Peter Willett - Profile on Academia.edu (original) (raw)
Papers by Peter Willett
Proceedings of SPIE, May 2, 2017
Proceedings of SPIE, May 17, 2016
Multiple target tracking (MTT) is a challenging task that aims to estimate the number of targets ... more Multiple target tracking (MTT) is a challenging task that aims to estimate the number of targets and their states in the presence of process noise, measurement noise and data association uncertainty. This paper considers a special MTT problem characterized by additional complexity. In this problem, multiple targets are launched simultaneously in nearby locations at the same speed with slightly different directions. As the distances between the initial locations of these targets are smaller than the resolution of the sensor, this results in merged measurements, i.e., unresolved tracks at the very beginning. To deal with this problem, the recently proposed Multi-Bernoulli (MB) filter is applied. Using a model for the merged measurements, simulation results with 2-D Cartesian measurements in an optical sensor's focal plane in the presence of clutter show that the initially unresolved tracks become resolved with MB filtering a few time steps after the measurements become resolved. Thus, the MB filter is capable of keeping track of the number of targets and their corresponding states when they are initially unresolved.
IEEE Transactions on Signal Processing, May 1, 2016
IEEE Aerospace and Electronic Systems Magazine, 2017
everal months hence I bent your ears about "citation stacking," this being a practice both seemin... more everal months hence I bent your ears about "citation stacking," this being a practice both seemingly weird in itself and apparently odd for me to get exercised about. It refers to the various means to encourage bibliographic references to a specific journal (or group of journals or body of work) with the aim of inflating the "numbers." For a researcher, these numbers are the citation count or h-index: a researcher with h=24, say, has authored 24 works each cited 24 or more times. And for a publication, the number is the impact factor (IF), the average number of times each published article is cited over a rolling period, usually two years. Both numbers are often (yes, too often) a proxy for quality. Bigger is better. I'm not sure how a researcher could manipulate his/her own citation count in a meaningful way: remember that for senior researchers these counts are quite high (see Google Scholar) and an extra few would have little import. And anyway, I don't know what would happen if such behavior was caught; but I'm forever in awe of my academic colleagues' creativity. On the other hand, publications are monitored ("indexed") regularly and professionally -in our field by Clarivate Analytics. Bibliometric manipulation can be observed indirectly by inexplicable improvements in key indices, most notably impact factor. If wrongdoing is confirmed, a publication can be suspended. A suspended journal has no impact factor. Even past-published articles in a suspended journal become suspect. If you've ever looked at a researcher's h-index to see if you really need to pay attention, or if you've ever decided where to submit your article based on impact … you're not alone, and actually, I'll admit, I've done it too. And I'm aware that many of my international colleagues are judged by where they publish more than what: a good and highly-cited article in a journal with a low IF may do less for a career than a mediocre one that scrapes into a journal with a high IF and then gets justly ignored. There is an excellent presentation by Gianluca Setti whose message -here distilled to far too few words -is that if you really need "numbers" please use several together, and not just (say) impact factor. And … please understand how they are calculated. I will give you more information from Dr. Setti in a future editorial. Let's go on to nicer matters. And a much nicer matter is Maria Sabrina Greco. Sabrina, my boss at Systems Magazine, is the incoming AESS VP of Publications. Sabrina will replace current VP of Publications Dale Blair in January 2018. Dale, whose term is ending, has done a wonderful job as VP Pubs these last three years, dealing with all sorts of matters that you all are thankfully shielded from, and facilitating promising publication initiatives like early-posting and enhanced archiving. I'm excited to work with Sabrina in the future. She has a lot to live up to in Dale, but I think she'll do it. This month we have (as usual) articles that make me proud. Leppinen (from Aalto) explores the benefits promised and issues posed by basing spacecraft information systems on Linux. As he notes: "Platform-independent, Linux-targeted software could even be developed and used across various missions" -but if so, there are concerns that must be addressed. Next, a large team from Wichita State discusses morphing aircraft that enable "a single aircraft to perform multiple missions during a single flight by executing its shape change feature." The article focuses on measurement of structural deformation, which of course is key when the deformation must stay controlled and stable. Fertig and Baden from GTRI and Guerci from ISL offer their expertise on the role of knowledge-aided processing in multipath-exploitation radar. MER is an exciting and emerging technology that facilitates surveillance in traditionally (mostly) denied venues such as downtown / urban. The results are intriguing, and show that "[c]ontrary to the view that multipath is a problem, it is evident that the proper exploitation of multipath enables localization and tracking superior to that obtained in the absence of multipath." Our last regular article is from a team based at the French-German Research Institute of Saint-Louis. It introduces the idea of the gun-launched micro air vehicle (GLMAV). The "GL" is key, since the ability of hovering MAVs to observe is of little use if their slow progress to the site of interest risks the site being … no longer of interest. The article focuses on the electronics, and especially the vision system -these must be effective but also robust due to the means of delivery. The issue ends with a Student Highlight and an AESS Historical Interview. The Student Highlight is a neat application of earth-mover's distance as a means to register objects prior to image-based tracking. EMD, an emerging metric from the image-processing community, offers a focused methodology to register and match scenes as observation perspectives and target appearances change. Following the Student Highlight is an interview with Professor Hugh Griffiths. This historical Interview is the Magazine's sixth. Lorenzo Lo Monte interviews Hugh about his career and inspirations and shares with us all he learns. Hugh's career is impressive, full of achievements, discoveries, awards, and honors. He regularly contributes historical articles to our magazine and as you will see when you read the interview, history and radar continue to fascinate him. Although he acknowledges that radar is a mature technology, he reminds us that all you have to do is look around at the conferences and journals on radar to see that there are "plenty of new things happening" and always something new to learn. I hope you enjoy this issue, and I look forward to our next meeting.
