We consider a lossy multicast network in which the reliability is provided by means of Random Linear Network Coding. Our goal is to characterise the performance of such network in terms of the probability that a source message is delivered to all destination nodes. Previous studies considered coding over large finite fields, small numbers of destination nodes or specific, often impractical, channel conditions. In contrast, we focus on a general problem, considering arbitrary field size and number of destination nodes, as well as a realistic channel. We propose a lower bound on the probability of successful delivery, which is more accurate than the approximation commonly used in the literature. In addition, we present a novel performance analysis of the systematic version of RLNC. The accuracy of the proposed performance framework is verified via extensive Monte Carlo simulations, where the impact of the network and code parameters are investigated. Specifically, we show that the mean square error of the bound for a ten-user network can be as low as 9 · 10 −5 for non-systematic RLNC.
Demographic changes such as the ageing population and the continuous rise of chronic medical conditions such as obesity, diabetes and depression make our healthcare systems economically unsustainable. Sensing technologies are promising solutions that can provide cost-effective answers to these challenges. In this paper, we focus on long-term in-house activity monitoring that aims at early detection and prevention of such conditions. In this context, we present and experimentally evaluate an ultra low-power (less than 100-μW long-term average power consumption) on-body activity sensing prototype system that is based on Bluetooth low energy (BLE). As part of a larger smart home monitoring architecture, the role of the presented system is to collect and reliably deliver acceleration data to the upper layers of the architecture. The system evaluation incorporates a thorough power consumption study that facilitates meaningful battery lifetime estimations, an insightful coverage study in an actual residential environment, and the investigation of energy-efficient packet loss mitigation techniques.
Abstract-In this paper, we analyze the performance of a single-relay network in which the reliability is provided by means of Random Linear Network Coding (RLNC). We consider a scenario when both source and relay nodes can encode packets. Unlike the traditional approach to relay networks, we introduce a passive relay mode, in which the relay node simply retransmits collected packets in case it cannot decode them. In contrast with the previous studies, we derive a novel theoretical framework for the performance characterization of the considered relay network. We extend our analysis to a more general scenario, in which coding coefficients are generated from non-binary fields. The theoretical results are verified using simulation, for both binary and non-binary fields. It is also shown that the passive relay mode significantly improves the performance compared with the active-only case, offering an up to two-fold gain in terms of the decoding probability. The proposed framework can be used as a building block for the analysis of more complex network topologies.
In this paper, we introduce error correction to the Bluetooth Low Energy (BLE) standard by utilising data redundancy provided by the Cyclic Redundancy Check (CRC) code used to detect erroneous packets. We assume a scenario with an energy-constrained transmitter and a constraint-free infrastructure, which allows us to introduce additional signal processing at the receiving side while keeping the transmitter intact. A novel approach of applying iterative decoding techniques to the BLE CRC code is investigated in this work. By using these techniques and real BLE packets collected in an office environment, we show that by enabling CRC error correction, the sensitivity of the BLE receiver can be improved by up to 3 dB. At the same time, up to 60% of corrupted packets can be corrected, which directly translates to a significant reduction in the number of retransmissions and a noticeable energy saving.
In this paper, we investigate various methods to combat packet loss in a residential communication system based on the Bluetooth Low Energy (BLE) standard, focusing on BLE's connectionless mode (undirected advertising) in which no retransmissions are possible. We start by introducing two orthogonally polarised antennas at the receiver, thus improving the probability of successful reception. This is followed by enabling error correction using redundancy introduced by the Cyclic Redundancy Check (CRC) code of BLE. The CRC error correction is based on a novel approach of applying iterative decoding algorithms. We then consider a BLE system deployed in a residential environment and utilise the presence of multiple receivers that are necessary to provide coverage. These three techniques come at no cost for the transmitter, thus preserving its energy efficiency. The final technique deals with error control coding in the application layer, in which some redundancy is added at the transmitter before data is sent to the physical layer. By combining all four methods, a distributed error correction algorithm is developed. Using real BLE packets collected in a typical 2-storey house, it is shown that the designed system can correct 80% of all corrupted packets.
General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms 1 Timing Channels in Bluetooth Low Energy Xenofon Fafoutis, Member, IEEE, Evgeny Tsimbalo, Student Member, IEEE, and Robert Piechocki Abstract-This letter introduces timing channels in connectionless Bluetooth Low Energy (BLE). The proposed standardcompliant enhancement, BLE-TC (BLE with Timing Channels), improves the energy efficiency of an energy-constrained connectionless BLE transmitter by encoding additional information in the interarrival time between BLE advertisements. BLE-TC is analytically compared to the connectionless BLE standard. Using realistic timing noise that is empirically determined through a proof-of-concept-implementation, the results indicate that more than 10% improvement in energy efficiency can be achieved for low-throughput applications, such as smart metering and environmental sensing for smart cities.
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