| 1. |
- Davide, Dardari, et al.
(författare)
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Innovative Signal Processing Techniques for Wireless Positioning
- 2012
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Ingår i: Satellite and Terrestrial Radio Positioning Techniques, Davide Dardari, Emanuela Falletti, and Marco Luise, editors. Oxford, Academic Press. - 9780123820846 ; , s. 207-315
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Gezici, Sinan, et al.
(författare)
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Optimal Jammer Placement in Wireless Localization Systems
- 2016
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X .- 1941-0476. ; 64:17, s. 4534-4549
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the optimal jammer placement problem is proposed and analyzed for wireless localization systems. In particular, the optimal location of a jammer node is obtained by maximizing the minimum of the Cramer-Rao lower bounds (CRLBs) for a number of target nodes under location related constraints for the jammer node. For scenarios with more than two target nodes, theoretical results are derived to specify conditions underwhich the jammer node is located as close to a certain target node as possible, or the optimal location of the jammer node is determined by two of the target nodes. Also, explicit expressions are provided for the optimal location of the jammer node in the presence of two target nodes. In addition, in the absence of distance constraints for the jammer node, it is proved, for scenarios with more than two target nodes, that the optimal jammer location lies on the convex hull formed by the locations of the target nodes and is determined by two or three of the target nodes, which have equalized CRLBs. Numerical examples are presented to provide illustrations of the theoretical results in different scenarios.
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| 3. |
- Gezici, Sinan, et al.
(författare)
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Optimal Jamming of Wireless Localization Systems
- 2015
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Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP. - : IEEE. - 9781467363051 ; , s. 877-882
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Konferensbidrag (refereegranskat)abstract
- In this study, optimal jamming of wireless localization systems is investigated. Two optimal power allocation schemes are proposed for jammer nodes in the presence of total and peak power constraints. In the first scheme, power is allocated to jammer nodes in order to maximize the average Cramer-Rao lower hound (CRLB) of target nodes whereas in the second scheme the power allocation is performed for the aim of maximizing the minimum CRLB of target nodes. Both schemes are formulated as linear programs, and a closed-form expression is obtained for the first scheme. Also, the full total power utilization property is specified for the second scheme. Simulation results are presented to investigate perlbrmance of the proposed schemes.
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| 4. |
- Gezici, Sinan, et al.
(författare)
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The tradeoff between processing gains of an impulse radio UWB system in the presence of timing jitter
- 2007
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Ingår i: IEEE Transactions on Communications. - 0090-6778. ; 55:8, s. 1504-1515
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Tidskriftsartikel (refereegranskat)abstract
- In time hopping impulse radio, N-f pulses of duration T. are transmitted for each information symbol. This gives rise to two types of processing gains: i) pulse combining gain, which is a factor N-f, and (ii) pulse spreading gain, which is N-c = T-f/T-c where T-f is the mean interval between two subsequent pulses. This paper investigates the tradeoff between these two types of processing gains in the presence of timing jitter. First, an additive white Gaussian noise (AWGN) channel is considered, and approximate closed-form expressions for bit error probability (BEP) are derived for impulse radio systems with and without pulse-based polarity randomization. Both symbol-synchronous and chip-synchronous scenarios are considered. The effects of multiple-access interference (MAI) and timing jitter on the selection of optimal system parameters are explained through theoretical analysis. Finally, a multipath scenario is considered, and the tradeoff between processing gains of a synchronous impulse radio system with pulse-based polarity randomization is analyzed. The effects of the timing jitter, MAI, and interframe interference (IFI) are investigated. Simulation, studies support the theoretical results.
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| 5. |
- Gholami, Mohammad Reza, 1976, et al.
(författare)
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A Concave-Convex Procedure for TDOA Based Positioning
- 2013
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; To appear:4, s. 765-768
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Tidskriftsartikel (refereegranskat)abstract
- This letter investigates the time-difference- of-arrival based positioning problem in wireless sensor networks. We consider the least-mean absolute, i.e., the l1 norm, minimization of the residual errors and formulate the positioning problem as a difference of convex function (DC) programming. We then employ a concave-convex procedure to solve the corresponding DC programming. Simulation results illustrate the improved performance of the proposed approach compared to existing methods.
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| 6. |
- Gholami, Mohammad Reza, 1976, et al.