IEEE Aerospace and Electronic Systems Magazine, 2018
elcome to our April issue. I write this in March from the northeast US, which means that we've ha... more elcome to our April issue. I write this in March from the northeast US, which means that we've had to put away our February T-shirts and golf clubs in favor of parkas and snow shovels. Good (weather) luck to us all for the Spring! I hope to see many of you at the Radar Conference in Oklahoma City in April -the AESS Board of Governors has its spring meeting there, which I'm sure is an added attraction for many of you. It's my pleasure to introduce a full and interesting issue of contributed papers this month -we are getting so many excellent papers, both contributed and Special Issue (invited), that sometimes there is a delay to publication. We apologize that some spend time "in the queue". First, Wahl & Turkoglu from San Jose State have given us Nonlinear Receding Horizon Control-Based Real-Time Guidance, Navigation, and Control Architecture for Launch Vehicles. As the title promises, the article suggests an RHC strategy for space vehicle guidance, and in fact gives a nice historical context for the solution. The article is rather more mathematical than the typical magazine offering; but, well, control is mathematical. Huang & Lin from Aphelion Orbitals in Florida offer Fully Optical Spacecraft Communications: Implementing an Omnidirectional PV-Cell Receiver and 8 Mb/s LED Visible Light Downlink With Deep Learning Error Correction that suggests use of the extant on-board photovoltaic systems for the visible-light communication (VLC) uplinks. There are significant challenges, perhaps the greatest being the high raw error rate caused by low SNR and non-coherent demodulation; the authors propose a deep-learning decoding strategy. Coupled with a LED downlink this may be an economical product for upcoming cubesats. Waseem & Sadiq from the Satellite Research and Development Centre in Pakistan have given us Application of Model-Based Systems Engineering in Small Satellite Conceptual Design-A SysML Approach which is a nice systems engineering case study. The article describes the experience of use of SysML, which is a modeling language used to design and verify systems … and systems of systems. Since many of our members are concerned with systems engineering as a large part of their daily work, and since the small-satellite focus is emerging, we hope the reader will find this article timely and useful. And as air traffic control is indeed a large scale "system," the theme is continued in Simulation Modelling of Traffic Collision Avoidance System With Wind Disturbance by Tang, Zhu & Fan, all from the National University of Defense Technology but with joint appointments at Barcelona and the Imperial College London. The application is air-traffic TCAS, and the focus is on the very necessary system description. A large team of authors from Airbus and the Universities of Valencia (Spain), Erlangen-Nurnberg (Germany) and Udine (Italy) have given us Multifunctional and Compact 3D FMCW MIMO Radar System With Rectangular Array for Medium-Range Applications. This is a particularly nice article that is exactly at the right technical level. Its title describes the subject, but only hints at the data fusion aspect: a camera also forms part of the system and aids considerably in tracking and classification. Further, this fusion facilitates change detection, which with its small size and economical design makes the system nicely suited for area protection or for UAV mounting. Finally, some words about the life of radar legend Philip Mayne Woodward, who passed from us on January 30 at age 98. Dr. Woodward's niece Suzette Woodward and colleague Susan Bond have kindly sent us their thoughts. I think most of us know of his contributions to radar, but his contributions to computer science (especially a language I remember fondly: Algol) and (this is surprising!) clock-making will be new at least to many of you. Thanks, Suzette!
![Research paper thumbnail of Highlights from the Sensor Array and Multichannel Technical Committee: Spotlight on the IEEE Signal Processing Society Technical Committees [In the Spotlight]](https://attachments.academia-assets.com/120562851/thumbnails/1.jpg)
](IEEE Signal Processing Magazine, 2018
IEEE Aerospace and Electronic Systems Magazine, 2019
'll begin with some (extremely!) happy AESS news: It was recently announced that Hugh Griffiths h... more 'll begin with some (extremely!) happy AESS news: It was recently announced that Hugh Griffiths has been appointed by the Queen of England as an "Officer in the Order of the British Empire" (OBE) for "Services to Engineering." I don't know that many details yet, and I'll share them with you when I do (it's quite new news); but I'm sure most of you know Dr. Griffiths well through his service to AESS (he was AESS President 2012 and 2013), his excellent AESS publications (for one example amongst many, see his "Radar Detection and Tracking of German V-2 Rocket Launches in WW2" in this publication, March 2013) and his enormous footprint in the radar research community. But I need also to share unhappy news, that of the passing of Dave Dobson. Dave left us on August 19, 2017 -not recently, and I am sorry we have not previously written of it. To many of us involved in our AES Society, Dave Dobson and AESS Publications were for many years synonymous. If one steps back through old issues of the Transactions and Magazine one can see references to him throughout. The first I saw was news in the February 1964 IEEE Transactions on Aerospace, which reported, regarding the minutes of the Professional Technical Group on AeroSpace contemplating a merger with another PTG, that "considerable discussion" occurred. It listed Dave's name as one of a short list of the meeting's attendees. I note this with a smile on my face because I know that Dave was sometimes opinionated, frequently irascible, often playful, generally right -and always involved. I was hugely saddened to hear, a few years ago, that Dave was not well; and very unhappy to hear that he had passed from us. But it is hard for me to write about him without that smile. Dave was extremely serious about the success and quality of AESS Publications. But he had, I think, a sense of lighthearted joy about what he did, and those of us who worked with him had fun being part of that. When I took over from Dale Blair as chief editor for the AES Transactions, Dale advised me that all I needed to do was "talk to Dave" to get things done. I