A Three-Dimensional Angular Scattering Response Including Path Powers

In this paper the angular power spectrum exhibited under a three-dimensional (3-D) Gaussian scatter distribution at fixed observation points in space is investigated. Typically, these correspond to the mobile and base units respectively. Unlike other spatial channel models, the derived model accounts for the distance to each scatterer from the observation point and transforms distances into power values under the assumption of free-space propagation. The proposed 3-D spatial channel model follows a non-central approach in terms of the scatter distribution in space, which means that the angular power field at the base unit need not be due to a scatter distribution centered exactly at the mobile. Derivations are provided for the angular and power domains and as shown by conditioning the distance, the angular field reduces to the von-Mises Fisher distribution. Most importantly, this work undertakes the problem of a Gaussian angular power spectrum observed in radio propagation channel measurements and provides a formal theoretical framework of the experimental investigations found in literature. The proposed model denotes that a Gaussian scatterer distribution in space gives rise to a Gaussian angular power spectrum and a Gaussian angular power density in the azimuth and elevations fields. The proposed 3-D spatial channel model might be used for evaluating the performance of current and future multi-element wireless communication networks

Link Quality and Path Based Clustering in IEEE802.15.4-2015 TSCH Networks

International audienceAdvance clustering techniques have been widely used in Wireless Sensor Networks (WSNs) since they can potentially reduce latency, improve scheduling, decrease end-to-end delay and optimise energy consumption within a dense network topology. In this paper, we present a novel clustering algorithm for high density IEEE 802.15.4-2015 Time-SlottedChannel Hopping (TSCH). In particular, the proposed methodology merges a variety of solutions into an integrated clustering design. Assuming an homogeneous network distribution, the proposed configuration deploys a hierarchical down-top approach of equally numbered sub-groups, in which the formation of the separate sub-groups is adapted to the network density and the node selection metric is based on the link quality indicator. The presented algorithm is implemented in Contiki Operating System(OS) and several test vectors have been designed in order to evaluate the performance of the proposed algorithm in a COOJA simulation environment. Performance results demonstrate the capability of the clustering structure since compared to the default scheme it significantly improves the energy efficiency up to 35%, packet drops more than 40% as well the packet retransmission rate. Last but not least, the outcome of this study indicates a major increase in the network lifetime,i.e., up to50%