Diana Fontanella

Fundamental Performance Limits of TOA-Based Cooperative Localization

Knowledge of node locations is desired in many types of wireless sensor network (WSN) technologies. Cooperative localization has been proved to provide self-calibration in the WSN even in presence of sparse reference nodes and noisy range estimates, as it relies on redundancy exploiting all the available inter-node measurements. In this paper we consider cooperative localization based on time-of-arrival (TOA) inter-node ranging. We analyze the Cramer-Rao bound on the positioning accuracy for one/two dimensional regular network topologies. The aim is to obtain some understanding of the behavior of localization accuracy for varying system settings, as a base for future evaluations of more realistic random network deployments.

Bayesian Localization in Sensor Networks: Distributed Algorithm and Fundamental Limits

Self-localization in ad-hoc sensor networks is becoming a crucial issue for several location-aware applications. This technology implies the combination of absolute anchor locations with relative inter-node information exchanged on a peer-to-peer basis. In this paper we investigate a distributed algorithm and fundamental performance bounds for Bayesian cooperative localization in stochastic networks. Nodes are assumed to be randomly deployed within a finite space according to a prior distribution. Bayesian inference is performed through an iterative local message passing procedure based on belief propagation and particle-filtering message representation. The algorithm performance is analyzed for a simplified scenario in which unknown node positions are randomly scattered along a line segment and anchors are fixed. Global Cramer-Rao bounds are derived and compared to the performance of the distributed algorithm.

FMT signal options and associated receiver architectures for GNSS

Non classical signals, signals not made of rectangular shaped pulses, are being analyzed as possible candidates for the next generation of GNSS signals. One such a signal is the filtered multi-tone (FMT) which is a multi-carrier signal (MC) having a MC-DS-CDMA structure: each subcarrier transports a classical GNSS signal but without using rectangular shaped pulses. Some studies have been conducted on the FMT signal performances such as the out-of-band (OOB) emission and multipath resistance. However, due to its MC nature, the distribution of the transmitted data onto the different subcarriers becomes a relevant factor to take into account on the final signal design. In this paper, different data distributions are proposed in order to enhance different signal performance and the receiver structure associated to each data distribution is also analyzed.

Code-Shift-Keying (CSK) with advanced FEC coding for GNSS applications in satellite multipath channel

In this paper, Code-Shift-Keying (CSK) is investigated in combination with Forward Error Correction (FEC) coding techniques, with an additional block interleaving scheme. The target of this analysis is to evaluate the CSK capability to increase data rate or data demodulation sensitivity in GNSS scenarios as compared to the use of traditional BPSK A particular set of advanced signal baselines is reported as example of application to SBAS signal formats, assessing the data delivery performance in Additive White Gaussian Noise (AWGN) channel, two-ray multipath and Land Mobile Satellite (LMS) channel in terms of Bit Error Rate (BER).

Innovative Signal Processing Techniques for Wireless Positioning

Publisher Summary This chapter presents a collection of the latest research results in the field of wireless positioning carried out within the European Network of Excellence NEWCOMCC. One of the most recent promising topics is cognitive positioning (CP) in which the main idea is to design the positioning system according to the cognitive radio (CR) paradigm with the purpose to use efficiently the radio spectrum and to optimize the system performance in the presence of interference. The algorithm needs a measure of the TOA at each array element to obtain the final joint TOA and AOA estimation. The frequency samples are processed without the knowledge of the specific pulse shape in the fine TOA estimator stage. The fine estimator requires a previous stage that provides a coarse symbol synchronization. In localization systems, a characteristic signal is detected and measured by a set of sensors with fixed or known positions, and the positioning problem is then often formulated as a weighted least-squares (WLS) optimization problem.

Fundamental Limits in the Accuracy of Wireless Positioning

Several factors impact in practice on the achievable accuracy of wireless positioning systems. However, theoretical bounds can be set to determine the best accuracy one may expect in certain conditions and to obtain useful benchmarks when assessing the performance of practical schemes. Chapter 4 is dedicated to the presentation of several such bounds, most derived from the Cramer-Rao bound (CRB) framework. Theoretical performance bounds related to the ranging estimation via time-of-arrival (TOA) from UWB signals are derived and discussed, also taking into account critical conditions such as the multipath propagation. Also the improved Ziv-Zakai bound family is introduced as a tighter benchmark in the case of dense scattering, where the CRB falls in the ambiguity region. Then, novel results are presented, related to the derivation of performance limits for innovative positioning approaches, such as direct position estimation (DPE) in GNSS, cooperative terrestrial localization, and a recent analysis on the interference-prone systems, such as multicarrier systems.