Non-Orthogonal Multiple Access for Broadcast Channels

Speaker: Majid Khormuji, Huawei Sweden

Title: Non-Orthogonal Multiple Access for Broadcast Channels

Abstract: In cellular wireless systems, multiple access is usually performed by allocating orthogonal sets of time-frequency resources to different users. This way, inter-user interference is reduced and the receiver task of separating users' signals is made easier. However, it is well known that orthogonal transmission schemes do not achieve the capacity of multiuser channels. In the downlink, multiple access schemes performing simultaneous transmission to multiple users, like those based on the principle of superposition coding, can be employed in order to achieve increased data rates. In this talk, we present a new scheme coined as Rate-Adaptive Constellation Expansion Multiple Access (RA-CEMA) in which different users are non-orthogonally multiplexed by storing their codewords into a multiplexing matrix according to properly designed patterns and then mapping the columns of the matrix onto the symbols of a higher-order constellation. RA-CEMA is an alternative to the conventional superposition coding and combines the benefits of an increased spectral efficiency with the advantages of reusing the coding and modulation schemes already used in contemporary communication systems, thereby facilitating its adoption in standards.