In Low Power Wide Area (LPWA) networks, radio localization based on Time Difference of Arrival measurements has major benefits: energy consumption of the node and spectrum usage are contained. Temporal resolution and hence positioning accuracy is however limited by the bandwidth of the LPWA narrowband signals. Multi-channel ranging, that relies on multiple narrowband signals that are sequentially transmitted on different and discontinuous channels, has recently been proposed to improve precision. However, the concept has not been adapted yet to differential uplink localization techniques. This paper studies and proposes adaptations to multi-channel ranging called Multi-Frequency Phase Difference of Arrival (MF-PDoA) for this purpose. It analyzes the impact of imperfect synchronization on its performance and concludes that MF-PDoA is robust and well adapted to the LPWA scenario.

Low power wide area (LPWA) wireless networks based on the LoRa physical layer have attracted huge attention in recent years, both from industry and from academic researchers. While this rising popularity is due to this technology's demonstrated effectiveness and low cost, unfortunately, due to their complexity, the timing and frequency synchronization algorithms required to detect LoRa-modulated frames, in the context of minimum sampling rate optimum receivers, have received little attention. The aim of this paper is to fill this gap and describe how robust frame detection can be performed while focusing on minimal complexity implementations of the proposed algorithms. The ultimate goal is to propose frame detection techniques applicable to recently proposed ultra-low power software-defined receivers.

In order to meet the contradictory requirements of long range, low power consumption and adaptive throughput, LPWA networks require a decision module based on cognitive functionalities to select the most appropriate RF/PHY configuration and to cover the large variety of LPWA applications. In this paper, we define a new adaptive LPWA network exploiting the flexibility of the Turbo-FSK waveform. The most relevant configurations are selected from the PHY and MAC layers point of view. At the PHY layer, a trade-off between data rate, spectral efficiency, energy consumption and range is considered while the MAC layer deals with the reliability, the latency, the network capacity, the multi-user access (number of users, traffic intensity) to adapt the network. Hence, thanks to this selection, several strategies switching between available selected configurations are defined to adapt the communication to the context and according to the criteria to optimize. The performance for each configuration is evaluated by simulation when all the users select the same configuration. To tackle the three requirements (i.e. range, network capacity and energy consumption), appropriate configurations are identified.

Accurate range estimation with narrowband low power radio devices is challenging due to limited signal bandwidth and high frequency offsets of low-cost oscillators. The present paper provides new results concerning the Cramer Rao bounds of narrowband ranging systems applying a multi-channel coherent processing approach. Particularly, compared to existing literature, oscillator frequency offsets and multipath influence are taken into account. By numerical simulation it is shown, how the radio channel frequency selectivity degrades the ranging precision. Finally, a few guidelines for the design of new long range low-cost ranging systems are provided.

Impulse Radio - Ultra Wideband (IR-UWB) ranging based on first detected path's Time-of-Arrival (ToA) theoretically enables high-accuracy localization in Line of Sight (LoS) contexts. However, performance can be severely degraded in practical indoor environments due to both dense multipath propagation and signal obstructions. To mitigate these effects, the space-time correlation of tracked multipath components (MPCs) under mobility can be beneficial to collectively reconstruct the missing direct path's ToA in case of detected NLoS situation. This paper aims at improving further the robustness of such Multipath-aided Direct Path Reconstruction (MDPR) in very dense multipath and generalized NLoS with respect to anchors, while considering constraints of real integrated IR-UWB receivers. More specifically, new strategies are introduced to better approximate and dynamically adjust the link between direct and secondary paths for longer-term correction validity, as well as to handle MPCs appearance/disappearance over NLoS portions of trajectory. The proposed solution is validated by means of semi-deterministic dynamic simulations based on IEEE 802.15.4a channel models.

In this paper a novel solution for coherent combination in ultra wide band (UWB) beamformings for real time locating systems (RTLS) is proposed. The architecture uses a double quadrature receiver and the time alignment is approached by digital phase-shifters. A comparison and evaluation with classical True Time delay (TTD) architectures is presented. Our proposed architecture achieves same performances than the TTD approach, showing that complex TTD modules could be replaced advantageously by a single base-band digital phase shifters. Moreover, our solution does not need higher sampling rates that make it suitable for low power consumption.

Wireless communications for body area network (BAN) applications require an adaptable, dynamic and flexible medium access control (MAC) to cope with a variety of application requirements. The proposed MAC adjusts its communication protocols and the parameters of the IEEE 802.15.4 superframe. It is based on to achieve low power consumption and low latency which are among the key requirements in BAN applications. In this paper, accordingly with measurements made in an anechoic chamber, we first define a BAN channel model useable in network simulations embedding a spatial and temporal dependency using ray tracing techniques. It is applied to the body postures and movements of a walking person. As body posture highly affects the performance of the MAC protocol, we second evaluate the effects of the varying body shadowing in the walking scenario on our MAC protocol performances.