did; and these talks usually had me laughing and looking forward to when he would get around to discussing, as he always did, "those […] in Piscataway," referring to the good-natured Thirty Years' War between him and IEEE Operations. I don't think I can compare anyone to Dave in terms of giving of himself so completely, selflessly and over such a period of time for the betterment of his profession. We at AESS have been blessed that Dave has made this gift to us. I strongly recommend taking a look at Dale Blair's interview with Dave (Bill Walsh helped) in the June 2015 issue of this magazine, from which a picture above has been extracted. Even better, go to center.aess.ieee.org and click on "Membership" to see a video of the interview. It makes me smile to hear his voice again. In this month's issue we have four nice articles. First, from Finland, we have a report on the Aalto-1 small satellite, with special attention to the reusable Linux software. We have from universities in Barcelona and Boston, along with the European Space Agency, a report on the vital synchronization issues in deep-space communications. A team from TU Munich and the LSE Space company (near Munich) explain space-based coordination -and especially of satellite communications -of search and rescue operations. Finally, since data security is of increasing importance, authors from Queens U in Belfast, (Northern Ireland) and from Radionavigation in Cork (Ireland), discuss measures to combat spoofing in GNSS systems, especially the associated costs of such. -Peter Willett
2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2016
Notice: Changes introduced as a result of publishing processes such as copy-editing and formattin... more Notice: Changes introduced as a result of publishing processes such as copy-editing and formatting may not be reflected in this document. For a definitive version of this work, please refer to the published source. Please note that access to the published version might require a subscription. Chalmers Publication Library (CPL) offers the possibility of retrieving research publications produced at Chalmers University of Technology. It covers all types of publications: articles, dissertations, licentiate theses, masters theses, conference papers, reports etc. Since 2006 it is the official tool for Chalmers official publication statistics. To ensure that Chalmers research results are disseminated as widely as possible, an Open Access Policy has been adopted. The CPL service is administrated and maintained by Chalmers Library.
This paper presents a model for tracking of extended targets whose extent cannot be described by ... more This paper presents a model for tracking of extended targets whose extent cannot be described by a simple geometric shape such as an ellipse or a rectangle. The extended target shape is represented by a number Ns of elliptic subobjects, where Ns is assumed known. Because an extended target is a rigid body, the subobject positions must necessarily be estimated as a single state with unified kinematics, and the full covariance matrix must be estimated. In addition to the position and kinematics, for each subobject the proposed model also estimates the number of measurements generated by the shape, as well as a random matrix as representation of the size and shape. A Gamma Gaussian inverse Wishart implementation is proposed, and the state prediction and update are given. A simulation study shows the merits of the model compared to extended target modeling without unified kinematics.
In this paper, a previously introduced data mining technique, utilizing the Mean Field Bayesian D... more In this paper, a previously introduced data mining technique, utilizing the Mean Field Bayesian Data Reduction Algorithm (BDRA), is extended for use in finding unknown data clusters in a fused multidimensional feature space. In the BDRA the modeling assumption is that the discrete symbol probabilities of each class are a priori uniformly Dirichlet distributed, and where the primary metric for selecting and discretizing all relevant features is an analytic formula for the probability of error conditioned on the training data. In extending the BDRA for this application, notice that its builtin dimensionality reduction aspects are exploited for isolating and automatically sorting out and mining all points contained in each unknown data cluster. In previous work, this approach was shown to have comparable performance to the classifier that knows all cluster information when mining a single feature containing multiple unknown clusters. Therefore, the primary contribution of the work presented here is to demonstrate that this approach can be extended to cases where the features are fused and contain more than one dimension. To illustrate performance, results are demonstrated using simulated data containing multiple clusters, and where the fused feature space contains relevant classification information.
IEEE Transactions on Aerospace and Electronic Systems, Oct 1, 2015
The IMM estimator outperforms fixed model filters, e.g. the Kalman filter, in scenarios where the... more The IMM estimator outperforms fixed model filters, e.g. the Kalman filter, in scenarios where the targets have periods of disparate behavior. Key to the good performance and low complexity is the mode mixing. Here we propose a systematic approach to mode mixing when the modes have states of different dimensions. The proposed approach is general and encompasses previously suggested solutions. Different mixing approaches are compared, and the proposed methodology is shown to perform very well.
Decentralized detection via running consensus
International Conference on Information Fusion, Jul 5, 2016
We propose a multisensor method for tracking an unknown number of targets. Low computational comp... more We propose a multisensor method for tracking an unknown number of targets. Low computational complexity and very good scalability in the number of targets, number of sensors, and number of measurements per sensor are achieved by running a belief propagation (BP) message passing scheme on a suitably devised factor graph. Using a redundant formulation of data association uncertainty and "augmented target states" including target indicators allows the proposed BP method to leverage statistical independencies for a drastic reduction of complexity. The proposed method is shown to outperform previously proposed multisensor methods for multitarget tracking, including methods with a less favorable scaling behavior.
