Nima Alam - Academia.edu (original) (raw)

Papers by Nima Alam

Abstract—Position information is a fundamental requirement for many vehicular applications such a... more Abstract—Position information is a fundamental requirement for many vehicular applications such as navigation, intelligent transportation systems (ITSs), collision avoidance, and locationbased services (LBSs). Relative positioning is effective for many applications, including collision avoidance and LBSs. Although Global Navigation Satellite Systems (GNSSs) can be used for absolute or relative positioning, the level of accuracy does not meet the requirements of many applications. Cooperative positioning (CP) techniques, fusing data from different sources, can be used to improve the performance of absolute or relative positioning in a vehicular ad hoc network (VANET). VANET CP systems are mostly based on radio ranging, which is not viable, despite being assumed in much of the literature. Considering this and emerging vehicular communication technologies, a CP method is presented to improve the relative positioning between two vehicles within a VANET, fusing the available low-level Gl...

Abstract—A novel approach is proposed to enable vehicles to estimate their instantaneous position... more Abstract—A novel approach is proposed to enable vehicles to estimate their instantaneous position with lane-level accuracy, which is not achievable using Global Navigation Satellite Systems (GNSSs). This system can be used to enhance position-based applications such as Intelligent Transportation Systems (ITSs), including navigation and lane-level traffic guidance and warning. The system uses the carrier frequency offset (CFO) of the dedicated short-range communication (DSRC) signal, broadcast by two infrastructure beacons. The main advantages of the proposed method over other potential technologies such as radio-frequency identification (RFID) and buried loops are its simpler required infrastructure and functionality using vehicular communication platforms. Analysis of the proposed technique indicates acceptable reliability and performance. Empirical test results confirm the viability of the method. Index Terms—Carrier frequency offset (CFO), dedicated shortrange communication (DSRC...

from the same university. He has been involved in a variety of projects in the automotive industr... more from the same university. He has been involved in a variety of projects in the automotive industry including industrial robotics, moving robots, factory automation, machine vision, GPS navigation, and fleet management

Vehicular Cooperative Positioning (CP) is a recently emerged concept to estimate or improve posit... more Vehicular Cooperative Positioning (CP) is a recently emerged concept to estimate or improve position information of vehicles in Vehicular Ad-Hoc Networks (VANETs). Using CP, positioning accuracy and availability is improved in the areas without (or with poor) availability of the Global Navigation Satellite System (GNSS) signals. CP is based on vehicular communication for which Dedicated Short Range Communication (DSRC) is considered as a standard medium. Considering the aspects and constraints of DSRC, participating infrastructure nodes in a CP system must be installed along the streets, especially in dense urban areas. This geometrical arrangement can lead to reduced Dilution of Precision (DOP) which has an impact on the performance of a CP technique. In this article, the effect of such typical geometry on the performance of two typical CP methods, rangebased and range-rate-based, is investigated. The DOP is analysed for these CP methods and a filtering method is proposed to improv...

BIOGRAPHY Nima Alam is pursuing his PhD in the field of "Vehicular Positioning Enhancement w... more BIOGRAPHY Nima Alam is pursuing his PhD in the field of "Vehicular Positioning Enhancement with DSRC" in the School of Surveying & Spatial Information Systems at the University of New South Wales commencing Feb. 2009. He achieved a Bachelor degree in Telecommunication Systems from Sharif University of Technology, Tehran, Iran, in 1998. He obtained his Masters degree in Control Systems in 2000 from the same university. He has been involved in a variety of projects in the automotive industry including industrial robotics, moving robots, factory automation, machine vision, GPS navigation, and fleet management between 2000 and 2008. Asghar Tabatabaei has a BE (1997) and MEngSc (2000) in Electrical Engineering from Sharif University of Technology, Tehran, Iran and PhD (2008) in global navigation satellite interference from the University of New South Wales, Sydney, Australia where he has also worked as a post doctoral research fellow in the School of Surveying and Spatial Infor...

Vehicular network with communication among vehicles and between roadside units and vehicles is a ... more Vehicular network with communication among vehicles and between roadside units and vehicles is a recently emerged field of challenge for researchers. Dedicated Short Range Communication (DSRC) is the nominated communication channel specifically designed for this network. Using DSRC, besides sharing information among vehicles, the distances between the nodes of the network can also be estimated for their positioning solutions. In the literature, many algorithms and strategies are presented for radio ranging with less emphasis on constraints and difficulties of distance estimation in vehicular networks. In this paper, different methods of radio ranging like Received Signal Strength (RSS), Time of Arrival (TOA), and Time Difference of Arrival (TDOA) for distance estimation are introduced with emphasis on some important aspects of these methods which should be taken into account by researchers and engineers. Considering some important concerns, related to ranging and positioning with ra...

