The present disclosure provides an uplink multiple access scheme and technique to enhance the overall spectral efficiency of wireless systems. The scheme and technique exploits an index modulation concept in orthogonal multiple access systems. A first subblock of transmitted data for a user is conventionally modulated, while a second subblock of the data determines the index of the active channel that will be used to communicate the modulated symbol. The scheme and technique enables all available orthogonal resources to be used for an arbitrary number of users as an extra source of information that is used to enhance the overall spectral efficiency in terms of error efficiency and energy efficiency.