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Shang W.,Queen's University | Jiang Z.M.,Queen's University | Adams B.,Queen's University | Hassan A.E.,Queen's University | And 3 more authors.
Proceedings - Working Conference on Reverse Engineering, WCRE | Year: 2011

A great deal of research in software engineering focuses on understanding the dynamic nature of software systems. Such research makes use of automated instrumentation and profiling techniques after fact, i.e., without considering domain knowledge. In this paper, we turn our attention to another source of dynamic information, i.e., the Communicated Information (CI) about the execution of a software system. Major examples of CI are execution logs and system events. They are generated from statements that are inserted intentionally by domain experts (e.g., developers or administrators) to convey crucial points of interest. The accessibility and domain-driven nature of the CI make it a valuable source for studying the evolution of a software system. In a case study on one large open source and one industrial software system, we explore the concept of CI and its evolution by mining the execution logs of these systems. Our study illustrates the need for better trace ability techniques between CI and the Log Processing Apps that analyze the CI. In particular, we find that the CI changes at a rather high rate across versions, leading to fragile Log Processing Apps. 40% to 60% of these changes can be avoided and the impact of 15% to 50% of the changes can be controlled through the use of the robust analysis techniques by Log Processing Apps. We also find that Log Processing Apps that track implementation-level CI (e.g., performance analysis) are more fragile than Log Processing Apps that track domain-level CI (e.g., workload modeling), because the implementation-level CI is often short-lived. © 2011 IEEE.


Malik H.,Queen's University | Adams B.,Queen's University | Hassan A.E.,Queen's University | Flora P.,Research in Motion RIM | Hamann G.,Research in Motion RIM
Proceedings - International Computer Software and Applications Conference | Year: 2010

Enterprise systems are load tested for every added feature, software updates and periodic maintenance to ensure that the performance demands on system quality, availability and responsiveness are met. In current practice, performance analysts manually analyze load test data to identify the components that are responsible for performance deviations. This process is time consuming and error prone due to the large volume of performance counter data collected during monitoring, the limited operational knowledge of analyst about all the subsystem involved and their complex interactions and the unavailability of up-to-date documentation in the rapidly evolving enterprise. In this paper, we present an automated approach based on a robust statistical technique, Principal Component Analysis (PCA) to identify subsystems that show performance deviations in load tests. A case study on load test data of a large enterprise application shows that our approach do not require any instrumentation or domain knowledge to operate, scales well to large industrial system, generate few false positives (89% average precision) and detects performance deviations among subsystems in limited time. © 2010 IEEE.


Malik H.,Queen's University | Jiang Z.M.,Queen's University | Adams B.,Queen's University | Hassan A.E.,Queen's University | And 2 more authors.
Proceedings of the European Conference on Software Maintenance and Reengineering, CSMR | Year: 2011

Load testing is crucial to uncover functional and performance bugs in large-scale systems. Load tests generate vast amounts of performance data, which needs to be compared and analyzed in limited time across tests. This helps performance analysts to understand the resource usage of an application and to find out if an application is meeting its performance goals. The biggest challenge for performance analysts is to identify the few important performance counters in the highly redundant performance data. In this paper, we employed a statistical technique, Principal Component Analysis (PCA) to reduce the large volume of performance counter data, to a smaller, more meaningful and manageable set. Furthermore, our methodology automates the process of comparing the important counters across load tests to identify performance gains/losses. A case study on load test data of a large enterprise application shows that our methodology can effectively guide performance analysts to identify and compare top performance counters across tests in limited time. © 2010 IEEE.


Hayward T.J.,U.S. Navy | Dhakal S.,U.S. Navy | Dhakal S.,Research in Motion RIM
Journal of the Acoustical Society of America | Year: 2012

The change-of-variables theorem of probability theory is applied to compute acoustic field and array beam power probability density functions (pdfs) in uncertain ocean environments represented by stratified, attenuating ocean waveguide models. Computational studies for one and two-layer waveguides investigate the functional properties of the acoustic field and array beam power pdfs. For the studies, the acoustic parameter uncertainties are represented by parametric pdfs. The field and beam response pdfs are computed directly from the parameter pdfs using the normal-mode representation and the change-of-variables theorem. For two-dimensional acoustic parameter uncertainties of sound speed and attenuation, the field and beam power pdfs exhibit irregular functional behavior and singularities associated with stationary points of the mapping, defined by acoustic propagation, from the parameter space to the field or beam power space. Implications for the assessment of orthogonal polynomial expansion and other methods for computing acoustic field pdfs are discussed. © 2012 U. S. Government.


