Throughput of a wireless cell using superposition based multiple-access with non-ideal interference cancellation

In current wireless standards like 3GPP LTE or IEEE 802.16 / WiMAX multiple access is based on orthogonal signalling using single-carrier frequency-division multiple access (SC-FDMA) or orthogonal frequency-division multiple access (OFDMA). Links between a base station and different terminals use mutually orthogonal radio resources. This paper studies potential gains in average cell throughput by using multiple-access based on non-orthogonal superposition on top of orthogonal multiple access taking into account different channel gains for different users and interference-cancellation errors. The study is done for a system with a single antenna both at the base station and the terminals. Multiple terminals share a single time-frequency resource and their signals are separated by successive interference cancellation or other kinds of joint detection. This could be called multi-user SISO (MU-SISO), because multiple users can be scheduled on a single time-frequency resource in a SISO system. Frequency flat non-fading channels with a pathloss according to a common model are assumed. Especially in the case where throughput with orthogonal multiple-access is limited by low cell-edge SNR significant throughput gains of more than 80 % can be expected. The method can be extended to multiple-antennas and used on top of space-division multiple access (SDMA).