The cellular industry is undergoing a major paradigm shift from voice-centric, structured homogeneous networks to a more data-driven, distributed and heterogeneous architecture. One of the more promising trends emerging from this cellular revolution is femtocells. Femtocells are primarily viewed as a cost-effective way to improve both capacity and indoor coverage, and they enable offloading data-traffic from macrocell network. However, efficient interference management in co-channel deployment of femtocells remains a challenge. Decentralized strategies such as femtocell access control have been identified as an effective means to mitigate cross-tier interference in two-tier networks. Femtocells can be configured to be either open access or closed access. Prior work on access control schemes show that, in the absence of any coordination between the two tiers in terms of power control and user scheduling, closed access is the preferred approach at high user densities. Present methods suggest that in the case of orthogonal multiple access schemes like TDMA/OFDMA, femtocell access control should be adaptive according to the estimated cellular user density. The approach we follow, in this work, is to adopt an open access policy at the femtocell access points with a cap on the maximum number of users allowed on a femtocell. This ensures the femto owner retains a significant portion of the femtocell resources. We design an iterative algorithm for hybrid access control for femtocells that integrates the problems of uplink power control and base station assignment. This algorithm implicitly adapts the femtocell access method to the current user density. The distributed power control algorithm, which is based on Yates' work on standard interference functions, enables users to overcome the interference in the system and satisfy their minimum QoS requirements. The optimal allocation of femtocell resources is incorporated into the access control algorithm through a constrained sum-rate maximization to protect the femto owner from starvation at high user densities. The performance of a two-tier OFDMA femtocell network is then evaluated under the proposed access scheme from a home owner viewpoint, and network operator perspective. System-level simulations show that the proposed access control method can provide a rate gain of nearly 52% for cellular users, compared to closed access, at high user densities and under moderate-to-dense deployment of femtocells. At the same time, the femto owner is prevented from going into outage and only experiences a negligible rate loss. The results obtained establish the quantitative performance advantage of using hybrid access at femtocells with power control at high user densities. The convergence properties of the proposed iterative hybrid access control algorithm are also investigated by varying the user density and the mean number of femto access points in the network. It is shown that for a given system model, the algorithm converges quickly within thirty iterations, provided a feasible solution exists.

Judges and lawyers have embraced class proceedings as fulfilling an access to justice objective. In the more than fifteen years since the introduction of class proceedings legislation in Ontario, however, few have sought to evaluate whether or to what extent class actions have improved access to justice. The author begins to fill that void by first exploring various meanings of access to justice, and then examining in detail the initiation and settlement of class actions, and the controversial issue of counsel fees, using both doctrinal analysis and empirical data representing the class action practices of more than 75 plaintiff-side lawyers. She concludes that there are several aspects of class action practice and jurisprudence that fall short of advancing access to justice to its fullest extent, and calls for further socio-legal analysis to measure the impact, and evaluate the success, of class actions.

The objectives of this thesis are to: 1) obtain a snapshot of callers of 211 Toronto, a free information and referral service, understanding how representative they are of Toronto’s general population; 2) understand how 211 Toronto callers seeking health-related information use the information they obtain when contacting the service and their overall level of satisfaction, and; 3) better understand the experience and information needs of recent immigrants struggling to navigate an unfamiliar health care system. The study had three phases: 1) a cross-sectional phone interview with 211 Toronto callers; 2) a follow-up phone interview of 211 Toronto callers who had asked health-related questions; and, 3) qualitative interviews with callers who were Spanish speakers from Latin American countries. Participants were randomly selected adult callers living within the boundaries of Toronto’s Census Metropolitan Area (CMA). Respondents were compared with the general adult population living in Toronto’s CMA, using 2001 Census data, to identify under- or overrepresented population groups. A sub-set of callers who had asked health-related questions was followed up to understand how they had used the information received and their level of satisfaction with the service. Qualitative interviews were conducted with callers who were recent immigrants and native Spanish speakers from Latin America to explore their post-migration experiences. Recent immigrants experience significant information challenges. Health-related questions reflect the multifaceted nature of the concept of health in the experience of users. Negative experiences with the health care system are common. Recent immigrants have access to disorganized, confusing, often poor quality information. 211 Toronto represents an efficient and effective way to gain access to information but does not achieve its full potential. Newcomers should receive timely, appropriate, and reliable information on existing health and health-related services as soon as possible after they relocate to Canada. Appropriate information should also be made available to potential immigrants in their countries of origin. Information and communication technologies should be used to support newcomers, increasing the efficiency and effectiveness of services such as 211 Toronto.

Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2007-09-27 21:48:20.594 / Wireless networks are less reliable than wired networks because channels are “exposed” to the surrounding environment that is susceptible to interference and noise. To minimize losses of data due to collisions, wireless networks need a mechanism to regulate the access on the transmission medium. Medium Access Control (MAC) protocols control access to the shared communication medium so that it can be used efficiently. In this thesis, we first describe the collision-controlled Dual Prohibition Multiple Access (DPMA) protocol [45]. The main mechanisms implemented in DPMA, such as binary dual prohibition, power control, interference control, and support for differentiated services (DiffServ), are presented in detail. We conducted a thorough simulation study on DPMA protocol from several aspects. First, we conduct simulations to observe the effects of binary competition number (BCN), unit slot length and safe margin on the performance of DPMA. Secondly, the DiffServ capability of DPMA is demonstrated through simulation results. Finally, we compare the DPMA protocol with the CSMA/CA protocol and find that DPMA with optimal configuration has better performance than CSMA/CA under both low and high network density. / Master

This thesis presents several simple, robust, and optimal resource management schemes for multihop wireless access networks with the main focus on multi-channel wireless mesh networks (MC WMNs). In this regard, various resource management optimization problems are formulated arid efficient algorithms are proposed to solve each problem. First, we consider the channel as signment problem in MC-WMNs and formulate different resource management problems within the general framework of network utility maximization (NUM). Unlike most of the previously proposed channel assignment schemes, our algorithms can not only assign the orthogonal (i.e., non-overlapped) channels, but also partially overlapped channels. This better utilizes the avail able frequency spectrum as a critical resource in MC-WMNs. Second, we propose two distributed random medium access control (MAC) algorithms to solve a non-convex NUM problem at the MAC layer. The first algorithm is fast, optimal, and robust to message loss and delay. It also only requires a limited message passing among the wireless nodes. Using distributed learning techniques, we then propose another NUM-based MAC algorithm which achieves the optimal performance without frequent message exchange. Third, based on our results on random MAC, we develop a distributed multi-interface multi-channel random access algorithm to solve the NUM problem in MC-WMNs. Different from most of the previous channel assignment schemes in the literature, where channel assignment is intuitively modeled in the form of combinatorial and discrete optimization problems, our scheme is based on formulating a novel continuous optimization model. This makes the analysis and implementation significantly easier. Finally, we consider the problem of pricing and monetary exchange in multi-hop wireless access networks, where each intermediate node receives a payment to compensate for its offered packet forwarding service. In this regard, we propose a market-based wireless access network model with two-fold pricing. It uses relay-pricing to encourage collaboration among the access points. It also uses interference pricing to leverage optimal resource management. In general, this thesis widely benefits from several mathematical techniques as both modeling and solution tools to achieve simple, robust, optimal, and practical resource management strategies for future wireless access networks.

This study highlights the role of humanitarian diplomacy to obtain humanitarian access to civilian victims of forced confinement in the municipality of Samaniego, Colombia. Humanitarian diplomacy is made of humanitarian negotiations, coordination and advocacy to provide suffering-alleviation to victims of armed conflicts, and these components will be discussed thoroughly. To inquire in the use of humanitarian diplomacy by international relief organizations, interviews with thirteen humanitarian workers, two public officers and a human rights worker were conducted. The findings, which are complemented with humanitarian and human rights reports and framed in the theoretical discussion, will be the base to discuss whether humanitarian diplomacy contributed to gain humanitarian access in villages of Samaniego facing restrictions in the mobility of civilians and limitations in the supply of basic means of livelihood and humanitarian assistance.

