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Ubiquitous Positioning Indoor Navigation and Location Based Service (UPINLBS), 2010

Date 14-15 Oct. 2010

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Displaying Results 1 - 25 of 49
  • Indoor multipath mitigation

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (876 KB) |  | HTML iconHTML  

    There are many applications that require continuous positioning in combined outdoor urban and indoor environments. GNSS has been used for a long time in outdoor environments, while indoor positioning is still a challenging task. One of the major degradations that GNSS receivers experience indoors is the presence of multipath. The current paper analyzes several available multipath mitigation techniques which would be suitable for indoor applications. A few deconvolution based techniques such as the Projection Onto Convex Sets and the Deconvolution Approach are selected for closer investigation and their performance is demonstrated by using a controlled environment setup. View full abstract»

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  • Vector tracking loop design for degraded signal environment

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (813 KB) |  | HTML iconHTML  

    This paper presents vector tracking algorithm for tracking the pseudorandom code of satellite navigation signals, which is suitable for degraded signal environment. The benefits of the vector tracking in comparison of scalar tracking are also explained. This vector tracking algorithm is based on the discriminator function. Conventional GPS receivers use scalar tracking methods and signals from each channel are processed independently. On the contrary, vector tracking loops process the signals in aggregate and can provide better tracking in degraded signal environment, since the channels are closely correlated in vector mode. In vector tracking approach the tracking control input is generated by the navigation filter. The vector tracking loops can operate in weak signal conditions and can rapidly reacquire the weak or attenuated signals. In this paper the ability of vector tracking loop to reacquire the signals is explored and is compared with conventional scalar tracking method. View full abstract»

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  • Joint Data-Pilot acquisition and tracking of Galileo E1 Open Service signal

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2456 KB) |  | HTML iconHTML  

    Global Navigation Satellite Systems (GNSSs), such as the modernized Global Positioning System (GPS) and the ongoing European satellite navigation system Galileo, incorporate the new composite GNSS signals (e.g., Galileo E1 Open Service (OS) signal), which consist of two different components, the data and pilot channels. The existence of dual channel allows one to adopt special techniques to acquire and track these new signals. In this paper, the authors analyze the performance of three different implementation strategies, namely, i. Data-only, ii. Pilot-only, and iii. Joint Data-Pilot, for two different receiver modes: one with Sine Binary Offset Carrier (1,1) (SinBOC(1,1)) reference receiver, and the other one with Composite BOC (CBOC) reference receiver. All the simulations have been carried out in TUT Galileo E1 open source signal simulator, based on the most recent Galileo Signal-In-Space Interface Control Document (SIS-ICD). The simulation results show that acquisition with individual channel is not the best approach to acquire the signal as intuitively expected. Joint Data-Pilot channel combines all the significant power from data and pilot channels non-coherently that ultimately improves the signal detection around 2.8 dB, which has been verified via simulations in the context of the paper. Joint Data-Pilot channel also provides around 3 dB improvement over any individual channel in terms of tracking error variance. It will also be shown in the paper that the performance deterioration caused by using Sine BOC(1,1) reference receiver instead of CBOC reference receiver is negligible. Most of the findings based on data-pilot combination are as intuitively expected. However, the main novelty of the paper stays in presenting a realistic and detailed Simulink-based simulator for Galileo E1 signal that takes into account two receiver modes, and has already been made open access for research purpose. View full abstract»

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  • Optimising Fault Detection and Exclusion in positioning

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1165 KB) |  | HTML iconHTML  

    Reliability and integrity has become increasingly important in ubiquitous positioning systems, and particularly in critical applications. To implement reliability and integrity measures, Fault Detection and Exclusion (FDE) procedures should be used. However, the current FDE procedures in the chi-square test and the outlier test are suboptimal in terms of continuity and availability. This is due to the assumption that the bias always corresponds with the measurement that has the largest Protection Level (PL), and in the setting of the continuity probability to a predefined value rather than being maximised. The FDE procedures assume that the bias always corresponds with the measurement that has the largest PL. However, this is not the case since a bias can occur in any one of the measurements. Consequently, a procedure of averaging the Missed Detection probabilities calculated at the Alert Limit (AL) across all measurements was proposed in the literature. However, simulations demonstrated that only a minor improvement in the availability is achieved. The FDE procedures in the chi-square test and the outlier test are also dependent on the user specifying the instantaneous continuity probability that is required to be met. It is then, once the continuity probability has been specified, that the procedures determine if there is sufficient integrity, via the monitoring of the maximum PL in relation to the AL. However, in general, ubiquitous positioning systems do not have a minimum continuity probability that is required to be met; but simply desire the continuity probability to be maximised. This paper develops an optimised FDE strategy for one or more biases, which assumes that the bias can exist in any one of the measurements and allows varying satellite failure rates. In addition, the procedure also aims to provide a position that has sufficient integrity continuously, via maximising the instantaneous continuity probability. View full abstract»

