electronics transmitters and receivers, reduced costs, simplified installation, and enhanced network expandability. The objective of the study is to generate understanding of the planning inherent in a broadband, fixed wireless telecommunication network and to implement that knowledge into an SDSS. Intermediate steps toward this goal include solutions to both fixed wireless point-to-multipoint (PMP) and fixed wireless mesh networks, which are developed and incorporated into the SDSS. This study explores the use of a Spatial Decision Support System (SDSS) for broadband fixed wireless connectivity to solve the wireless network planning problem. The spatial component of the DSS is a Geographic Information System (GIS), which displays visibility for specific tower locations. The SDSS proposed here incorporates cost, revenue, and performance capabilities of a wireless technology applied to a given area. It encompasses cost and range capabilities of wireless equipment, the customers' propensity to pay, the market penetration of a given service offering, the topology of the area in which the wireless service is proffered, and signal obstructions due to local geography. This research is both quantitative and qualitative in nature. Quantitatively, the wireless network planning problem may be formulated as integer programming problems (IP). The line-of-sight restriction imposed by several extant wireless technologies necessitates the incorporation of a GIS and the development of an SDSS to facilitate the symbiosis of the mathematics and geography. The qualitative aspect of this research involves the consideration of planning guidelines for the general wireless planning problem. Methodologically, this requires a synthesis of the literature and insights gathered from using the SDSS above in a what-if mode. / Ph. D.

Mobile Ad hoc Network (MANET) routing protocols are designed to provide connectivity between wireless mobile nodes that do not have access to high-speed backbone networks. While many unicast MANET protocols have been explored, research involving multicast protocols has been limited. Existing multicast algorithms attempt to reduce routing overhead, but few, if any, attempt to reduce data overhead. The broadcast nature of wireless communication creates a unique environment in which overlaps in coverage are common. When designed properly, a multicast algorithm can take advantage of these overlaps and reduce data overhead. Unlike a unicast route, in which there is one path between a sender and receiver, a multicast tree can have multiple branches between the sender and its multiple receivers. Some of these paths can be combined to reduce redundant data rebroadcasts. The extensions presented in this thesis are a combination of existing and original routing techniques that were designed to reduce data rebroadcasts by aggregating multicast data flows. One such optimization takes advantage of the multipoint relay (MPR) nodes used by the Optimized Link State Routing (OLSR) unicast protocol. These nodes are used in unicast routing to reduce network broadcast, but can be used to help create efficient multicast data flows. Additionally, by listening to routing messages meant for other nodes, a host can learn a bit about its network and may be able to make routing changes that improve the multicast tree. This protocol was implemented as a software router in Linux. It should be emphasized that this is a real implementation and not a simulation. Experiments showed that the number of data packets in the network could be reduced by as much as 19 percent. These improvements were accomplished while using only a small amount of routing overhead. / Master of Science