This thesis examines the problem of using 802.11 hotspots for vehicular Internet access. In this access paradigm, a user in a vehicle performs batch transfers by opportunistically communicating with roadside 802.11 access points while driving along a highway. Despite the short connection duration, a significant amount of data can be transferred. Because complete coverage is not needed, this method of Internet access provides a low-cost alternative to using cellular technology for applications that can tolerate some delay and require large data transfer such as sending or receiving music, movies, or digital photographs. Although vehicular opportunistic connections offer the potential to transfer a large of amount of data, utilizing this potential is non-trivial because existing transport and data-link layer network protocols were not designed for this use. This thesis presents an experimental analysis of transport and data-link layer protocol operation at a level of detail not previously explored. We identify ten problems that cause a reduction of up to 50% of the amount of data that could have been transferred in this scenario. Our primary finding is that transmission errors during connection setup and inadequate MAC data rate selection are the main causes of the under-utilization of the connection. Based on these findings we make preliminary recommendations for best practices for using vehicular opportunistic connections. In particular, we argue that overall throughput could be significantly improved if environmental information was available to the lower layer network protocols.

This thesis examines the problem of using 802.11 hotspots for vehicular Internet access. In this access paradigm, a user in a vehicle performs batch transfers by opportunistically communicating with roadside 802.11 access points while driving along a highway. Despite the short connection duration, a significant amount of data can be transferred. Because complete coverage is not needed, this method of Internet access provides a low-cost alternative to using cellular technology for applications that can tolerate some delay and require large data transfer such as sending or receiving music, movies, or digital photographs. Although vehicular opportunistic connections offer the potential to transfer a large of amount of data, utilizing this potential is non-trivial because existing transport and data-link layer network protocols were not designed for this use. This thesis presents an experimental analysis of transport and data-link layer protocol operation at a level of detail not previously explored. We identify ten problems that cause a reduction of up to 50% of the amount of data that could have been transferred in this scenario. Our primary finding is that transmission errors during connection setup and inadequate MAC data rate selection are the main causes of the under-utilization of the connection. Based on these findings we make preliminary recommendations for best practices for using vehicular opportunistic connections. In particular, we argue that overall throughput could be significantly improved if environmental information was available to the lower layer network protocols.

We consider the distributed access enforcement problem for Role-Based Access Control (RBAC) systems. Such enforcement has become important with RBAC's increasing adoption, and the proliferation of data that needs to be protected. We provide a platform for assessing candidates for access enforcement in a distributed architecture for enforcement. The platform provides the ability to encode data structures and algorithms for enforcement, and to measure time-, space- and administrative efficiency. To validate our platform, we use it to compare the state of the art in enforcement, CPOL [6], with two other approaches, the directed graph and the access matrix [9, 10]. We consider encodings of RBAC sessions in each, and propose and justify a benchmark for the assessment. We conclude with the somewhat surprising observation that CPOL is not necessarily the most efficient approach for access enforcement in distributed RBAC deployments.

This thesis addresses the problem of usability in the context of administration of access control systems. We seek to relate the notion of declarative semantics, a recurring theme in research in access control, with usability. We adopt the concrete context of POSIX ACLs and the traditional interface for it that comprises two utilities getfacl and setfacl. POSIX ACLs are the de facto standard to which POSIX conformant systems such as Linux and OpenBSD adhere. The natural semantics of getfacl and setfacl is operational. By operational we mean that the semantics of these are speci ed procedurally. We have designed and implemented an alternate interface that we call askfacl whose natural semantics is declarative. Declarative semantics means "what you see is what it is." We also discuss our design of askfacl and articulate the following thesis that underlies our work: If the natural semantics of the interface for ACLs is declarative, then a user is able to more quickly, accurately and confidently, inspect and edit ACLs than if the semantics is operational. To validate our thesis we conducted a between participant human-subject usability study with 42 participants. The results of our study measurably demonstrate the goodness of declarative semantics in access control.