Publications

Documents

Order by : Name | Date | Hits [ Ascendant ]

Architectures and protocols for fast identification in large-scale RFID systems Architectures and protocols for fast identification in large-scale RFID systems

hot!
Date added: 02/12/2015
Date modified: 02/12/2015
Filesize: 286 Bytes
Downloads: 918

Passive tags based on backscattered signals yield low energy consumption for large-scale applications of RFIDs. In this paper, system architectures and protocol enhancements for fast identifications in ISO/IEC 18000-6C systems that integrate UWB technology are investigated. The anti-collision protocol is studied by considering various tag populations. A novel algorithm is proposed to adapt the UHF air interface parameters with the use of UWB ranging information. The results show that the proposed algorithm yields up to 25% potential performance improvement compared to the ISO/IEC 18000-6C standard.

Compressed Sensing Reconstruction of Convolved Sparse Signals Compressed Sensing Reconstruction of Convolved Sparse Signals

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 957

This paper addresses the problem of efficient sampling and reconstruction of sparse spike signals, which have been convolved with low-pass filters. A modified compressed sensing (CS) framework is proposed, termed dictionary-based deconvolution CS (DDCS) to achieve this goal. DDCS builds on the assumption that a low-pass filter can be represented sparsely in a dictionary of blurring atoms. Identification of both the sparse spike signal and the sparsely parameterized blurring function is performed by an alternating scheme that minimizes each variable independently, while keeping the other constant. Simulation results reveal that the proposed DDSS scheme achieves an improved reconstruction performance when compared to traditional CS recovery.

Random Sensing Order in Cognitive Radio Systems: Performance Evaluation and Optimization Random Sensing Order in Cognitive Radio Systems: Performance Evaluation and Optimization

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 949

Developing an efficient spectrum access policy enables cognitive radios to dramatically increase spectrum utilization while assuring predetermined quality of service levels for the primary users. In this abstract, modeling, performance evaluation, and optimization of a distributed secondary network with random sensing order policy are studied. Specifically, the secondary users create a random order of the available channels upon primary users return, and then find an optimal transmission opportunity in a distributed manner. After modeling the behavior of the SUs by a Markov chain, the average throughputs of the secondary users and interference level among the secondary and primary users are evaluated. Then, a maximization of the secondary network performance in terms of throughput while keeping under control the average interference is proposed. A simple and practical adaptive algorithm is developed to optimize the network. Interestingly, the proposed algorithm follows the variations of the wireless channels in non-stationary conditions and outperforms even static brute force optimization, while demanding few computations. Finally, numerical results are provided to demonstrate the efficiencies of the proposed schemes. It is shown that fully distributed algorithms can achieve substantial performance improvements in cognitive radio networks without the need of centralized management or message passing among the users.

Reaction-Diffusion on Dynamic Inhibition Areas: A Bio-Inspired Link Scheduling Algorithm Reaction-Diffusion on Dynamic Inhibition Areas: A Bio-Inspired Link Scheduling Algorithm

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 1088

We present the Dynamic Inhibition Areas Reaction-Diffusion (DIA-RD) algorithm, a distributed medium access control protocol that globally maximizes the spatial reusability (number of simultaneous transmissions per unit area) of wireless sensor networks. This algorithm is able, in consequence, to minimize the number of time slots needed to schedule the set of demanded links, making it very efficient to solve the Shortest Link Schedule problem. DIA-RD combines accurate interference management, provided by the use of dynamic inhibition areas based on the physical interference model; and global intelligent behavior, provided by the bio-inspired technique known as Reaction-Diffusion. This technique ensures global convergence to dense feasible transmission patterns (no active link inside the inhibition area of other active link) in a decentralized way. Experimental results show that our DIA-RD algorithm provides superior performance, in terms of spatial reusability, than the best state-of-the-art approaches, namely the DIA-LS, RD-MAC, GOW* and ML2 S algorithms.

Dynamic Optimization of Generalized Least Squares Handover Algorithms Dynamic Optimization of Generalized Least Squares Handover Algorithms

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 932

Efficient handover algorithms are essential for highly performing mobile wireless communications. These algorithms depend on numerous parameters, whose settings must be appropriately optimized to offer a seamless connectivity. Nevertheless, such an optimization is difficult in a time varying context, unless adaptive strategies are used. In this paper, a new approach for the handover optimization is proposed. First, a new modeling of the handover process by a hybrid system that takes as input the handover parameters is established. Then, this hybrid system is used to pose some dynamical optimization approaches where the probability of outage and the probability of handover are considered. Since it is shown that these probabilities are difficult to compute, simple approximations of adequate accuracy are developed. Based on these approximations, a new approach to the solution of the handover optimizations is proposed. A distributed optimization algorithm is then developed to maximize handover performance. From an extensive set of results obtained by numerical computations and simulations, it is shown that the proposed algorithm improves performance of the handover considerably when compared to more traditional approaches.

Optimizing Client Association for Load Balancing and Fairness in Millimeter-Wave Wireless Networks Optimizing Client Association for Load Balancing and Fairness in Millimeter-Wave Wireless Networks

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 985

Millimeter-wave communications in the 60-GHz band are considered one of the key technologies for enabling multigigabit wireless access. However, the special characteristics of such a band pose major obstacles to the optimal utilization of the wireless resources, where the problem of efficient client association to access points (APs) is of vital importance. In this paper, the client association in 60-GHz wireless access networks is investigated. The AP utilization and the quality of the rapidly vanishing communication links are the control parameters. Because of the tricky nonconvex and combinatorial nature of the client association optimization problem, a novel solution method is developed to guarantee balanced and fair resource allocation. A new distributed, lightweight, and easy-to-implement association algorithm, based on Lagrangian duality theory and subgradient methods, is proposed. It is shown that the algorithm is asymptotically optimal, that is, the relative duality gap diminishes to zero as the number of clients increases.

