Opportunistic Spectrum Sharing using Dumb Basis Patterns: The Line-of-Sight Interference Scenario

We investigate a spectrum-sharing system with non-severely faded mutual interference links, where both the secondary-to-primary and primary-to-secondary channels have a Line-of-Sight (LoS) component. Based on a Rician model for the LoS channels, we show, analytically and numerically, that LoS interference hinders the achievable secondary user capacity. This is caused by the poor dynamic range of the interference channels fluctuations when a dominant LoS component exists. In order to improve the capacity of such system, we propose the usage of an Electronically Steerable Parasitic Array Radiator (ESPAR) antenna at the secondary terminals. An ESPAR antenna requires a single RF chain and has a reconfigurable radiation pattern that is controlled by assigning arbitrary weights to M orthonormal basis radiation patterns. By viewing these orthonormal patterns as multiple virtual dumb antennas, we randomly vary their weights over time creating artificial channel fluctuations that can perfectly eliminate the undesired impact of LoS interference. Because the proposed scheme uses a single RF chain, it is well suited for compact and low cost mobile terminals

Spectrum Sensing Via Reconfigurable Antennas: Is Cooperation of Secondary Users Indispensable?

This work presents an analytical framework for characterizing the performance of cooperative and noncooperative spectrum sensing schemes by figuring out the tradeoff between the achieved diversity and coding gains in each scheme. Based on this analysis, we try to answer the fundamental question: can we dispense with SUs cooperation and still achieve an arbitrary diversity gain? It is shown that this is indeed possible via a novel technique that can offer diversity gain for a single SU using a single antenna. The technique is based on the usage of a reconfigurable antenna that changes its propagation characteristics over time, thus creating an artificial temporal diversity. It is shown that the usage of reconfigurable antennas outperforms cooperative as well as non-cooperative schemes at low and high Signal-to-Noise Ratios (SNRs). Moreover, if the channel state information is available at the SU, an additional SNR gain can also be achieved.Comment: Accepted for IEEE WCNC 201

Utilization of the dynamic laser scanning technology for monitoring, locating and classification of the city trees.

One of the significant issues related to the city trees is the transmission overhead cables damages caused by the trees growth that would sometime generate power disconnections. Currently the city progress monitoring technologies have three major challenges. Firstly, the spatial resolution of the collected data is critical factor in all monitoring technologies that would reflect the utilization of the extracted data and physical consistency with the ground features. Secondly, the temporal resolution where in all progress monitoring or change detection technologies the duration and time coverage is a basic for validating extracted features. Finally, the human resources and the operational capital is also primary cost when monitoring city trees is needed on a regular basis. Therefore, the research is intended to verify the feasibility of allocating the trees that overheads the electrical cables especially where the transmission overhead cables passing the forests. The area of interest is extended along the highways where most of the overhead cables are placed. The research is utilizing the dynamic laser scanning system for progress monitoring and spatially locating the well recognized and accessed city trees