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  • A CPU-friendly approach to on-demand positioning with a software GNSS receiver

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1207 KB) |  | HTML iconHTML  

    We present our recent work on developing a more flexible client-server software architecture for software GNSS receivers, targeted mainly for applications where position fixes are needed only occasionally. The receiver architecture is based on an IQ snapshot approach, where instead of tracking a continuous stream of IQ samples, the receiver stores a snapshot of IQ data and processes the stored samples separately. This approach relaxes the strict real time requirements of the software, compared to a continuously tracking software receiver. We present a number of operating contexts to which the software architecture can easily be adapted, and show our preliminary test results. View full abstract»

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  • GRAMMAR: Challenges and solutions for multi-constellation Mass Market user Receivers

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    In this paper we describe the prototype concept of multi-constellation GNSS receivers investigated in the Galileo Ready Advanced Mass Marker Receiver (GRAMMAR) EU FP7 project. The purpose of our work is to provide technology solutions with their implementations for multi-system GNSS mass market receivers by motivating the need for both hardware and software research and present the functional blocks for a multi-constellation GNSS receiver. View full abstract»

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  • Distributed-weighted multidimensional scaling for hybrid Peer-to-Peer localization

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1346 KB) |  | HTML iconHTML  

    This paper presents a hybrid localization algorithm for a Peer-to-Peer (P2P)-Positioning scenario, where “peers” are devices equipped with both a GNSS (Global Navigation Satellite System) receiver and a wireless communications interface. Through their GNSS receiver, peers obtain pseudorange estimates from satellites while they use their wireless interface both to communicate with each other and to obtain terrestrial range estimates. The proposed algorithm is an extended version of the distributed-weighted multidimensional scaling (dwMDS) algorithm to be compatible with the hybrid P2P scenario where unknown peers infer their own positions by fusing both GNSS pseudorange and terrestrial range estimates. Simulation results show that the proposed hybrid dwMDS (hdwMDS) algorithm out-performs the cooperative version of the least squares algorithm. Moreover, they show the related benefits in term of positioning performance in a cooperative scenario in comparison to a non cooperative one based on GNSS-only positioning. View full abstract»

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  • Positioning in resource-constrained ultra low-power Wireless Sensor Networks

    Page(s): 1 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1745 KB) |  | HTML iconHTML  

    Wireless Sensor Networks (WSNs) consist of densely deployed, independent, and collaborating low cost sensor nodes. The nodes are highly resource-constrained in terms of energy, processing, and data storage capacity. Thus, the protocols used in WSNs must be highly energy-efficient. WSN communication protocols achieving the lowest power consumption minimize radio usage by accurately synchronizing transmissions and receptions with their neighbors. In this paper, we show how network signaling frames of state-of-the-art synchronized communication protocols for low-power WSNs supporting mobile nodes can be used for positioning. We derive mathematical models for node power consumption analysis. The models provide a tool for estimating what kind of network lifetimes can be expected when average positioned node speed, the amount of anchor nodes required by the location estimation algorithm, and the location refresh rate required by the application are known. The presented analysis results are based on two kinds of node hardware: real node hardware prototypes having no Received Signal Strength Indicator (RSSI) support and typical values of an integrated chip using an IEEE 802.15.4 compliant radio with RSSI. View full abstract»

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  • The FMCW technology-based indoor localization system

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1597 KB) |  | HTML iconHTML  

    Indoor localization with the accuracy being better than few meters may be a quite challenging task when the system costs are an issue. This paper presents a frequency modulation continuous wave (FMCW) technology-based indoor localization system that has been built in the EU FP7 Confidence project. The main objective of the Confidence project is the development and integration of innovative technologies to build a care system for the detection of abnormal events, e.g. falls or unexpected behaviors that may be related to health problems of elderly people. In this paper, details on the hardware, firmware, and software parts of the developed prototype are provided. The localization algorithm based on the Kalman filter with the Gaussian averaging is presented. The localization performance is evaluated in the laboratory setting. Our first results indicate that in the case of localization in two dimensions the mean absolute position error is about 1 meter. View full abstract»

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  • TUTGNSS University based hardware/software GNSS receiver for research purposes

