Sharif Digital Repository

In this paper, an algorithm for positioning error reduction of a low-cost global positioning system (GPS) receiver for kinematical applications has been proposed. Proposed algorithm is mainly based on determining jittered data points (outliers) in the data file based on the correlation among positioning data in three different directions. The main point of applicability of proposed algorithm for kinematical applications is aforementioned correlation. The proposed algorithm and a recursive averaging algorithm has been implemented and tested on the output raw position data collected from a low-cost GPS receiver. Experimental results demonstrate the superior performance of the proposed... 

Positioning for kinematic applications is of great importance in terms of accuracy and computational complexity. In this paper, we present an algorithm based on correlation between error components in three directions, i.e. Δx, Δy, Δz to decrease positioning error of a GPS receiver for kinematic applications. The main feature of proposed algorithm is that it modifies data at each instant and in each direction using data of two other directions at the same instant (i.e. some sort of online modification). This feature was acquired using an approach introduced to model state transition matrix using AR coefficients of two other directions. The algorithm was implemented on the output raw position... 

A very low-power RF front-end based on a new current reuse QLMV cell (Quadrature VCO-LNA-Mixer) is proposed for GPS applications. The front-end, designed in 0.18μm CMOS technology, provides improved performance characteristics while consuming only 1 mA current. Simulation results are presented and compared with recently published works in the field  

We present an asymptotically convergent nonlinear attitude estimator using a rate gyro and GPS. Double-difference (DD) carrier phase measurements are provided by at least two GPS antennas. The unknown integer ambiguity factor related to GPS carrier phase measurement is estimated along with the attitude. An observability condition is derived to guarantee the convergence of the estimator when a single baseline vector is available with more than four satellites in view. A systematic procedure for tuning observer parameters is also presented. Finally, the experimental test from a light fixed-wing aircraft illustrates the performance of the proposed observer. © 1993-2012 IEEE  

This paper presents an asymptotically-convergent nonlinear attitude estimator for rigid bodies using a rate gyro and GPS. Double-difference carrier phase measurement are provided by at least two GPS antennas. The unknown integer ambiguity factor related to GPS carrier phase measurement is estimated along with the attitude. An observability condition is derived to guarantee convergence of the estimator when a single baseline vector is available with more than four satellites in view. Finally, experimental test from a survey boat illustrates performance of the proposed observer. © 2018 IEEE  

With the advent of new positioning services, one can reach more satellites these days to find his position. Using a combination of satellites which belong to different constellations needs some considerations like addressing biases between their time references. Each constellation has progressed to the point that they have enough satellites to provide accurate position separately. According to this fact, we propose to find the position in each constellation and fusion their results in a way that final position has the minimum possible variance instead of combining the constellations in a satellite level and dealing with inter system biases. Experimental studies are conducted based on IGS... 

A new low-power current reuse topology is proposed for the GPS receiver's RF front-end that combines the higher conversion gain and suppressed noise figure characteristics of cascade structures with the low power consumption of stacked architectures. The presented circuit, called 1.5-stage LMV cell, consists of LNA, Mixer and VCO (LMV) in such a formation that boosts LNA gain and suppresses mixer's noise figure by cascading the two stages while reusing their currents in the two stacked quadrature VCOs and placing the mixer's upper tree switches at the vicinity of on-off regions. The circuit is designed and its layout is generated in TSMC 0.18μm CMOS technology. Post-layout simulations using... 

Authentication is an essential security requirement in safety-related vehicle-to-vehicle applications in VANETs. TESLA is one of the most popular broadcast source authentication protocols proposed and standardized for this purpose. Having strict time constraints and being prone to GPS synchronization errors make the analysis of this protocol challenging. In this paper, we utilize a timed model checking approach based on timed colored Petri nets to model and verify TESLA considering its time-sensitive behaviors. In this way, we show how neglecting timing aspects in protocol design and in protocol modelling can lead to successfully launched attacks and erroneous analyses respectively, and how... 

Systems based on machine vision are used more and more these days. Machine vision is used widely in different industries for increasing efficiency and automating processes, and one of the reasons which makes these techniques so popular is the speed of producing more powerful hardware which in recent times became more accessible, so real time using of many algorithms is possible Our group is designing and producing a stereo vision based system for detection, tracking, and accurate speed measurement of multi vehicles in, both mobile and stationary status, different weather condition, day and night, urban streets and highways, which is now used by police for law enforcement. The system offers...