Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 5 Articles
Location awareness is a key enabling feature and fundamental challenge in present and future wireless networks. Most existing\r\nlocalization methods rely on existing infrastructure and thus lack the flexibility and robustness necessary for large ad hoc networks.\r\nIn this paper, we build upon SPAWN (sum-product algorithm over a wireless network), which determines node locations through\r\niterative message passing, but does so at a high computational cost. We compare different message representations for SPAWN\r\nin terms of performance and complexity and investigate several types of cooperation based on censoring. Our results, based on\r\nexperimental data with ultra-wideband (UWB) nodes, indicate that parametric message representation combined with simple\r\ncensoring can give excellent performance at relatively low complexity....
The spatial techniques currently used in accurate time transfer are based on GPS, TWSTFT, and GLONASS. The International\r\nBureau of Weights and Measures (BIPM) is mandated for the generation of Coordinated Universal Time (UTC) which is\r\npublished monthly in the BIPM Circular T. In 2009, the international Consultative Committee for Time and Frequency (CCTF)\r\nrecommended the use of multitechniques in time transfer to ensure precision, accuracy, and robustness in UTC. To complement\r\nthe existing GPS and TWSTFT time links, in November 2009 the first two GLONASS time links were introduced into the UTC\r\nworldwide time link network. By November 2011, 6 GLONASS time links are used in the UTC computation. In the frame of\r\nthe application in the UTC computation, we establish the technical features of GLONASS time transfer: the short- and long-term\r\nstabilities, the calibration process, and in particular the impact of themultiple GLONASS frequency biases.We then outline various\r\nconsiderations for future developments, including the uses of P-codes and carrier-phase information....
GPS-dependent positioning, navigation, and timing synchronization procedures have a significant impact on everyday life.\r\nTherefore, such a widely used system increasingly becomes an attractive target for illicit exploitation by terrorists and hackers\r\nfor various motives. As such, spoofing and antispoofing algorithms have become an important research topic within the GPS\r\ndiscipline. This paper will provide a review of recent research in the field of GPS spoofing/anti-spoofing. The vulnerability of GPS\r\nto a spoofing attack will be investigated and then different spoofing generation techniques will be discussed. After introducing\r\nspoofing signal model, a brief review of recently proposed anti-spoofing techniques and their performance in terms of spoofing\r\ndetection and spoofing mitigation will be provided. Limitations of anti-spoofing algorithms will be discussed and some methods\r\nwill be introduced to ameliorate these limitations. In addition, testing the spoofing/anti-spoofing methods is a challenging topic\r\nthat encounters some limitations due to stringent emission regulations. This paper will also provide a review of different test\r\nscenarios that have been adopted for testing anti-spoofing techniques....
One of the most promising features of the modernized global navigation satellite systems signals is the presence of pilot channels\r\nthat, being data-transition free, allow for increasing the coherent integration time of the receivers. Generally speaking, the increased\r\nintegration time allows to better average the thermal noise component, thus improving the postcorrelation SNR of the receiver\r\nin the acquisition phase. On the other hand, for a standalone receiver which is not aided or assisted, the acquisition architecture\r\nrequires that only the pilot channel is processed, at least during the first steps of the procedure. The aim of this paper is to present\r\na detailed investigation on the impact of the code cross-correlation properties in the reception of Galileo E1 Open Service and\r\nGPS L1C civil signals. Analytical and simulation results demonstrate that the S-curve of the code synchronization loop can be\r\naffected by a bias around the lock point. This effect depends on the code cross-correlation properties and on the receiver setup.\r\nFurthermore, in these cases, the sensitivity of the receiver to other error sources might increase, and the paper shows how in\r\npresence of an interfering signal the pseudorange bias can be magnified and lead to relevant performance degradation....
The majority of 3G mobile phones have an integrated GPS chip enabling them to calculate a navigation solution. But to deliver\r\ncontinuous and accurate location information, the satellite tracking process has to be stable and reliable. This is still challenging, for\r\nexample, in heavymultipath and non-line of sight (NLOS) environments. New families of Galileo and GPS navigation signals, such\r\nas Alternate Binary Offset Carrier (AltBOC), Composite Binary Offset Carrier (CBOC), and Time-Multiplex Binary Offset Carrier\r\n(TMBOC), will bring potential improvements in the pseudorange calculation, including more signal power, better multipath\r\nmitigation capabilities, and overall more robust navigation. However, GNSS signal tracking strategies have to be more advanced in\r\norder to profit from the enhanced properties of the new signals.In this paper, a tracking algorithm designed for Galileo E1 CBOC\r\nsignal that consists of two steps, coarse and fine, with different tracking parameters in each step, is presented and analyzed with\r\nrespect to tracking accuracy, sensitivity and robustness. The aim of this paper is therefore to provide a full theoretical analysis of\r\nthe proposed two-step tracking algorithm for Galileo E1 CBOC signals, as well as to confirm the results through simulations as\r\nwell as using real Galileo satellite data....
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