According to an example embodiment, a method may include allocating, within a single physical resource unit (PRU), a plurality of channel sounding groups. Wherein each channel sounding group includes a frequency-time domain code division multiplexing (CDM) allocation. The method may also include broadcasting, in a downlink direction to one or more mobile stations in a wireless network, a signal that causes the receiving mobile stations to transmit a channel sounding signal. The method may further include receiving at least one channel sounding signal from at least one of the one or more mobile stations, the channel sounding signal being received in an uplink direction via one or more channel sounding groups. And, the method may include estimating the channel quality, of the channel used by the physical resource unit, based upon the received at least one channel sounding signal.