Detection of Burst Users and Symbols for Grant-Free Communication in the Presence of Massive Connected Users

We investigate user activity detection (UAD) and symbol detection (SD) for grant-free communication in the presence of massive users that are actively connected to base station (BS), where a small portion of to-be-connected users wake up in a burst. The number of effective interfering connected users is reduced to only one, by applying a preconditioning matrix to the received signals from multiple antennas at BS. Subsequently, an iterative UAD and SD scheme is applied, where the
priori
information about the remaining interfering user is exploited and the symbols of the burst users as well as the signature connected user are simultaneously detected by iterative exchanging of the soft information of user activity and symbols. The proposed system outperforms the existing work in terms of the success rate of UAD and bit error rate.