{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:21:36Z","timestamp":1760242896965,"version":"build-2065373602"},"reference-count":35,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2016,10,10]],"date-time":"2016-10-10T00:00:00Z","timestamp":1476057600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100018621","name":"Program for Changjiang Scholars and Innovative Research Team in University","doi-asserted-by":"publisher","award":["IRT1299"],"award-info":[{"award-number":["IRT1299"]}],"id":[{"id":"10.13039\/501100018621","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61301126","61471077"],"award-info":[{"award-number":["61301126","61471077"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100012507","name":"Special Fund of Chongqing Key Laboratory","doi-asserted-by":"publisher","award":["CSTC"],"award-info":[{"award-number":["CSTC"]}],"id":[{"id":"10.13039\/501100012507","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The aim of this paper is to present a new indoor localization approach by employing the Angle-of-arrival (AOA) and Received Signal Strength (RSS) measurements in Wi-Fi network. To achieve this goal, we first collect the Channel State Information (CSI) by using the commodity Wi-Fi devices with our designed three antennas to estimate the AOA of Wi-Fi signal. Second, we propose a direct path identification algorithm to obtain the direct signal path for the sake of reducing the interference of multipath effect on the AOA estimation. Third, we construct a new objective function to solve the localization problem by integrating the AOA and RSS information. Although the localization problem is non-convex, we use the Second-order Cone Programming (SOCP) relaxation approach to transform it into a convex problem. Finally, the effectiveness of our approach is verified based on the prototype implementation by using the commodity Wi-Fi devices. The experimental results show that our approach can achieve the median error 0.7 m in the actual indoor environment.<\/jats:p>","DOI":"10.3390\/s16101664","type":"journal-article","created":{"date-parts":[[2016,10,10]],"date-time":"2016-10-10T10:35:19Z","timestamp":1476095719000},"page":"1664","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":22,"title":["PILA: Sub-Meter Localization Using CSI from Commodity Wi-Fi Devices"],"prefix":"10.3390","volume":"16","author":[{"given":"Zengshan","family":"Tian","sequence":"first","affiliation":[{"name":"Chongqing Key Lab of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ze","family":"Li","sequence":"additional","affiliation":[{"name":"Chongqing Key Lab of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mu","family":"Zhou","sequence":"additional","affiliation":[{"name":"Chongqing Key Lab of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yue","family":"Jin","sequence":"additional","affiliation":[{"name":"Chongqing Key Lab of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zipeng","family":"Wu","sequence":"additional","affiliation":[{"name":"Chongqing Key Lab of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2016,10,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Kumar, S., Gil, S., and Rus, D. (2014, January 7\u201311). Accurate indoor localization with zero start-up cost. Proceedings of the 20th Annual International Conference on Mobile Computing and Networking, Maui, HI, USA.","DOI":"10.1145\/2639108.2639142"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Kawauchi, K., Miyaki, T., and Rekimoto, J. (2009, January 7\u20138). Directional beaconing: A robust WiFi positioning method using Angle-of-Emission information. Proceedings of the 4th International Symposium on Location and Context Awareness, Tokyo, Japan.","DOI":"10.1007\/978-3-642-01721-6_7"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"276","DOI":"10.1109\/TAP.1986.1143830","article-title":"Multiple emitter location and signal parameter estimation","volume":"34","author":"Schmidt","year":"1986","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Gjengset, J., Xiong, J., Mcphillips, G., and Jamieson, K. (2014, January 7\u201311). Phaser: Enabling phased array signal processing on commodity WiFi access points. Proceedings of the 20th Annual International Conference on Mobile Computing and Networking, Maui, HI, USA.","DOI":"10.1145\/2639108.2639139"},{"key":"ref_5","first-page":"1","article-title":"Fingerprint indoor positioning algorithm based on affinity propagation clustering","volume":"1","author":"Tian","year":"2013","journal-title":"Euras. J. Wirel. Commun. Netw."