Performance Evaluation of an IEEE 802.15.4a Physical Layer with Energy Detection and Multi-User Interference

We evaluate the performance of an IEEE 802.15.4a ultra-wide band (UWB) physical layer, with an energy-detection receiver, in the presence of multi-user interference (MUI). A complete packet based system is considered. We take into account packet detection and timing acquisition, the estimation of the power delay profile of the channel, and the recovery of the encoded payload. Energy detectors are known to have a low implementation complexity and to allow for avoiding the complex channel estimation needed by a Rake receiver. However, our results show that MUI severely degrades the performance of the energy detection receiver, even at low traffic rate. We demonstrate that using an IEEE 802.15.4a compliant energy detection receiver significantly diminishes one of the most appealing benefits of UWB, namely its robustness to MUI and thus the possibility to allow parallel transmissions. We further find that timing acquisition and data decoding both equally suffer from MUI

Synchronization for Impulse-Radio UWB With Energy-Detection and Multi-User Interference: Algorithms and Application to IEEE 802.15.4a

Energy-detection (ED) receivers can take advantage of the ranging and multipath resistance capabilities of impulse-radio ultra-wideband (IR-UWB) physical layers at a much lower complexity than coherent receivers. However, ED receivers are extremely vulnerable to multi-user interference (MUI). Therefore, the design of IR-UWB ED architectures must take MUI into account. In this paper, we present the design and evaluation of two complementary algorithms for reliable and robust synchronization of IR-UWB ED receivers in the presence of MUI: 1) power-independent detection and preamble code interference cancellation (PICNIC) and 2) detection of start-frame-delimiter through sequential ratio tests (DESSERT). PICNIC addresses packet detection and timing acquisition while DESSERT focuses on start-frame-delimiter (SFD) detection. Both algorithms are evaluated with the IEEE 802.15.4a IR-UWB physical layer, standardized for low data-rate networks. The performance evaluation with extensive simulations show that our algorithms outperform nonrobust synchronization algorithms by up to two orders of magnitude in the presence of MUI

Interference management in impulse-radio ultra-wide band networks

We consider networks of impulse-radio ultra-wide band (IR-UWB) devices. We are interested in the architecture, design, and performance evaluation of these networks in a low data-rate, self-organized, and multi-hop setting. IR-UWB is a potential physical layer for sensor networks and emerging pervasive wireless networks. These networks are likely to have no particular infrastructure, might have nodes embedded in everyday life objects and have a size ranging from a few dozen nodes to large-scale networks composed of hundreds of nodes. Their average data-rate is low, on the order of a few megabits per second. IR-UWB physical layers are attractive for these networks because they potentially combine low-power consumption, robustness to multipath fading and to interference, and location/ranging capability. The features of an IR-UWB physical layer greatly differ from the features of the narrow-band physical layers used in existing wireless networks. First, the bandwidth of an IR-UWB physical layer is at least 500 MHz, which is easily two orders of magnitude larger than the bandwidth used by a typical narrow-band physical layer. Second, this large bandwidth implies stringent radio spectrum regulations because UWB systems might occupy a portion of the spectrum that is already in use. Consequently, UWB systems exhibit extremely low power spectral densities. Finally IR-UWB physical layers offer multi-channel capabilities for multiple and concurrent access to the physical layer. Hence, the architecture and design of IR-UWB networks are likely to differ significantly from narrow-band wireless networks. For the network to operate efficiently, it must be designed and implemented to take into account the features of IR-UWB and to take advantage of them. In this thesis, we focus on both the medium access control (MAC) layer and the physical layer. Our main objectives are to understand and determine (1) the architecture and design principles of IR-UWB networks, and (2) how to implement them in practical schemes. In the first part of this thesis, we explore the design space of IR-UWB networks and analyze the fundamental design choices. We show that interference from concurrent transmissions should not be prevented as in protocols that use mutual exclusion (for instance, IEEE 802.11). Instead, interference must be managed with rate adaptation, and an interference mitigation scheme should be used at the physical layer. Power control is useless. Based on these findings, we develop a practical PHY-aware MAC protocol that takes into account the specific nature of IR-UWB and that is able to adapt its rate to interference. We evaluate the performance obtained with this design: It clearly outperforms traditional designs that, instead, use mutual exclusion or power control. One crucial aspect of IR-UWB networks is packet detection and timing acquisition. In this context, a network design choice is whether to use a common or private acquisition preamble for timing acquisition. Therefore, we evaluate how this network design issue affects the network throughput. Our analysis shows that a private acquisition preamble yields a tremendous increase in throughput, compared with a common acquisition preamble. In addition, simulations on multi-hop topologies with TCP flows demonstrate that a network using private acquisition preambles has a stable throughput. On the contrary, using a common acquisition preamble exhibits an effect similar to exposed terminal issues in 802.11 networks: the throughput is severely degraded and flow starvation might occur. In the second part of this thesis, we are interested in IEEE 802.15.4a, a standard for low data-rate, low complexity networks that employs an IR-UWB physical layer. Due to its low complexity, energy detection is appealing for the implementation of practical receivers. But it is less robust to multi-user interference (MUI) than a coherent receiver. Hence, we evaluate the performance of an IEEE 802.15.4a physical layer with an energy detection receiver to find out whether a satisfactory performance is still obtained. Our results show that MUI severely degrades the performance in this case. The energy detection receiver significantly diminishes one of the most appealing benefits of UWB, specifically its robustness to MUI and thus the possibility of allowing for parallel transmissions. This performance analysis leads to the development of an IR-UWB receiver architecture, based on energy detection, that is robust to MUI and adapted to the peculiarities of IEEE 802.15.4a. This architecture greatly improves the performance and entails only a moderate increase in complexity. Finally, we present the architecture of an IR-UWB physical layer implementation in ns-2, a well-known network simulator. This architecture is generic and allows for the simulation of several multiple-access physical layers. In addition, it comprises a model of packet detection and timing acquisition. Network simulators also need to have efficient algorithms to accurately compute bit or packet error rates. Hence, we present a fast algorithm to compute the bit error rate of an IR-UWB physical layer in a network setting with MUI. It is based on a novel combination of large deviation theory and importance sampling

