Contention-Based Early Data Transmission for 3GPP IoT Over Non-Terrestrial Networks

Kurzfassung

3GPP Release-19 is introducing an interesting new feature for narrowband Internet of things (NB-IoT) and enhanced machine type communications (eMTC). The solution, currently enabled only for IoT over non-terrestrial networks, consists in the use of contention-based early data transmission (CB-EDT) procedures to allow a UE send data over shared uplink resources following a random access approach. In contrast to the existing EDT solution, the new feature does not rely on the exchange of a random access preamble and random access response, but rather foresees the UE directly transmitting its message, thus saving overhead and reducing delay. Moreover, CB-EDT implements diversity slotted ALOHA (DSA), so that a UE transmits multiple replicas of its packet over the available uplink resources, aiming to enhance the probability of having at least one of its messages not collided. Further improvements are attained by using a multicast acknowledgment (message 4), addressing multiple UEs and saving downlink capacity. This article provides a description of the new feature, starting from its basic working principles and adding up details that cover the current 3GPP implementation status. The potential of the solution is demonstrated and discussed by means of numerical results, also identifying potential developments in future releases.