A transmission power control method subdivides one or more transmission power steps as defined in a system specification into multiple sub-steps. A base station (290) instructs a mobile station (280) to use a defined power step, and the mobile station (280) initially selects a maximum power sub-step within the requested power step during an initial RACH (225) transmission. During the duration of the call, the mobile station (280) dynamically adjusts the power sub-step based on measured signal reception quality and channel conditions. The result is an improvement in call completion rates with only a minor reduction in battery life.