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Showing papers by "Mehran Abolhasan published in 2015"


Journal ArticleDOI
TL;DR: This article presents a new network architecture that eliminates the need of multi-hop flooding for route discovery, thereby enabling WDNs to scale and substantially improve scalability and reliability of Wdns, especially in mobile environments.
Abstract: Scalability is a key issue in large scale WDNs, such as vehicular networks and device-to-device networks. To address the issue, this article extends the SDN concept, and presents a new network architecture that eliminates the need of multi-hop flooding for route discovery, thereby enabling WDNs to scale. The key idea of the new architecture is to split network control and data forwarding by using two separate frequency bands. Another important aspect of the architecture is that computational complexity of routing is split between the SDN controller and the forwarding nodes, thereby allowing nodes to make distributed routing decisions. As a result, network control of the new architecture has a hybrid structure, which improves the operability and scalability of large scale WDNs. Our case study shows that the new architecture is able to substantially improve scalability and reliability of WDNs, especially in mobile environments.

71 citations


Journal ArticleDOI
TL;DR: A conditional gradient descent method is developed, which performs gradient descent on the boundary of the search space and projects out-of-boundary points back into the space and can achieve 92% of the efficiency of perfectly aligned coils in 90% of operations.
Abstract: To maximize power transfer for inductively charging electric vehicles (EVs), charger and battery coils must be aligned. Wireless sensors can be installed to estimate misalignments; however, existing ranging techniques cannot satisfy the precision requirements of the misalignment estimation. We propose a high-precision wireless ranging and misalignment estimation scheme, where high precision is achieved by iteratively measuring, estimating, and aligning the coils. Another key aspect is to convert the nonconvex misalignment estimation to a more tractable problem with a convex objective. We develop a conditional gradient descent method to solve the problem, which performs gradient descent (or conditional gradient descent on the boundary of the search space) and projects out-of-boundary points back into the space. Employing experimentally validated models, we show that our scheme can achieve 92% of the efficiency of perfectly aligned coils in 90% of operations, and tolerate correlated distance measurement errors. In contrast, the prior art is susceptible to correlation, undergoing a significant efficiency degradation of 18.5%.

47 citations


Journal ArticleDOI
TL;DR: A clique-based software-defined online network management approach is proposed that captures traffic imbalance and fluctuation of small cells and optimally plans frequencies, infrastructures, and network structure at any instant.
Abstract: Network planning is facing new and critical challenges due to ad hoc deployment, unbalanced and drastically varying traffic demands, as well as limited backhaul and hardware resources in emerging small cell architectures. We discuss the application of graph theory to address the challenges. A clique-based software-defined online network management approach is proposed that captures traffic imbalance and fluctuation of small cells and optimally plans frequencies, infrastructures, and network structure at any instant. Its applications to three important small cell scenarios of cloud radio, point-to-point microwave backhaul, and interoperator spectrum sharing are demonstrated. Comparison studies show that in each of the scenarios, this new approach is able to significantly outperform conventional static offline network planning schemes in terms of throughput and satisfaction levels of small cells with regard to allocated bandwidths. Specifically, the throughput can be improved by 155 percent for the cloud radio scenario and 110.95 percent for the microwave backhaul scenario. The satisfaction level can be improved by 40 percent for interoperator spectrum sharing.

24 citations


Proceedings ArticleDOI
01 Jan 2015
TL;DR: A cooperative coverage hole recovery model is proposed which utilises the simple geometrical procedure of circle inversion, and the performance of the proposed model performance is compared with a force-based approach.
Abstract: Unlike sporadic node failures, coverage holes emerging from multiple temporally-correlated node failures can severely affect quality of service in a network and put the integrity of entire wireless sensor networks at risk. Conventional topology control schemes addressing such undesirable topological changes have usually overlooked the status of participating nodes in the recovery process with respect to the deployed sink node(s) in the network. In this paper, a cooperative coverage hole recovery model is proposed which utilises the simple geometrical procedure of circle inversion. In this model, autonomous nodes consider their distances to the deployed sink node(s) in addition to their local status, while relocating towards the coverage holes. By defining suitable metrics, the performance of our proposed model performance is compared with a force-based approach.

6 citations


Journal ArticleDOI
TL;DR: Good agreement between the model and experimental data was obtained over short-range communication links, demonstrating the suitability of the model in urban VANETs.

5 citations


Proceedings ArticleDOI
03 Dec 2015
TL;DR: A novel primitive for self-organization amongst multiple coexisting Wireless Body Area Networks (WBANs) that allows for coexisting WBANs to use delayed information from previous transmissions to adjust to a collision-free TDMA schedule amongst each other for future communications.
Abstract: This paper presents a novel primitive for self-organization amongst multiple coexisting Wireless Body Area Networks (WBANs). It follows a biologically inspired approach based on the theory of pulse-coupled oscillators. Our proposal allows for coexisting WBANs to use delayed information from previous transmissions to adjust to a collision-free TDMA schedule amongst each other for future communications. Most importantly, it does not require a global coordinator as all nodes achieve synchronization in a completely self-organized manner. Simulation results show that our protocol achieves a significantly fast convergence time despite little information from its coexisting networks. Moreover, the proposed approach is shown to be robust to variations in channel conditions, density of sensor nodes within each network and the number of coexisting WBANs. We conduct extensive simulations to evaluate the efficiency of the proposed protocol using the NS-2 simulator.

4 citations