P. Jörke, T. Gebauer, and C. Wietfeld. 2022. From LENA to LENA-NB: Implementation and Performance Evaluation of NB-IoT and Early Data Transmission in ns-3. In Proceedings of the Workshop on ns-3 (WNS3 2022). ACM, New York, NY, USA.

With the growing Internet of Things, more small devices require internet connections. To address the scaling number of Internet of Things devices, the Cellular-IoT solution Narrowband Internet of Things has been extended with new features for more efficient transmission of small data. With Early Data Transmission, a promising new feature has been introduced in 3GPP Release 15, which aims to reduce the overall overhead of NB-IoT data transmissions by transmitting data without an active Radio Resource Control connection. To evaluate the impact of Early Data Transmission on the efficiency and scalability from a user and network provider perspective, we have implemented NB-IoT in ns-3, called LENA-NB framework. It features NB-IoT performance improvements from 3GPP Release 13 to 15, such as Cellular-IoT C-Plane Optimization, Early Data Transmission, RRC Resume procedure, as well as a new cross-subframe scheduler, adaptive modulation and coding, and a detailed energy state machine. Using LENA-NB, a performance comparison of different NB-IoT transmission modes is performed, which results in a clear recommendation to use Early Data transmission per default, since it improves latency, battery lifetime, and spectral efficiency, especially in scenarios with a large number of devices. In terms of spectrum usage, Early Data Transmission uses 3.7x less spectrum for the same transmissions compared to the default NB-IoT transmission mode, thus making the network much more scalable. Besides the impact in the spectrum usage, our work determined the currenty used Random Access windows of public NB-IoT networks as a potential bottleneck, which indicates the necessity of a Random Access optimization in the future. In addition, our implementation of LENA-NB is provided as an open-source project.