IEEE Transactions on Signal Processing, Jul 1, 2017
We propose a method for tracking an unknown number of targets based on measurements provided by m... more We propose a method for tracking an unknown number of targets based on measurements provided by multiple sensors. Our method achieves low computational complexity and excellent scalability by running belief propagation on a suitably devised factor graph. A redundant formulation of data association uncertainty and the use of "augmented target states" including binary target indicators make it possible to exploit statistical independencies for a drastic reduction of complexity. An increase in the number of targets, sensors, or measurements leads to additional variable nodes in the factor graph but not to higher dimensions of the messages. As a consequence, the complexity of our method scales only quadratically in the number of targets, linearly in the number of sensors, and linearly in the number of measurements per sensors. The performance of the method compares well with that of previously proposed methods, including methods with a less favorable scaling behavior. In particular, our method can outperform multisensor versions of the probability hypothesis density (PHD) filter, the cardinalized PHD filter, and the multi-Bernoulli filter.
Detection of Changes in Tracked Targets
Constrained Target Localization for Multiplatform Radar Systems
MILCOM 2021 - 2021 IEEE Military Communications Conference (MILCOM), Nov 29, 2021
A new algorithm for 3D localization in multiplat-form radar networks, comprising one transmitter ... more A new algorithm for 3D localization in multiplat-form radar networks, comprising one transmitter and multiple receivers, is proposed. To take advantage of the monostatic sensor radiation pattern features, angular constraints are imposed in the target localization process, restricting the azimuth-elevation location of any illuminated target. This is formulated as a non-convex constrained Least Squares (LS) optimization problem globally solved in a quasi-closed-form leveraging Karush-Kuhn-Tucker (KKT) conditions. The performance of the new algorithm is assessed in terms of the Root Mean Square Error (RMSE) and compared with the benchmark Root Cramer Rao Lower Bound (RCRLB) and some competitors from literature. The results corroborate the effectiveness of the new strategy which is capable of ensuring a lower RMSE than the counterpart methodologies especially in the low Signal to Noise Ratio (SNR) regime.
Ship Detection using GNSS-R delay-Doppler Maps via simulation tools
Recent research activities have investigated the feasibility of detecting ship targets from Globa... more Recent research activities have investigated the feasibility of detecting ship targets from Global Navigation Satellite System-Reflectometry (GNSS-R) receivers. It was concluded by both experimental and theoretical analyses that ship detection is infeasible from spaceborne receivers working in a conventional configuration. On the other hand, it was demonstrated that performance might be boosted by receiving the right-hand circular polarization (RHCP) channel in a backscattering configuration. In this paper, we assess the detectability of ship targets in GNSS-R delay-Doppler maps by means of a reliable stochastic GNSS-R simulation tool capable of accounting for the presence of the target. The results mainly confirm the previous theoretical analyses and demonstrate the feasibility of the ship detection problem using low-altitudes RHCP-backscattering GNSS-R.
A comparison of multiple-IMM estimation approaches using EKF, UKF, and PF for impact point prediction
Proceedings of SPIE, Jun 13, 2014
ABSTRACT We discuss a procedure to estimate the state of thrusting/ballistic endoatmospheric proj... more ABSTRACT We discuss a procedure to estimate the state of thrusting/ballistic endoatmospheric projectiles for the purpose of impact point prediction (IPP). The short observation time and the estimation ambiguity between drag and thrust in the dynamic model motivate the development of a multiple interacting multiple model (MIMM) estimator with various drag coefficient initializations. In each IMM estimator used, as the mode-matched state estimators for its thrusting mode and ballistics mode are of unequal dimension, an unbiased mixing is required. We explore the MIMM estimator with unbiased mixing (UM) using extended Kalman filter (EKF), unscented Kalman filter (UKF) and particle filter (PF). For 30 real trajectories, the IPP based on the MIMM-UM estimation approach is carried out with various sets of tuning parameters selected. The MIMM-UM-EKF, MIMM-UM-UKF and MIMM-UM-PF are compared based on the resulting IPP performance, estimator consistency and computational complexity.
On the Probability of Cross-Radar Assignment Error
If two radar sensors observe the same target their measurements can be combined to produce a fuse... more If two radar sensors observe the same target their measurements can be combined to produce a fused target-state estimate that is of higher quality than that from one radar alone. If there are multiple targets whose information is shared, a necessary first step to fusion is to “assign” each measurement from the first sensor to that at the other in such a way that both refer to the same underlying object, a task generally accomplished by minimizing a global cost involving distance. An assignment error occurs when the measurement originated by target i at the first radar is wrongly associated to a measurement originated by target jjj (not i) at the second radar. Naturally, when such an error occurs the result is fusion of information describing disparate objects, resulting in degraded estimation performance and poor self-assessment in terms of posterior uncertainty. Here we address the issue, and derive approximate assignment error probability. Remarkably, performance depends only upon the parameters combined to a single scalar constant.
Adaptive filtering of imprecisely time-stamped measurements with application to AIS networks
International Conference on Information Fusion, Jul 6, 2015
Driven by real-world issues in maritime surveillance, we consider the problem of estimating the t... more Driven by real-world issues in maritime surveillance, we consider the problem of estimating the target state from a sequence of observations that can be imprecisely time-stamped. That is, the time between two consecutive observations can be affected by an unknown error or delay. We propose an adaptive filtering strategy able to sequentially detect the time delays and correctly estimate the target state. Two decision statistics for the presence of delay are derived, the first is non-parametric while the second is based on the Generalized Likelihood Ratio Test (GLRT). When a delayed measurement is detected, the Maximum Likelihood (ML) estimate of the delay can be used to correct the timestamps of the target observation used in the filter. The validation of the proposed method is carried out using Monte Carlo computer simulations and analyzing real-world data collected by a global network of Automatic Identification System (AIS) receivers.