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Chintalapudi, K., Padmanabha Iyer, A., and Padmanabhan, V.N. (2010, January 20\u201324). Indoor localization without the pain. Proceedings of the 16th Annual International Conference on Mobile Computing and Networking, Chicago, IL, USA.","DOI":"10.1145\/1859995.1860016"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"560","DOI":"10.1109\/TWC.2004.843040","article-title":"Nonline-of-sight error mitigation in mobile location","volume":"4","author":"Cong","year":"2005","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Sen, S., Lee, J., Kim, K.H., and Congdon, P. (2013, January 25\u201328). Avoiding multipath to revive inbuilding WiFi localization. Proceedings of the 11th Annual International Conference on Mobile Systems, Applications, and Services, Taipei, Taiwan.","DOI":"10.1145\/2462456.2464463"},{"key":"ref_9","first-page":"3473","article-title":"3-D localization error analysis in wireless networks","volume":"6","author":"Yu","year":"2007","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Wang, S., Jackson, B.R., and Inkol, R. (2012, January 28\u201329). Hybrid RSS\/AOA emitter location estimation based on least squares and maximum likelihood criteria. Proceedings of the 26th Biennial Symposium on Communications, Kingston, ON, Canada.","DOI":"10.1109\/QBSC.2012.6221344"},{"key":"ref_11","unstructured":"Paolo, B., Stefano, L., Stefano, C., and Gaetano, G. (2009, January 26\u201329). A novel approach to indoor RSSI localization by automatic calibration of the wireless propagation model. Proceedings of the 2009 Vehicular Technology Conference, Barcelona, Spain."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Youssef, M., and Agrawala, A. (2005, January 6\u20138). The horus WLAN location determination system. Proceedings of the 3rd International Conference on Mobile Systems, Applications, and Services, Seattle, WA, USA.","DOI":"10.1145\/1067170.1067193"},{"key":"ref_13","unstructured":"Bahl, P., and Padmanabhan, V.N. (2000, January 26\u201330). Radar: An in-building RF-based user location and tracking system. Proceedings of the 2000 19th Annual Joint Conference of the IEEE Computer and Communications Societies, Stockholm, Sweden."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"3626","DOI":"10.1109\/TWC.2006.256985","article-title":"RSS-based location estimation with unknown pathloss model","volume":"5","author":"Li","year":"2006","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"821","DOI":"10.1109\/JSTSP.2009.2029191","article-title":"Robust indoor positioning provided by real-time RSSI values in unmodified WLAN networks","volume":"3","author":"Mazuelas","year":"2009","journal-title":"IEEE J. Sel. Top. Signal Process."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Pajovic, M., Orlik, P., Koike-Akino, T., Kim, K.J., Aikawa, H., and Hori, T. (2015, January 6\u201310). An unsupervised indoor localization method based on received signal strength RSS measurements. Proceedings of the 2015 IEEE Global Communications Conference (GLOBECOM), San Diego, CA, USA.","DOI":"10.1109\/GLOCOM.2015.7417708"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"347","DOI":"10.3390\/mi6030347","article-title":"Smartphone-based indoor integrated WiFi\/MEMS positioning algorithm in a multi-floor environment","volume":"6","author":"Tian","year":"2015","journal-title":"Micromachines"},{"key":"ref_18","first-page":"1","article-title":"Pedestrian dead reckoning for MARG navigation using a smartphone","volume":"1","author":"Tian","year":"2014","journal-title":"EURASIP J. Adv. Signal Process."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Mariakakis, A.T., Sen, S., Lee, J., and Kim, K.H. (2014, January 16\u201319). SAIL: Single access point-based indoor localization. Proceedings of the 12th Annual International Conference on Mobile Systems, Applications, and Services, Bretton Woods, NH, USA.","DOI":"10.1145\/2594368.2594393"},{"key":"ref_20","unstructured":"Xiong, J., and Jamieson, K. (2013, January 2\u20135). ArrayTrack: A fine-grained indoor location system. Proceedings of the 10th Usenix Symposium on Networked Systems Design and Implementation, Lombard, IL, USA."