5 research outputs found

    Asynchronous two-way ranging using Tomlinson-Harashima precoding and UWB signaling

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    This paper demonstrates two methods which simultaneously undertake synchronization and ranging based on a time-of-arrival approach with bidirectional communication to bypass the need for accurate synchronous clocking. In order to alleviate multipath effects, Tomlinson-Harashima precoding and UWB signaling are used to measure the distance between pairs of sensors. The proposed schemes are shown to be effective under certain assumptions and the analysis is supported by simulation and numerical studies. Copyright (C) 2008 Chih-Yu Wen et al

    Frequency Rendezvous and Physical Layer Network Coding for Distributed Wireless Networks

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    In this thesis, a transmission frequency rendezvous approach for secondary users deployed in decentralized dynamic spectrum access networks is proposed. Frequency rendezvous is a critical step in bootstrapping a wireless network that does not possess centralized control. Current techniques for enabling frequency rendezvous in decentralized dynamic spectrum access networks either require pre-existing infrastructure or use one of several simplifying assumptions regarding the architecture, such as the use of regularly spaced frequency channels for communications. Our proposed approach is designed to be operated in a strictly decentralized wireless networking environment, where no centralized control is present and the spectrum does not possess pre-defined channels. In our proposed rendezvous algorithm, the most important step is pilot tone detection and receiver query. In order to realize a shortest search time for the target receiver, an efficient scanning rule should be employed. In this thesis, three scanning rules are proposed and evaluated, namely: frequency sequence scanning, pilot tone strength scanning, and cluster scanning. To validate our result, we test our scanning rules with actual paging band spectrum measurements. Previous research on security of network coding focuses on the protection of data dissemination procedures and the detection of malicious activities such as pollusion attacks. The capabilities of network coding to detect other attacks has not been fully explored. In this thesis, a new mechanism based on physical layer network coding to detect wormhole attacks is proposed. When two signal sequences collide at the receiver, the difference between the two received sequences is determined by its distances to the senders. Therefore, by comparing the differences between the received sequences at two nodes, we can estimate the distance between them and detect those fake neighbor connections through wormholes. While the basic idea is clear, we design many schemes at both physical and network layers to turn the idea into a practical approach. Simulations using BPSK modulation at the physical layer show that the wireless nodes can effectively detect fake neighbor connections without the adoption of any special hardware on them

    Hybrid Data Fusion Techniques for Localization in UWB Networks

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    International audienceIn this paper, we exploit the concept of data fusion in UWB (Ultra Wide Band) localization systems by using different location-dependent observables. We combine ToA (Time of Arrival) and RSS (Received Signal Strength) in order to get accurate positioning algorithms.We assume that RSS observables are usually available and we study the effect of adding ToA observables on the positioning accuracy. The proposed architecture of Hybrid Data Fusion (HDF) is based on two stages: Ranging using RSS and ToA; and Estimation of position by the fusion of estimated ranges. In the first stage, we propose a new estimator of ranges from RSS observables assuming a path loss model. In the second stage, a new ML estimator is developed to merge different ranges with different variances. In order to evaluate these algorithms, simulations are carried out in a generic indoor environment and Cramer Rao Lower Bounds (CRLB) are investigated. Those algorithms show enhanced positioning results at reasonable noise levels

    Asynchronous Two-Way Ranging Using Tomlinson-Harashima Precoding and UWB Signaling

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    <p>Abstract</p> <p>This paper demonstrates two methods which simultaneously undertake synchronization and ranging based on a time-of-arrival approach with bidirectional communication to bypass the need for accurate synchronous clocking. In order to alleviate multipath effects, Tomlinson-Harashima precoding and UWB signaling are used to measure the distance between pairs of sensors. The proposed schemes are shown to be effective under certain assumptions and the analysis is supported by simulation and numerical studies.</p

    Asynchronous Two-Way Ranging Using Tomlinson-Harashima Precoding and UWB Signaling

    No full text
    This paper demonstrates two methods which simultaneously undertake synchronization and ranging based on a time-of-arrival approach with bidirectional communication to bypass the need for accurate synchronous clocking. In order to alleviate multipath effects, Tomlinson-Harashima precoding and UWB signaling are used to measure the distance between pairs of sensors. The proposed schemes are shown to be effective under certain assumptions and the analysis is supported by simulation and numerical studies
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