A method for operating a transmitting device using semi-orthogonal multiple access (SOMA) in a wireless local area network (WLAN) includes determining a first quadrature amplitude modulation (QAM) bit allocation, a first coding rate, and a first SOMA group for a first receiving device and a second QAM bit allocation, a second coding rate, and a second SOMA group for a second receiving device in accordance with channel information associated with the first receiving device and the second receiving device, generating a frame including indicators of the first and second QAM bit allocations, the first and second coding rates, and the first and second SOMA groups, and sending the frame to the first receiving device and the second receiving device.