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1486 KB) |  | HTML iconHTML  

    Recently a lot of research has been going on in the field of Global Navigation Satellite System receivers. Only few projects have been providing open source hardware receivers. In this paper we present a university based GNSS receiver intended for open source release. The highly modular design of the receiver is described in detail. We also provide description of the software parts and advanced user interface of the receiver. In the end of the paper a test scenario is provided proving the functionality of the receiver design. The presented GNSS receiver architecture is expected to be valuable prototype for research purposes. View full abstract»

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  • Phase smoothing in a virtually synchronized pseudolite system using stochastic clock modelling

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB) |  | HTML iconHTML  

    A derivation of phase smoothing for a pseudolite system is given. The distinction to phase smoothing known from literature arises from the setup of the system. As of the employed free-running pseudolites, the main challenge is to properly estimate the pseudolite clocks. The better the pseudolite clocks are estimated, the more precise are the phase measurements and the more effective is phase smoothing. Two different methods for clock estimation are examined in terms of their applicability to phase smoothing. Simulated as well as real data are used in order to evaluate the precision gain by phase smoothing. Optimal solutions according to system restrictions are presented. View full abstract»

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  • Database updating through user feedback in fingerprint-based Wi-Fi location systems

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1621 KB) |  | HTML iconHTML  

    Wi-Fi fingerprinting is a technique which can provide location in GPS-denied environments, relying exclusively on Wi-Fi signals. It first requires the construction of a database of “fingerprints”, i.e. signal strengths from different access points (APs) at different reference points in the desired coverage area. The location of the device is then obtained by measuring the signal strengths at its location, and comparing it with the different reference fingerprints in the database. The main disadvantage of this technique is the labour required to build and maintain the fingerprints database, which has to be rebuilt every time a significant change in the wireless environment occurs, such as installation or removal of new APs, changes in the layout of a building, etc. This paper investigates a new method to utilise user feedback as a way of monitoring changes in the wireless environment. It is based on a system of “points” given to each AP in the database. When an AP is switched off, the number of points associated with that AP will gradually reduce as the users give feedback, until it is eventually deleted from the database. If a new AP is installed, the system will detect it and update the database with new fingerprints. Our proposed system has two main advantages. First it can be used as a tool to monitor the wireless environment in a given place, detecting faulty APs or unauthorised installation of new ones. Second, it regulates the size of the database, unlike other systems where feedback is only used to insert new fingerprints in the database. View full abstract»

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  • Optimizing radio map for WLAN fingerprinting

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (899 KB) |  | HTML iconHTML  

    In this paper, questions related to design of WLAN radio map for fingerprinting based positioning were investigated. The experiment results show that with histogram based algorithms, the positioning accuracy improves as the number of histogram bins increases until the number of bins reaches eight. With the number of bins lower than this, the uneven bin distribution with separate bin for missing samples gives better accuracy than even bin widths. If the calibration data contains samples from several measurement directions, it is beneficial to combine them into one fingerprint, as this decreases the size of the radio map and gives at least the same accuracy as having separate fingerprints for different measurement directions. In the experiments, the combination of the signals from correlating sources before the computation of the radio map and position estimate decreases the positioning accuracy only by 1-2 m, but decreases significantly the size of the radio map. The best method for signal combinations depends on the bin configuration and position estimation algorithm. View full abstract»

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  • Rao-Blackwellized particle filter for pattern matching indoor localisation

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (763 KB) |  | HTML iconHTML  

    Pattern matching localisation based on Received Signal Strength Indication (RSSI) is widely implemented in the Wireless Local Area Network (WLAN). This implementation is commonly with a filtering method to achieve better location estimation accuracy. A Kalman filter (KF) is an optimal filter, if requirements on linear/Gaussian state space model are met. Otherwise, a particle filter (PF) should be used to deal with nonlinear/non-Gaussian state space model. However, in the real situation especially in the localisation field, the state space model may be linear/Gaussian and nonlinear/non-Gaussian. Therefore, there should be a filtering method that can accommodate both linear/Gaussian and nonlinear/non-Gaussian state space model such as Rao Blackwellized particle filter (RBPF). RBPF implemented in the pattern matching localisation system is described and its performance is compared against KF and PF. Those three filtering methods are evaluated in the test bed. To the best of our knowledge, implementing RBPF and performance comparison against KF and PF in the pattern matching indoor localisation in WLAN environment have never been published before. View full abstract»

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  • Mobile tracking in unknown non-line-of-sight conditions

