An address for data bits is determined by categorizing the bits into a first, second, third and fourth case. The first case is for bits transferred in only one resource unit in a time slot; the second case is for bits transferred in a plurality of downlink resource units; the third case is for bits transferred in an uplink resource unit where a spreading factor of data in a first resource unit is greater than or equal to a spreading factor of a second resource unit; and the fourth case is for bits transferred in an uplink resource unit where a spreading factor of data in a first resource unit is less than a spreading factor of a second resource unit.