Abstract
The article addresses the modeling and performance analysis of wireless sensor network localization with direct-sequence spread-spectrum signals and network-based, time difference of arrival measurements. Realistic radio channel propagation and interference conditions are taken into account. Synchronization by means of a delay-locked loop is adopted for sensor signal tracking at the wireless sensor network anchor nodes. A comprehensive timing estimation analysis is presented with channel impairments, including pathloss attenuation, shadowing, multipath fading, and multi-access interference. The full statistics of the delay-locked loop tracking jitter are derived, which serves to assess the practically achievable synchronization accuracy and its variability with radio channel conditions and specific sensor location. The time difference of arrival measurements are then used for sensor localization based on an efficient iterative maximum likelihood estimation approach shown to outperform weighted least squar...
Highlights
Wireless sensor networks (WSNs) have several advantages and are recently finding widespread use and many applications in various fields.1–3 One of the features of WSNs is the ability to support node localization and tracking with good accuracy, and several WSN localization techniques have received a lot of interest in the literature
The Cramer–Rao lower bound (CRLB) provides a benchmark for assessing the optimality of estimation techniques and is obtained from the Fisher Information Matrix (FIM), which depends on the probability density function (PDF) of the measurements, parameterized by the sensor position u
The cumulative distribution functions (CDFs) are shown for the representative sensor locations SN1 through SN6, and the results confirm the previous observations and clearly demonstrate that positioning is more accurate for centrally located sensors at comparable distance from all anchor nodes (ANs), while the accuracy worsens as they move further away from the center
Summary
Wireless sensor networks (WSNs) have several advantages and are recently finding widespread use and many applications in various fields. One of the features of WSNs is the ability to support node localization and tracking with good accuracy, and several WSN localization techniques have received a lot of interest in the literature (see, for example, the works of Kulaib et al., Boukerche et al., and Mao et al., and references therein). Network-based localization can be achieved by means of statistical signal processing algorithms that exploit time of arrival (TOA), time difference of arrival (TDOA), angle of arrival (AOA), and received signal strength (RSS) measurements from. TDOA schemes, which use the differences of sensor signal epochs of arrival at the receiving ANs, do not require perfect timing alignment of SNs with the network infrastructure and have less stringent synchronization requirements, which make them amenable to low-complexity WSN implementations. The present work focuses on TDOA-based localization and analyzes the achievable localization accuracy in realistic WSN propagation environments.. The analysis shows that the accuracy of timing estimation is highly sensitive to the radio propagation environment and SN relative position vis-a -vis different ANs, which provides important insights into the limits of timing measurements under realistic operating conditions. In the ‘‘TDOA localization performance analysis’’ section, the maximum likelihood TDOA localization algorithm is presented, and numerical results and discussions are given in the ‘‘Results and analysis’’ section, with final conclusions summarized in the ‘‘Conclusion’’ section
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