{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,2,21]],"date-time":"2025-02-21T02:06:05Z","timestamp":1740103565777,"version":"3.37.3"},"reference-count":12,"publisher":"Wiley","license":[{"start":{"date-parts":[[2017,1,1]],"date-time":"2017-01-01T00:00:00Z","timestamp":1483228800000},"content-version":"unspecified","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003329","name":"Ministerio de Econom\u00eda y Competitividad","doi-asserted-by":"publisher","award":["TEC2014-57821-R"],"award-info":[{"award-number":["TEC2014-57821-R"]}],"id":[{"id":"10.13039\/501100003329","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Wireless Communications and Mobile Computing"],"published-print":{"date-parts":[[2017]]},"abstract":"<jats:p>One of the key challenges in railway engineering is how to provide passengers an efficient, secure, and safe service. To achieve this, operators and stakeholders demand robust and high-capacity train-to-wayside broadband radio. Current radio technologies implement MIMO (Multiple-Input Multiple-Output) technology, whose use requires a good characterization of the propagation. In this paper, the results of an experimental campaign on MIMO propagation in subway tunnels are presented. The campaign makes use of an OFDM testbed at roughly 600\u2009MHz, allowing the measurement of the <mml:math xmlns:mml=\"http:\/\/www.w3.org\/1998\/Math\/MathML\" id=\"M1\"><mml:mn fontstyle=\"italic\">2<\/mml:mn><mml:mo>\u00d7<\/mml:mo><mml:mn fontstyle=\"italic\">2<\/mml:mn><\/mml:math> channel transfer matrix under different conditions regarding polarization, antenna separation, tunnel cross section, power allocation algorithm, and so forth. Particular attention is paid to the probability of appearance of keyholes, which imply a severe degradation of the MIMO performance even when transmitter and receiver antennas are uncorrelated. The measurements are carried out using a train that travels at the normal operative velocities. As a result of the measurements, it has been found that the use of vertical polarization at both terminals is advantageous and that, on average but for a narrow margin, <jats:italic>\u03bb<\/jats:italic>-spaced antennas outperform <jats:italic>\u03bb<\/jats:italic>\/2-spaced ones (90% capacities of 7.00 and 6.76\u2009bps\/Hz, resp.), although the latter show a lower probability of keyholes. However, keyhole probabilities are always below 2%, so their influence on the performance of the whole system is limited.<\/jats:p>","DOI":"10.1155\/2017\/9068272","type":"journal-article","created":{"date-parts":[[2017,8,7]],"date-time":"2017-08-07T17:03:19Z","timestamp":1502125399000},"page":"1-7","source":"Crossref","is-referenced-by-count":1,"title":["Keyholes in MIMO-OFDM: Train-to-Wayside Communications in Railway Tunnels"],"prefix":"10.1155","volume":"2017","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4626-1535","authenticated-orcid":true,"given":"Juan","family":"Moreno Garc\u00eda-Loygorri","sequence":"first","affiliation":[{"name":"Teor\u00eda de la Se\u00f1al y Comunicaciones Department, ETSIS Telecomunicaci\u00f3n, Universidad Polit\u00e9cnica de Madrid (UPM), Campus Sur, Calle Nikola Tesla s\/n, 28031 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Leandro","family":"de Haro","sequence":"additional","affiliation":[{"name":"ETSI Telecomunicaci\u00f3n, Universidad Polit\u00e9cnica de Madrid (UPM), Ciudad Universitaria, 28040 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jos\u00e9 Manuel","family":"Riera","sequence":"additional","affiliation":[{"name":"ETSI Telecomunicaci\u00f3n, Universidad Polit\u00e9cnica de Madrid (UPM), Ciudad Universitaria, 28040 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Luis","family":"Cu\u00e9llar","sequence":"additional","affiliation":[{"name":"ETSI Telecomunicaci\u00f3n, Universidad Polit\u00e9cnica de Madrid (UPM), Ciudad Universitaria, 28040 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Carlos","family":"Rodr\u00edguez","sequence":"additional","affiliation":[{"name":"The Engineering Department of Metro de Madrid S.A., Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","reference":[{"key":"4","doi-asserted-by":"publisher","DOI":"10.1109\/mcom.2010.5458368"},{"key":"5","doi-asserted-by":"publisher","DOI":"10.1109\/jsac.2003.810294"},{"key":"6","doi-asserted-by":"publisher","DOI":"10.1109\/JSAC.2003.809458"},{"key":"7","doi-asserted-by":"publisher","DOI":"10.1109\/7693.994830"},{"key":"8","doi-asserted-by":"publisher","DOI":"10.1109\/twc.2006.256982"},{"key":"9","doi-asserted-by":"publisher","DOI":"10.1109\/LAWP.2014.2356076"},{"key":"10","doi-asserted-by":"publisher","DOI":"10.1109\/LAWP.2015.2424321"},{"key":"11","doi-asserted-by":"publisher","DOI":"10.1109\/JSAC.2003.809627"},{"key":"12","doi-asserted-by":"publisher","DOI":"10.1109\/LAWP.2009.2035299"},{"key":"13","doi-asserted-by":"publisher","DOI":"10.1109\/LAWP.2012.2191130"},{"key":"14","doi-asserted-by":"publisher","DOI":"10.1109\/TBC.2010.2046433"},{"key":"16","doi-asserted-by":"publisher","DOI":"10.1109\/49.730453"}],"container-title":["Wireless Communications and Mobile Computing"],"original-title":[],"language":"en","link":[{"URL":"http:\/\/downloads.hindawi.com\/journals\/wcmc\/2017\/9068272.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"http:\/\/downloads.hindawi.com\/journals\/wcmc\/2017\/9068272.xml","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"http:\/\/downloads.hindawi.com\/journals\/wcmc\/2017\/9068272.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2017,8,7]],"date-time":"2017-08-07T17:03:22Z","timestamp":1502125402000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.hindawi.com\/journals\/wcmc\/2017\/9068272\/"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017]]},"references-count":12,"alternative-id":["9068272","9068272"],"URL":"https:\/\/doi.org\/10.1155\/2017\/9068272","relation":{},"ISSN":["1530-8669","1530-8677"],"issn-type":[{"type":"print","value":"1530-8669"},{"type":"electronic","value":"1530-8677"}],"subject":[],"published":{"date-parts":[[2017]]}}}