Proceedings of SPIE, May 2, 2017
Proceedings of SPIE, May 17, 2016
Multiple target tracking (MTT) is a challenging task that aims to estimate the number of targets ... more Multiple target tracking (MTT) is a challenging task that aims to estimate the number of targets and their states in the presence of process noise, measurement noise and data association uncertainty. This paper considers a special MTT problem characterized by additional complexity. In this problem, multiple targets are launched simultaneously in nearby locations at the same speed with slightly different directions. As the distances between the initial locations of these targets are smaller than the resolution of the sensor, this results in merged measurements, i.e., unresolved tracks at the very beginning. To deal with this problem, the recently proposed Multi-Bernoulli (MB) filter is applied. Using a model for the merged measurements, simulation results with 2-D Cartesian measurements in an optical sensor's focal plane in the presence of clutter show that the initially unresolved tracks become resolved with MB filtering a few time steps after the measurements become resolved. Thus, the MB filter is capable of keeping track of the number of targets and their corresponding states when they are initially unresolved.
IEEE Transactions on Signal Processing, May 1, 2016
IEEE Aerospace and Electronic Systems Magazine, 2017
everal months hence I bent your ears about "citation stacking," this being a practice both seemin... more everal months hence I bent your ears about "citation stacking," this being a practice both seemingly weird in itself and apparently odd for me to get exercised about. It refers to the various means to encourage bibliographic references to a specific journal (or group of journals or body of work) with the aim of inflating the "numbers." For a researcher, these numbers are the citation count or h-index: a researcher with h=24, say, has authored 24 works each cited 24 or more times. And for a publication, the number is the impact factor (IF), the average number of times each published article is cited over a rolling period, usually two years. Both numbers are often (yes, too often) a proxy for quality. Bigger is better. I'm not sure how a researcher could manipulate his/her own citation count in a meaningful way: remember that for senior researchers these counts are quite high (see Google Scholar) and an extra few would have little import. And anyway, I don't know what would happen if such behavior was caught; but I'm forever in awe of my academic colleagues' creativity. On the other hand, publications are monitored ("indexed") regularly and professionally -in our field by Clarivate Analytics. Bibliometric manipulation can be observed indirectly by inexplicable improvements in key indices, most notably impact factor. If wrongdoing is confirmed, a publication can be suspended. A suspended journal has no impact factor. Even past-published articles in a suspended journal become suspect. If you've ever looked at a researcher's h-index to see if you really need to pay attention, or if you've ever decided where to submit your article based on impact … you're not alone, and actually, I'll admit, I've done it too. And I'm aware that many of my international colleagues are judged by where they publish more than what: a good and highly-cited article in a journal with a low IF may do less for a career than a mediocre one that scrapes into a journal with a high IF and then gets justly ignored. There is an excellent presentation by Gianluca Setti whose message -here distilled to far too few words -is that if you really need "numbers" please use several together, and not just (say) impact factor. And … please understand how they are calculated. I will give you more information from Dr. Setti in a future editorial. Let's go on to nicer matters. And a much nicer matter is Maria Sabrina Greco. Sabrina, my boss at Systems Magazine, is the incoming AESS VP of Publications. Sabrina will replace current VP of Publications Dale Blair in January 2018. Dale, whose term is ending, has done a wonderful job as VP Pubs these last three years, dealing with all sorts of matters that you all are thankfully shielded from, and facilitating promising publication initiatives like early-posting and enhanced archiving. I'm excited to work with Sabrina in the future. She has a lot to live up to in Dale, but I think she'll do it. This month we have (as usual) articles that make me proud. Leppinen (from Aalto) explores the benefits promised and issues posed by basing spacecraft information systems on Linux. As he notes: "Platform-independent, Linux-targeted software could even be developed and used across various missions" -but if so, there are concerns that must be addressed. Next, a large team from Wichita State discusses morphing aircraft that enable "a single aircraft to perform multiple missions during a single flight by executing its shape change feature." The article focuses on measurement of structural deformation, which of course is key when the deformation must stay controlled and stable. Fertig and Baden from GTRI and Guerci from ISL offer their expertise on the role of knowledge-aided processing in multipath-exploitation radar. MER is an exciting and emerging technology that facilitates surveillance in traditionally (mostly) denied venues such as downtown / urban. The results are intriguing, and show that "[c]ontrary to the view that multipath is a problem, it is evident that the proper exploitation of multipath enables localization and tracking superior to that obtained in the absence of multipath." Our last regular article is from a team based at the French-German Research Institute of Saint-Louis. It introduces the idea of the gun-launched micro air vehicle (GLMAV). The "GL" is key, since the ability of hovering MAVs to observe is of little use if their slow progress to the site of interest risks the site being … no longer of interest. The article focuses on the electronics, and especially the vision system -these must be effective but also robust due to the means of delivery. The issue ends with a Student Highlight and an AESS Historical Interview. The Student Highlight is a neat application of earth-mover's distance as a means to register objects prior to image-based tracking. EMD, an emerging metric from the image-processing community, offers a focused methodology to register and match scenes as observation perspectives and target appearances change. Following the Student Highlight is an interview with Professor Hugh Griffiths. This historical Interview is the Magazine's sixth. Lorenzo Lo Monte interviews Hugh about his career and inspirations and shares with us all he learns. Hugh's career is impressive, full of achievements, discoveries, awards, and honors. He regularly contributes historical articles to our magazine and as you will see when you read the interview, history and radar continue to fascinate him. Although he acknowledges that radar is a mature technology, he reminds us that all you have to do is look around at the conferences and journals on radar to see that there are "plenty of new things happening" and always something new to learn. I hope you enjoy this issue, and I look forward to our next meeting.
