Felemban E.,University of Umm Al - Qura |
Ekici E.,Ohio State University
IEEE Transactions on Wireless Communications | Year: 2011
Analytical models for IEEE 802.11 Distributed Coordination Function (DCF) play important roles in performance estimation, protocol optimization and admission control for wireless networks utilizing this MAC protocol. While a myriad of models for IEEE 802.11 DCF channel access delay and throughput exist, such models' accuracy is generally limited to rather narrow ranges of scenario parameters. Our investigations single out the inaccuracy in modeling the backoff process as the primary reason for the said deviations. In this paper, we introduce two highly accurate models for IEEE 802.11 DCF protocol in a single-hop setting under both saturated and unsaturated traffic loads. First, a crucial augmentation to the classical model proposed by Bianchi is presented for the saturation load analysis to account for channel state during the backoff countdown process, resulting in a highly accurate estimation of collision probability, channel throughput and channel access delay. We then extend this accurate model to unsaturated traffic cases through an iterative approach which similarly results in highly accurate performance metric estimations for a wide range of parameters. Both models have been evaluated through simulations and in comparison with existing analytical models. © 2011 IEEE. Source
El-Shahawi M.S.,King Abdulaziz University |
Al-Saidi H.M.,University of Umm Al - Qura
TrAC - Trends in Analytical Chemistry | Year: 2013
Recent years have seen an upsurge of interest in developing a low-cost, easy-to-operate, reliable preconcentration technique for precise determination of ultra-trace concentrations of metal ions in aqueous matrices. Dispersive liquid-liquid microextraction (DLLME) is a novel sample-preparation technique offering high enrichment factors from low volumes of water samples.We compare DLLME, cloud-point extraction and other microextraction techniques. We also highlight the current best practices for analysis and chemical speciation of metal ions in highly salted media.We strongly recommend the stripping voltammetric technique at modified electrodes coupled to DLLME and other microextraction techniques to develop low-cost, precise methods for ultra-trace concentrations of metal ions in biological and environmental samples. © 2012. Source
University of Umm Al - Qura | Date: 2015-03-02
The present invention relates to a novel catalyst and a process for a photo-catalytic degradation of ether-based contaminants such as methyl tertiary-butyl ether (MTBE) in water using a visible light source. The catalyst composition demonstrated complete degradation of MTBE at a room temperature in a photo-catalytic reaction conducted using a visible light source.
University of Umm Al - Qura | Date: 2015-07-07
This invention relates to the process of using a catalyst for the photo-catalytic degradation of methyl tertiary butyl ether (MTBE) in water.
University of Umm Al - Qura | Date: 2015-03-18
Knowledge of the vehicles lane position is required for several location-based services such as advanced driver assistance systems, driverless cars, and predicting drivers intent, among many other emerging applications. We present LaneQuest: a system and method that leverages the ubiquitous and low-energy inertial sensors available in commodity smart-phones to provide an accurate estimate of the vehicles current lane. LaneQuest leverages the phone sensors about the surrounding environment to detect the vehicles lane. For example, a vehicle making a right turn most probably will be in the right-most lane, a vehicle passing by a pothole will be in a specific lane and the vehicle angular velocity when driving through a curve reflects its lane. The ambiguous location, sensors noise, and fuzzy lane anchors; LaneQuest employs a novel probabilistic lane estimation algorithm. Furthermore, it uses an unsupervised crowd-sourcing approach to learn the position and lane span distribution of the different lane-level anchors.