A method for operating an adapting device includes selecting a first access mode out of a plurality of access modes for a first transmission between a first communications device and a second communications device, wherein the selection of the first access mode is made in accordance with an access mode criterion, and at least one of communications system information, and user equipment information, and determining sparse code multiple access (SCMA) parameters from the first access mode in accordance with a SCMA parameter mapping rule. The method also includes providing information about the first access mode to at least one of the first communications device and the second communications device.