Pilot-Based TI-ADC Mismatch Error Calibration for IR-UWB Receivers

4openopenSchmidt C.A.; Figueroa J.L.; Cousseau J.E.; Tonello A.M.Schmidt, C. A.; Figueroa, J. L.; Cousseau, J. E.; Tonello, A. M

Pilot-Based TI-ADC Mismatch Error Calibration for IR-UWB Receivers

In this work, we rst provide an overviewof the state of the art in mismatch error estimation and correction for time-interleaved analog to digital converters (TI-ADCs). Then, we present a novel pilot-based on-line adaptive timing mismatch error estimation approach for TI-ADCs in the context of an impulse radio ultra wideband (IR-UWB) receiver with correlation-based detection. We introduce the developed method and derive the expressions for both additive white Gaussian noise (AWGN) and Rayleigh multipath fading (RMPF) channels. We also derive a lower bound on the required ADC resolution to attain a certainestimation precision. Simulations show the effectiveness of the technique when combined with an adequate compensator. We analyze the estimation error behavior as a function of signal to noise ratio (SNR) and investigate the ADC performance before and after compensation. While all mismatches combined cause the effective number of bits (ENOB) to drop to 3 bits and to 6 bits when considering only timing mismatch, estimation and correction of these errors with the proposed technique can restore a close to ideal behavior.We also show the performance loss at the receiver in terms of bit error rate (BER) and how compensation is able to signicantly improve performance.Fil: Schmidt, Christian Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; ArgentinaFil: Figueroa, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; ArgentinaFil: Cousseau, Juan Edmundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; ArgentinaFil: Lopez Tonellotto, Mariana Andrea. University Of Klagenfurt; Austri

Doctor of Philosophy

dissertationLow-cost wireless embedded systems can make radio channel measurements for the purposes of radio localization, synchronization, and breathing monitoring. Most of those systems measure the radio channel via the received signal strength indicator (RSSI), which is widely available on inexpensive radio transceivers. However, the use of standard RSSI imposes multiple limitations on the accuracy and reliability of such systems; moreover, higher accuracy is only accessible with very high-cost systems, both in bandwidth and device costs. On the other hand, wireless devices also rely on synchronized notion of time to coordinate tasks (transmit, receive, sleep, etc.), especially in time-based localization systems. Existing solutions use multiple message exchanges to estimate time offset and clock skew, which further increases channel utilization. In this dissertation, the design of the systems that use RSSI for device-free localization, device-based localization, and breathing monitoring applications are evaluated. Next, the design and evaluation of novel wireless embedded systems are introduced to enable more fine-grained radio signal measurements to the application. I design and study the effect of increasing the resolution of RSSI beyond the typical 1 dB step size, which is the current standard, with a couple of example applications: breathing monitoring and gesture recognition. Lastly, the Stitch architecture is then proposed to allow the frequency and time synchronization of multiple nodes' clocks. The prototype platform, Chronos, implements radio frequency synchronization (RFS), which accesses complex baseband samples from a low-power low-cost narrowband radio, estimates the carrier frequency offset, and iteratively drives the difference between two nodes' main local oscillators (LO) to less than 3 parts per billion (ppb). An optimized time synchronization and ranging protocols (EffToF) is designed and implemented to achieve the same timing accuracy as the state-of-the-art but with 59% less utilization of the UWB channel. Based on this dissertation, I could foresee Stitch and RFS further improving the robustness of communications infrastructure to GPS jamming, allow exploration of applications such as distributed beamforming and MIMO, and enable new highly-synchronous wireless sensing and actuation systems

