A system and method in an unlicensed-radio access network for transporting a circuit-switched payload between an access network controller and a mobile station utilizing a packet-based transmission protocol. The controller sends to the mobile station, a channel activation message that includes a minimum acceptable sample size of the circuit-switched payload to be included in each packet. The mobile station determines whether it can support communications utilizing the minimum acceptable sample size, and if not, selects a larger sample size. The mobile station may send an acknowledgment message that indicates the sample size to be utilized. Alternatively, the mobile station begins transmitting packets, and the controller analyzes received packets to determine the sample size the mobile station is using. The controller then encodes transmissions to the mobile station utilizing the determined sample size.