My Abdelkader Youssefi Jamal El Abbadi Optimal Spacing Design for Pilots in OFDM Systems over Multipath Fading Channels. 221-229 2010 2 Commun. Netw. 4 https://doi.org/10.4236/cn.2010.24032 db/journals/comnet/comnet2.html#YoussefiA10