Realizing asynchronous massive MIMO with trellis-based channel estimation and superimposed pilots

摘要: In this paper, we investigate channel estimation for the massive Multiple-Input Multiple-Output (MIMO) systems, by deploying superimposed pilots. The pilots are a priori known spreading sequences, repeated cyclically and to signal layer. They reserve marginal fraction of total transmit energy. Thus, initial estimates can be initially obtained separating users with respect corresponding code-division orthogonality robustness against asynchronicity. Further, during second stage, iterative is considered, integrating trellis-based estimator, which significantly enhance iterations, reusing Notice that so-called turbo-effect clearly observed, in both data detection jointly improved between consecutive iterations.