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We address the problem of estimating the carrier-to-noise ratio (C/N0) in weak signal conditions. There are several environments, such as forested areas, indoor buildings and urban canyons, where high-sensitivity global navigation satellite system (HS-GNSS) receivers are expected to work under these reception conditions. The acquisition of weak signals from the satellites requires the use of post-detection...
Global navigation satellite systems (GNSSs) remain, by far, the most reliable and widely spread sources of accurate outdoor positioning. With the advent of the new and modernized signals, novel challenges related to GNSS receivers have also been recognized. One of the most important challenges in dealing with modernized GNSS signals is posed by the oscillatory behavior of the autocorrelation of some...
This work investigates the distributed quickest detection problem, where a set of sensors receive independent observations and send messages to a fusion center, which makes a final decision. We are interested in detecting an event as soon as possible even though the set of affected sensors is unknown. We consider a scenario where the sensors are randomly spaced along a path, and then the affected...
This paper studies the pilot placement for power-efficient uplink positioning within future fifth generation (5G) enhanced vehicle to everything (eV2X) networks. The optimal pilot allocation of multicarrier signals may help to fulfil the stringent requirements, in terms of vehicle position accuracy and latency, within vehicular applications, such as autonomous driving. Contiguous and non-contiguous...
The positioning support is under study within the narrowband (NB) Internet of things (IoT) standard of Long Term Evolution (LTE) cellular networks. However, the limited signal bandwidth of this technology poses serious difficulties to achieve a position accuracy below 50 meters, which may be required in current 4G and future 5G standards. This work studies the impact of a frequency-hopping (FH) scheme...
In the context of global navigation satellite systems, this paper addresses the problem of refining the Doppler frequency estimation provided in the acquisition stage for highorder binary offset carrier (BOC) signals in post-correlation. The refinement of Doppler frequency must be done because the estimation obtained from the acquisition stage is not usually accurate enough to track the signal in...
The proliferation of GNSS-based (Global Navigation Satellite Systems) services and applications providing ubiquitous, seamless and secure/reliable positioning is driving the use of high-performance devices. This implies the requirement of a higher computational capability in miniaturized size and low power consumption devices such as smartphones or Smart- City sensors. In this context, a possible...
Severe performance degradation of Global Navigation Satellite Systems (GNSS) is produced in urban scenarios, mainly due to dense multipath and non-line-of-sight (NLoS) conditions. Thus, the integration of GNSS with additional positioning systems, such as the location methods in Long Term Evolution (LTE) cellular systems, may cope with these challenging scenarios. This work proposes a generic evaluation...
One of the difficulties faced by high-sensitivity GNSS receivers is the so-called near-far problem, where the acquisition of weak signals is hampered by the presence of more powerful signals. If countermeasures are not implemented, the presence of near-far may result in loss or false acquisition of weak signals, and consequently the user's position may exhibit a huge error. In this sense, subspace...
This paper addresses the problem of acquiring weak high-order binary offset carrier (BOC) signals in the context of high-sensitivity global navigation satellite system (HS-GNSS) receivers. The use of high-order BOC modulations provides an improvement over conventional BPSK modulation in terms of positioning accuracy, at the cost of secondary peaks appearing in the correlation function. The acquisition...
The current study discusses the results of a survey on the topic of “GNSS applications: user preferences”. The aim is to understand user preferences of GNSS applications in order to develop competitive research projects, new GNSS products / services and further increases in global GNSS market shares. The questionnaire was conducted during September – October 2015. The results of the questionnaire...
5G assisted driving applications demand the provision of centimetre-accurate positioning. Automated vehicles typically use several positioning systems, such as radars, cameras and sensors, in addition to Global Navigation Satellite Systems (GNSS). This is necessary to ensure integrity and reliability, as well as precise positioning. The deployment of 5G cellular networks along roads are envisaged...
Multipath is one of the major impairments threatening the integrity of terrestrial Global Navigation Satellite Systems (GNSS). For this reason, multipath mitigation has attracted the attention of many researchers, thus leading to outstanding contributions in the past years. These techniques are useful when the Line of Sight (LOS) is not obstructed. Otherwise, they are not applicable, and thus we should...
This paper addresses the use of generalized correlations in the context of High-Sensitivity Global Navigation Satellite System (HS-GNSS) receivers. Generalized correlations are also referred to as post-detection integration (PDI) techniques or simply as non-coherent integration methods. The contributions of this work are twofold. On the one hand, a novel PDI method is presented, which improves the...
The widespread deployment of GNSS (Global Navigation Satellite Systems) is pushing the current receiver technology to its limits due to the stringent demands for providing seamless, ubiquitous and secure/reliable positioning. This fact is further aggravated by the advent of new applications where the miniaturized size, low power consumption and limited computational capabilities of user terminals...
In Global Navigation Satellite Systems, receivers have to cope with ionospheric scintillation, which is of paramount importance for high-precision positioning applications. However, the design of robust carrier tracking techniques under these condition still remains an open problem. The time-varying correlated scintillation phase can be modeled as an AR(p) process, whose linear nature fits very well...
Due to the increasing interest in Global Navigation Satellite Systems (GNSSs) for safety-critical applications, one of the major challenges to be solved is the provision of integrity to urban environments. In the past years, it has been noted that to do so, the integrity of the received signal must be analyzed with the aim of detecting any local effect disturbing the GNSS signal. Moreover, the detection...
In indoor and dense urban environments, Global Navigation Satellite System (GNSS) receivers have to cope with extremely low received power levels. In these circumstances, GNSS receivers become vulnerable to adverse propagation effects such as near-far interference, where acquisition is affected by large cross-correlation peaks because signals from different satellites experience very different attenuation...
Vertical positioning is nowadays a topic of high interest in indoor environments, due to the stringent requirements on indoor location accuracy for emergency calls, such as E911. Thus, indoor positioning techniques are investigated to achieve floor detection in order to fulfill these legal mandates. The use of Long Term Evolution (LTE) heterogeneous networks is an attractive solution due to the combination...
Recently, there has been an increasing interest in GNSS-based safety and liability applications. These applications, which are often associated to urban environments or in general to vehicular applications, have very stringent requirements in terms of accuracy, continuity and integrity of the provided position solution. In this paper, we present simple quickest threat detectors for being used in low-cost...
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