B. Alavi | Worcester Polytechnic Institute (original) (raw)
Papers by B. Alavi
![Research paper thumbnail of Distance measurement error modeling for time-of-arrival based indoor geolocation [electronic resource]](https://attachments.academia-assets.com/105607249/thumbnails/1.jpg)
](Text (pdf). Dissertation (Ph.D.)--Worcester Polytechnic Institute. Includes bibliographical refer... more Text (pdf). Dissertation (Ph.D.)--Worcester Polytechnic Institute. Includes bibliographical references (p.168-171). Mode of access : World Wide Web via internet. Keywords: Ranging Error, Ranging, Positioning, Indoor Geolocation, Distance Measurement Error.
2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, 2006
... Using UWB measurements and modeling of the ranging error in a typical office building we comp... more ... Using UWB measurements and modeling of the ranging error in a typical office building we compare the performance of this cooperative localization algorithm with a non-channel based algorithm for indoor ad-hoc sensor environments. KEYWORDS ...
VTC-2005-Fall. 2005 IEEE 62nd Vehicular Technology Conference, 2005.
ABSTRACT First Page of the Article
IEEE Wireless Communications and Networking Conference, 2006. WCNC 2006., 2006
ABSTRACT In this paper we study the effect of bandwidth on performance of positioning systems. We... more ABSTRACT In this paper we study the effect of bandwidth on performance of positioning systems. We introduce a benchmark for performance evaluation, distance measurement error (DME). We analyze DME and introduce a model for it. We show that there are two causes for DME, multipath dispersion and undetected direct path (UDP), and we study the effect of bandwidth on each of these components in DME. We show that increasing the bandwidth can decrease the multipath DME, but for the UDP effect, beyond a certain point it increases the DME. Thus there is an optimum bandwidth for minimizing overall error. The results were obtained using a database of UWB measurements conducted in an indoor propagation environment
Interdisciplinary Information Sciences, 2006
As more location aware services are emerging in the market, the needs for accurate and reliable l... more As more location aware services are emerging in the market, the needs for accurate and reliable localization has increased and in response to this need a number of technologies and associated algorithms are introduced in the literature. Severe multipath fading in indoor areas, poses a challenging environment for accurate localization. In this article we provide a comprehensive overview of existing indoor localization techniques. We address the bandwidth requirement, advantages and disadvantages of received-signal-strength (RSS) and time-of-arrival (TOA) based localization algorithms. We describe a repeatable framework for comparative performance evaluation of localization algorithms. Using this framework we compare the performances of two TOA-based and two RSS-based algorithms. The TOA-based algorithms are the least square TOA (LS-TOA) and closest neighbor with TOA grid (CN-TOAG). The RSS-based algorithms are the maximum likelihood estimator and the recently introduced ray tracing assisted closest neighbor (RT-CN).
International Journal on Wireless & Optical Communications, 2006
In this paper we use UWB measurements for bandwidths up to 3GHz to present a framework for statis... more In this paper we use UWB measurements for bandwidths up to 3GHz to present a framework for statistical modeling of the indoor radio channel propagation characteristics that are pertinent to precise indoor geolocation using time-of-arrival (TOA) estimations. Accuracy of indoor geolocation systems relies on the strength and TOA of the direct path (DP) in the channel profile. Based on UWB measurements in a typical office building, we introduce empirical models for the path-loss and TOA of the DP. We use path-loss model for the DP to analyze the occurrence of the undetected direct path (UDP) conditions which cause large errors in indoor geolocation systems. Then we introduce a novel statistical model for the ranging or distance measurement error (DME) which is needed for comparative performance evaluation of the indoor positioning algorithms. The DME is a function of the bandwidth of the system, occurrence of the UDP conditions, and the distance between the transmitter and the receiver.
Electronics Letters, 2007
A novel empirical approach is presented for modelling the path loss behaviour of the direct path ... more A novel empirical approach is presented for modelling the path loss behaviour of the direct path (DP) between the transmitter and receiver, which is important for time-of-arrival-based indoor geolocation coverage characterisation. Using ultra wideband (UWB) measurements in four sites and three ranging scenarios, pathloss models at 500 MHz and 3 GHz system bandwidths are provided, centred on 4.5 GHz for DP and total signal power. In addition, ranging coverage analysis is provided using the DP models.
