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Winnipeg, Canada

Phunchongharn P.,University of Manitoba | Hossain E.,University of Manitoba | Le L.B.,University of Quebec | Camorlinga S.,Trlabs
IEEE Transactions on Wireless Communications

We study the robust transmission scheduling and power control problem for spectrum sharing between secondary and primary users in a spatial reuse time-division multiple access (STDMA) network. The objective is to find a robust minimum-length schedule for secondary users (in terms of time slots) subject to the interference constraints for primary users and the traffic demand of secondary users. We consider the fact that power allocation based on average (or estimated) link gains can be improper since actual link gains can be different from the average link gains. Therefore, transmission of the secondary links may fail and require more time slots. We also consider this demand uncertainty arising from channel gain uncertainty. We propose a column generation-based algorithm to solve the scheduling and power control problem for secondary users. The column generation method breaks the problem down to a restricted master problem and a pricing problem. However, the classical column generation method can have convergence problem due to primal degeneracy. We propose an improved column generation algorithm to stabilize and accelerate the column generation procedure by using the perturbation and exact penalty methods. Furthermore, we propose an efficient heuristic algorithm for the pricing problem based on a greedy algorithm. For the simulation scenario considered in this paper, the proposed stabilized column generation algorithm can obtain the optimal schedules with 18.85% reduction of the number of iterations and 0.29% reduction of the number of time slots. Also, the heuristic algorithm can achieve the optimality with 0.39% of cost penalty but 1.67 × 10 4 times reduction of runtime. © 2002-2012 IEEE. Source

Chieochan S.,University of Manitoba | Hossain E.,University of Manitoba | Diamond J.,Trlabs
IEEE Communications Surveys and Tutorials

Efficient channel assignment is crucial for successful deployment and operation of IEEE 802.11-based WLANs. In this article we present a survey on the state of the art channel assignment schemes in IEEE 802.11-based WLANs. After detailing out all the schemes, we provide a qualitative comparison among different schemes in terms of algorithm execution behaviors, complexity, and scalability. We then conclude the survey with several research issues open for further investigation. © 2010 IEEE. Source

Mousavi P.,Trlabs | Miners B.,Intelligent Mechatronic Systems | Basir O.,Intelligent Mechatronic Systems
IEEE Antennas and Wireless Propagation Letters

A wideband circularly polarized L-shaped monopole slot antenna with a single C-shaped feed is designed and fabricated. The measured results demonstrate that the antenna has an axial ratio (AR) < dB, a reflection coefficient <-10 dB, and 23% circular polarization (CP) bandwidth. The monopole quarter-wavelength slot antenna design occupies half of the area on the corner of circuit board as compared to a half-wavelength slot antenna thatrequires double the area at the center of the board. This feature is attractive for compact wireless devices that operate at low frequencies in which planning for the smallest circuit board area combined with the shortest length for signal routing are the two major concerns. The antenna is extremely low-cost and does not require any truncation corner, reflector surfaces, or via connections, all of which increase the fabrication cost. © 2010 IEEE. Source

Shrestha B.,University of Manitoba | Hossain E.,University of Manitoba | Camorlinga S.,Trlabs
IEEE Transactions on Information Technology in Biomedicine

In wireless personal area networks, such as wireless body-area sensor networks, stations or devices have different bandwidth requirements and, thus, create heterogeneous traffics. For such networks, the IEEE 802.15.4 medium access control (MAC) can be used in the beacon-enabled mode, which supports guaranteed time slot (GTS) allocation for time-critical data transmissions. This paper presents a general discrete-time Markov chain model for the IEEE 802.15.4-based networks taking into account the slotted carrier sense multiple access with collision avoidance and GTS transmission phenomena together in the heterogeneous traffic scenario and under nonsaturated condition. For this purpose, the standard GTS allocation scheme is modified. For each non-identical device, the Markov model is solved and the average service time and the service utilization factor are analyzed in the non-saturated mode. The analysis is validated by simulations using network simulator version 2.33. Also, the model is enhanced with a wireless propagation model and the performance of the MAC is evaluated in a wheelchair body-area sensor network scenario. © 2006 IEEE. Source

Mousavi P.,Trlabs | Mousavi P.,University of Alberta
IEEE Transactions on Antennas and Propagation

The concept, design procedure, and measurement results of a novel low profile integrated monopole slots antenna for multiband multipolarization applications are presented. The antenna operates at both GPS and Iridium frequencies of 1.575 GHz and 1.62 GHz with circular polarization and GSM850/GSM900/DCS/PCS bands with a vertical linear polarization. The antenna meets stringent requirements on pattern/polarization performance in all bands. The antenna structure is based on an L-shaped monopole slot with a C-shaped feed to generate a wideband circular polarization. With the integration of two monopole slots inside this structure, the antenna covers quad-band GSM. The integrated monopole slots antenna occupies half of the area on the corner of a circuit board compared to a half-wavelength slot antenna that requires a larger area at the center of the board. This is an attractive feature for compact low frequency telematics devices, whose circuit board floor planning and signal routing are major concerns. © 2011 IEEE. Source

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