The Global Positioning System has already provided the positioning information for a variety of a... more The Global Positioning System has already provided the positioning information for a variety of applications in vehicular navigation systems. However, the limited accuracy of pseudorange-based GPS for civilian usage makes it unsuitable for many safety applications. Cooperative positioning in vehicular networks is a relatively new concept for enhancing positioning in a group of vehicles which can communicate with each other. Sharing each node's data in the network of nodes and measuring distance between nodes are the main aspects of almost all cooperative positioning algorithms. However, distance measurement is very challenging and problematic for mobile networks and especially for the harsh environment of vehicular networks. The most common techniques of radio ranging such as Received Signal Strength (RSS), Time of Arrival (TOA), and Time Difference of Arrival (TDOA) are often considered in cooperative positioning algorithms without considering their essential shortcomings and l...

BIOGRAPHY Nima Alam is pursuing his PhD in the field of "Vehicular Positioning Enhancement w... more BIOGRAPHY Nima Alam is pursuing his PhD in the field of "Vehicular Positioning Enhancement with DSRC" at the University of New South Wales commencing Feb. 2009. He has a BE (1998) in Telecommunication Systems from Sharif University of Technology, Tehran, Iran and a MEngSc (2000) in Control Systems from the same university. He has been involved in a variety of projects in the automotive industry including industrial robotics, moving robots, factory automation, machine vision, GPS navigation, and fleet management between 2000 and 2008. ABSTRACT Limited availability of the Global Navigation Satellite System (GNSS) signals in urban canyons is a preventive factor for implementing many position-based systems. Specifically for vehicles, a variety of applications such as Intelligent Transportation Systems (ITS), navigation, and Location-Based Services (LBS) are not properly functional in dense urban areas due to constrained visibility of the GNSS signals. Tackling this problem, a ...

Vehicular positioning in urban canyons or covered areas such as car parks is a challenging issue ... more Vehicular positioning in urban canyons or covered areas such as car parks is a challenging issue due to the limited availability or lack of Global Navigation Satellite System (GNSS) signals. Tackling this problem, the concept of Cooperative Positioning (CP) has recently emerged for positioning or positioning enhancement in Vehicular Ad-Hoc Networks (VANETs). In the literature, CP techniques are generally based on vehicular communication and range estimates between the vehicle and some reference nodes with known position. The viability and performance of conventional radio ranging methods such as Received Signal Strength (RSS), Time of Arrival (TOA), and Time Difference of Arrival (TDOA) for vehicular environments is questionable. Avoiding the constraints and shortcomings of radio-ranging methods, a new CP technique is presented. This technique is based on range-rate estimates between the vehicle and reference nodes. Range-rate is estimated using Carrier Frequency Offset (CFO) of the...

The concept of Cooperative Positioning (CP) has emerged recently to improve the quality of positi... more The concept of Cooperative Positioning (CP) has emerged recently to improve the quality of positioning, provided by Global Navigation Satellite System (GNSS), in terms of accuracy and availability. This is necessary to meet the requirements of the vehicular position-based applications such as collision avoidance, which cannot rely only on GNSS performance. CP systems are based on fusing data from different sources, including GNSS, for positioning quality improvement. A typical class of CP is based on the GNSS-based position estimates and distances between the participating vehicles. Inter-vehicle ranging and GNSS errors are limiting factors for achievable performance using CP systems. Inter-vehicle range-rate is also a potential observable for CP systems. In this article, the performance boundaries for range-based and range-rate-based CP systems are investigated. The limits on the achievable performance with different topologies and observations are investigated. Also, the required ...

The Global Positioning System (GPS) signals reflected from the ocean surface have been considered... more The Global Positioning System (GPS) signals reflected from the ocean surface have been considered for estimating geophysical parameters includingocean near-surface wind speed and wave height. A variety of models, methods, and experimental campaigns have verified the level of viability and reliability of the bistatic GPS radars. In this article, we analyse the ocean roughness information inherent in the reflected GPS signals in terms of the ocean state, the number of visible satellites and the altitude of the receiver. Through this theoretical analysis the Cramer-Rao lower bound (CRLB) can be derived to benchmark the performance of surface roughness estimation. In the analysis the impact of different surface wind speeds and surface roughness on the sea state estimation error is studied. Real position data of observed satellites are used to calculate the CRLB in a certain area over 24 hours. The applicability of the theoretical results to airborne and spaceborne receivers is also disc...

