Dynamic Topology Adaptation Based on Adaptive Link Selection Algorithms for Distributed Estimation

This paper presents adaptive link selection algorithms for distributed estimation and considers their application to wireless sensor networks and smart grids. In particular, exhaustive search--based least--mean--squares(LMS)/recursive least squares(RLS) link selection algorithms and sparsity--inspired LMS/RLS link selection algorithms that can exploit the topology of networks with poor--quality links are considered. The proposed link selection algorithms are then analyzed in terms of their stability, steady--state and tracking performance, and computational complexity. In comparison with existing centralized or distributed estimation strategies, key features of the proposed algorithms are: 1) more accurate estimates and faster convergence speed can be obtained; and 2) the network is equipped with the ability of link selection that can circumvent link failures and improve the estimation performance. The performance of the proposed algorithms for distributed estimation is illustrated via simulations in applications of wireless sensor networks and smart grids.Comment: 14 figure

Efficient Covariance Matrix Reconstruction with Iterative Spatial Spectrum Sampling

This work presents a cost-effective technique for designing robust adaptive beamforming algorithms based on efficient covariance matrix reconstruction with iterative spatial power spectrum (CMR-ISPS). The proposed CMR-ISPS approach reconstructs the interference-plus-noise covariance (INC) matrix based on a simplified maximum entropy power spectral density function that can be used to shape the directional response of the beamformer. Firstly, we estimate the directions of arrival (DoAs) of the interfering sources with the available snapshots. We then develop an algorithm to reconstruct the INC matrix using a weighted sum of outer products of steering vectors whose coefficients can be estimated in the vicinity of the DoAs of the interferences which lie in a small angular sector. We also devise a cost-effective adaptive algorithm based on conjugate gradient techniques to update the beamforming weights and a method to obtain estimates of the signal of interest (SOI) steering vector from the spatial power spectrum. The proposed CMR-ISPS beamformer can suppress interferers close to the direction of the SOI by producing notches in the directional response of the array with sufficient depths. Simulation results are provided to confirm the validity of the proposed method and make a comparison to existing approachesComment: 14 pages, 8 figure

Study of Robust Adaptive Beamforming Algorithms Based on Power Method Processing and Spatial Spectrum Matching

Robust adaptive beamforming (RAB) based on interference-plus-noise covariance (INC) matrix reconstruction can experience performance degradation when model mismatch errors exist, particularly when the input signal-to-noise ratio (SNR) is large. In this work, we devise an efficient RAB technique for dealing with covariance matrix reconstruction issues. The proposed method involves INC matrix reconstruction using an idea in which the power and the steering vector of the interferences are estimated based on the power method. Furthermore, spatial match processing is computed to reconstruct the desired signal-plus-noise covariance matrix. Then, the noise components are excluded to retain the desired signal (DS) covariance matrix. A key feature of the proposed technique is to avoid eigenvalue decomposition of the INC matrix to obtain the dominant power of the interference-plus-noise region. Moreover, the INC reconstruction is carried out according to the definition of the theoretical INC matrix. Simulation results are shown and discussed to verify the effectiveness of the proposed method against existing approaches.Comment: 7 pages, 2 figure

Evaluation and Selection of the MEUST Submarine Site

http://meust.cnrs.fr/MEUST_site_choice_report.pdfThis report summarizes the results of the investiga tions performed to select the MEUST submarine site. Measurement campaigns have been conducted during 2012 on several locations off shore of Toulon. During this period the most distant site has s hown a higher sensitivity to bioluminescence seasonal variations, whereas the more coastal sites had simila r conditions as Antares. This observation combined with logistic constraints leads to select a site located at similar latitude as Antares but more western on the other side of the CC5 telecommunication cable to Cors ica. The route of the MEUST Main Electro-Optical Cable has been defined accordingly, with some flexib ility to allow fine tuning of its end point as function of the outcome of the final site characterizations scheduled in 2013

Six Improved Cameroonian Potato Varieties Introduced In Vitro Through Meristem Culture

Introduction:Availability of disease-free, high yielding potato planting material is a major challenge to producers. This study focused on evaluating the ability of locally improved varieties to be introduced for the first time in vitro. Meristem tip culture was used to regenerate in vitro plantlets from improved potato varieties in Cameroon. Materials and methods: Six varieties including Cipira, Mafo, Jacob 2005, Bambui Wonder, Tubira and Irad 2005 were taken from IRAD potato breeding program. Ten meristems were cultured per replicate (4) per variety.The number of meristem tips sprouting, rooting, the number of nodes and shoot length were recorded weekly over a period of 4 weeks. Results and discussion: Meristem tips of all potato varieties regenerated plantlets with vigorous shoots and roots. Sprouting began in the first week and ranged from 40% (Tubira) to 75% (Cipira and Jacob 2005). Rooting began in the 2nd week and ranged from 7.5 % (Cipira) to 37.5 % (Irad 2005 and Tubira). Regenerated shoots of all varieties had nodes averaging from 10.0 to 12.5, thus ready for micro-propagation. Conclusion: All six improved potato varieties can be introduced in vitro for rapid multiplication of planting material. Regenerated plantlets should be serologically tested to check they are free from diseases especially viruses