A method and apparatus of selecting a number of uplink sounding sub-carriers are disclosed. One method includes estimating an uplink channel of between a base station and a subscriber. A time domain channel response is determined from the estimated uplink channel. A sub-carrier distribution of uplink sounding sub-carriers is selected based on characteristics of the time domain channel response, wherein the distribution defines a spacing of pilot sub-carriers within the uplink sounding symbol. The subscriber transmits uplink sounding symbols having the selected sub-carrier distribution.