Qinghai Yang Kyung Sup Kwak Optimum Superimposed Training Design for Estimating of OFDM Channels. 2605-2608 2007 90-B IEICE Transactions 9 http://dx.doi.org/10.1093/ietcom/e90-b.9.2605 db/journals/ieicet/ieicet90b.html#YangK07