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (545 KB) |  | HTML iconHTML  

    This paper studies the mobile tracking problem in mixed line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, where the statistics of NLOS error are assumed unknown. Three different models are used to describe the NLOS errors. A Rao-Blackwellized particle filtering with parameter learning (RBPF-PL) is presented, in which the posterior of sight conditions is estimated by particle filtering while the mobile state and NLOS parameters are analytically computed. Simulation results are provided to evaluate the performance of RBPF-PL variants in different situations. Simulation show that unless it is known that NLOS noise has the same bias and variance in all the observations, the more complicated models should be employed as they work correctly even in NLOS model mismatch, with only slightly more computational complexity. View full abstract»

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  • UbiSpot - A user trained always best positioned engine for mobile phones

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2555 KB) |  | HTML iconHTML  

    We implemented a positioning engine for mobile phones that can be trained by the users to recognize places as personal landmarks by their wireless communication fingerprint. Our always-best-positioned approach integrates heterogeneous sensor data, such as Bluetooth (BT) device addresses, WLAN MACs, GSM cell ids and GPS coordinates, if available. As an alternative to measuring the signal strength of wireless access points, our positioning engine measures the relative frequency of their appearance and disappearance over time, which closely correlates to their distance. The user can add new places as symbolic names to a hierarchical location model at any time using their mobile phone. For each place, the wireless sensor fingerprint can be trained by the user to define a landmark. Once landmarks have been trained, the positioning engine continuously matches the current sensor profile against the database of learned fingerprints and chooses the most likely place. In case that no BT or WLAN APs are visible, the hierarchical data model can at least derive a higher-level description of the current region based on GSM or GPS as fallback strategy in the sense of being always best positioned. We evaluated the positioning accuracy in our university's lab environment in terms of hits and misses and investigated the effect of various time window sizes for the frequency measurement of the fingerprint. The symbolic location model can be applied for example to adapt the mobile device to different contexts, e.g. automatically mute the ringtone in meeting rooms, trigger location-dependent rules and events, or disclose the current location to friends. View full abstract»

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  • Movement tracking of sports team players with wireless sensor network

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1941 KB) |  | HTML iconHTML  

    In this paper, we provide a study of applying location aware wireless sensor network system for tracking movements and gathering sensor data from sports team players. A set of system design requirements are developed that cover the design of the sensor network system, the hardware design of the mobile nodes, the design of the position algorithm, the design of communication protocols, and the design of testbed for testing positioning accuracy. Based on the field experiments, we propose a system architecture that fulfills these requirements. The architecture proposed implements e.g. hybrid location technologies for better accuracy and data aggregation for energy efficiency. View full abstract»

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  • Software for journey-planning with public transport in Skopje

    Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3381 KB) |  | HTML iconHTML  

    The increasing popularity of GPS (Global Positioning System) device has boosted many applications, especially those for GPS information visualization. Information visualization techniques are invaluable tools in numerous applications. The goal of this work is to provide visual access to GPS information through the proposed trip planning web application. The main focus is on visualization, organization, fast retrieval, and effective understanding of GPS data mainly for public use, and the simplest way to plan the journey through the city. The main objective is to introduce this internet-based application to the users of the public transport services. The GPS technology is a new technology in Macedonia and trip planning is not implemented yet, although it has been used in many countries remarkably within the last years. Combining the collected GPS and timetable data in order to bring passengers to a desired location, the goal of journey planner is to reduce travel related risks and uncertainties for passengers who want to travel to an unknown part of the city, or tourists, elderly people or people who usually do not use public transport service. View full abstract»

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  • Data matrix technology for linking mobile maps in a web-based multi-channel service

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4324 KB) |  | HTML iconHTML  

    In the paper we discuss how data matrices are being applied in an experimental way in the MenoMaps research project. One of the outcomes of the project is a map-based service prototype with multipublishing channels capable of delivering the same map data for the users via different media. We demonstrate how the data matrices could be displayed on paper maps as a link to location-specific information. The most promising applications are those where the content is very dynamic. We also show how a map application on a multitouch wall display can be linked through a data matrix to a map application on a mobile phone, to support the user's smooth switch from one channel to another. We carried out a user study on experimental hiking maps among the visitors of a national park in Finland. The survey reveled that user-awareness of the 2D barcode technology and usage is still low. View full abstract»

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  • Advanced MDS based localization algorithm for location based services in Wireless Sensor Network

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2107 KB) |  | HTML iconHTML  

    Wireless Sensor Networks (WSNs) are increasingly being used for various information collection in the future. For many applications, a large number of sensors in an active wireless network are more effective and preferable to a few expensive wireless sensors. Location discovery of sensor nodes after they have been deployed is known as a challenge, especially for moving sensors. Algorithms based on radio signal strength indication are considered as the lowest cost method to solve localization problem. But in practice, the accuracy of signal strength indication algorithm varies with the average distances between wireless nodes - the nearer, the better. This paper describes a new integrated dynamic localization algorithm, based on Received Signal Strength Indication (RSSI) and Multidimensional Scaling (MDS) algorithm. In this concept, signals with RSSI values among beacon nodes could help to generate a real time 2D map of the network by self iterations. Unknown nodes use the map to determine their locations in this region. A software simulator is created to test the performance of the algorithm, and practical experiments also show the development of localization accuracy and efficiency. View full abstract»