IEEE Aerospace and Electronic Systems Magazine, 2018
elcome to our April issue. I write this in March from the northeast US, which means that we've ha... more elcome to our April issue. I write this in March from the northeast US, which means that we've had to put away our February T-shirts and golf clubs in favor of parkas and snow shovels. Good (weather) luck to us all for the Spring! I hope to see many of you at the Radar Conference in Oklahoma City in April -the AESS Board of Governors has its spring meeting there, which I'm sure is an added attraction for many of you. It's my pleasure to introduce a full and interesting issue of contributed papers this month -we are getting so many excellent papers, both contributed and Special Issue (invited), that sometimes there is a delay to publication. We apologize that some spend time "in the queue". First, Wahl & Turkoglu from San Jose State have given us Nonlinear Receding Horizon Control-Based Real-Time Guidance, Navigation, and Control Architecture for Launch Vehicles. As the title promises, the article suggests an RHC strategy for space vehicle guidance, and in fact gives a nice historical context for the solution. The article is rather more mathematical than the typical magazine offering; but, well, control is mathematical. Huang & Lin from Aphelion Orbitals in Florida offer Fully Optical Spacecraft Communications: Implementing an Omnidirectional PV-Cell Receiver and 8 Mb/s LED Visible Light Downlink With Deep Learning Error Correction that suggests use of the extant on-board photovoltaic systems for the visible-light communication (VLC) uplinks. There are significant challenges, perhaps the greatest being the high raw error rate caused by low SNR and non-coherent demodulation; the authors propose a deep-learning decoding strategy. Coupled with a LED downlink this may be an economical product for upcoming cubesats. Waseem & Sadiq from the Satellite Research and Development Centre in Pakistan have given us Application of Model-Based Systems Engineering in Small Satellite Conceptual Design-A SysML Approach which is a nice systems engineering case study. The article describes the experience of use of SysML, which is a modeling language used to design and verify systems … and systems of systems. Since many of our members are concerned with systems engineering as a large part of their daily work, and since the small-satellite focus is emerging, we hope the reader will find this article timely and useful. And as air traffic control is indeed a large scale "system," the theme is continued in Simulation Modelling of Traffic Collision Avoidance System With Wind Disturbance by Tang, Zhu & Fan, all from the National University of Defense Technology but with joint appointments at Barcelona and the Imperial College London. The application is air-traffic TCAS, and the focus is on the very necessary system description. A large team of authors from Airbus and the Universities of Valencia (Spain), Erlangen-Nurnberg (Germany) and Udine (Italy) have given us Multifunctional and Compact 3D FMCW MIMO Radar System With Rectangular Array for Medium-Range Applications. This is a particularly nice article that is exactly at the right technical level. Its title describes the subject, but only hints at the data fusion aspect: a camera also forms part of the system and aids considerably in tracking and classification. Further, this fusion facilitates change detection, which with its small size and economical design makes the system nicely suited for area protection or for UAV mounting. Finally, some words about the life of radar legend Philip Mayne Woodward, who passed from us on January 30 at age 98. Dr. Woodward's niece Suzette Woodward and colleague Susan Bond have kindly sent us their thoughts. I think most of us know of his contributions to radar, but his contributions to computer science (especially a language I remember fondly: Algol) and (this is surprising!) clock-making will be new at least to many of you. Thanks, Suzette!
IEEE Signal Processing Magazine, 2018
IEEE Aerospace and Electronic Systems Magazine, 2019
'll begin with some (extremely!) happy AESS news: It was recently announced that Hugh Griffiths h... more 'll begin with some (extremely!) happy AESS news: It was recently announced that Hugh Griffiths has been appointed by the Queen of England as an "Officer in the Order of the British Empire" (OBE) for "Services to Engineering." I don't know that many details yet, and I'll share them with you when I do (it's quite new news); but I'm sure most of you know Dr. Griffiths well through his service to AESS (he was AESS President 2012 and 2013), his excellent AESS publications (for one example amongst many, see his "Radar Detection and Tracking of German V-2 Rocket Launches in WW2" in this publication, March 2013) and his enormous footprint in the radar research community. But I need also to share unhappy news, that of the passing of Dave Dobson. Dave left us on August 19, 2017 -not recently, and I am sorry we have not previously written of it. To many of us involved in our AES Society, Dave Dobson and AESS Publications were for many years synonymous. If one steps back through old issues of the Transactions and Magazine one can see references to him throughout. The first I saw was news in the February 1964 IEEE Transactions on Aerospace, which reported, regarding the minutes of the Professional Technical Group on AeroSpace contemplating a merger with another PTG, that "considerable discussion" occurred. It listed Dave's name as one of a short list of the meeting's attendees. I note this with a smile on my face because I know that Dave was sometimes opinionated, frequently irascible, often playful, generally right -and always involved. I was hugely saddened to hear, a few years ago, that Dave was not well; and very unhappy to hear that he had passed from us. But it is hard for me to write about him without that smile. Dave was extremely serious about the success and quality of AESS Publications. But he had, I think, a sense of lighthearted joy about what he did, and those of us who worked with him had fun being part of that. When I took over from Dale Blair as chief editor for the AES Transactions, Dale advised me that all I needed to do was "talk to Dave" to get things done. I did; and these talks usually had me laughing and looking forward to when he would get around to discussing, as he always