Design of Cooperative NOMA for Live Video Broadcast

Recently, live video is getting more and more attention due to its tremendous growth in mobile traffic data. We focus on the scenario that large-scale users gather under a base station watching several different video sources’ live video contents. And users can change their receiving rates freely which can be divided into different levels. Therefore, we study a cooperative strategy enabled with non-orthogonal multiple access (NOMA) to make all users share the common time, code, and frequency resource. Specifically, we consider a scheme which can be divided into two phases, where the base station (BS) broadcasts a mixed message to all users in the broadcast transmission (BT) phase, and in the user-aided relaying (UR) phase, a user is selected as the helper to forward a mixed message including the information needed by users who fail to decode the message in the BT phase. Two methods are utilized for setting power allocation coefficients during the two phases. The first method is fixed power allocation (FPA) method in which the power allocation coefficients are fixed. While the second method is dynamic power allocation (DPA) method in which the power allocation coefficients is dynamically determined according to instantaneous channel state information (CSI). Moreover, two best helper selection approaches are proposed corresponding to the two power allocation methods. Simulation results show the advantage of the proposed cooperative strategy in terms of the system outage probability.