Wang Xin Youzheng Wang Jianhua Lu Superimposed or time-division multiplexed pilots in time-varying channels: an informative consideration. 770-774 2009 IWCMC http://doi.acm.org/10.1145/1582379.1582546 conf/iwcmc/2009 db/conf/iwcmc/iwcmc2009.html#XinWL09