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Qian, K., Wu, C., Yang, Z., Zhou, Z., Wang, X., and Liu, Y. (2016, January 10\u201314). Tuning by turning: Enabling phased array signal processing for WiFi with inertial sensors. Proceedings of the 35th Annual IEEE International Conference on Computer Communications, San Francisco, CA, USA.","DOI":"10.1109\/INFOCOM.2016.7524452"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Zheng, Z.W. (2010, January 7\u20139). Channel estimation and channel equalization for the OFDM-based WLAN systems. Proceedings of the 2010 International Conference on E-Business and E-Government (ICEE), Guangzhou, China.","DOI":"10.1109\/ICEE.2010.428"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"360","DOI":"10.1109\/TCOM.1963.1088793","article-title":"Characterization of randomly time-variant linear channels","volume":"11","author":"Bello","year":"1963","journal-title":"IEEE Trans. Commun. Syst."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Zhou, Z., Yang, Z., Wu, C., and Sun, W. (May, January 27). LiFi: Line-of-sight identification with WiFi. Proceedings of the 2014 Proceedings IEEE INFOCOM, Toronto, ON, Canada.","DOI":"10.1109\/INFOCOM.2014.6848217"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Laxmikanth, P., Surendra, L., Ratnam, D.V., and Babu, S.S. (2015, January 2\u20133). Enhancing the performance of AOA estimation in wireless communication using the MUSIC algorithm. Proceedings of the 2015 International Conference on Signal Processing and Communication Engineering Systems, Vijayawada, India.","DOI":"10.1109\/SPACES.2015.7058304"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"806","DOI":"10.1109\/TASSP.1985.1164649","article-title":"On spatial smoothing for direction-of-arrival estimation of coherent signals","volume":"33","author":"Shan","year":"1985","journal-title":"IEEE Trans. Acoust. Speech Signal Process."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"4482","DOI":"10.1109\/TWC.2012.112012.120104","article-title":"Indirect path detection based on wireless propagation measurements","volume":"11","author":"Shen","year":"2012","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1515","DOI":"10.1109\/TVT.2004.832384","article-title":"A novel ToA location algorithm using LoS range estimation for NLoS environments","volume":"53","author":"Venkatraman","year":"2004","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Sen, S., Radunovic, B., Choudhury, R.R., and Minka, T. (2012, January 25\u201329). You are facing the Mona Lisa: Spot localization using PHY layer information. Proceedings of the 10th International Conference on Mobile Systems, Applications, and Services, Lake District, UK.","DOI":"10.1145\/2307636.2307654"},{"key":"ref_30","unstructured":"Joshi, K., Hong, S., and Katti, S. (2013, January 2\u20135). PinPoint: Localizing interfering radios. Proceedings of the 10th Usenix Conference on Networked Systems Design and Implementation, Lombard, IL, USA."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Boyd, S., and Vandenberghe, L. (2004). Convex Optimization, Cambridge University Press.","DOI":"10.1017\/CBO9780511804441"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1016\/S0024-3795(98)10032-0","article-title":"Applications of second-order cone programming","volume":"284","author":"Boyd","year":"1998","journal-title":"Linear Algebra Appl."},{"key":"ref_33","unstructured":"Grant, M., and Boyd, S. CVX: Matlab Software for Disciplined Convex Programming. Available online: http:\/\/cvxr.com\/cvx."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1145\/1925861.1925870","article-title":"Tool release: Gathering 802.11n traces with channel state information","volume":"41","author":"Halperin","year":"2011","journal-title":"Comput. Commun. Rev."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1622","DOI":"10.1109\/TAP.2005.846804","article-title":"L-shape 2-dimensional arrival angle estimation with propagator method","volume":"53","author":"Tayem","year":"2005","journal-title":"IEEE Trans. Antennas Propag."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/16\/10\/1664\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T19:32:40Z","timestamp":1760211160000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/16\/10\/1664"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2016,10,10]]},"references-count":35,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2016,10]]}},"alternative-id":["s16101664"],"URL":"https:\/\/doi.org\/10.3390\/s16101664","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2016,10,10]]}}}