BLITZ: Wireless Link Quality Estimation in the Dark

Abstract. We present BLITZ, a novel link quality estimator that relies on physical-layer synchronization errors to estimate the expected packet delivery ratio of wireless links. In contrast to all existing link quality estimators which estimate the packet delivery based on statistics from packets that are successfully decoded, our technique works even when packets at the receiver are not correctly received, i.e., when the synchronization fails. The core idea of BLITZ is to exploit informa-tion from chip errors in the received preamble of any transmitted direct sequence spread spectrum signals such as IEEE 802.15.4. Using extensive measurements over cable, wireless static and wireless mobile scenarios, we show that our pro-posed estimator outperforms existing estimators in terms of both accuracy and speed. Across diverse environmental conditions and the full range of possible link qualities, BLITZ provides packet delivery ratio estimates with an absolute error below six percent within just a few milliseconds.

Microcellular Electrode Material for Microbial Bioelectrochemical Systems Synthesized by Hydrothermal Carbonization of Biomass Derived Precursors

V.F. acknowledges a UQ Postdoctoral Fellowship. This work was supported by the Australian Research Council Grant DP110100539. The authors acknowledge the facilities and the scientific and technical assistance of the Australian Microscopy & Microanalysis Research Facility at the Centre for Microscopy and Microanalysis (The University of Queensland). The Ghent University Special Research Fund (BOF) is acknowledged for the postdoctoral grant of M.N.B

PTNet: An efficient and green data center network

International audienceIn recent years, data centers have witnessed an exponential growth for hosting hundreds of thousands of servers as well as to accommodating a very large demand for resources. To fulfill the required level of demand, some approaches tackled network aspects so to host a huge number of servers while others focused on delivering rapid services to the clients by minimizing the path length between any two servers. In general, network devices are often designed to achieve 1:1 oversubscription. Alternatively, in a realistic data center environment, the average utilization of a network could vary between 5% and 25%, and thus the energy consumed by idle devices is wasted. This paper proposes a new parameterizable data center topology, called PTNet. PTNet offers a gradual scalability that interconnects small to large networks covering different ranges of sizes. This new interconnection network provides also a small path length between any two servers even in large sized data centers. PTNet does not only reduce path length and latency, it also uses a power-aware routing algorithm which saves up to 40% of energy with an acceptable computation time. In comparison to existing solutions (e.g. Flatnet, BCube, DCell and Fat-tree), PTNet shows substantial improvements in terms of capacity, robustness, cost-effectiveness and power efficiency: this improvement reaches up to 50% in some cases. (C) 2017 Elsevier Inc. All rights reserved

An empirical study of link quality estimation techniques for disconnection detection in WBANs

Sensor nodes in many Wireless Body Area Network (WBAN) architectures are supposed to deliver sensed data to a gateway node on the body. To satisfy the data delivery requirements, the network needs to adapt itself to the changes in connection status of the body nodes to the gateway. As a prerequisite, Link Quality Estimation (LQE) needs to be done to detect the connection status of the nodes. The quality of links in WBANs is highly time-varying. The LQE technique should be agile to react fast to such link quality dynamics while avoiding frequent fluctuations to reduce the network adaptation overhead. In this paper, we present an empirical study on using different LQE methods for detecting the connection status of body nodes to the gateway in WBANs. A set of experiments using 16 wireless motes deployed on a body are performed to log the behavior of the wireless links. We explore the trade-offs made by each LQE method in terms of agility, stability, and reliability in detecting connection changes by analyzing the experimental data. Moreover, different LQE methods are used in an adaptive multi-hop WBAN mechanism, as a case study, and their impact on the Quality-of-Services (QoS) are investigated. © 2013 ACM

Connectivity Restoration and Amelioration in Wireless Ad-Hoc Networks: A Practical Solution

International audienceConnectivity restoration after a node failure is one of the major issues in wireless ad-hoc networks. In particular, failures can lead to a network partitioning and a huge loss of information. Therefore, a fast mechanism is needed to heal the network between the partitions. In this paper, we consider the scenario where an intermediate node failures and a mobile system is moving autonomously to restore connectivity and provide the best service. We propose a fast connectivity restoration algorithm that is based only on local information. We implement our solution on a real robotic platform and we present some experimental results using a simple case scenario