2007 IEEE 18th International Symposium on Personal, Indoor and Mobile Radio Communications, 2007
ABSTRACT This paper provides the results of comprehensive measurement and modelling of time of ar... more ABSTRACT This paper provides the results of comprehensive measurement and modelling of time of arrival (TOA) based UWB ranging in different indoor environments and ranging scenarios. We show that ranging accuracy of UWB systems is directly related to the physical constraints of the environment and system bandwidth. In addition we show through empirical measurement and modelling that the spatial characteristics of the ranging error depend on the presence and absence of the Direct Path (DP). In the former, the spatial error follow a normal distribution, while in the latter, the error behaviour is best modelled as lognormal.
IEEE Transactions on Vehicular Technology, 2009
In this paper, we present the results of the measurement and modeling of ultrawideband (UWB) time... more In this paper, we present the results of the measurement and modeling of ultrawideband (UWB) time of arrival (TOA)-based ranging in different indoor multipath environments. We provide a detailed characterization of the spatial behavior of ranging, where we focus on the statistics of the ranging error in the presence and absence of the direct path (DP) and evaluate the path loss behavior in the former case, which is important for indoor geolocation coverage characterization. The frequencydomain measurements were conducted, with a nominal frequency of 4.5 GHz with two different bandwidths, i.e., 500 MHz and 3 GHz. The parameters of the ranging error probability distributions and path loss models are provided for different environments (e.g., an old office, a modern office, a house, and a manufacturing floor) and different ranging scenarios [e.g., indoor to indoor (ITI), outdoor to indoor (OTI), and roof to indoor (RTI)].
One of the new frontiers in wireless networking research is location awareness. Knowledge of a us... more One of the new frontiers in wireless networking research is location awareness. Knowledge of a user's location enables a number of locationbased services (LBS) to be delivered to that user. However, while this problem has been largely addressed for the outdoor environment, indoor positioning is an open area of research. Here, the problem of accurate indoor positioning is discussed, and the current state of the art in accurate position estimation techniques is reviewed.
ABSTRACT In this paper we introduce a model for the distance error measured from the estimated ti... more ABSTRACT In this paper we introduce a model for the distance error measured from the estimated time of arrival (TOA) of the direct path (DP) between the transmitter and the receiver in a typical multipath indoor environment. We use the results of a calibrated Ray tracing software in a sample office environment. First we divide the whole floor plan into LOS and Obstructed LOS (OLOS), and then we model the distance error in each environment considering the variation of bandwidth of the system. We show that the behavior of the distance error in LOS environment can be modeled as Gaussian, while behavior of the OLOS is a mixture of Gaussian and exponential distribution. We also related the statistics of the distributions to the bandwidth of the system.
... Geolocation Bardia Alavi Kaveh Pahlavan Center for Wireless Information Network Studies Elect... more ... Geolocation Bardia Alavi Kaveh Pahlavan Center for Wireless Information Network Studies Electrical Engineering Department Worcester Polytechnic Institute Worcester, MA 01609, USA {bardia, kaveh}@wpi.edu ... 316-320. [4] A. Falsafi, K. Pahlavan, and G. Yang, Transmission ...
ABSTRACT The presence of undetected direct path (UDP) conditions presents significant challenges ... more ABSTRACT The presence of undetected direct path (UDP) conditions presents significant challenges for TOA-based indoor geolocation, since it introduces major errors into distance measurements. Therefore, it is critical to characterize the performance of indoor geolocation systems in the presence of UDP conditions. Until now, however, there has been no standard method of performance benchmarking for such cases. Towards that end, we present an analysis tool, known as the MSE profile, that can aid in this task. We use the MSE profile to analyze the performance of two TOA-based geolocation algorithms and show how the MSE profile can be used to gain insight into their performance, in the presence of distance measurement error (DME) models derived from Ultra-Wideband (UWB) measurements.