did, "those […] in Piscataway," referring to the good-natured Thirty Years' War between him and IEEE Operations. I don't think I can compare anyone to Dave in terms of giving of himself so completely, selflessly and over such a period of time for the betterment of his profession. We at AESS have been blessed that Dave has made this gift to us. I strongly recommend taking a look at Dale Blair's interview with Dave (Bill Walsh helped) in the June 2015 issue of this magazine, from which a picture above has been extracted. Even better, go to center.aess.ieee.org and click on "Membership" to see a video of the interview. It makes me smile to hear his voice again. In this month's issue we have four nice articles. First, from Finland, we have a report on the Aalto-1 small satellite, with special attention to the reusable Linux software. We have from universities in Barcelona and Boston, along with the European Space Agency, a report on the vital synchronization issues in deep-space communications. A team from TU Munich and the LSE Space company (near Munich) explain space-based coordination -and especially of satellite communications -of search and rescue operations. Finally, since data security is of increasing importance, authors from Queens U in Belfast, (Northern Ireland) and from Radionavigation in Cork (Ireland), discuss measures to combat spoofing in GNSS systems, especially the associated costs of such. -Peter Willett
2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2016
Notice: Changes introduced as a result of publishing processes such as copy-editing and formattin... more Notice: Changes introduced as a result of publishing processes such as copy-editing and formatting may not be reflected in this document. For a definitive version of this work, please refer to the published source. Please note that access to the published version might require a subscription. Chalmers Publication Library (CPL) offers the possibility of retrieving research publications produced at Chalmers University of Technology. It covers all types of publications: articles, dissertations, licentiate theses, masters theses, conference papers, reports etc. Since 2006 it is the official tool for Chalmers official publication statistics. To ensure that Chalmers research results are disseminated as widely as possible, an Open Access Policy has been adopted. The CPL service is administrated and maintained by Chalmers Library.
This paper presents a model for tracking of extended targets whose extent cannot be described by ... more This paper presents a model for tracking of extended targets whose extent cannot be described by a simple geometric shape such as an ellipse or a rectangle. The extended target shape is represented by a number Ns of elliptic subobjects, where Ns is assumed known. Because an extended target is a rigid body, the subobject positions must necessarily be estimated as a single state with unified kinematics, and the full covariance matrix must be estimated. In addition to the position and kinematics, for each subobject the proposed model also estimates the number of measurements generated by the shape, as well as a random matrix as representation of the size and shape. A Gamma Gaussian inverse Wishart implementation is proposed, and the state prediction and update are given. A simulation study shows the merits of the model compared to extended target modeling without unified kinematics.
In this paper, a previously introduced data mining technique, utilizing the Mean Field Bayesian D... more In this paper, a previously introduced data mining technique, utilizing the Mean Field Bayesian Data Reduction Algorithm (BDRA), is extended for use in finding unknown data clusters in a fused multidimensional feature space. In the BDRA the modeling assumption is that the discrete symbol probabilities of each class are a priori uniformly Dirichlet distributed, and where the primary metric for selecting and discretizing all relevant features is an analytic formula for the probability of error conditioned on the training data. In extending the BDRA for this application, notice that its builtin dimensionality reduction aspects are exploited for isolating and automatically sorting out and mining all points contained in each unknown data cluster. In previous work, this approach was shown to have comparable performance to the classifier that knows all cluster information when mining a single feature containing multiple unknown clusters. Therefore, the primary contribution of the work presented here is to demonstrate that this approach can be extended to cases where the features are fused and contain more than one dimension. To illustrate performance, results are demonstrated using simulated data containing multiple clusters, and where the fused feature space contains relevant classification information.
IEEE Transactions on Aerospace and Electronic Systems, Oct 1, 2015
The IMM estimator outperforms fixed model filters, e.g. the Kalman filter, in scenarios where the... more The IMM estimator outperforms fixed model filters, e.g. the Kalman filter, in scenarios where the targets have periods of disparate behavior. Key to the good performance and low complexity is the mode mixing. Here we propose a systematic approach to mode mixing when the modes have states of different dimensions. The proposed approach is general and encompasses previously suggested solutions. Different mixing approaches are compared, and the proposed methodology is shown to perform very well.
Decentralized detection via running consensus
International Conference on Information Fusion, Jul 5, 2016
We propose a multisensor method for tracking an unknown number of targets. Low computational comp... more We propose a multisensor method for tracking an unknown number of targets. Low computational complexity and very good scalability in the number of targets, number of sensors, and number of measurements per sensor are achieved by running a belief propagation (BP) message passing scheme on a suitably devised factor graph. Using a redundant formulation of data association uncertainty and "augmented target states" including target indicators allows the proposed BP method to leverage statistical independencies for a drastic reduction of complexity. The proposed method is shown to outperform previously proposed multisensor methods for multitarget tracking, including methods with a less favorable scaling behavior.
