{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T15:34:17Z","timestamp":1771515257285,"version":"3.50.1"},"reference-count":30,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2019,1,9]],"date-time":"2019-01-09T00:00:00Z","timestamp":1546992000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This work addresses the problem of target localization in adverse non-line-of-sight (NLOS) environments by using received signal strength (RSS) and time of arrival (TOA) measurements. It is inspired by a recently published work in which authors discuss about a critical distance below and above which employing combined RSS-TOA measurements is inferior to employing RSS-only and TOA-only measurements, respectively. Here, we revise state-of-the-art estimators for the considered target localization problem and study their performance against their counterparts that employ each individual measurement exclusively. It is shown that the hybrid approach is not the best one by default. Thus, we propose a simple heuristic approach to choose the best measurement for each link, and we show that it can enhance the performance of an estimator. The new approach implicitly relies on the concept of the critical distance, but does not assume certain link parameters as given. Our simulations corroborate with findings available in the literature for line-of-sight (LOS) to a certain extent, but they indicate that more work is required for NLOS environments. Moreover, they show that the heuristic approach works well, matching or even improving the performance of the best fixed choice in all considered scenarios.<\/jats:p>","DOI":"10.3390\/s19020230","type":"journal-article","created":{"date-parts":[[2019,1,10]],"date-time":"2019-01-10T03:22:31Z","timestamp":1547090551000},"page":"230","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":24,"title":["Target Localization via Integrated and Segregated Ranging Based on RSS and TOA Measurements"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5537-6716","authenticated-orcid":false,"given":"Slavisa","family":"Tomic","sequence":"first","affiliation":[{"name":"COPELABS, Universidade Lus\u00f3fona de Humanidades e Tecnologias, Campo Grande 376, 1749-024 Lisboa, Portugal"},{"name":"ISR\/IST, LARSyS, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7315-8739","authenticated-orcid":false,"given":"Marko","family":"Beko","sequence":"additional","affiliation":[{"name":"COPELABS, Universidade Lus\u00f3fona de Humanidades e Tecnologias, Campo Grande 376, 1749-024 Lisboa, Portugal"},{"name":"CTS\/UNINOVA, Campus da FCT\/UNL, Monte de Caparica, 2829-516 Caparica, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2019,1,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"54","DOI":"10.1109\/MSP.2005.1458287","article-title":"Locating the Nodes: Cooperative Localization in Wireless Sensor Networks","volume":"22","author":"Patwari","year":"2005","journal-title":"IEEE Signal Process. Mag."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1109\/SURV.2009.090308","article-title":"A Survey on TOA Based Wireless Localization and NLOS Mitigation Techniques","volume":"11","author":"Guvenc","year":"2009","journal-title":"IEEE Commun. Surv. Tutor."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1026","DOI":"10.1109\/JSAC.2010.100907","article-title":"NLOS Identification and Mitigation for Localization Based on UWB Experimental Data","volume":"28","author":"Marano","year":"2009","journal-title":"IEEE J. Sel. Areas Commun."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"18410","DOI":"10.3390\/s141018410","article-title":"Distributed RSS-Based Localization in Wireless Sensor Networks Based on Second-Order Cone Programming","volume":"14","author":"Tomic","year":"2014","journal-title":"Sensors"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"4119","DOI":"10.1109\/TWC.2014.2314640","article-title":"NLOS Error Mitigation for TOA-Based Localization via Convex Relaxation","volume":"13","author":"Wang","year":"2014","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2037","DOI":"10.1109\/TVT.2014.2334397","article-title":"RSS-based Localization in Wireless Sensor Networks Using Convex Relaxation: Noncooperative and Cooperative Schemes","volume":"64","author":"Tomic","year":"2015","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2210","DOI":"10.1109\/LCOMM.2015.2482979","article-title":"Robust NLOS Error Mitigation for TOA-based Localization via Second-Order Cone Relaxation","volume":"19","author":"Zhang","year":"2015","journal-title":"IEEE Commun. Lett."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1109\/LCOMM.2015.2498179","article-title":"Wireless Sensor Network Localization in Harsh ENvironments Using SDP Relaxation","volume":"20","author":"Ghari","year":"2016","journal-title":"IEEE Commun. Lett."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Tomic, S., Beko, M., Dinis, R., and Gomes, J.P. (2017). Target Tracking with Sensor Navigation Using Coupled RSS and AoA Measurements. Sensors, 17.","DOI":"10.3390\/s17112690"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"3197","DOI":"10.1109\/TVT.2016.2589923","article-title":"3-D Target Localization in Wireless Sensor Network Using RSS and AoA Measurement","volume":"66","author":"Tomic","year":"2017","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"158","DOI":"10.1016\/j.phycom.2017.10.005","article-title":"Bayesian Methodology for Target Tracking Using RSS and AoA Measurements","volume":"25","author":"Tomic","year":"2017","journal-title":"Phys. Commun."