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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 Montreal | 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.

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.

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.

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.

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