IEEE Transactions on Signal Processing, Jul 1, 2017
We propose a method for tracking an unknown number of targets based on measurements provided by m... more We propose a method for tracking an unknown number of targets based on measurements provided by multiple sensors. Our method achieves low computational complexity and excellent scalability by running belief propagation on a suitably devised factor graph. A redundant formulation of data association uncertainty and the use of "augmented target states" including binary target indicators make it possible to exploit statistical independencies for a drastic reduction of complexity. An increase in the number of targets, sensors, or measurements leads to additional variable nodes in the factor graph but not to higher dimensions of the messages. As a consequence, the complexity of our method scales only quadratically in the number of targets, linearly in the number of sensors, and linearly in the number of measurements per sensors. The performance of the method compares well with that of previously proposed methods, including methods with a less favorable scaling behavior. In particular, our method can outperform multisensor versions of the probability hypothesis density (PHD) filter, the cardinalized PHD filter, and the multi-Bernoulli filter.
Detection of Changes in Tracked Targets
Constrained Target Localization for Multiplatform Radar Systems
MILCOM 2021 - 2021 IEEE Military Communications Conference (MILCOM), Nov 29, 2021
A new algorithm for 3D localization in multiplat-form radar networks, comprising one transmitter ... more A new algorithm for 3D localization in multiplat-form radar networks, comprising one transmitter and multiple receivers, is proposed. To take advantage of the monostatic sensor radiation pattern features, angular constraints are imposed in the target localization process, restricting the azimuth-elevation location of any illuminated target. This is formulated as a non-convex constrained Least Squares (LS) optimization problem globally solved in a quasi-closed-form leveraging Karush-Kuhn-Tucker (KKT) conditions. The performance of the new algorithm is assessed in terms of the Root Mean Square Error (RMSE) and compared with the benchmark Root Cramer Rao Lower Bound (RCRLB) and some competitors from literature. The results corroborate the effectiveness of the new strategy which is capable of ensuring a lower RMSE than the counterpart methodologies especially in the low Signal to Noise Ratio (SNR) regime.
Ship Detection using GNSS-R delay-Doppler Maps via simulation tools
Recent research activities have investigated the feasibility of detecting ship targets from Globa... more Recent research activities have investigated the feasibility of detecting ship targets from Global Navigation Satellite System-Reflectometry (GNSS-R) receivers. It was concluded by both experimental and theoretical analyses that ship detection is infeasible from spaceborne receivers working in a conventional configuration. On the other hand, it was demonstrated that performance might be boosted by receiving the right-hand circular polarization (RHCP) channel in a backscattering configuration. In this paper, we assess the detectability of ship targets in GNSS-R delay-Doppler maps by means of a reliable stochastic GNSS-R simulation tool capable of accounting for the presence of the target. The results mainly confirm the previous theoretical analyses and demonstrate the feasibility of the ship detection problem using low-altitudes RHCP-backscattering GNSS-R.
A comparison of multiple-IMM estimation approaches using EKF, UKF, and PF for impact point prediction
Proceedings of SPIE, Jun 13, 2014
ABSTRACT We discuss a procedure to estimate the state of thrusting/ballistic endoatmospheric proj... more ABSTRACT We discuss a procedure to estimate the state of thrusting/ballistic endoatmospheric projectiles for the purpose of impact point prediction (IPP). The short observation time and the estimation ambiguity between drag and thrust in the dynamic model motivate the development of a multiple interacting multiple model (MIMM) estimator with various drag coefficient initializations. In each IMM estimator used, as the mode-matched state estimators for its thrusting mode and ballistics mode are of unequal dimension, an unbiased mixing is required. We explore the MIMM estimator with unbiased mixing (UM) using extended Kalman filter (EKF), unscented Kalman filter (UKF) and particle filter (PF). For 30 real trajectories, the IPP based on the MIMM-UM estimation approach is carried out with various sets of tuning parameters selected. The MIMM-UM-EKF, MIMM-UM-UKF and MIMM-UM-PF are compared based on the resulting IPP performance, estimator consistency and computational complexity.
On the Probability of Cross-Radar Assignment Error
If two radar sensors observe the same target their measurements can be combined to produce a fuse... more If two radar sensors observe the same target their measurements can be combined to produce a fused target-state estimate that is of higher quality than that from one radar alone. If there are multiple targets whose information is shared, a necessary first step to fusion is to “assign” each measurement from the first sensor to that at the other in such a way that both refer to the same underlying object, a task generally accomplished by minimizing a global cost involving distance. An assignment error occurs when the measurement originated by target i at the first radar is wrongly associated to a measurement originated by target jjj (not i) at the second radar. Naturally, when such an error occurs the result is fusion of information describing disparate objects, resulting in degraded estimation performance and poor self-assessment in terms of posterior uncertainty. Here we address the issue, and derive approximate assignment error probability. Remarkably, performance depends only upon the parameters combined to a single scalar constant.
Adaptive filtering of imprecisely time-stamped measurements with application to AIS networks
International Conference on Information Fusion, Jul 6, 2015
Driven by real-world issues in maritime surveillance, we consider the problem of estimating the t... more Driven by real-world issues in maritime surveillance, we consider the problem of estimating the target state from a sequence of observations that can be imprecisely time-stamped. That is, the time between two consecutive observations can be affected by an unknown error or delay. We propose an adaptive filtering strategy able to sequentially detect the time delays and correctly estimate the target state. Two decision statistics for the presence of delay are derived, the first is non-parametric while the second is based on the Generalized Likelihood Ratio Test (GLRT). When a delayed measurement is detected, the Maximum Likelihood (ML) estimate of the delay can be used to correct the timestamps of the target observation used in the filter. The validation of the proposed method is carried out using Monte Carlo computer simulations and analyzing real-world data collected by a global network of Automatic Identification System (AIS) receivers.