Two-Dimensional Pilot Design for Non-Orthogonal Multiple Access in Multicarrier System

As being adopted as an important candidate Multiple Access (MA) scheme of future wireless communications, Non-Orthogonal Multiple Access (NOMA) recently attracts more and more attention. In this paper, we propose a solution of two-dimensional superimposed pilot design for NOMA. The proposed scheme exploits Walsh Hadamard matrix and its modifications to create the two-dimensional superimposed pilot, occupying approximately 5% to 10% of total transmit power and covering a certain time-frequency allocation. Deploying coherent processing in a moving average manner, adequate performance as initial channel estimates can be achieved even under asynchronous communications. Then, the two-dimensional superimposed pilots are dual-purposely exploited by the trellis-based detector, by jointly further improving the channel estimation and multiuser detection in NOMA system. Throughout our investigation, we demonstrate that the proposed pilot scheme can support not only big data block, but also relatively small data block.