A method and apparatus are described including allocating one of a plurality of sub-channels to one of a plurality of multicast group clients for a multicast session and performing bit-loading for the allocated sub-channel, wherein said performing act further includes finding one of the plurality of multicast group clients having a lowest received bit rate, finding one of the plurality of sub-channels needing a lowest power to transmit one more bit to the one of the plurality of multicast group clients having the lowest received bit rate, comparing the needed power to a residual power, adding one more transmission bit to the sub-channel if the needed power is not greater than the residual power and updating a multicast rate, the residual power and the power need to transmit one more bit if the needed power is not greater than the residual power.