(författare)
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A distributed positioning algorithm for cooperative active and passive sensors
- 2010
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Ingår i: in Proc. 21st Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2010). - 9781424480166 ; , s. 1711-1716
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Konferensbidrag (refereegranskat)abstract
- The problem of positioning of an unknown targetin cooperative active and passive wireless sensor network isaddressed. Two-way time of arrival and time difference of arrivalmeasurements in active and passive nodes are used to estimate theposition of the target. A maximum likelihood estimator (MLE)can be employed to solve the problem. Due to nonlinear nature ofthe cost function in the MLE, the iterative search might convergeto local minima resulting in large error of estimation. To avoidthe MLE drawback, we formulate the problem of positioning asthe intersection of some convex sets. To nd the position estimate,we apply projection onto convex sets approach which is robustand can be implemented in a distributed manner. Simulationsare performed to compare the performance of the MLE andnew method.
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| 7. |
- Gholami, Mohammad Reza, 1976, et al.
(författare)
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Characterizing the Worst-Case Position Error in Bearing-Only Target Localization
- 2015
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Ingår i: Workshop on Positioning, Navigation and Communication (WPNC).
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Konferensbidrag (refereegranskat)abstract
- The worst-case position error provides valuable information for efficiently designing location based services in wireless networks. In this study, a technique based on a geometric approach is investigated for deriving a reasonable upper bound on the position error in bearing-only target localization. Assuming bounded measurement errors, it is first observed that the target node location belongs to a polytope. When a single estimate of the target location is available, the maximum distance from the estimate to extreme points of the polytope gives an upper bound on the position error. In addition, a technique based on outer approximation is proposed to confine the location of the target node to an ellipsoid. Simulation results show that the proposed upper bound is tight in many situations. It is also observed that the proposed techniques can be effectively used to derive sets containing the location of target nodes.
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| 8. |
- Gholami, Mohammad Reza, et al.
(författare)
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Cooperative Positioning in Wireless Networks
- 2016
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Ingår i: Wiley Encyclopedia of Electrical and Electronics Engineering. - : John Wiley & Sons. - 9780471346081 ; , s. 1-19
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Bokkapitel (refereegranskat)abstract
- In this article, we study cooperative positioning in wireless networks in which target nodes at unknown locations locally collaborate with each other to find their locations. We review different models available for positioning and categorize the model-based algorithms in two groups: centralized and distributed. We then investigate a lower bound on the variance of unbiased estimators, namely the Cramer–Rao lower bound, which is a common benchmark in the positioning literature. We finally discuss some open problems and research topics in the area of positioning that are worth exploring in future studies.
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| 9. |
- Gholami, Mohammad Reza, 1976, et al.
(författare)
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Distributed Bounding of Feasible Sets in Cooperative Wireless Network Positioning
- 2013
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 17:8, s. 1596-1599
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Tidskriftsartikel (refereegranskat)abstract
- Locations of target nodes in cooperative wireless sensor networks can be confined to a number of feasible sets in certain situations, e.g., when the estimated distances between sensors are larger than the actual distances.Quantifying feasible sets is often challenging in cooperative positioning. In this letter, we propose an iterative technique to cooperatively outer approximate the feasible sets containing the locations of the target nodes. We first outer approximate a feasible set including a target node location by an ellipsoid. Then, we extend the ellipsoid with the measured distances between sensor nodes and obtain larger ellipsoids. The larger ellipsoids are used to determine the intersections containing other targets. Simulation results show that the proposed technique converges after a small number of iterations.
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| 10. |
- Gholami, Mohammad Reza, 1976, et al.
(författare)
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Hybrid TW-TOA/TDOA Positioning Algorithms for Cooperative Wireless Networks
- 2011
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Ingår i: IEEE International Conference on Communications. - : IEEE. - 1550-3607. - 9781612842332
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Konferensbidrag (refereegranskat)abstract
- The problem of positioning an unknown target is studied for a cooperative wireless sensor network using hybrid two-way time-of-arrival and time-difference-of-arrival measurements. A maximum likelihood estimator (MLE) can be employed to solve the problem. Due to the non-linear nature of the cost function in the MLE, a numerical method, e.g., an iterative search algorithm with a good initial point, should be taken to accurately estimate the target. To avoid drawbacks in a numerical method, we insteadlinearize the measurements and obtain a new two-step estimator that has a closed-form solution in each step.Simulation results confirm that the proposed linear estimator can attain Cram\'er-Rao lower bound for sufficiently high SNR.
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