Secure Neighbor Discovery and Ranging in Wireless Networks

This thesis addresses the security of two fundamental elements of wireless networking: neighbor discovery and ranging. Neighbor discovery consists in discovering devices available for direct communication or in physical proximity. Ranging, or distance bounding, consists in measuring the distance between devices, or providing an upper bound on this distance. Both elements serve as building blocks for a variety of services and applications, notably routing, physical access control, tracking and localization. However, the open nature of wireless networks makes it easy to abuse neighbor discovery and ranging, and thereby compromise overlying services and applications. To prevent this, numerous works proposed protocols that secure these building blocks. But two aspects crucial for the security of such protocols have received relatively little attention: formal verification and attacks on the physical-communication-layer. They are precisely the focus of this thesis. In the first part of the thesis, we contribute a formal analysis of secure communication neighbor discovery protocols. We build a formal model that captures salient characteristics of wireless systems such as node location, message propagation time and link variability, and we provide a specification of secure communication neighbor discovery. Then, we derive an impossibility result for a general class of protocols we term "time-based protocols", stating that no such protocol can provide secure communication neighbor discovery. We also identify the conditions under which the impossibility result is lifted. We then prove that specific protocols in the time-based class (under additional conditions) and specific protocols in a class we term "time- and location-based protocols," satisfy the neighbor discovery specification. We reinforce these results by mechanizing the model and the proofs in the theorem prover Isabelle. In the second part of the thesis, we explore physical-communication-layer attacks that can seemingly decrease the message arrival time without modifying its content. Thus, they can circumvent time-based neighbor discovery protocols and distance bounding protocols. (Indeed, they violate the assumptions necessary to prove protocol correctness in the first part of the thesis.) We focus on Impulse Radio Ultra-Wideband, a physical layer technology particularly well suited for implementing distance bounding, thanks to its ability to perform accurate indoor ranging. First, we adapt physical layer attacks reported in prior work to IEEE 802.15.4a, the de facto standard for Impulse Radio, and evaluate their performance. We show that an adversary can achieve a distance-decrease of up to hundreds of meters with an arbitrarily high probability of success, with only a minor cost in terms of transmission power (few dB). Next, we demonstrate a new attack vector that disrupts time-of-arrival estimation algorithms, in particular those designed to be precise. The distance-decrease achievable by this attack vector is in the order of the channel spread (order of 10 meters in indoor environments). This attack vector can be used in previously reported physical layer attacks, but it also creates a new type of external attack based on malicious interference. We demonstrate that variants of the malicious interference attack are much easier to mount than the previously reported external attack. We also provide design guidelines for modulation schemes and devise receiver algorithms that mitigate physical layer attacks. These countermeasures allow the system designer to trade off security, ranging precision and cost in terms of transmission power and packet length

Performance evaluation of wake-up radio based wireless body area network

Abstract. The last decade has been really ambitious in new research and development techniques to reduce energy consumption especially in wireless sensor networks (WSNs). Sensor nodes are usually battery-powered and thus have very limited lifetime. Energy efficiency has been the most important aspect to discuss when talking about wireless body area network (WBAN) in particular, since it is the bottleneck of these networks. Medium access control (MAC) protocols hold the vital position to determine the energy efficiency of a WBAN, which is a key design issue for battery operated sensor nodes. The wake-up radio (WUR) based MAC and physical layer (PHY) have been evaluated in this research work in order to contribute to the energy efficient solutions development. WUR is an on-demand approach in which the node is woken up by the wake-up signal (WUS). A WUS switches a node from sleep mode to wake up mode to start signal transmission and reception. The WUS is transmitted or received by a secondary radio transceiver, which operates on very low power. The energy benefit of using WUR is compared with conventional duty-cycling approach. As the protocol defines the nodes in WUR based network do not waste energy on idle listening and are only awakened when there is a request for communication, therefore, energy consumption is extremely low. The performance of WUR based MAC protocol has been evaluated for both physical layer (PHY) and MAC for transmission of WUS and data. The probabilities of miss detection, false alarm and detection error rates are calculated for PHY and the probabilities of collision and successful data transmission for channel access method Aloha is evaluated. The results are obtained to compute and compare the total energy consumption of WUR based network with duty cycling. The results prove that the WUR based networks have significant potential to improve energy efficiency, in comparison to conventional duty cycling approach especially, in the case of low data-reporting rate applications. The duty cycle approach is better than WUR approach when sufficiently low duty cycle is combined with highly frequent communication between the network nodes