2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications, 2005
ABSTRACT In this paper we introduce a model for the distance error measured from the estimated ti... more ABSTRACT In this paper we introduce a model for the distance error measured from the estimated time of arrival (TOA) of the direct path (DP) in a typical multipath indoor environment. We use the results of our ultra-wideband (UWB) measurement database in a sample office environment. To begin modeling, first we separate the causes of the error into multipath and undetected direct path (UDP), and then we model them separately considering the variation of bandwidth of the system. We show that the behavior of the distance error consists of two parts; one that is from multipath, and the other one from UDP. Both errors can be modeled as Gaussian, so the final distance error is a mixture of two Gaussian distributions. We also related the statistics of the distributions to the bandwidth of the system
2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, 2006
The performance of Ultra-Wideband (UWB) indoor positioning systems based on Time of Arrival (TOA)... more The performance of Ultra-Wideband (UWB) indoor positioning systems based on Time of Arrival (TOA) techniques is generally affected by the density of reference points (RPs), as well as undetected direct path (UDP) conditions. For a fixed number of reference points (RPs), the performance of some indoor positioning algorithms tends to degrade as the size of the area is increased, i.e. the RP density is decreased. In this paper, we evaluate the effects of RP density on the performance of different positioning algorithms in the presence of empirical distance measurement error (DME) models derived from UWB measurements in typical indoor environments. We then present functional relationships between RP density and positioning mean-square error (MSE) for these algorithms. These relationships can be used for more effective indoor positioning system design and deployment. Finally, we investigate the effects of bandwidth with respect to improving the performance of these algorithms.
Physical review. B, Condensed matter, 1994
We have measured the low-temperature nonlinear conductivity in the spin-density-wave state of (TM... more We have measured the low-temperature nonlinear conductivity in the spin-density-wave state of (TMTSF)2X alloys. We find that an expression of sigma(E)=sigma0Eexp(-E0/E), suggestive of a tunneling process, describes the nonlinear conduction with the characteristic field E0 increasing with increasing disorder while sigma0E is independent of the impurity concentration within experimental error. We also discuss the implications of our findings.
Text (pdf). Dissertation (Ph.D.)--Worcester Polytechnic Institute. Includes bibliographical refer... more Text (pdf). Dissertation (Ph.D.)--Worcester Polytechnic Institute. Includes bibliographical references (p.168-171). Mode of access : World Wide Web via internet. Keywords: Ranging Error, Ranging, Positioning, Indoor Geolocation, Distance Measurement Error.
2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, 2006
... Using UWB measurements and modeling of the ranging error in a typical office building we comp... more ... Using UWB measurements and modeling of the ranging error in a typical office building we compare the performance of this cooperative localization algorithm with a non-channel based algorithm for indoor ad-hoc sensor environments. KEYWORDS ...
VTC-2005-Fall. 2005 IEEE 62nd Vehicular Technology Conference, 2005.
ABSTRACT First Page of the Article
IEEE Wireless Communications and Networking Conference, 2006. WCNC 2006., 2006
ABSTRACT In this paper we study the effect of bandwidth on performance of positioning systems. We... more ABSTRACT In this paper we study the effect of bandwidth on performance of positioning systems. We introduce a benchmark for performance evaluation, distance measurement error (DME). We analyze DME and introduce a model for it. We show that there are two causes for DME, multipath dispersion and undetected direct path (UDP), and we study the effect of bandwidth on each of these components in DME. We show that increasing the bandwidth can decrease the multipath DME, but for the UDP effect, beyond a certain point it increases the DME. Thus there is an optimum bandwidth for minimizing overall error. The results were obtained using a database of UWB measurements conducted in an indoor propagation environment
Interdisciplinary Information Sciences, 2006
As more location aware services are emerging in the market, the needs for accurate and reliable l... more As more location aware services are emerging in the market, the needs for accurate and reliable localization has increased and in response to this need a number of technologies and associated algorithms are introduced in the literature. Severe multipath fading in indoor areas, poses a challenging environment for accurate localization. In this article we provide a comprehensive overview of existing indoor localization techniques. We address the bandwidth requirement, advantages and disadvantages of received-signal-strength (RSS) and time-of-arrival (TOA) based localization algorithms. We describe a repeatable framework for comparative performance evaluation of localization algorithms. Using this framework we compare the performances of two TOA-based and two RSS-based algorithms. The TOA-based algorithms are the least square TOA (LS-TOA) and closest neighbor with TOA grid (CN-TOAG). The RSS-based algorithms are the maximum likelihood estimator and the recently introduced ray tracing assisted closest neighbor (RT-CN).
