Interference Existence and Modulation Order Estimation for Downlink Multiuser Superposition Transmission

In this paper, we address the problem of intra-cell Interference Existence and Modulation Order Estimation in Downlink Multiuser Superposition Transmission(DL-MUST). In practical systems, the receiver needs to know the existence of interference before performing serial interference cancellation (SIC). An improved blind detection algorithm (SREBDA) which expands the searching range of candidate constellation points is proposed. The key point of the proposed algorithm is to find the suitable searching range for each candidate constellation, in order to improve the estimation accuracy as well as to reduce the computation complexity under high-order QAM. In addition, other factors, such as the range of SNR and the relation between all the selected candidate constellations points are considered. Simulation results show that the detection rate of proposed algorithm SREBDA not only enhances 31.3% under 256-QAM and 1024-QAM, but also reaches 100% under 4096-QAM, while the computation complexity reduces nearly 75%.