2009 IEEE International Conference on Vehicular Electronics and Safety (ICVES), 2009

Vehicular communication technologies are on their way to be recognized as icons of modern societi... more Vehicular communication technologies are on their way to be recognized as icons of modern societies. One important scientific challenge to the safety related applications of vehicular communication is indeed semi-precise positioning. Cooperative positioning is an idea for that purpose, and of course from research point of view is very attractive. From the practical point of view the attractiveness of cooperative positioning lies in its independence from any major additional infrastructure other than the vehicular communication systems. This paper introduces a new positioning algorithm for localization of mobile networks, in general, that nicely applies to vehicular networks. The algorithm is based on the well known multidimensional algorithm and shows remarkable performance compared to its counterparts in the vehicular positioning literature.

2010 IEEE 72nd Vehicular Technology Conference - Fall, 2010

Global Navigation Satellite Systems (GNSS) can be used for navigation purposes in vehicular envir... more Global Navigation Satellite Systems (GNSS) can be used for navigation purposes in vehicular environments. However, the limited accuracy of GNSS makes it unsuitable for applications such as vehicle collision avoidance. Improving the positioning accuracy in vehicular networks, Cooperative Positioning (CP) algorithms have emerged. CP algorithms are based on data communication among vehicles and estimation of the distance between the nodes of the network. Among the variety of radio ranging techniques, Received Signal Strength (RSS) is very popular due to its simplicity and lower cost compared to other methods like Time of Arrival (TOA), and Time Difference of Arrival (TDOA). The main drawback of RSSbased ranging is its inaccuracy, which mostly originates from the uncertainty of the path loss exponent. Without knowing the environment path loss exponent, which is a time-varying parameter in the mobile networks, RSS is effectively useless for distance estimation. There are many approaches and techniques proposed in the literature for dynamic estimation of the path loss exponent within a certain environment. Most of these methods are not functional for mobile applications or their efficiency decreases dramatically with increasing mobility of the nodes. In this paper, we propose a method for dynamic estimation of the path loss exponent and distance based on the Doppler Effect and RSS. Since this method is fundamentally based on the Doppler Effect, it can be implemented within networks with mobile nodes. The higher the mobility of the nodes, the better performance of the proposed technique. This contribution is important because vehicles will be equipped with Dedicated Short Range Communication (DSRC) in the near future.

Present and Future Challenges

Despite the fact that drivers are often blamed for fatal accidents on the roads, the significant ... more Despite the fact that drivers are often blamed for fatal accidents on the roads, the significant number of deaths on the roads indicate a systematic failure to exploit intelligence in the vehicular road system. The need for novel and comprehensive approaches to road safety has led major industrial and government bodies to accept the DSRC (Dedicated Short Range Communication) as a solution for urban safety. DSRC is a 75 MHz bandwidth communication medium between 5.85 GHz and 5.925GHz. It will enable VANET (Vehicular Adhoc NETworks), allowing the spontaneous set up of networks between vehicles, roadside infrastructure and pedestrians, in the form of autonomous message exchanges. Many safety applications can be addressed in the context of VANET; an important example is collision avoidance systems. All the safety applications can be considered to be Location-Based Services (LBS) and require continual position estimation. For the most important applications, such as collision avoidance, position must be estimated at a frequency of 10Hz with an accuracy of no less than 50 cm [1]. Currently satellite-based positioning systems known as GNSS (Global Navigation Satellite Systems) are the only comprehensive positioning tool for vehicles. In spite of the fact that different GNSS systems such as the Global Positioning System (GPS), Russia's GLObal NAvigation Satellite System (GLONASS), and Europe's Galileo can be used for positioning in good open-sky environments, the issue that is often neglected is that these systems cannot satisfy the requirements of DSRC safety applications. For example, single frequency GPS receivers that are widely used for vehicular navigation are position estimation engines with 10 m accuracy reported at 1 Hz. In addition to this accuracy issue, since the satellites can be easily masked by high rise buildings in the city centers, there are reliability issues with GNSS positioning for DSRC safety applications. Note that any solution technology for DSRC positioning needs to be extremely cost effective for mass production. This eliminates the possibility of using highly accurate MEMS (Micro Electrical and Mechanical Sensors) gyros because these are very expensive. Cooperative Positioning (CP) refers to any method which combines different positioning tools and sensor data in order to improve the quality of positioning for different purposes. The fundamental elements of CP are communication and data fusion. Specifically, for vehicular applications, CP methods can be classified into conventional and modern CP. Conventional Cooperative Positioning methods that have been developed for different applications than vehicular include Differential GPS (DGPS), Real Time kinematic (RTK) GPS, Assisted-GPS (AGPS), Satellite Based Augmentation System (SBAS), and Ground Based Augmentation System (GBAS). These methods have shortcomings when it comes to vehicular applications, especially in urban areas and these will be clarified later in the chapter. Because of these concerns, the necessity of innovative approaches for CP in vehicular applications is evident. {I would put a list here of the traditional and modern CP methods we discuss} Cooperative Network Positioning (CNP) is a modern CP technique which can provide safe and reliable position information for road safety applications. This is effectively the ad hoc sensor network localization problem revisited specifically for vehicles. This problem, using pseudorange measurements, is usually tackled by trilateration, and multilateration. These situations correspond to when the nodes with unknown positions measure their distances respectively from three anchor points, and more than three anchor points. However, in networks, it is possible to use the information from the pseudorange measurements between

