A method of downlink subchannelization in a wireless communication system includes: transmitting a network entry and network discovery information including an open loop (OL) region parameter; and mapping a physical resource unit (PRU) to a contiguous resource unit (CRU) or a distributed resource unit (DRU) with respect to ith frequency partition based on the OL region parameter, wherein a permutation sequence used for mapping a PRU of the ith frequency partition (PRUFPi) to a CRU of the ith frequency partition (CRUFPi) or a DRU of the ith frequency partition (DRUFPi) is determined by a seed value, and the seed value is set to be a particular value according to the value of the OL region parameter.