Ultra-wideband Based Indoor Localization of Mobile Nodes in ToA and TDoA Configurations

Zandian R. Ultra-wideband Based Indoor Localization of Mobile Nodes in ToA and TDoA Configurations. Bielefeld: Universität Bielefeld; 2019.This thesis discusses the utilization of ultra-wideband (UWB) technology in indoor localization scenarios and proposes system setup and evaluates different localization algorithms in order to improve the localization accuracy and stability of such systems in non-ideal conditions of the indoor environment. Recent developments and advances of technology in the areas of ubiquitous Internet, robotics and internet of things (IoT) have resulted in emerging new application areas in daily life in which localization systems are vital. The significant demand for a robust and accurate localization system that is applicable in indoor areas lacking satellites link, can be sensed. The UWB technology offers accurate localization systems with an accuracy of below 10 cm and covering the range of up to a few hundred meters thanks to their dedicated large bandwidth, modulation technique and signal power. In this thesis, the technology behind the UWB systems is discussed in detail. In terms of localization topologies, different scenarios with the focus on time-based methods are introduced. The main focus of this thesis is on the differential time of arrival localization systems (TDoA) with unilateral constellation that is suitable for robotic localization and navigation applications. A new approach for synchronization of TDoA topology is proposed and influence of clock inaccuracies in such systems are thoroughly evaluated. For localization engine, two groups of static and dynamic iterative algorithms are introduced. Among the possible dynamic methods, extended Kalman filter (EKF), H∞ and unscented Kalman filter (UKF) are discussed and meticulously evaluated. In order to tackle the non-line of sight (NLOS) problem of such systems, for detection stage several solutions which are based on parametric machine learning methods are proposed. Furthermore, for mitigation phase two solutions namely adjustment of measurement variance and innovation term are suggested. Practical results prove the efficiency and high reliability of the proposed algorithms with positive NLOS condition detection rate of more than 87%. In practical trials, the localization system is evaluated in indoor and outdoor arenas in both line of sight and non-line of sight conditions. The results show that the proposed detection and mitigation methods can be successfully applied for both small and large-scale arenas with the higher performance of the localization filters in terms of accuracy in large-scale scenarios

Ultra Wideband Wearable Sensors for Motion Tracking Applications

The increasing interest and advancements in wearable electronics, biomedical applications and digital signal processing techniques have led to the unceasing progress and research in novel implementations of wireless communications technology. Human motion tracking and localisation are some of the numerous promising applications that have emerged from this interest. Ultra-wideband (UWB) technology is particularly seen as a very attractive solution for microwave-based localisation due to the fine time resolution capabilities of the UWB pulses. However, to prove the viability of utilizing UWB technology for high precision localisation applications, a considerable amount of research work is still needed. The impact of the presence of the human body on localisation accuracy needs to be investigated. In addition, for guaranteeing accurate data retrieval in an impulse-radio based system, the study of pulse distortion becomes indispensable. The objective of the research work presented in this thesis is to study and carry out experimental investigations to formulate new techniques for the development of an Impulse-radio UWB sensor based localisation system for human motion tracking applications. This research work initiates a new approach for human motion tracking by making use of pulsed UWB technology which will allow the development of advanced tracking solutions with the capacity to meet the needs of professional users. Extensive experimental studies involving several ranging and three dimensional localisation investigations have been undertaken, and the potential of achieving high precision localisation using ultra-wideband technology has been demonstrated. Making use of the upper portion of the UWB band, a novel miniature antenna designed for integration in the UWB localisation system is presented and its performance has been examined. The key findings and contributions of this research work include UWB antenna characterisation for pulse based transmission, evaluation of comprehensive antenna fidelity patterns, impact of pulse fidelity on the communication performance of a UWB radio system, along with studies regarding the effect of the human body on received pulse quality and localisation accuracy. In addition, an innovative approach of making use of antenna phase centre information for improving the localisation accuracy has been presented