International Association of Geodesy Symposia, 2013

GPS augmentation in the form of multi-sensor systems is an accepted approach to positioning in GP... more GPS augmentation in the form of multi-sensor systems is an accepted approach to positioning in GPS-challenged environments. An extension of this is the concept of collaborative or cooperative positioning, through which a network of GPS users may collectively receive any available satellite signals, augmented by inter-nodal ranging and other sensory measurements to achieve joint and potentially improved position determination. This paper presents an analysis of CP techniques for robust GPS positioning in vehicular ad-hoc networks (VANETs) based around the availability of dedicated short range communications infrastructure (DSRC). Preliminary performance assessments based on simulated and field data collected at the Ohio State University in November 2011 verify that the CP algorithm developed here offers improved accuracy compared to a CP solution that uses standalone GPS positions: 50 % improvement for the duration of the OSU test and 38 % with outages simulated to represent periods of 100 % satellite unavailability.

ABSTRACT Cooperative Positioning (CP) techniques in vehicular ad hoc networks rely primarily on m... more ABSTRACT Cooperative Positioning (CP) techniques in vehicular ad hoc networks rely primarily on measurements from the Global Positioning System (GPS) to deliver measurements or positions that describe the location of individual vehicles. In urban environments, the reduced quality or complete unavailability of GPS measurements challenge the effectiveness of any CP algorithm. In this paper we propose the fusion of measurements from low cost inertial sensors as a means of improving the CP algorithm when GPS is unavailable. This paper presents results obtained from a practical experiment coordinated under the International Association of Geodesy (IAG) – Commission 4 and the International Federation of Surveyors (FIG) Commission 5, in which ranging information derived from Dedicated Short Range Communications (DSRC) hardware is combined with low-cost GPS and INS measurements communicated between vehicles. The experimental configuration sensors used and data analysis are detailed in this paper as well as preliminar

ABSTRACT GNSS alone is not a reliable source for DSRC safety applications. Cooperative Positionin... more ABSTRACT GNSS alone is not a reliable source for DSRC safety applications. Cooperative Positioning (CP) in VANET refers to a technique based on communication via a DSRC channel and information fusion. CP combines the information gathered from several road users to refine self-position. CP can require range measurement between vehicles by some radio ranging technique. Two types of CP are introduced in this paper, loose and tight GPS/DSRC integration, which differ in the type of data being communicated. For loose CP, the position, velocity and measured ranges are broadcast to all neighbouring vehicles. For tight CP, the pseudo-ranges are communicated, instead of the positions. The two algorithms are compared using a Cramar Rao Lower Bound (CRLB) analysis and their effectiveness is evaluated. Tight integration proves to perform better, as might be expected.

