Providing connectivity in massive Machine Type Communications (mMTC) poses interesting challenges. In this paper, we propose and study a time diversity beamformer for reception in grant-free access in order to support massive uplink connectivity within the paradigm of the Internet of Things (IoT). The proposed access technique does not require channel estimation or prior network scheduling and provides benefits in terms of Probability of Collision and/or achievable Rate. The combination of our frame structure proposal with spatial signal processing at the receiver side yields a reduction on the probability of collision between devices, which, ultimately, implies that more users can access to the media.

Grant numbers : TERESA - Hybrid TERrEstrial/Satellite Air Interface for 5G and Beyond (TEC2017-90093-C3-1-R). © 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.