International Journal on Wireless & Optical Communications, 2006
In this paper we use UWB measurements for bandwidths up to 3GHz to present a framework for statis... more In this paper we use UWB measurements for bandwidths up to 3GHz to present a framework for statistical modeling of the indoor radio channel propagation characteristics that are pertinent to precise indoor geolocation using time-of-arrival (TOA) estimations. Accuracy of indoor geolocation systems relies on the strength and TOA of the direct path (DP) in the channel profile. Based on UWB measurements in a typical office building, we introduce empirical models for the path-loss and TOA of the DP. We use path-loss model for the DP to analyze the occurrence of the undetected direct path (UDP) conditions which cause large errors in indoor geolocation systems. Then we introduce a novel statistical model for the ranging or distance measurement error (DME) which is needed for comparative performance evaluation of the indoor positioning algorithms. The DME is a function of the bandwidth of the system, occurrence of the UDP conditions, and the distance between the transmitter and the receiver.
Electronics Letters, 2007
A novel empirical approach is presented for modelling the path loss behaviour of the direct path ... more A novel empirical approach is presented for modelling the path loss behaviour of the direct path (DP) between the transmitter and receiver, which is important for time-of-arrival-based indoor geolocation coverage characterisation. Using ultra wideband (UWB) measurements in four sites and three ranging scenarios, pathloss models at 500 MHz and 3 GHz system bandwidths are provided, centred on 4.5 GHz for DP and total signal power. In addition, ranging coverage analysis is provided using the DP models.
2007 IEEE 18th International Symposium on Personal, Indoor and Mobile Radio Communications, 2007
ABSTRACT This paper provides the results of comprehensive measurement and modelling of time of ar... more ABSTRACT This paper provides the results of comprehensive measurement and modelling of time of arrival (TOA) based UWB ranging in different indoor environments and ranging scenarios. We show that ranging accuracy of UWB systems is directly related to the physical constraints of the environment and system bandwidth. In addition we show through empirical measurement and modelling that the spatial characteristics of the ranging error depend on the presence and absence of the Direct Path (DP). In the former, the spatial error follow a normal distribution, while in the latter, the error behaviour is best modelled as lognormal.
IEEE Transactions on Vehicular Technology, 2009
In this paper, we present the results of the measurement and modeling of ultrawideband (UWB) time... more In this paper, we present the results of the measurement and modeling of ultrawideband (UWB) time of arrival (TOA)-based ranging in different indoor multipath environments. We provide a detailed characterization of the spatial behavior of ranging, where we focus on the statistics of the ranging error in the presence and absence of the direct path (DP) and evaluate the path loss behavior in the former case, which is important for indoor geolocation coverage characterization. The frequencydomain measurements were conducted, with a nominal frequency of 4.5 GHz with two different bandwidths, i.e., 500 MHz and 3 GHz. The parameters of the ranging error probability distributions and path loss models are provided for different environments (e.g., an old office, a modern office, a house, and a manufacturing floor) and different ranging scenarios [e.g., indoor to indoor (ITI), outdoor to indoor (OTI), and roof to indoor (RTI)].
One of the new frontiers in wireless networking research is location awareness. Knowledge of a us... more One of the new frontiers in wireless networking research is location awareness. Knowledge of a user's location enables a number of locationbased services (LBS) to be delivered to that user. However, while this problem has been largely addressed for the outdoor environment, indoor positioning is an open area of research. Here, the problem of accurate indoor positioning is discussed, and the current state of the art in accurate position estimation techniques is reviewed.