2013 10th Workshop on Positioning, Navigation and Communication (WPNC), 2013

ABSTRACT Collaborative (or cooperative) positioning or navigation uses multiple location sensors ... more ABSTRACT Collaborative (or cooperative) positioning or navigation uses multiple location sensors with different accuracy on different platforms for sharing of their absolute and relative localizations. Typical application scenarios are dismounted soldiers, swarms of UAV's, team of robots, emergency crews and first responders. This paper studies the challenges to realize a public and low-cost solution, based on mass users of multiple-sensor platforms. For the investigation field experiments revolved around the concept of collaborative navigation in a week at the University of Nottingham in May 2012. Different sensor platforms have been fitted with similar type of sensors, such as geodetic and low-cost high-sensitivity GNSS receivers, tactical grade IMU's, MEMS-based IMU's, miscellaneous sensors, including magnetometers, barometric pressure and step sensors, as well as image sensors, such as digital cameras and Flash LiDAR, and ultra-wide band (UWB) receivers. The employed platforms in the tests include a train o

2012 International Conference on Indoor Positioning and Indoor Navigation (IPIN), 2012

Abstract An integrated positioning solution termed &amp;amp;amp;amp;amp;amp;amp;amp;#x27;... more Abstract An integrated positioning solution termed &amp;amp;amp;amp;amp;amp;amp;amp;#x27;collaborative positioning&amp;amp;amp;amp;amp;amp;amp;amp;#x27;employs multiple location sensors with different accuracy on different platforms for sharing of their absolute and relative localizations. Typical application scenarios are dismounted soldiers, swarms of UAV&amp;amp;amp;amp;amp;amp;amp;amp;#x27;s, team of robots, emergency crews and first responders. The stakeholders of the solution (ie, mobile sensors, users, fixed stations and external databases) are involved in an iterative algorithm to estimate or improve the accuracy of each node&amp;amp;amp;amp;amp;amp;amp;amp;#x27;s position based ...

2012 International Conference on Indoor Positioning and Indoor Navigation (IPIN), 2012

ABSTRACT Cooperative Positioning (CP) techniques are used to enhance the performance of positioni... more ABSTRACT Cooperative Positioning (CP) techniques are used to enhance the performance of positioning through sharing position-related data among a number of agents. These agents are usually users with mobility and, possibly, the infrastructure node(s). In CP systems, position-related data are shared among the participating nodes using a communication medium. Inter-node distance is a common parameter considered in CP techniques, especially for those in the environments with limited Global Navigation Satellite System (GNSS) visibility including dense urban areas and indoor environments. Radio ranging based on Received Signal Strength (RSS) is popular among researchers for its simplicity. However, the accuracy of this method is far beyond the requirements of CP systems. Here, we introduce Carrier Frequency Offset (CFO) as a potential observable to improve RSS ranging. Regardless of the content of the data communicated among the agents, RSS and CFO always exist in the communication signal. Therefore, the results of this work can be applied to improve the performance of any other CP method. Here, a hybrid CFO-RSS ranging method is presented to improve the accuracy of RSS ranging. The experimental results show up to 80% accuracy improvement over RSS using the proposed hybrid CFO-RSS technique. Although the examples used here are for outdoor situations, the outcomes are directly applicable indoors or any situation where GNSS signals are not available.

BIOGRAPHY Nima Alam is pursuing his PhD in the field of "Vehicular Positioning Enhancement w... more BIOGRAPHY Nima Alam is pursuing his PhD in the field of "Vehicular Positioning Enhancement with DSRC" at the University of New South Wales commencing Feb. 2009. He has a BE (1998) in Telecommunication Systems from Sharif University of Technology, Tehran, Iran and a MEngSc (2000) in Control Systems from the same university. He has been involved in a variety of projects in the automotive industry including industrial robotics, moving robots, factory automation, machine vision, GPS navigation, and fleet management between 2000 and 2008. ABSTRACT Limited availability of the Global Navigation Satellite System (GNSS) signals in urban canyons is a preventive factor for implementing many position-based systems. Specifically for vehicles, a variety of applications such as Intelligent Transportation Systems (ITS), navigation, and Location-Based Services (LBS) are not properly functional in dense urban areas due to constrained visibility of the GNSS signals. Tackling this problem, a ...

2009 IEEE International Conference on Vehicular Electronics and Safety (ICVES), 2009

2010 IEEE 72nd Vehicular Technology Conference - Fall, 2010

Present and Future Challenges

International Association of Geodesy Symposia, 2013

2013 10th Workshop on Positioning, Navigation and Communication (WPNC), 2013

2012 International Conference on Indoor Positioning and Indoor Navigation (IPIN), 2012