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1016\/j.pmcj.2016.09.013","article-title":"Distributed Algorithm for Target Localization in Wireless Sensor Networks Using RSS and AoA Measurements","volume":"37","author":"Tomic","year":"2017","journal-title":"Pervasive Mob. Comput."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"328","DOI":"10.1016\/j.sigpro.2017.09.019","article-title":"A Bisection-based Approach for Exact Target Localization in NLOS Environments","volume":"143","author":"Tomic","year":"2018","journal-title":"Signal Process."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"531","DOI":"10.1109\/LSP.2018.2810829","article-title":"Exact Robust Solution to TW-ToA-based Target Localization Problem with Clock Imperfections","volume":"25","author":"Tomic","year":"2018","journal-title":"IEEE Signal Process. Lett."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2849","DOI":"10.3390\/s18092849","article-title":"Elephant Herding Optimization for Energy-Based Localization","volume":"18","author":"Correia","year":"2018","journal-title":"Sensors"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Tomic, S., Beko, M., Dinis, R., and Bernardo, L. (2018). On Target Localization Using Combined RSS and AoA Measurements. Sensors, 18.","DOI":"10.3390\/s18041266"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2488","DOI":"10.1109\/LCOMM.2017.2737985","article-title":"A Robust Bisection-based Estimator for TOA-based Target Localization in NLOS Environments","volume":"21","author":"Tomic","year":"2017","journal-title":"IEEE Commun. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"503707","DOI":"10.5402\/2012\/503707","article-title":"A Hybrid RSS\/TOA Method for 3D Positioning in an Indoor Environment","volume":"2012","author":"Tiwari","year":"2012","journal-title":"ISRN Signal Process."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1186\/s13634-016-0385-4","article-title":"Robust Time-of-arrival Source Localization Employing Error Covariance of Sample Mean and Sample Median in Line-of-sight\/Non-line-of-sight Nuxture Environments","volume":"2016","author":"Park","year":"2016","journal-title":"EURASIP J. Adv. Signal Process."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1109\/TWC.2017.2766628","article-title":"On the Hybrid TOA\/RSS Range Estimation in Wireless Sensor Networks","volume":"17","author":"Coluccia","year":"2018","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1062","DOI":"10.1109\/LWC.2018.2858248","article-title":"Target Localization in NLOS Environments Using RSS and TOA Measurements","volume":"7","author":"Tomic","year":"2018","journal-title":"IEEE Wirel. Commun. Lett."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1109\/LSP.2018.2879720","article-title":"A Robust NLOS Bias Mitigation Technique for RSS-TOA-based Target Localization","volume":"26","author":"Tomic","year":"2019","journal-title":"IEEE Signal Process. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1049\/el.2015.2403","article-title":"Measurement-based Indoor NLOS TOA\/RSS Range Error Modelling","volume":"52","author":"Zhang","year":"2016","journal-title":"Electron. Lett."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1770","DOI":"10.1109\/TSP.2007.909342","article-title":"Exact and Approximate Solutions of Source Localization Problems","volume":"56","author":"Beck","year":"2008","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1382","DOI":"10.1109\/LCOMM.2015.2442580","article-title":"Cooperative Localization in NLOS Environments Using Semidefinite Programming","volume":"19","author":"Vaghefi","year":"2015","journal-title":"IEEE Commun. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"271984","DOI":"10.1155\/2008\/271984","article-title":"NLOS Identification and Weighted Leasr-Squares Localization for UWB Systems Using Multipath Channel Statistics","volume":"2008","author":"Guvenc","year":"2008","journal-title":"EURASIP J. Adv. Signal Process."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1109\/TIM.2012.2209918","article-title":"A Data Fusion Technique for Wireless Ranging Performance Improvement","volume":"62","author":"Macii","year":"2013","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_28","unstructured":"Kay, S.M. (1993). Fundamentals of Statistical Signal Processing: Estimation Theory, Prentice Hall. [1st ed.]."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"392","DOI":"10.1109\/LWC.2016.2567394","article-title":"Distributed RSS-AoA Based Localization with Unknown Transmit Powers","volume":"5","author":"Tomic","year":"2016","journal-title":"IEEE Wirel. Commun. Lett."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"680","DOI":"10.1109\/LWC.2016.2615614","article-title":"A Closed-form Solution for RSS\/AoA Target Localization by Spherical Coordinates Conversion","volume":"5","author":"Tomic","year":"2016","journal-title":"IEEE Wirel. Commun. Lett."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/2\/230\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:24:41Z","timestamp":1760185481000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/2\/230"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,1,9]]},"references-count":30,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2019,1]]}},"alternative-id":["s19020230"],"URL":"https:\/\/doi.org\/10.3390\/s19020230","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,1,9]]}}}