Description of the deliverable content and purpose
The objective of this activities is to provide a feasibility study on RF sensing techniques based on the UWB technology and exploitation of situation awareness (e.g. position) to support cross-layer and cross-functionality optimisation. This deliverable will provide results obtained on two sub-activities in the framework.
The first sub-activity is focused on a State-Of-The-Art (SOTA) on proximity ranging using Impulse Radio Ultra WideBand (IR-UWB) technology. Location aware applications are becoming increasingly important. Such applications rely on accurate and reliable localisation and tracking. In principle, the potential accuracy varies with the inverse of the bandwidth; the larger the bandwidth, the finer the time resolution, therefore the greater the potential accuracy. This is why UWB transmission techniques present good alternatives for substantial improvement over narrowband solutions. Furthermore, techniques other than RSSI may be exploited in UWB receivers and especially, in IR-UWB. In the first part of this document, the focus is on the investigation of IR-UWB based ranging algorithms for situation awareness (e.g. position).
In this perspective, we start our contribution by explaining the UWB transmission technique, highlight the background behind and explain its adequacy for ranging purposes. Then we focus on the use of IR-UWB based techniques for ranging procedures. We start by describing the communication system model and then we explain the used channel model in the performed simulations. Using the obtained simulation results we compare the performance of the proposed ranging algorithms and we evaluate the ranging errors and compare them to the performance bounds (Cramer-Rao bounds). The performed analysis targets the selection of adequate IR-UWB algorithms for proximity ranging and potential solutions for multipath (e.g. LOS and NLOS). The main algorithms are the classical first and strongest path detection for the high SNR region, and the more complex maximum likelihood for the low SNR regions.
In parallel, the second part of activities is focused on the review and the design of a directional UWB antenna operating in high-band frequencies for wireless sensor applications.
The gain provided by the directional antenna offers the potential for more energy efficient implementation of the sensor node and improvement of the co-existence, which is important in wireless sensor networks.
We also briefly concluded on how the potential offered by directional communications can actually be exploited only if a cross-layer approach is followed when designing the MAC layer. Starting from the limits of a simple extension of 802.11 or 802.15.4 to the new scenario, and considering some solutions proposed in the literature, we have shown some of the main issues that an effective directional medium access policy should consider and address, namely handshake, virtual carrier sense and deafness.
As a first step, the main aspects of UWB antenna, which can affect the overall system performance, are analysed. Secondly the state of the art in UWB antenna design is made through discussions on several recent design examples. Finally the design of a small compact UWB Strip Slot Foam Inverted Patch (SSFIP) antenna is described and its simulation results are discussed in detail.
The design of this single element SSFIP antenna will be used as an input for further investigation of a novel small and compact, electrically pointed antenna (foreseen in the task 3.3) which has the potential to reduce the global power consumption in the WSN and facilitate cross-functionality optimisation given the knowledge of context and situation awareness.
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