Traditionally, achieving good performance for a multi-hop wireless network is known to be difficult. The main approach to control the operation of such a network relies on a distributed paradigm, assuming that a centralized approach is not feasible. Relying on a distributed paradigm could be justified at the time when the basic technical building blocks (e.g., node computational power, communication technology, positioning technology) were the bottlenecks. Recent advances and breakthroughs in these technical areas along with the emergence of programmable networks with softwarized control plane intelligence allow us to consider employing a centralized optimization paradigm to control and manage the operation of a multi-hop wireless network. The programmable control provides a platform on which the centralized global network optimization paradigm can be supported. The benefits of a centralized network optimization lie specially in that a network may be configured in such a way that offers optimal performance, which is hardly possible for a network relying on distributed operation. The objectives of this dissertation are to fully understand the potential benefits of a centralized control plane for a multi-hop wireless network, to identify any new challenges under this new paradigm, and to devise innovative solutions for optimal performance via a centralized control plane. Given that the performance of a wireless network heavily depends on its physical layer capabilities, we will consider a number of advanced wireless technologies, including MIMO, full duplex, and interference cancellation at the physical layer. The focus is on building tractable computational models for these wireless technologies that can be used for modeling, analysis and optimization in the centralized control plane. Problem formulation and efficient solution procedures are developed for various centralized optimization problems across multiple layers. End-to-end throughput maximization is a key objective among these optimization problems on the centralized control plane and is used to demonstrate the superior advantage of this paradigm. We study several problems: • Integration of SIC and MIMO DoF IC. We propose to integrate MIMO Degree-of-Freedom (DoF) interface cancellation (IC) and Successive Interference Cancellation (SIC) in MIMO multi-hop network under DoF protocol model. We show that DoF-based IC and SIC can be jointly integrated to combat the interference more effectively and improve the end-to-end throughput significantly. We develop the necessary mathematical models to realize the idea in a multi-hop wireless network. • Full-Duplex MIMO Wireless Networks Throughput. We investigate the performance of MIMO full-duplex (FD) in a multi-hop network. We show that if IC is exploited, MIMO FD can achieve significant throughput gain over MIMO HD in a multi-hop network, which is contrary to the recent literature suggesting an unexpected marginal gain. Our proposed model handles the additional network interference by joint efficient link scheduling and interference cancellation. • PCP in Tactical Wireless Networking. We propose the idea of the Programmable Control Plane (PCP) for the tactical wireless network under the protocol model. PCP decouples the control and data plane and allows the network control layer functionalities to be dynamically configured to adapt to specific wireless channel conditions, customized applications and/or certain tactical situations. The proposed PCP functionalities are cast into a centralized optimization problem, which can be updated as needed and provide a centralized intelligence to manage the operation of a wireless MIMO multi-hop network under the protocol model. • UPCP in Heterogeneous Wireless Networks. We propose the idea of the Unified Programmable Control Plane (UPCP) for tactical heterogeneous wireless networks with interference management capabilities under the SINR model. The UPCP abstracts the complexity of the underlying network comprised of heterogeneous wireless technologies and provides a centralized intelligence over the network resources. We develop necessary mathematical model to realize the UPCP. / Ph. D. / In the past decades, wireless ad hoc communication networks have found a number of applications in both civilian and military environments. Such networks are comprised of a set of smart nodes, which are able to organize themselves into a multi-hop network (able to communicate from the source nodes to the destination nodes across multiple intermediary relay nodes) to provide various services such as unattended and real-time surveillance. Their capabilities of selfform and self-heal make them attractable for network deployment and maintenance, especially in the scenarios where infrastructure is hard to establish. Because of their ease of deployment and independence of infrastructure, wireless ad hoc network have motivated more and more research efforts to sustain their continued growth and well-being. Nevertheless, with rapidly increasing demand for data rate from various applications, we find ourselves still very much in the infancy of the development of such networks, which have the potential to offer orders-of-magnitude higher network-level throughput. Traditionally, the main approach to control the operation of wireless ad hoc network relies on a distributed paradigm, assuming that a centralized approach is not feasible. Relying on a distributed paradigm could be justified at the time when were the bottlenecks. Recent advances and breakthroughs in basic technical areas the basic technical building blocks (e.g., node computational power, communication technology, positioning technology) along with the emergence of programmable networks with softwarized control plane intelligence allow us to consider employing a centralized optimization paradigm to control and manage the operation of a multi-hop wireless network. The objectives of this dissertation are to fully understand the potential benefits of a centralized optimization paradigm in multi-hop wireless network, to identify any new challenges under this new paradigm, and to devise innovative solutions for optimal performance.

No description available.

We consider optimal power allocation policies for a single server, multiuser wireless communication system. The transmission channel may experience multipath fading. We obtain very efficient, low computational complexity algorithms which minimize power and ensure stability of the data queues. We also obtain policies when the users may have mean delay constraints. If the power required is a linear function of rate then we exploit linearity and obtain linear programs with low complexity. We also provide closed-form optimal power policies when there is a hard deadline delay constraint. Later on, we also extend single hop results to multihop networks. First we consider the case, when the transmission rate is a linear function of power. We provide low complexity algorithms for joint routing, scheduling and power control which ensure stability of the queues, certain minimum rates, end-to-end hard deadlines, and/or upper bounds on the end-to-end mean delays. Further we extend these results to the multihop networks where the power is a general monotonically increasing function of rate. For our algorithms, we also provide rates of convergence to the stationary distributions for the queue length process and also approximate end-to-end mean delays. Finally, we provide computationally efficient algorithms that minimize the total power when there is a end-to-end hard deadline delay constraint.