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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).

International audience; 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.

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.

Ultra-wideband (UWB) technology is now becoming mature enough to play a crucial role in a large variety of pervasive wireless sensor network applications. One of these applications is represented by land seismic exploration for oil and gas reservior. Seismic exploration requires a large number (2000 nodes/sqkm) of sensors to be deployed in outdoor over large areas (typ. 30 sqkm) to measure backscattered wave fields. A storage/processing unit (sink node) collects the measurements from all the sensors to obtain an image of the sub-surface in real-time. The UWB technology is proposed in this paper for replacing the cable connections between the sensors and the sink. UWB is the most suitable wireless technology for this application as it guarantees high data rate over short range links and self-localization with sub-meter accuracy. An UWB sensor network based on Multi-Band OFDM is designed for the specific problem. Amendmends to ECMA 368 specifications are also identified to allow for energy aware beaconing and self-localization.

With the advent of new Global Navigation Satellite Systems (GNSS) and signals, Satellite Based Augmentation Systems (SBAS) will rely also on them to provide higher position accuracy. For services based on such systems it is fundamental to protect the user against potential signal distortions in order to ensure the required integrity and performance. SBAS systems usually implement signal deformation monitors which are capable to recognize payload imperfections affecting the received signals in order to discard the corrupted information. The advent of new GNSS signals introduces the necessity to extend already accepted failure models to the new modulations techniques. This paper considers in particular the 2nd-Order Step threat model adopted by the International Civilian Aviation Organization (ICAO) for GPS signals. Starting from the ICAO model, a general threat model affecting the signal generation and transmission hardware is here proposed for Binary Offset Carrier (BOC) signals, and then extended also to Multiplexed Binary Offset Carrier (MBOC), and to Alternate BOC (AltBOC) modulated signals. As a first analysis, the correlation peaks affected by the proposed threat model are shown for the aforementioned signals, and some evaluations on the parameters space are carried out. In order to evaluate the effect of deformations on the performance of a GNSS receiver, the tracking error behavior is studied for two types of discriminator (early late, double delta) and different correlators' spacing.

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.

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.

We present preliminary results for a single-crystal silicon gyroscope with decoupled drive and sense oscillators. The gyroscope is fabricated using a plasma micromachining process on a six-inch MEMS production line at Kionix, Inc. The process yields high-aspect-ratio structures, large structure-to- substrate separation, and low-parasitic electrodes, unlike designs that rely on silicon-on-insulator substrates, polysilicon, or thick epitaxial layers. We describe the fabrication process and emphasize the design, operation, and testing of the sensor. Results to date have yielded resolutions of 0.15 deg/sec over a 100 Hz bandwidth, short term bias stabilities less than 100 deg/hr, and quadrature signals less than 25 deg/sec.

Draper Laboratory's experience with Interferometer Fiber Optic Gyro (IFOG) technology started via an Internal Research and Development effort in 1978. This work led to developing fiber optic gyros in which significant advances in IFOG component technologies, assembly, integration, and test were achieved. In excess of 30 patents have been issued to Draper as a result of this pioneering effort. More recently, Draper collaborated with JPL to transition their fiber optic breadboard gyro to a space qualifiable instrument for interplanetary long duration missions. During the initial phase, brassboard gyros were designed and fabricated that demonstrated performance that bettered NASA's CRAF-Cassini spacecraft objectives. In the second phase, the Engineering Model gyro was developed to meet mission qualification tests. Concurrent with this later phase, analysis, tests and qualification activities were performed to validate that gyro components would realize the required 16 year life. Two major inventions (patent pending) were conceived; one provides for continuous adaptive scale factor stability and the other integrates the optical source and photodetector into a single component [Source Integrated Detector (SID)], thereby eliminating a coupler and several splices thus reducing loss by 6 db. Using the above technologies and the implementation of common mode rejection of laser noise, Draper has defined a low noise high performance gyro in which rate power spectral density (PSD) is projected to be < 7 X 10-7 (deg/hr)2/Hz. In those applications, where the PSD < 4 X 10-5 (deg/hr)2/Hz is sought, a small size three component (SID, integrated optics circuit and fiber coil) gyro is easily implemented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.