Al-Khasib T.,University of British Columbia | Al-Khasib T.,Research in Motion RIM | Shenouda M.B.,University of British Columbia | Lampe L.,University of British Columbia
IEEE Transactions on Wireless Communications | Year: 2011

In this paper, we study the problem of resource allocation and optimization for multiple-input multiple-output (MIMO) cognitive radio (CR) systems under the assumption of imperfect channel state information (CSI) of the channels between the secondary users (SUs) and the primary users (PUs) at the SUs. We formulate robust design optimization problems for CR systems with one or more SUs communicating over a single or multiple frequency carriers in the presence of multiple PUs. We propose a linear matrix inequality (LMI) transformation that facilitates proper treatment of channel uncertainty at the SU transmitter and we provide solutions to the design problems based on convex optimization and Lagrange dual decomposition techniques. Finally, we demonstrate the importance of the proposed formulations and the implications of ignoring channel uncertainties when designing for CR systems. © 2006 IEEE.


Bakr M.H.,McMaster University | Ghassemi M.,McMaster University | Sangary N.,Research in Motion RIM
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2011

We present a novel approach for extending the bandwidth of narrow band antennas exploiting geometry evolution. The geometry of the antenna is allowed to evolve subject to constraints on the shape feasibility. The sensitivities of the objective function with respect to the coordinates of a number of control vertices are utilized to determine how the shape evolves. We illustrate our approach by showing that a narrow band antenna can be evolved to an Ultra Wide Band (UWB) antenna using our approach. © 2011 IEEE.


Ghassemi M.,McMaster University | Bakr M.H.,McMaster University | Sangary N.,Research in Motion RIM
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2012

This paper presents an approach for reducing the size of multi-input multi-output (MIMO) system antennas. In this approach, we minimize the spacing between elements such that both the return loss of each element and the coupling between any two elements are less than 10 dB. To reduce the spacing, the shape of individual antenna elements is allowed to evolve using a gradient-based optimization. Adjoint sensitivities are utilized to efficiently solve the optimization problem. We illustrate this approach by designing a 1-by-2 ultra-wideband (UWB) microstrip MIMO array. © 2012 IEEE.


Zhang Y.,Research In Motion RIM | Sampalli S.,Dalhousie University
2010 IEEE 6th International Conference on Wireless and Mobile Computing, Networking and Communications, WiMob'2010 | Year: 2010

Denial of Service (DoS) attacks on 802.11 wireless LANs can be caused by management frames sent by rogue access points. Unfortunately, such attacks can be successful even if the wireless network is protected by a high-level security protocol such as WiFi Protected Access Version 2 (WPA2). We present a novel client-based scheme for the prevention of such intrusions. By using a Medium Access Control (MAC) filtering mechanism, the "smart" client is able to differentiate between legitimate and forged management frames. The proposed mechanism is non-cryptographic, has low overheads and can be deployed in existing IEEE 802.11 WLANs. We have built and tested a prototype of our scheme. We demonstrate that our mechanism can protect wireless clients against management frame DoS attacks launched at the MAC layer. © 2010 IEEE.


Wong M.,Research in Motion RIM | Sebak A.R.,Concordia University at Montréal | Sebak A.R.,King Saud University | Denidni T.A.,INRS EMT
IEEE Transactions on Antennas and Propagation | Year: 2012

The design, simulation, and measurement of a complete microstrip line-fed dielectrically guided horn antenna are presented. The proposed antenna achieves similarly high gains as compared to traditional air-filled horn antennas, is simpler than a typical array design, and can easily be fabricated using typical two dimensional substrate machining processes. An H-guide, operating in the fundamental TE 00 mode, slowly tapers into a "gapped" H-guide, or dielectrically guided horn, where a large air gap separates the center dielectric and metallic plates. A wideband Bézier shaped microstrip to H-guide transition feeding structure is fabricated using a low loss Rogers 5880 substrate and integrated with the proposed antenna. The fabricated prototype operates from 8 to 16 GHz with a peak gain of approximately 16 dBi. © 2011 IEEE.


Balakrishnan D.,Research in Motion RIM | Nayak A.,University of Ottawa
IEEE Transactions on Parallel and Distributed Systems | Year: 2012

Due to the heterogeneity involved in smart interconnected devices, cellular applications, and surrounding (GPS-aware) environments there is a need to develop a realistic approach to track mobile assets. Current tracking systems are costly and inefficient over wireless data transmission systems where cost is based on the rate of data being sent. Our aim is to develop an efficient and improved geographical asset tracking solution and conserve valuable mobile resources by dynamically adapting the tracking scheme by means of context-aware personalized route learning techniques. We intend to perform this tracking by proactively monitoring the context information in a distributed, efficient, and scalable fashion. Context profiles, which indicate the characteristics of a route based on environmental conditions, are utilized to dynamically represent the values of the asset's properties. We designed and implemented an adaptive learning based scheme that makes an optimized judgment of data transmission. This manuscript is complemented with theoretical and practical evaluations that prove that significant costs can be saved and operational efficiency can be achieved. © 2006 IEEE.

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