ABSTRACT In this paper we introduce a model for the distance error measured from the estimated ti... more ABSTRACT In this paper we introduce a model for the distance error measured from the estimated time of arrival (TOA) of the direct path (DP) between the transmitter and the receiver in a typical multipath indoor environment. We use the results of a calibrated Ray tracing software in a sample office environment. First we divide the whole floor plan into LOS and Obstructed LOS (OLOS), and then we model the distance error in each environment considering the variation of bandwidth of the system. We show that the behavior of the distance error in LOS environment can be modeled as Gaussian, while behavior of the OLOS is a mixture of Gaussian and exponential distribution. We also related the statistics of the distributions to the bandwidth of the system.
... Geolocation Bardia Alavi Kaveh Pahlavan Center for Wireless Information Network Studies Elect... more ... Geolocation Bardia Alavi Kaveh Pahlavan Center for Wireless Information Network Studies Electrical Engineering Department Worcester Polytechnic Institute Worcester, MA 01609, USA {bardia, kaveh}@wpi.edu ... 316-320. [4] A. Falsafi, K. Pahlavan, and G. Yang, Transmission ...
ABSTRACT The presence of undetected direct path (UDP) conditions presents significant challenges ... more ABSTRACT The presence of undetected direct path (UDP) conditions presents significant challenges for TOA-based indoor geolocation, since it introduces major errors into distance measurements. Therefore, it is critical to characterize the performance of indoor geolocation systems in the presence of UDP conditions. Until now, however, there has been no standard method of performance benchmarking for such cases. Towards that end, we present an analysis tool, known as the MSE profile, that can aid in this task. We use the MSE profile to analyze the performance of two TOA-based geolocation algorithms and show how the MSE profile can be used to gain insight into their performance, in the presence of distance measurement error (DME) models derived from Ultra-Wideband (UWB) measurements.
2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications, 2005
ABSTRACT In this paper we introduce a model for the distance error measured from the estimated ti... more ABSTRACT In this paper we introduce a model for the distance error measured from the estimated time of arrival (TOA) of the direct path (DP) in a typical multipath indoor environment. We use the results of our ultra-wideband (UWB) measurement database in a sample office environment. To begin modeling, first we separate the causes of the error into multipath and undetected direct path (UDP), and then we model them separately considering the variation of bandwidth of the system. We show that the behavior of the distance error consists of two parts; one that is from multipath, and the other one from UDP. Both errors can be modeled as Gaussian, so the final distance error is a mixture of two Gaussian distributions. We also related the statistics of the distributions to the bandwidth of the system
2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, 2006
The performance of Ultra-Wideband (UWB) indoor positioning systems based on Time of Arrival (TOA)... more The performance of Ultra-Wideband (UWB) indoor positioning systems based on Time of Arrival (TOA) techniques is generally affected by the density of reference points (RPs), as well as undetected direct path (UDP) conditions. For a fixed number of reference points (RPs), the performance of some indoor positioning algorithms tends to degrade as the size of the area is increased, i.e. the RP density is decreased. In this paper, we evaluate the effects of RP density on the performance of different positioning algorithms in the presence of empirical distance measurement error (DME) models derived from UWB measurements in typical indoor environments. We then present functional relationships between RP density and positioning mean-square error (MSE) for these algorithms. These relationships can be used for more effective indoor positioning system design and deployment. Finally, we investigate the effects of bandwidth with respect to improving the performance of these algorithms.
Physical review. B, Condensed matter, 1994
We have measured the low-temperature nonlinear conductivity in the spin-density-wave state of (TM... more We have measured the low-temperature nonlinear conductivity in the spin-density-wave state of (TMTSF)2X alloys. We find that an expression of sigma(E)=sigma0Eexp(-E0/E), suggestive of a tunneling process, describes the nonlinear conduction with the characteristic field E0 increasing with increasing disorder while sigma0E is independent of the impurity concentration within experimental error. We also discuss the implications of our findings.