Ghassemi M.,McMaster University |
Bakr M.,McMaster University |
Sangary N.,Research in Motion RIM Ltd
IET Microwaves, Antennas and Propagation | Year: 2013
The authors present a new approach for evolutionary antenna design. Through exploiting efficient adjoint sensitivity analysis techniques, the antenna structure evolves to better satisfy the design constraints. The coordinates of a selected number of control vertices are chosen as optimisation parameters thus enabling evolution to arbitrary shapes. The authors approach is illustrated through the design of a number of microstrip structures. © The Institution of Engineering and Technology 2013.
Samuel H.,University of Waterloo |
Zhuang W.,University of Waterloo |
Preiss B.,Research in Motion RIM Ltd
Eurasip Journal on Wireless Communications and Networking | Year: 2011
With limited coverage of wireless networks and frequent roaming of mobile users, providing a seamless communication service poses a technical challenge. In our previous research, we presented a supernode system architecture that employs the delay-tolerant network (DTN) concept to provide seamless communications for roaming users over interconnected heterogeneous wireless networks. Mobile ad hoc networks (MANETs) are considered a key component of the supernode system for services over an area not covered by other wireless networks. Within the super node system, a dominating-set routing technique is proposed to improve message delivery over MANETs and to achieve better resource utilization. The performance of the dominating-set routing technique depends on estimation accuracy of the probability of a future contact between nodes. This paper studies how node mobility can be modeled and used to better estimate the probability of a contact. We derive a distribution for the node-to-node intermeeting time and present numerical results to demonstrate that the distribution can be used to improve the dominating-set routing technique performance. Moreover, we investigate how the distribution can be employed to relax the constraints of selecting the dominating-set members in order to improve the system resource utilization. © 2011 Hany Samuel et al.
Pourahmadi V.,University of Waterloo |
Kohandani F.,Research in Motion RIM Ltd |
Mobasher A.,Research in Motion RIM Ltd
IEEE Vehicular Technology Conference | Year: 2010
We investigate how accurate Kronecker model is compared to Spatial Channel Model (SCM) for MIMO link layer simulations. The simulation results show that Kronecker model is a good approximation for MIMO in link layer simulations compared to SCM. ©2010 IEEE.
Bakr M.H.,McMaster University |
Ali S.M.,Research in Motion RIM Ltd |
Warden J.,Research in Motion RIM Ltd |
Sheynman A.,Research in Motion RIM Ltd
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2012
In this article, we introduce an effective approach for dynamic impedance tuning of antenna matching circuits in both the transmitting and receiving modes. The tuning problem is described mathematically by a system of two nonlinear equations. These nonlinear equations are constructed by perturbing the tunable components of the matching circuit. We introduce a closed form solution to the proposed system of equations in addition to a numerical one. The outcome of our algorithm is the exact calculation of the instantaneous antenna input impedance. This impedance is then used to determine the optimal matching circuit values. The proposed algorithm takes place on the handset in real-time. Additionally, it does not limit the number of tunable components of the tunable matching circuit as the computational overhead is independent of their cardinality. The proposed approach can also be expanded to the case of real-time broadband tuning of antennas in a dynamic environment. © 2011 Wiley Periodicals, Inc.
Ebrahimi M.,Research in Motion RIM Ltd |
Harrison R.M.,Research in Motion RIM Ltd |
Jia Y.,Research in Motion RIM Ltd
IEEE Vehicular Technology Conference | Year: 2011
In this paper, a framework for designing transmit diversity schemes for LTE PUCCH format 1b with channel selection is introduced. The design criterion is to utilize the same number of orthogonal resources as in the single transmit antenna mode while exploiting the full diversity order. It is shown that the code design is decoupled into resource coding and modulation coding. A sample code is presented and its performance is compared with single antenna transmission. © 2011 IEEE.