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  • A client-server architecture for audio-supported mobile route guiding for hiking

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (693 KB) |  | HTML iconHTML  

    An architecture for speech- and auditory cue-based route instructions is introduced in the paper. The server side architecture is composed of a set of web services. The architecture allows connecting different route services behind a single interface. The route instructions can be transferred as recorded speech, vibration patterns, auditory cues and in textual form between the server and client side. The OpenLS Route Service schema is extended to include in the route instruction responses references to the recorded speech, auditory cues, vibration patterns, encoded textual instructions and brief instructions. The auditory cues may include auditory icons, earcons or spearcons. The textual instructions are based on the Speech Synthesis Markup Language, and a text-to-speech engine on the client side can automatically translate them. The presented holistic approach is aiming to increase the accessibility of route services, especially for visually impaired and elderly people. View full abstract»

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  • Perspective federated testbed for public safety communications, ubiquitous positioning, indoor navigation and location based services

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (856 KB) |  | HTML iconHTML  

    This paper presents a description of major principles of federated testbed for public safety communications activities, its concept, structure, objectives, and trial scenarios. View full abstract»

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  • Towards precise car navigation: Detection of relative vehicle position on highway for collision avoidance

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3416 KB) |  | HTML iconHTML  

    In this paper, we focus on evaluating the performance of NTrip/RTK solutions for accurate and precise car navigation (analysis of both the accuracy and availibility of RTK data using mobile communication). Our approach is to develop a functional system of determining lane positions on highways. A system is based on wireless radio communication among surrounding vehicles what complement and enhance the current vehicle driving system needs (lane change collision avoidance systems, vehicle tracking, lane keeping and obstacle avoidance). Because lane change collision avoidance system requires very high relative accuracies between moving objects, therefore we are introducing "moving basestation" option into our system. Relative Moving Base Software (RMBS) package is implemented in real-time into NovAtel Propak-v3 GNSS receivers. This solution provides centimeter level baseline accuracy in relative vehicle positioning. For the RMBS implementation, the moving base position is only single point position, and must be recomputed for every epoch. Therefore, RTK/Ntrip base solution is required in this system. Exchanging Position, baseline and velocity information among surrounding vehicles using the twoway PacificCrest radiomodem link, definitely improves safety and efficiency of automobile transportation on the highways. Two experiments were conducted on test routes using two cars in the combined driving conditions (highway + downtown). Both tests took place at Wuhan University, GNSS Research Center, China. One additional test was performed using an NTrip stream delivered by a free-standing mount point obtaining data from the reference Trimble NetR5 receiver. We demonstrate the versatility of the system, showing the advantages and disadvantages of each component. View full abstract»

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  • Content aggregation in personal location-aware mashup

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1142 KB) |  | HTML iconHTML  

    A personal location context mashup solution called LBS 2.0 is introduced in this paper. A widget based on the LBS 2.0 idea is implemented on a mobile phone to aggregate multiple contents from the internet. A Symbian-based web runtime location service is applied for calculating the location information including position, distance, time, and speed. A geolocation service offers an interpretation capability between coordinates and addresses. The principles for indentifying mashup sources are described. Contents retrieving and parsing processes are explained. Finally, a personal location aware utilization scenario is presented to show the contexts combined in the LBS 2.0 mashup on a Nokia 5800 XpressMusic handset. View full abstract»

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  • An approach of 3D model simplification for mobile phone based navigation application

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (747 KB) |  | HTML iconHTML  

    Nowadays 3D concepts are tightly related to our lives. However one of the challenges for 3D applications is the huge amount of datasets. Therefore data reduction is critical for the increasing applications, especially for limited memory and storage space devices, e.g. mobile phone. In this paper, we propose an approach of 3D model simplification for mobile phone based navigation application. This method is developed based on the data from 3D models of Finnish pavilion. Our objectives are to reduce the model to the reasonable size and keep original appearance and realize the localization of data storage for the display, rendering and navigating on mobile phone. We use 2D projections of 3D data and line sweeping methods to extract the key points of models and data reduce to almost 4 percent of the original data. As a result, the indoor models of Finnish pavilion are successfully shown and apply for indoor navigation. View full abstract»

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