An Original Correction Method for Indoor Ultra Wide Band Ranging-Based Localisation System
During this decade, Wireless Sensor Networks (WSNs) brought an increasing interest in the industrial and research world. One of their applications is indoor localization. The ranging, i.e. the distance evaluation mechanism between nodes, is required to de
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tract. During this decade, Wireless Sensor Networks (WSNs) brought an increasing interest in the industrial and research world. One of their applications is indoor localization. The ranging, i.e. the distance evaluation mechanism between nodes, is required to determine the position of the nodes. The research work presented in this article aims to use Ultra Wide Band (UWB) radio links to achieve an efficient ranging, based on Time of Flight (ToF) measurement. A good solution consists in integrating ranging traffic into the usual network messages. However, the ToF ranging process is based on information exchanges which are temporally constrained. Once this information is encapsulated into the usual messages, the temporal constraint cannot be honoured, resulting in important ranging errors due to clock drifts. To mitigate these errors, we have introduced an original dynamic correction technique which enables a precision of twenty centimetres allowing the inclusion of ranging traffic in usual traffic. Keywords: Indoor localisation Time of Flight SDS-TWR Prototyping Testbed
UWB Ranging TWR
1 Introduction The industrial world is a major application area for mobile localisation systems. Spatial and temporal mappings are useful for many applications. GPS is generally used for outdoor localisation, but suffers from a significant power consumption and a reduced performance in indoor environments. Indoor localisation and positioning based on other technologies is therefore required. They can take advantage of Wireless Sensor Networks (WSNs) and other wireless communication systems increasingly used in the industrial domain for the exchange of data from the sensors. The ranging, i.e. the distance evaluation mechanism between nodes, is essential to locate the nodes. Localisation based on range-free methods, as illustrated by the well-known DV-hop algorithm [1, 2] is simple to implement and is based on hypotheses of cellular connectivity between nodes. However, it is not very accurate. Range-based techniques can improve the localisation accuracy. Most wireless nodes can provide an indication of the power level of the received frames, but this method suffers from several drawbacks [3] © Springer International Publishing Switzerland 2016 N. Mitton et al. (Eds.): ADHOC-NOW 2016, LNCS 9724, pp. 79–92, 2016. DOI: 10.1007/978-3-319-40509-4_6
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and is not reliable because of the influence of the antenna’s polarisation and the existence of Non Line Of Sight (NLOS) paths. One of the best solutions is to rely on the Time of Flight (ToF) [4] between sender node and receiver node. This technique requires a precise signal timestamping at the physical layer, which is made possible through a radio transmission technology like Ultra-Wide Band (UWB) or even Chirp Spread Spectrum (CSS). In this sense, the DWM1000 [5] is a very interesting solution. As it complies with the IEEE 802.15.4 standard, it provides picoseconds-level precision on the timing of reception and transmission of the R-MARKER (Ranging Marker) bit
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