Joint Sensor Selection and Multihop Routing for Distributed Estimation in Ad-hoc Wireless Sensor Net Joint Sensor Selection and Multihop Routing for Distributed Estimation in Ad-hoc Wireless Sensor Net

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 1112

This paper considers the problem of power-efficient distributed estimation of vector parameters related to localized phenomena so that both sensor selection and routing structure in a Wireless Sensor Network (WSN) are jointly optimized to obtain the best possible estimation performance at a given querying node, for a given total power budget. First, we formulate our problem as an optimization problem and show that it is an NP-Hard problem. Then, we design two algorithms: a Fixed-Tree Relaxation-Based Algorithm (FTRA) and a very efficient Iterative Distributed Algorithm (IDA) to optimize the sensor selection and routing structure. We also provide a lower bound for our optimization problem and show that our IDA provides a performance that is close to this bound, and it is substantially superior to the previous approaches presented in the literature. An important result from our work is the fact that because of the interplay between communication cost and estimation gain when fusing measurements from different sensors, the traditional Shortest Path Tree (SPT) routing structure, widely used in practice, is no longer optimal. To be specific, our routing structure provides a better trade-off between the overall power efficiency and estimation accuracy. Comparing to more conventional sensor selection and fixed routing algorithms, our proposed algorithms yield a significant amount of energy saving for the same estimation accuracy.

Harmonizing MAC and Routing in Low Power and Lossy Networks Harmonizing MAC and Routing in Low Power and Lossy Networks

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 910

Medium access control (MAC) and routing protocols are fundamental blocks in the design of low power and lossy networks (LLNs). As new networking standards are being proposed and different existing research solutions patched, evaluating the performance of the network becomes challenging. Specific solutions that can be individually efficient, when stacked together may have unexpected effects on the overall network behavior. In this paper, we provide an analysis of the fundamental MAC and routing protocols for LLNs: IEEE 802.15.4 MAC and IETF RPL. Moreover, a characterization of their cross-layer interactions is presented by a mathematical description, which is essential to truly understand the protocols mutual effects and their dynamics. Novel metrics that guide the interaction between MAC and routing are compared to existing metrics. Furthermore, a protocol selection mechanism is implemented to select the appropriate routing metric and MAC parameters given specific performance constraints. Analytical and experimental results show that the behavior of the MAC protocol can hurt the performance of the routing protocol and vice versa, unless these two are carefully optimized together.

Auction-based Resource Allocation in 60 GHz mmW Wireless Access Networks Auction-based Resource Allocation in 60 GHz mmW Wireless Access Networks

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 984

The resource allocation problem of optimal assignment of the stations to the available access points in 60 GHz millimeterWave wireless access networks is investigated. The problem is posed as a multi-assignment optimization problem. The proposed solution method converts the initial problem to a minimum cost flow problem and allows to design an efficient algorithm by a combination of auction algorithms. The solution algorithm exploits the network optimization structure of the problem, and thus is much more powerful than computationally intensive general-purpose solvers. Theoretical and numerical results evince numerous properties, such as optimality, convergence, and scalability in comparison to existing approaches.

Duty-Cycle Optimization for IEEE 802.15.4 Wireless Sensor Networks Duty-Cycle Optimization for IEEE 802.15.4 Wireless Sensor Networks

hot!
Date added: 02/11/2015
Date modified: 02/11/2015
Filesize: 286 Bytes
Downloads: 945

Most applications of wireless sensor networks require reliable and timely data communication with maximum possible network lifetime under low traffic regime. These requirements are very critical especially for the stability of wireless sensor and actuator networks. Designing a protocol that satisfies these requirements in a network consisting of sensor nodes with traffic pattern and location varying over time and space is a challenging task. We propose an adaptive optimal duty-cycle algorithm running on top of the IEEE 802.15.4 medium access control to minimize power consumption while meeting the reliability and delay requirements. Such a problem is complicated because simple and accurate models of the effects of the duty cycle on reliability, delay, and power consumption are not available. Moreover, the scarce computational resources of the devices and the lack of prior information about the topology make it impossible to compute the optimal parameters of the protocols. Based on an experimental implementation, we propose simple experimental models to expose the dependency of reliability, delay, and power consumption on the duty cycle at the node and validate it through extensive experiments. The coefficients of the experimental-based models can be easily computed on existing IEEE 802.15.4 hardware platforms by introducing a learning phase without any explicit information about data traffic, network topology, and medium access control parameters. The experimental-based model is then used to derive a distributed adaptive algorithm for minimizing the power consumption while meeting the reliability and delay requirements in the packet transmission. The algorithm is easily implementable on top of the IEEE 802.15.4 medium access control without any modifications of the protocol. An experimental implementation of the distributed adaptive algorithm on a test bed with off-the-shelf wireless sensor devices is presented. The experimental performance of the algorithms is compared to the existing solutions from the literature. The experimental results show that the experimental-based model is accurate and that the proposed adaptive algorithm attains the optimal value of the duty cycle, maximizing the lifetime of the network while meeting the reliability and delay constraints under both stationary and transient conditions. Specifically, even if the number of devices and their traffic configuration change sharply, the proposed adaptive algorithm allows the network to operate close to its optimal value. Furthermore, for Poisson arrivals, the duty-cycle protocol is modeled as a finite capacity queuing system in a star network. This simple analytical model provides insights into the performance metrics, including the reliability, average delay, and average power consumption of the duty-cycle protocol.